Mercury in Crude Oil Refined
in Canada
Mercury in Crude Oil Refined in Canada
Prepared by:
B.P. Hollebone
Emergencies Science and Technology Division
Science and Technology Branch
Environment Canada
335 River Road
Ottawa, Ontario K1A 0H3
and
C.X. Yang
Environmental Protection Operation Division – Ontario
Environmental Stewardship Branch
Environment Canada
4905 Dufferin Street
Toronto, Ontario M3H 5T4
October, 2007
ii
This report may be cited as:
Hollebone, B.P. and C.X. Yang, “Mercury in Crude Oil Refined in Canada”, Environment
Canada, Ottawa, ON, 2007.
iii
This report contains technical and scientific information from a joint project conducted by
Environment Canada and the Canadian Petroleum Products Institute to study the amount of
mercury in various types of crude oils. The report is intended to make information available that
is of interest to a limited audience. The demand for such technical reports is usually confined to
participants in the project and specialists in the fields concerned. These reports are therefore
produced in small quantities. Copies are available from the address below. The recommended
citation is provided on the back of the title page.
This report is available in Environment Canada libraries and is listed in the catalogue of the
National Library of Canada. It is printed in the official language chosen by the author to meet the
language preference of the likely audience, with an abstract in the second official language. To
determine whether there is significant demand for making this report available in the second
official language, Environment Canada invites users to specify their official language preference.
Copies of this report are available from:
Environmental Protection Operations Division - Ontario Region
Environment Canada
4905 Dufferin Street, Second Floor
Toronto, Ontario, Canada
M3H 5T4
© Minister of Public Works and Government Services Canada 2007
Catalogue No.
ISBN
iv
v
Acknowledgements
We would like to thank the Canadian refineries who participated in this study. Sampling for
work reported here was done by personnel at these refineries. The refineries are listed here in
alphabetical order.
Chevron Canada Ltd.
Consumers' Co-op Refinery Ltd.
Husky Energy Inc.
Imperial Oil Ltd.
North Atlantic Refinery
NOVA Chemicals (Canada) Ltd.
Petro-Canada Ltd.
Shell Canada Products
Suncor Energy Products Incorporated
Ultramar Ltée
Thanks are also extended to the following individuals who were members of the review
committee and their organizations which provided advice and financial support for this project.
Canadian Petroleum Products Institute
Jack Belletrutti
Environment Canada
Atlantic Region
Emissions Inventory Reporting and Outreach
National Mercury Program
Oil, Gas and Energy Division
Ontario Region
Pacific and Yukon Region
Prairie and Northern Region
Michael Hingston
David Niemi
Tonya Bender and Lorrie Hayes
Bruce McEwen, Elizabeth Escorihuela,
Lynne Patenaude, Andrew Snider,
Francine Beaudet, Shannon Castellarin,
Carl Chenier, and Saviz Mortazavi
Shawn Michajluk
Stan Liu
Maureen Brown
Ottawa University
Department of Biology
David Lean and Ogo Nwobu
Shell Canada
Shell Canada Products
Gerry Ertel
Thanks to Lisa Graham of the Emissions Measurement and Research Division of Environment
Canada for her initial proposal on this project, Dr. Yi-Fan Li of Environment Canada for
generating digital maps, and Feng Hou of Statistics Canada for his advice on sampling design.
Thanks are also due to our American counterparts, Mark Wilhelm of Mercury Technology
Services and David Kirchgessner of the U.S. E.P.A., for their advice throughout the project.
Finally, we would like to commend all involved for the spirit of cooperation that characterized
this work. This project required wide-ranging collaboration between government, industry, and
academia. With mutual interests in environmental issues, all stakeholders worked together to
achieve these results.
vi
List of Acronyms
AA
AFS
API
ASTM
CA
CEPA
CPPI
CVAA
CVAFS
DQO
EC
ESTD
ICP-AES
ICP/MS
MDL
NIC
NIST
NPRA
NPRI
NVLAP
OU
Ppb
Ppbw
Ppm
Ppmw
PSA
PTFE
QA
QC
RPD
RSD
SD
[THg]
U.S. EPA
Atomic absorption (spectrometry)
Atomic fluorescence spectrometry
American Petroleum Institute
Originally the American Society of Testing and Materials, now the
organization is simply known as ASTM International.
CEBAM Analytical Laboratories
Canadian Environmental Protection Act
Canadian Petroleum Products Institute
Cold vapour atomic absorption
Cold vapour atomic emission spectrometry
Data quality objective
Environment Canada
Emergencies Science and Technology Division (Environment
Canada)
Inductively-coupled plasma-atomic emission spectrometry
Inductively-coupled plasma/mass spectrometry
Method detection limit
Nippon Instrument Corporation
National Institute of Standards and Technology (U.S.)
National Petrochemical and Refiners Association (U.S.)
National Pollutant Release Inventory (Environment Canada)
NationalVoluntary Laboratory Accreditation Program, run by
NIST (U.S.)
Ottawa University laboratory
Parts per billion by weight (ng/g oil) or by volume (µg/L oil)
Parts per billion by weight (ng/g oil)
Parts per million: by weight (µg/g oil) or by volume (mg/L oil)
Parts per million by weight (µg/g oil)
PS Analytical
Poly-TetraFluoroEthylene
Quality assurance
Quality control
Relative percent difference
Relative standard deviation
Standard deviation
Total mercury concentration (in crude oil)
United States Environmental Protection Agency
vii
Executive Summary
A quantitative assessment of the amount of mercury processed by the petroleum sector is
necessary for many programs and initiatives. Mercury is identified as a priority toxic substance
in the Canadian Environmental Protection Act, 1999. Despite this, mercury emissions from the
petroleum-refining sector are not well quantified. For the past three decades, researchers in both
Canada and the United States have attempted to quantify the concentration of mercury in crude
oil and to estimate potential releases of mercury from petroleum sources. It has been difficult to
estimate emissions based on these past studies, however, due to problems with sample selection
and handling and the variety of analytical methods used.
To obtain an inventory of mercury in the petroleum-refining sector, Environment Canada, in
collaboration with the Canadian Petroleum Products Institute (CPPI) and most Canadian
refineries (including both CPPI members and independents), have measured the mercury
concentrations in 32 types of crude oil used in Canadian refineries. The goal of this study is to
determine the average concentration of total mercury present in crude oils refined in Canada and
the total amount of mercury in all the crude oil refined in Canada in a single year.
The study was conducted from November 2003 to June 2006. The project was a collaboration
between the federal government, the petroleum-refining industry, and academia. Environment
Canada provided overall project coordination, technical management, and sample analysis. The
Canadian Petroleum Products Institute ensured sample confidentiality and liaised between the
industry and the government. Processing data for the year 2002 was used for sampling design.
The participating refineries conducted sampling throughout 2004 and 2005, ensuring that the
samples taken were representative of the processing of crude oil in 2002. Sample management
and analysis were carried out by the University of Ottawa. Duplicate sample analysis was
performed by CEBAM Analytical of Seattle, Washington.
The volume-weighted average of total mercury concentration from refineries has been computed
from the total mercury concentration for each type of oil. This was used to estimate the total
amount of mercury in all crude oils refined in Canada, as well as the maximum potential for
mercury releases from refineries. The most significant release pathway for mercury in petroleum
products is through emission to the atmosphere by combustion of refined fuels. Refineries,
however, can also release mercury to water and land as well as to air.
More than 100 types of crude oil were processed by the participating refineries in the year 2002.
Approximately half were produced in Canada. Imported oils originated in Europe (17%), Africa
(6%), the Middle East (6%), the U.S. (9%), South America (9%), Mexico (5%), and Asia (1%).
A set of 32 oil types was chosen to be sampled, representing 72% by refined volume of all crude
oils refined in Canada in 2002. A total of 109 grab-samples was collected at the entry point to the
refineries. The total mercury concentration in each sample was measured by two different
laboratories using cold vapour atomic absorption (CVAA) and cold vapour atomic fluorescence
spectrometry (CVAFS). The oil density and total sulphur content were also determined. Strict
quality control was observed for all measurements.
viii
Findings
The average total mercury concentration in crude oil was 2.6 ± 0.5 ng of mercury/g of oil,
weighted by the volume refined in Canada in 2002. This corresponds to a total of 227 ± 30 kg of
mercury contained in all crude oil processed in Canada in 2002. This value agrees well with the
mean value of 2.1 ng/g for Canadian oils reported by the U.S. EPA and the American Petroleum
Institute (API) in a parallel survey of crude oils processed in the U.S. from 2003 to 2007.
Average volume-weighted mercury concentrations in oil were calculated for the geographical
source of the crude oils: 1.1 ± 0.2 ng/g from eastern Canada (including the Maritimes and
Ontario); 1.6 ± 0.3 ng/g from western Canada (Alberta, British Columbia, and Saskatchewan);
and 4.5 ± 0.8 ng/g for oils produced outside of Canada. The average volume-weighted mercury
concentration in synthetic crude oils, included in the western average concentration, produced
from the Alberta tar sand was estimated to be 2.2 ± 0.4 ng/g.
Average volume-weighted mercury concentrations in oil were calculated by refinery location:
1.4 ± 0.3 ng/g for western Canada (British Columbia, Alberta, and Saskatchewan); 2.1 ± 0.4 ng/g
for Ontario; and 4.5 ± 0.8 ng/g for Quebec and Atlantic provinces (Quebec, New Brunswick,
Nova Scotia, and Newfoundland).
Additional significant findings include the following.
o The range of mercury concentrations in crude oil was observed to be 0.1 to 50 ng/g.
o The average concentration and the range measured are significantly lower than those
reported in the literature.
o No strong correlations were found between the total mercury concentration in crude oil
and either total sulphur content or density of the oil.
o Canadian oils have lower concentrations of total mercury than oils from foreign sources.
Refineries on the east coast of Canada handle crude oils with higher levels of mercury
than those in Ontario or western Canada. This is almost entirely due to their use of higher
levels of foreign crude oils.
Recommendations
1.
The refined volume-weighted average of total mercury concentration in Canadian crude
oil is 2.6 ± 0.5 ng of mercury/g of oil (ppbw). From this average mercury concentration,
the total amount of mercury in crude oil processed in Canada is estimated to be 227 kg in
2002, 231 kg in 2003, 240 kg in 2004, and 233 kg in 2005. This is based on the total
amount of crude oil refined in Canada in those years.
2.
The processing pattern for crude oil reported here was that for 2002. In 2002, eight types
of crude oil accounted for 30% of the Canadian processing volume but contained more
than 80% of all the mercury in crude oil processed in Canada. These eight crude oils
originated from western Canada, Europe, and Africa. However, the processing pattern for
crude oil in Canada has changed slightly each year. If crude oil use deviates significantly
in the future from the usage pattern evaluated in this work, the results of this study will
need to be re-evaluated.
3.
The total amount of mercury in all crude oil processed in Canada in 2002 (227 ± 30 kg)
can be used as an estimate of the upper limit of potential mercury emissions from the
refining sector. This includes potential mercury emissions from all refined petroleum
products and all the potential mercury releases from refineries. This study targeted only
ix
the crude oil received by the refinery at the feedstock. Actual emissions from refineries
were not measured. In addition, mercury released from upstream oil and gas extraction,
handling, and transport to refineries should not be included in this estimate. Mercury
from other refinery inputs, such as natural gas, may also affect this estimate.
4.
The value for the total amount of mercury in crude oil refinery inputs can also be used as
an estimate of the upper limit of mercury in refined fuels. Emissions of mercury into the
atmosphere from the exhaust of on-road motor vehicles as a result of combustion of
refined petroleum products can be estimated to be no more than 227 ± 30 kg/yr. Using
this worst-case estimate, the maximum potential anthropogenic atmospheric emissions of
mercury from combustion of refined fuel would be 3.6% of the Canadian total (6,340 kg
of mercury) in 2002. Note that the actual disposition of mercury in each stream of the
petroleum products used to power on-road motor vehicles, including gasoline and diesel
fuels, was not measured in the present study.
x
xi
Sommaire-recommandations
De nombreux programmes et initiatives ont besoin d’une évaluation quantitative de la quantité
de mercure traitée par le secteur pétrolier. Par exemple, le mercure est désigné comme substance
toxique d’intérêt prioritaire dans la Loi canadienne sur la protection de l’environnement de 1999.
Les émissions de mercure des raffineries de pétrole sont mal quantifiées. Pendant les trois
dernières décennies, des chercheurs canadiens et états-uniens ont tenté de chiffrer la
concentration de mercure dans le pétrole brut et d’estimer les rejets potentiels de cet élément par
le secteur pétrolier. La sélection et la manutention des échantillons ainsi que la diversité des
méthodes d’analyse ont rendu difficile l’estimation des émissions d’après ces études antérieures.
Pour obtenir un inventaire du mercure dans le secteur du raffinage, Environnement Canada (EC)
a mesuré, en collaboration avec l’Institut canadien des produits pétroliers (ICPP) et la plupart des
raffineries canadiennes (membres de l’ICPP et indépendants), la teneur en mercure de 32 types
de bruts raffinés au Canada. L’objet de l’étude était de déterminer la teneur moyenne en mercure
total des bruts raffinés au Canada et la quantité totale de mercure présent dans tout le brut raffiné
en une année au Canada.
L’étude a été effectuée de novembre 2003 à juin 2006. Le projet était une collaboration entre
l’administration fédérale, l’industrie du raffinage et des universités. Environnement Canada a
assuré la coordination globale du projet, sa gestion technique et l’analyse des échantillons.
L’ICPP a assuré la confidentialité des échantillons et servi de trait d’union entre l’industrie et
l’administration fédérale. Les résultats du traitement des données de l’année 2002 ont servi à
l’élaboration du plan d’échantillonnage. Les raffineries participantes ont effectué les
prélèvements d’échantillons en 2004 et en 2005, en s’assurant qu’ils étaient représentatifs du
traitement effectué en 2002. La gestion et l’analyse des échantillons ont été confiées à
l’Université d’Ottawa. CEBAM Analytical, de Seattle (Washington) a effectué l’analyse des
échantillons en double.
On a calculé la concentration moyenne de mercure total, pondérée en fonction du volume, qui
provient des raffineries à partir de la concentration de mercure total dans chaque type de brut. On
s’en est ensuite servi pour estimer la quantité totale de mercure dans tous les bruts raffinés au
Canada ainsi que le tonnage potentiel maximal des rejets de mercure par les raffineries. La
principale voie de rejet du mercure des produits pétroliers passe par l’émission de l’élément dans
l’atmosphère suite à la combustion des carburants raffinés. Les raffineries, cependant, peuvent
également rejeter du mercure dans l’eau et le sol ainsi que dans l’atmosphère.
En 2002, les raffineries participantes ont traité plus de 100 types de bruts. La moitié de ces bruts
étaient canadiens. Les bruts importés provenaient d’Europe (17 %), d’Afrique (6 %), du
Moyen-Orient (6 %), des États-Unis (9 %), d’Amérique du Sud (9 %), du Mexique (5 %) et
d’Asie (1 %). Pour l’échantillonnage, on a choisi un ensemble de 32 types de brut, qui
représentaient 72 % du volume raffiné de tous les bruts raffinés au Canada en 2002. On a prélevé
en tout 109 échantillons au hasard, au point d’entrée dans les raffineries. On a dosé le mercure
total de chaque échantillon dans deux laboratoires, par spectrométrie d’absorption atomique en
vapeur froide (CVAA) et spectrométrie de fluorescence atomique en vapeur froide (CVAFS). On
a également mesuré la densité du pétrole et dosé son soufre total. Dans toutes les analyses et
mesures, on s’est rigoureusement conformé aux normes de contrôle de qualité.
xii
Constatations
La concentration moyenne de mercure total (Hg) dans le brut était de 2,6 ± 0,5 ng/g, pondérée en
fonction du volume raffiné au Canada en 2002. Cela correspond à un total de 227 ± 30 kg de
mercure se trouvant dans tout le brut raffiné au Canada en 2002. Cette valeur correspond bien à
la valeur moyenne de 2,1 ng/g dans les bruts canadiens signalée par l’Agence de protection de
l’environnement des États-Unis (USEPA) et l’American Petroleum Institute (API), dans une
étude parallèle de bruts raffinés aux États-Unis, de 2003 à 2007.
On a calculé, en tenant compte de l’origine géographique des bruts, leur teneur moyenne en
mercure, pondérée en fonction du volume : dans les bruts de l’est du Canada (y compris des
Maritimes et de l’Ontario), elle était de 1,1 ± 0,2 ng/g ; dans ceux de l’Ouest et du Nord du
Canada (Alberta, Colombie-Britannique, Saskatchewan), elle était de 1,6 ± 0,3 ng/g ; tandis que
dans les bruts importés, elle était de 4,5 ± 0,8 ng/g. En ce qui concerne les bruts de synthèse
produits à partir des sables bitumineux albertains, leur teneur moyenne en mercure, pondérée en
fonction du volume, est estimée à 2,2 ± 0,4 ng/g.
On a calculé, selon l’emplacement des raffineries, les teneurs moyennes en mercure, pondérées
en fonction du volume : dans l’Ouest du Canada (C.-B., Alb., Sask.), elle était de 1,4 ± 0,3 ng/g ;
en Ontario, elle était de 2,1 ± 0,4 ng/g ; tandis que dans l’Est (Qc, N.-B., N.-É., T.-N.), elle était
de 4,5 ± 0,8 ng/g.
Voici notamment d’autres constatations faites à la faveur de cette étude :
o Les concentrations de mercure observées dans le brut allaient de 0,1 à 50 ng/g.
o La concentration moyenne et l’intervalle mesurés sont sensiblement plus bas que ceux
que l’on trouve dans les publications.
o On n’a trouvé aucune corrélation étroite entre la teneur en mercure total dans le brut
d’une part et la teneur en soufre total ou la densité du brut d’autre part.
o Les pétroles canadiens renferment moins de mercure total que ceux de l’étranger.
o Les raffineries de la côte est du Canada manutentionnent des concentrations de mercure
supérieures à celles que l’on observe en Ontario ou dans l’Ouest. Cela est presque
entièrement attribuable à l’emploi de plus grandes quantités de bruts étrangers.
Recommandations
1.
La teneur moyenne du brut canadien en mercure total, pondérée en fonction du volume
raffiné, est de 2,6 ± 0,5 ng/g (milliardièmes) de brut. À partir de cette concentration
moyenne, on estime la quantité totale de mercure dans le brut raffiné au Canada à 227 kg
en 2002, 231 en 2003, 240 en 2004 et 233 en 2005. Ces chiffres se fondent sur la quantité
totale de brut raffiné au Canada au cours de ces années.
2.
Les types de bruts raffinés dont il est question concernaient l’année 2002. En 2002, huit
types de brut, qui ne constituaient que 30 % du volume total raffiné au Canada,
renfermaient plus de 80 % de tout le mercure présent dans le brut raffiné au Canada. Ces
huit bruts provenaient de l’Ouest du Canada, d’Europe et d’Afrique. Cependant, la liste
des bruts raffinés au Canada a légèrement changé d’une année à l’autre. Si les types de
bruts raffinés dans les prochaines années s’écartent sensiblement des types évalués dans
l’étude, les résultats de cette dernière devront être réévalués.
3.
La quantité totale de mercure se trouvant dans la totalité des bruts raffinés au Canada en
2002 (227 ± 30 kg) peut servir d’estimateur de la limite supérieure des émissions
potentielles de mercure par le secteur du raffinage. Cela comprend les émissions
xiii
potentielles de mercure par tous les produits raffinés du pétrole et la totalité des rejets
potentiels de mercure par les raffineries. L’étude ne s’est intéressée qu’au brut reçu par la
raffinerie en tant que matière première. On n’a pas mesuré les émissions réelles des
raffineries. En outre, le mercure libéré en amont, lors de l’extraction pétrolière et gazière,
du traitement et du transport de ces matières vers les raffineries ne devrait pas être inclus
dans cette estimation. Le mercure d’autres intrants des raffineries tels que le gaz naturel
peut également modifier cette estimation.
4.
On peut également utiliser, comme estimation de la limite supérieure de la quantité de
mercure dans des carburants raffinés, la valeur de la quantité totale de mercure dans les
intrants des raffineries de brut. Les émissions atmosphériques annuelles de mercure dans
les gaz d’échappement des véhicules automobiles routiers, du fait de la combustion des
produits pétroliers raffinés, peuvent s’estimer à 227 ± 30 kg au maximum. D’après cette
estimation la plus pessimiste, les émissions potentielles maximales de mercure
anthropique dans l’atmosphère par la combustion des carburants raffinés constitueraient
3,6 % du total canadien (6 340 kg de Hg) en 2002. À noter que, dans cette étude, on n’a
pas mesuré le devenir réel du mercure présent dans chaque produit pétrolier utilisé
comme carburant des véhicules automobiles routiers, y compris dans l’essence et les
carburants Diesel.
xiv
xv
Table of Contents
Acknowledgements ........................................................................................................................v
List of Acronyms
........................................................................................................................vi
Executive Summary ........................................................................................................................vii
Sommaire-recommandations ..........................................................................................................xi
1
Introduction ........................................................................................................................1
1.1
Background ................................................................................................................1
1.2
Project and Research Team........................................................................................2
1.3
US EPA/API/NPRI Study..........................................................................................2
1.4
Scope of Work ...........................................................................................................2
2
Mercury in Crude Oil..........................................................................................................2
3
Sampling Design...................................................................................................................5
3.1
Refining in Canada ....................................................................................................5
3.2
Selection of Oils for Sample List...............................................................................6
3.2.1 Refined Volume .............................................................................................7
3.2.2 Geographic Origin .........................................................................................7
3.2.3 Type of Input Oil ...........................................................................................7
3.2.4 Location of Refinery ......................................................................................9
3.2.5 Availability ....................................................................................................10
3.2.6 U.S. EPA/API/NPRI Parallel Study...............................................................10
3.2.7 Sample Variability .........................................................................................11
3.3
Sample List Selection ................................................................................................11
3.4
Sampling Schedule.....................................................................................................12
4
Sample Collection Process...................................................................................................12
4.1
Sampling Protocol......................................................................................................12
4.2
Sample Custody and Information Management. .......................................................14
5
Laboratory Measurement ...................................................................................................16
5.1
Ottawa University: Cold Vapour Atomic Absorption ...............................................16
5.1.1 Method Summary...........................................................................................16
5.1.2 Quality Control ..............................................................................................17
5.2
CEBAM Analytical: Cold Vapour Atomic Fluorescence Spectrometry ...................17
5.2.1 Method Summary...........................................................................................17
5.2.2 Quality Control ..............................................................................................18
5.3
Environment Canada: Density and Sulphur Content .................................................18
5.3.1 Method for Determining Density and API Gravity .......................................19
5.3.2 Method for Determining Sulphur Content.....................................................19
5.4
PS Analytical: Confirmation Laboratory Testing ......................................................19
5.4.1 Method Summary...........................................................................................19
xvi
6
Quality Assurance and Quality Management ...................................................................20
6.1
Analysis Requirements ..............................................................................................20
6.2
Quality Assurance for Ottawa University Laboratory ...............................................21
6.2.1 Internal Quality Control.................................................................................21
6.2.2 Challenge Samples.........................................................................................22
6.2.3 Results of Pooled Replicates..........................................................................22
6.2.4 Estimated Uncertainties in the Results from
Ottawa University Laboratory .......................................................................25
6.3
Quality Assurance for CEBAM Analytical ...............................................................25
6.3.1 Internal Quality Control.................................................................................25
6.3.2 Challenge Samples.........................................................................................25
6.3.3 Results of Pooled Replicates..........................................................................27
6.3.4 Estimated Uncertainty in CEBAM Analytical Results..................................28
6.4
Inter-laboratory Differences: Ottawa University and CEBAM Analytical ...............28
6.5
Inter-laboratory Differences: PS Analytical ..............................................................30
7
Total Mercury Concentrations ...........................................................................................32
7.1
Sample Data ...............................................................................................................32
7.2
Correlation of Density and Sulphur Content with Mercury Concentration...............35
7.3
Averaged Crude Oil Data...........................................................................................35
7.4
Mean and Median Total Mercury Concentration.......................................................37
8
Data Analysis ........................................................................................................................39
8.1
Volume-weighted Averages of Total Mercury .........................................................39
8.2
Total Mass of Mercury in Crude Oil Refined in Canada...........................................43
8.3
Total Mercury in Crude Oil in the Context of Canadian Emissions..........................44
9
Conclusions and Recommendations...................................................................................46
9.1
Main Findings ............................................................................................................48
9.2
Recommendations......................................................................................................49
10
References
........................................................................................................................50
Appendices
A
Crude Oils and Refined Volumes Processed by Reporting Refineries in 2002.....................54
B
Sampling Protocol..................................................................................................................58
C
Sampling Kits, Packing Materials, and Documentation ........................................................60
D
Chain of Custody Forms ........................................................................................................62
List of Tables
1
Refineries and Refinery Districts in Canada in 2002.............................................................6
2
Geographic Origins of Crude Oils and Locations of Reporting Refineries...........................8
3
Sample List ........................................................................................................................13
4
Results of Challenge Samples for Ottawa University Laboratory.........................................24
5
Results of Challenge Samples for CEBAM Analytical .........................................................26
6
Results for Ottawa University, CEBAM Analytical, and PS Analytical...............................30
7
Sample Data ........................................................................................................................32
8
Averaged Crude Oil Data.......................................................................................................37
9
Arithmetic Mean and Median Total Mercury in Oil Concentrations ....................................38
xvii
10
11
12
13
Volume-weighted Averages of Total Mercury Concentrations.............................................37
Mass of Mercury in Canadian Crude Oil...............................................................................43
Total Mercury Emissions in 2002 Compared to Mercury in Processed Crude Oils..............44
Mercury in Crude Oil Processed in Canada from 2002 to 2005............................................46
List of Figures
1
Values from Literature for Concentrations of Mercury in Crude Oil....................................4
2
Canadian Refineries Reporting to NPRI in 2002...................................................................5
3
Volumes of Crude Oils Refined in Canada by Geographic Origin .......................................8
4
Geographic Origin of Crude Oils Refined in Canada in 2002...............................................9
5
Volume of Crude Oil Processed in Canadian Refinery Districts in 2002..............................10
6
Sampling Schedule.................................................................................................................14
7
Sample Management and Documentation .............................................................................15
8
Absolute Standard Deviation Plotted against Measured Mercury Concentration
for the Ottawa University Laboratory (top) and Absolute Difference Plotted against
Mercury Concentration for CEBAM Analytical (bottom).....................................................23
9
Measured Concentration of Total Mercury Plotted against Nominal Values
for Ottawa University Laboratory Challenge Samples..........................................................24
10
Measured Concentration of Total Mercury Plotted against Nominal Values
for CEBAM Analytical Challenge Samples ..........................................................................27
11
Measured Total Mercury Concentration for 109 Samples of Crude Oil, Ottawa
University Plotted against CEBAM Analytical. ....................................................................29
12
Results from Ottawa University (top) and CEBAM Analytical (bottom) Plotted against
PS Analytical Results (bottom)..............................................................................................31
13
Total Mercury Concentration [THg] and Density of Oil .......................................................36
14
Total Mercury Concentration [THg] and Sulphur Content of Oil .........................................36
15
Distribution of Total Mercury Concentration by Type of Oil ...............................................38
16
Comparison of Volume-Weighted Average Total Mercury Concentrations [THg]
in Crude Oil ........................................................................................................................40
17
Measured Total Mercury Concentration [THg] Compared to Historical
Ranges of Mercury.................................................................................................................41
18
Total Canadian Mercury Emissions in 2002 Compared to Mercury
in Refined Crude Oils ............................................................................................................45
xviii
xix
1
1.1
Introduction
Background
The concentration of mercury (Hg) in crude oils and other naturally occurring
hydrocarbons has come under increasing scrutiny in recent years, due not only to environmental
concerns, but also to industrial and regulatory needs. In collaboration with the Canadian
Petroleum Products Institute (CPPI) and most Canadian refineries, including CPPI members and
independents, Environment Canada initiated the present study to determine the total amount of
mercury that could be accounted for in the processing of crude oil. This effort was motivated by
the facts that mercury is an inhibitor to many refining processes (Wilhelm and Bloom, 2000) and
is difficult to remove from the refinery outputs (Wilhelm, 1999, Spiric, 2001). It was also
influenced by the requirements of the Canadian Environmental Protection Act (CEPA, 1999)
that both government and industry monitor mercury emissions.
Of particular recent interest is the potential for mercury emissions to the air as a result of
petroleum combustion. Sunderland and Chmura (2000) estimated mercury emissions from
petroleum sources in Maritime Canada. Environment Canada commissioned a preliminary study
of mercury emissions from the transportation sector, focusing on diesel fuels (Levelton
Engineering, 2000). The United States Environmental Protection Agency (U.S. EPA) has made
several estimates of mercury emissions from crude oil combustion, starting with the report on
mercury pollution to Congress (U.S. EPA, 1997) and with later refinements reported by
Wilhelm, 2001b. Wilhelm (2001a) is the most comprehensive estimate to date, based on data
from 1970 to 2000 and more than 20 separate studies.
Estimates of the average total mercury concentrations in crude oil have ranged widely from
10 ng/g of oil (Wilhelm, 2001a) to 3,500 ng/g of oil (U.S. EPA, 1997). Wilhelm based his
estimate on about 20 studies, but stated that a proper statistical analysis was not possible due to
the limitations of the report data and the wide variety of experimental procedures used. In its
report to Congress, the U.S. EPA based its estimate on mass-balances calculated from oil-burner
smokestack emissions (U.S. EPA, 1997). Mercury concentrations in crude oil have been reported
from as low as 0.1 ng/g of oil to as high as 50,000 ng/g of oil (Wilhelm and Bloom, 2000). With
this enormous range, it has been difficult to estimate the contributions of the petroleum sector to
the total budget of mercury emissions. This has had significant implications for both industry and
government.
An estimate of 10 ng/g of oil (Wilhelm, 2001a) implies that there is approximately 900 kg of
mercury in the crude oil processed in Canada each year. This is based on 2002 production
volumes. Using the U.S. EPA (1997) estimate of 3,600 ng of mercury/g of oil implies that over
300,000 kg of mercury is processed by petroleum refineries each year in Canada. In 2000,
atmospheric mercury emissions from all major sources ranged from 100 kg to 2,000 kg per
sector, with the total anthropogenic atmospheric emissions of mercury in Canada being 8,000 kg
(NPRI, 2000). According to the Pollution Data Division of Environment Canada, the most recent
measurement of atmospheric emissions of mercury from all anthropogenic sources in Canada is
approximately 6,340 kg in 2002.
A better estimate is required because of the wide range of historical data and the CEPA 1999
requirements for reporting releases from transporting of crude oils and their refined products.
Ideally, estimates should be based on the actual crude oil used and weighted according to the
amount of each oil used by industry.
1.2
Project and Research Team
Many industrial, academic, and government organizations contributed to the study
described in this report. Ten Canadian refineries participated in this study and sampling was
done by personnel at these refineries. These refineries, along with members of the review
committee and their organizations which contributed financial and material support to the project
are listed in the Acknowledgments section of this report.
1.3
U.S. EPA/API/NPRA Study
In 2003, the U.S. EPA, the American Petroleum Institute (API), and the National
Petrochemical and Refiners Association (NPRA) began a comprehensive survey of mercury in
crude oils refined in the United States (Wilhelm and Kirchgessner, 2003). The joint U.S.
EPA/API/NPRI project consisted of three phases: a comprehensive examination of methods for
measuring mercury in crude oil, including round-robin testing of several laboratories; an
investigation of sampling and measurement procedures, including sample storage, handling and
manipulation; and a measurement phase of more than 300 oil samples.
The survey of mercury in crude oils refined in Canada is designed to be comparable to that
conducted by the U.S. EPA/API/NPRA. This will allow a composite estimate of mercury
concentrations between the two countries to be calculated, while still providing a stand-alone,
definitive estimate for Canadian stakeholders.
1.4
Scope of Work
The study presented in this report was designed to measure the concentration of mercury
in crude oil as it enters a refinery before processing. A mean value of the mercury concentration
is to be determined, weighted by the refinery processing volumes of the types of crude oil. From
this mean value, a total amount of mercury in all crude oil processed in Canada is to be
determined and used as the estimate of the potential upper limit of the total mercury in all refined
products. This estimate can then be used as the upper limit of mercury concentrations in
petroleum products or to quantify the potential for maximum mercury concentrations in the
exhaust emissions of motor vehicles.
2
Mercury in Crude Oil
Mercury concentrations in crude oil have been reported from as low as sub-parts-per
billion (Kelly, 2003) to as high as 50,000 ng/g of oil (Wilhelm and Bloom, 2000). Historically,
the U.S. EPA based its estimates on data compiled by Brooks (1989). Brooks relied primarily on
concentrations measured by neutron activation reported by Shah et al. (1970) and Filby et al.
(1975). Of these oils, which were mostly American, several Californian oils were found to have
very high mercury contents. These estimates resulted in the U.S. EPA estimating very high
values of mercury in crude oil for many years. In 1977, the U.S. EPA estimated mercury
emissions in crude oil to be 3.5 ppmw (3,500 ppbw) (U.S. EPA, 1977).
Other researchers, however, reported much lower ranges of total mercury concentration than the
U.S. EPA estimate. Hitchon and Filby (1983) found that in 86 Alberta crude oils and two tar
sands bitumens, approximately half the samples had values below their detection limit of
2 ppbw. Their mean concentration was 50 ppbw with a maximum of 399 ppbw. Using
microwave-digested inductively-coupled plasma-atomic emission spectrometry (ICP-AES), Cao
found that all 24 crude oils tested had an average total mercury concentration below his detection
limit of 15 ppbw (Cao, 1992). In 1995, using neutron activation analysis, Musa et al. (1995)
reported an average total mercury concentration of 3.1 ppbw in 6 Libyan oils.
2
More recent reports have also suggested lower values for mercury concentrations. Tao et al.
(1998) reported an average total mercury concentration of 40 ppbw for 7 condensate oils of
Asian origin using gas chromatography/inductively-coupled plasma-mass spectrometry
(GC/ICP-MS). Using a cold-vapour atomic fluorescence spectrometry technique, Shafawi et al.
(1999) reported a similar range of values for Asian condensates.
Using cold vapour atomic absorption (CVAA), Magaw and co-workers reported an average of
65 ppbw for 26 oils from refineries on the west coast of the U.S., ranging from 10 to 1,560 ppbw
(Magaw et al., 1999). Liang and co-workers reported an average value of 7.2 ppbw in 11 oils
using cold-vapour atomic fluorescence (Liang et al., 2000). Levelton Engineering reported on 8
crude oils refined in Canada, accounting for approximately half of the refined volume at that
time (Levelton Engineering, 2000). Using an acid digestion/CVAA technique, they found that all
oils had total mercury concentrations less than 9 ppbw and an average value of 1.5 ppbw.
Additional data for 17 oils provided by private communication from an independent refiner
confirmed their main findings (Levelton Engineering, 2000).
In a large survey of 76 types of oil, Bloom found that total mercury concentrations covered a
wide range of values, from less than his detection limit of 0.1 to more than 1,500 ppbw (Bloom,
2000). Many of his samples with the highest concentration came from a low-volume oil field in
South American or were Asian condensates. In 2000, Morris reported that the mean amount of
mercury in crude oil imported to refineries on the U.S. east coast was less than 5 ppb (Morris,
2000).
The ranges, and recommended or mean values reported by these studies are summarized in
Figure 1.
While more than 20 studies have been conducted over the last 30 years, the limitations and
unique nature of each study severely restrict the use of the combined dataset (Wilhelm and
Bloom, 2000; Wilhelm, 2001b). The wide variety of measurement techniques, ranging from
neutron activation to many types of digestion systems with detectors as diverse as mass
spectrometers, ICP/MS, atomic absorption, and AFS, have poorly known correlations and are
very difficult to compare.
More important, however, is the lack of information on sampling conditions, handling of
samples, and the age of the samples at the time of analysis. Both the condition of the oil during
sampling and the subsequent handling of the samples must be controlled to quantify mercury in
crude oil.
Mercury in crude oil can take many chemical forms, including forms that dissolve in oil and
mercury compounds that precipitate from oil-forming suspensions. While speciation of the
mercury compounds has been attempted (Corns, 2004; Tao, 1998), in this work only the total
mercury concentration in crude oil is measured. Because of these various forms of mercury in
crude oil, homogeneity of the samples is a significant concern. Stratification of the various
mercury compounds and suspended particles in a pipeline or tank may significantly affect
sampling.
3
100000
10000
[THg] (ppb)
1000
100
10
1
0.1
Wilhelm 2001
Schmit (Levelton 2000)
Schmit (Levelton 2000)
Schmit (Levelton 2000)
Morris 2000
Liang et al. 2000
Levelton 2000
Bloom 2000
Shafawi et al. 1999
Magaw et al. 1999
Tao et al. 1998
Tao et al. 1998
Olsen et al. 1997
Musa et al. 1995
Cao 1992
Hitchon and Filby 1983
Filby and Shah.1975
Shah et al. 1970
Figure 1
Values from Literature for Concentrations of Mercury in Crude Oil
(range shown by vertical; average, or recommended value indicated by circle)
The handling of samples can also significantly affect the measured results. A recent study found
that the number of times a sample bottle had been opened could significantly affect the measured
value (U.S. EPA, 2003). The effects of light, temperature, and sample-holding time on mercury
concentrations in oil are largely unknown.
These factors of crude oil variability and sample management combined with the lack of
knowledge of the oils’ origins and their refinery usage volumes make a meaningful statistical
analysis of the existing data sets unfeasible. The enormous range of estimates in the literature,
which vary by a factor of 100 or more as shown in Figure 1, have made it difficult to estimate the
contributions of the petroleum and refining sectors to the total budget of anthropogenic mercury
emissions.
Despite the large number of studies reporting total mercury concentrations in crude oil, because
of the complications of sampling, sample handling and variability in measurement technique,
several reviews have stated that a good estimate of total mercury concentrations in crude oil is
only possible if a comprehensive study is done of a wide variety of crude oil types using well
defined sampling, handling, and measurement techniques (Wilhelm 2001; Wilhelm and Bloom,
4
2000). Fuelled by the requirements of both regulatory agencies and private industrial
stakeholders, this was the impetus for conducting the present study.
3
3.1
Sampling Design
Refining in Canada
2002 was chosen as the baseline year for all refinery volume usage in this study, as this
was the most recent year for which complete usage data was available. In 2002, data for 19
refineries in Canada was reported to the National Pollutant Release Inventory of Environment
Canada. These 19 refineries processed a total volume of 104,719,128 m3 of crude oils, upgraded
bitumens, “synthetic crudes”, and natural gas condensates. Refineries in western Canada,
Ontario, and the Quebec and Atlantic regions processed about 28%, 28%, and 44% of the
Canadian total respectively. This is shown in Figure 2. The geographical distribution of active
refineries in Canada in 2002 is shown in Table 1.
Figure 2
Canadian Refineries Reporting to NPRI in 2002
Participating refineries reported their crude oil usage for the present study. Note that the
production data available covers only 32% of crude oils processed in Quebec and Atlantic
regions. These refineries processed 91,884,390 m3 of 103 types of crude oil (crude oil,
bitumen/oil sands, and natural gas condensates) in 2002, which was 88% of the Canadian total
for that year. In Appendix A, the total refined volume is shown for each type of crude oil used by
the reporting refineries, broken down by volume refined in each region and the percentage of the
Canadian total volume for 2002. These oils came from both domestic and foreign sources. In
2002, no single crude oil was processed in a volume of more than 10% of the Canadian total.
There were 26 crude oils with a volume percentage over 1%. For the purposes of this study, all
5
oils refined in volumes greater than 1% of the national total in 2002 are classified as major crude
oils. Those less than 1% are considered minor crude oils.
Table 1
Refineries and Refinery Districts in Canada in 2002*
Location
Western
Canada
Ontario
Quebec
and
Atlantic
Province
Company
Refinery Name
1
British Columbia
2
British Columbia
Chevron-Burnaby
Burnaby
2776
Refinery
Husky-Prince George Prince George 405
3
4
British Columbia
Alberta
5
Alberta
Chevron Canada
Ltd.
Husky Energy
Inc.
Petro-Canada
Husky Energy
Inc.
Petro-Canada
6
Alberta
7
Saskatchewan
8
Ontario
Shell Canada
Products
Consumers' Coop Refinery Ltd.
Imperial Oil Ltd.
9
Ontario
Imperial Oil Ltd.
10
Ontario
11
12
Ontario
Ontario
13
Ontario
14
Quebec
Nova Chemicals
Canada Ltd.
Petro-Canada
Shell Canada
Products
Suncor Energy
Products Inc.
Petro-Canada
15
Quebec
16
Quebec
Shell Canada
Products
Ultramar Ltee
17
Nova Scotia
Imperial Oil Ltd.
18
Newfoundland
and Labrador
New Brunswick
North Atlantic
Refining Ltd.
Irving Oil Ltd.
19
PC-Port Moody
Husky-Lloydminster
Refinery
PC-Edmonton
Refinery
Shell-Scotford
Refinery
Consumers' Co-opRegina Refinery
Imperial-Sarnia
Refinery
Imperial-Nanticoke
Refinery
Nova ChemicalsCorunna Site
PC-Oakville Refinery
Shell-Sarnia Refinery
Suncor-Sarnia
Refinery
PC-Raffinerie de
Montréal
Shell-Raffinerie de
Montréal
Ultramar-Raffinerie
Jean-Gaulin
Imperial-Dartmouth
Refinery
North Atlantic-North
Atlantic Refinery
Irving Oil-Saint John
Refinery
City
NPRI ID
Port Moody
Lloydminster
3905
403
Edmonton
3903
Fort
2960
Saskatchewan
Regina
4048
Sarnia
3704
Nanticoke
3701
Corunna
1776
Oakville
Sarnia
3901
3962
Sarnia
3071
Montreal
3897
Montreal
3127
St-Romuald
3928
Dartmouth
3698
Come By
Chance
Saint John
4316
4101
* Only refineries reporting to NPRI are included in this table.
3.2
Selection of Oils for Sample List
Many factors were considered when choosing oils for use in this survey. These included
the annual processed volumes of a type of oil, its geographical origin, the types of crude oil
(crude oils, condensates, and oil sands products), and the location of the refineries. Practical
considerations also included whether oils used in 2002 were available for sampling in 2004 and
2005, which crude oils were available for sampling in these years, compatibility with the U.S.
EPA/API/NPRA project, and sample variability.
6
The types of crude oil were chosen to be reasonably representative of crude oils used by
Canadian refineries as a whole. The origin and type of the oil as well as the location of the
refinery were well represented in the sample list. The factors considered in choosing this sample
list are discussed individually in this section.
3.2.1
Refined Volume
The 103 types of crude oil processed by the participating refineries in Canada are listed in
Appendix A in descending order of refined volume. These volumes range from 8.4% of the total
volume of crude oils refined domestically in 2002 to just over zero. The 26 major crude oils
(volume > 1%) are listed first, followed by the 77 minor types of crude oil (volume < 1%).
Because of their volume of usage, the 26 major crude oils have the highest potential for mercury
emissions of all 103 types of oil. The 77 minor crude oils are potentially less significant to the
overall mercury budget. As many of the major crude oils as possible were included in the sample
list because of their potential significance. The remainder of the analytical effort focused on
minor types of oil. As shown in Appendix A, 24 of the 26 major types of crude oil (those with
production volumes > 1%) were analyzed in this study. Two types were no longer being used in
Canada when the sampling took place.
3.2.2 Geographic Origin
Approximately half of the crude oil processed in Canada in 2002 was produced from
Canadian wells. For the purpose of this study, the Canadian domestic crude oils were split into
two groups: Canada West and Canada East. Canada West includes all types of oil from British
Columbia, Alberta, Saskatchewan, and Manitoba. The types of oil from Canada East originate
from Ontario, Quebec, Nova Scotia, Newfoundland and Labrador, New Brunswick, and Prince
Edward Island.
The remaining half of crude oils processed in 2002 came from foreign sources, including
Europe, the U.S., South America, the Middle East, Africa, Mexico, and Asia. All oils from nonCanadian sources were designated as Foreign. The number of oils from each source is shown in
Figure 3. The volumes from each source of origin are summarized in Table 2.
A number of “minor” crude oils, those with total processed volumes of less than 1%, were
chosen at random from each group to ensure that crude oils from each major geographical region
were sampled. The regions from which Canada imported significant amounts of crude oil
processed in 2002 are shown in Figure 4.
3.2.3
Type of Input Oil
Several commercially important refinery input streams are not typical crude oils. Natural
gas condensates and “synthetic” crude oils are significant components of the Canadian crude oil
market. Several crude oils of each type were included in the sampling program. The highest
processed volumes of each type were included to make the sampling program representative. For
example, as shown in Appendix A, samples CCAF45 and CCCN36 are natural gas condensates.
Samples CCCN66, and CCCN67 are “synthetic” crude oils created by upgrading bitumen from
the Alberta oil sands. CCCN 43 is a bitumen produced from oil sands that has not been upgraded
upstream of the refinery
7
Asia
Mexico
Canada West
South America
U.S.A.
Middle East
Foreign
Africa
Europe
Canada East
Figure 3
Volumes of Crude Oils Refined in Canada by Geographic Origin (2002,
reporting refineries only)
Table 2
Geographic Origins of Crude Oils and Locations of Reporting Refineries
Volume
Fraction of
Crude Oil
Geographic
Processed in
Canadian
2002 (m3/y)
Origins
Total (%)
Location of Refinery
Canada West
45,545,029
43.5
Western Canada and Ontario
Canada East
6,049,216
5.8
Ontario, and Quebec and Atlantic
Africa
8,220,795
7.9
Ontario, and Quebec and Atlantic
Asia
52,365
0.05
Ontario
Europe
20,602,634
19.7
Ontario, and Quebec and Atlantic
Mexico
1,271,672
1.2
Quebec and Atlantic
Middle East
5,471,951
5.2
Quebec and Atlantic
South America
2,147,459
2.1
Quebec and Atlantic
U.S.
2,523,269
2.4
Ontario, Quebec and Atlantic
Study Total
91,884,390
88
8
Figure 4
Geographic Origin of Crude Oils Refined in Canada in 2002
3.2.4
Location of Refinery
To better understand the effects of refinery usage patterns, the geographic region of the
processing refineries was also included in the study design. The processing refineries were
categorized into three geographical districts:
• Western Canada (British Columbia, Alberta, and Saskatchewan);
• Ontario; and
• Quebec and the Atlantic Provinces (Quebec, Newfoundland and Labrador, Nova Scotia, and
New Brunswick).
Note that there is not a refinery in every province in Canada (See Table 1). This grouping
identifies processing patterns in the refinery district while still protecting commercial
confidentiality. The volume distribution according to the geographic location of the refineries is
shown in Table 2, Figure 4, and Figure 5. Refer to Appendix A for detailed information on the
types of oil used in each location. Each region was approximately equally well represented on
the sampling list.
9
Quebec & Atlantic
32% by volume
Ontario
28% by volume
Western Canada
28% by volume
Figure 5
Volume of Crude Oil Processed in Canadian Refinery Districts in 2002
3.2.5
Availability
While some Canadian refineries handle crude oils and other inputs from the same set of
suppliers or fields over a long period of time, others are active participants in the world spot
markets for oil, buying crude oils based on best price and other commercial factors. This is
particularly true for refineries in the Quebec and Atlantic region. The major effect of this activity
for the present study is that some refinery inputs processed in 2002 were no longer available for
sampling in 2004 and 2005.
All major and minor types of crude oils reported for 2002 are listed in Appendix A. Of the 26
major types of crude oils, CCME57 and CCAF46 were no longer used in Canada during the
sampling period. Several of the minor oil types were also unavailable. It was decided not to seek
replacements or substitutes for the unavailable types. In addition, several oils were only available
to be sampled once. These oils are noted as such in Table 3.
3.2.6
U.S. EPA/API/NPRA Parallel Study
As discussed in Section 1.3, this study was developed in parallel with and to compliment
an ongoing study by the U.S. EPA/API/NPRA of mercury in crude oils refined in the United
States (Wilhelm and Kirchgessner, 2003). Many types of crude oil are processed in both
countries. About 45 of the 103 types of Canadian crude oil are also processed in the U.S. To
make the best use of available resources, the sample list presented here and the U.S. sample lists
were designed to overlap as little as possible.
For the 26 major types of crude oil processed in Canada in 2002, those with refined
volumes greater than 1%, 21 types were included in the U.S. study.
There were 77 types of oil with refined volumes of less than 1% in Canada in 2002. Of
these “minor” crude types, 22 were included in the U.S. study. There were 55 minor types that
were only refined in Canada in that year.
10
3.2.7
Sample Variability
Preliminary work by the U.S. EPA has shown that mercury concentrations in crude oils
can vary significantly over time (Wilhelm and Kirchgessner, 2003). The mercury concentration
of one batch of oil may be significantly different from that of the nominally identical crude oil
available at a later date. In order to capture this variability in the study, multiple samples (at least
three) of each type of oil were taken from different batches of oil. For the purposes of this study,
a batch is considered to be a discrete tanker shipment or individual pipeline transfer, as
appropriate for each refinery.
3.3
Sample List Selection
It was budgeted for a maximum of 35 types of crude oil to be sampled. The oils were
divided into 26 major types of oil with refined volumes of more than 1%, of which only 24 were
available, and 77 minor types of oil with refined volumes of less than 1% in 2002. For all sample
selection strategies, the following two constraints were present: to include all the 24 major crude
oil types available and the remainder of samples were to be chosen from the 55 minor crude oils
not included in the US EPA/API/NPRA study to maximize the coverage of oil types.
Based on the factors discussed in Section 3.2, the following sampling strategies were considered
for the study sample list:
1.
Choose 11 types of minor crude oil with the highest refined volume.
Pro: This provides the highest volume coverage.
Con: This is not necessarily representative of the types of oil with smaller refined
volume.
2.
Choose 11 types of minor crude oil at random.
Pro: This provides average volume coverage.
Con: This covers the whole sample population, but may not be representative of each
geographical region.
3.
Randomly choose 6 types of minor crude oil with refined volumes of more than 0.1% and
5 types of minor crude with refined volumes of less than 0.1%.
Pro: Average volume coverage is higher than that provided by strategy #2.
Con: This covers the whole sample population, but may not be representative of each
geographical region.
4.
Choose the 6 types of minor crude oil with refined volumes of more than 0.1% and the
5 types of minor crude oil with refined volumes of less than 0.1% volume.
Pro: Average volume coverage is higher than that provided by strategy #2.
Con: As in strategy #1, this covers the whole sample population, but is not necessarily
representative of the types of oil used in smaller volume.
5.
Divide minor types of crude oil with refined volumes of more than 0.1% volume into
9 regions based on geographic origin (see section 3.2.2) and randomly select one or more
from each region.
Pro: This provides the highest volume coverage and is representative of all oils.
Con: This is similar to strategy #1, but is more representative of minor types of oil.
11
After some consideration, strategy #5 was adopted for this survey. One or a few crude oils were
randomly selected from each region to ensure that all oils and regions were well represented. A
total of 11 crude oils were randomly selected to make up a list of 35 crude oils. With help from
the participating refineries, all the major types of crude oil from Canada West and Canada East
were included as well as natural gas condensates, oil sands products, and synthetic crude oils.
After eliminating a few unavailable types, a final sample list of 32 types of crude oil was
developed. This list is provided in Table 3.
These 32 types of oil make up 71% of the total volume of crude oils used by Canadian refineries
in 2002. The list includes representative samples from seven of the nine geographical regions
from which crude oil originated for Canadian refineries in 2002. The two regions not included
are Mexico due to the discontinuation of the crude oils and Asia due to a negligible process
volume in 2002.
3.4
Sampling Schedule
Crude oils were sampled by personnel at the refineries for 18 months from May 2004 to
November 2005. The number of samples collected each month is shown in Figure 6. At least
three samples of each crude oil were collected at different times of the year to minimize seasonal
variations.
4
4.1
Sample Collection Process
Sampling Protocol
Sampling techniques can significantly affect the mercury concentrations measured in
crude oil. If samples are handled in a haphazard manner, the mercury content of the crude oil can
be much lower than its true value. To minimize losses of mercury during sampling, a standard
sampling protocol and sampling kit were developed for this work. These are provided in
Appendix B and C.
A standardized sampling procedure is critical to the success of any survey project. One of the
major concerns that has arisen out of the comprehensive reviews of previous surveys of total
mercury in crude oil (Wilhelm and Bloom, 2000; Wilhelm, 2001) has been inconsistent and/or
unreported sampling and sample-handling procedures. The sampling procedure followed in the
present study was designed to be compatible with that of the ongoing U.S. EPA/API/NPRA
parallel study.
A major complication for sampling is that mercury is present in naturally occurring
hydrocarbons in many chemical forms (Corns, 2004; Bloom, 2000). Elemental mercury and
organo-mercury compounds, such as methyl- and dimethyl-mercury, are very volatile and can
easily be lost to the atmosphere. Some inorganic mercury species, such as mercury sulphide and
chlorides, can be formed by oxidative exposure. Inorganic mercury compounds are generally
poorly soluble in oils and can settle out of oil. Many mercury species will concentrate on the
walls of bottles or on metal surfaces.
Glass vials were used for sampling. All oils were sampled into precleaned, certified, 40-mL
amber PTFE-septa vials (I-Chem, U.S.) meeting U.S. EPA specifications for contaminant-free
containers (U.S. EPA, 1992).
12
Table 3
Code
Sample List
Origin of Crude Oil
CCCN67
Canada West
CCEP30
Foreign (Europe)
CCCN65
Canada West
CCAF43
Foreign (Africa)
CCEP33
Foreign (Europe)
CCCN32
Canada East
CCCN64
Canada West
CCCN51
Canada West
CCCN43
Canada West
CCCN38
Canada West
CCCN62
Canada West
CCEP29
Foreign (Europe)
CCEP32
Foreign (Europe)
CCCN42
Canada West
CCCN66
Canada West
CCEP22
Foreign (Europe)
CCCN53
Canada West
CCUS105 Foreign (US)
CCME56 Foreign (Middle East)
CCCN60
Canada West
CCEP24
Foreign (Europe)
CCCN71
Canada West
CCCN37
Canada East
CCCN50
Canada West
CCCN30
Canada West
CCCN49
Canada West
CCSA38
Foreign (S. America)
CCCN36
Canada East
CCAF45
Foreign (Africa)
CCCN39
Canada West
CCCN40
Canada West
CCCN33
Canada East
Study Total
Refinery Location(s)
Ontario & Western Canada
Ontario & QC/Atlantic
Western Canada
Ontario & QC/Atlantic
QC/Atlantic
Ontario & QC/Atlantic
Western Canada
Ontario
Ontario & Western Canada
Western Canada
Western Canada
QC/Atlantic
Ontario & QC/Atlantic
Ontario
Western Canada
Ontario & QC/Atlantic
Ontario
Ontario & QC/Atlantic
QC/Atlantic
Ontario
QC/Atlantic
Ontario
Ontario & QC/Atlantic
Western Canada
Western Canada
Ontario
QC/Atlantic
Ontario
Ontario
Ontario
Western Canada
Ontario
13
Volume
Processed
in 2002
(m3/year)
8,760,725
6,095,688
5,819,171
5,645,287
4,297,500
3,738,838
3,346,093
3,331,872
2,806,402
2,586,216
2,494,699
2,194,478
2,171,157
2,068,005
2,050,758
1,894,392
1,862,063
1,618,401
1,416,160
1,371,238
1,209,664
1,170,900
1,142,046
1,083,517
798,232
611,571
538,738
536,416
511,017
458,998
313,560
175,542
75,382,939
Fraction of
2002 Total
Refined
Volume (%)
8.37%
5.82%
5.56%
5.39%
4.10%
3.57%
3.20%
3.18%
2.68%
2.47%
2.38%
2.10%
2.07%
1.97%
1.96%
1.81%
1.78%
1.55%
1.35%
1.31%
1.16%
1.12%
1.09%
1.03%
0.76%
0.58%
0.51%
0.51%
0.49%
0.44%
0.30%
0.17%
71.00%
Notes
Synthetic crude
Oil Sands Bitumen
Synthetic crude
One sample
One sample
One sample
One sample
Gas Condensate
Gas Condensate
One sample
25
Number of Samples
20
15
10
Nov-05
Oct-05
Sep-05
Aug-05
Jul-05
Jun-05
May-05
Apr-05
Mar-05
Feb-05
Jan-05
Dec-04
Nov-04
Oct-04
Sep-04
Aug-04
Jun-04
May-04
0
Jul-04
5
Sampling Date
Figure 6
Sampling Schedule
Crude oil samples were taken as close as practical to the point of entry into a refinery. When
sampling from a pipeline or a tanker, samples were taken from a fresh batch or shipment. The oil
was thoroughly mixed and sampled directly into the supplied vial either by autosampler or by dip
sampling, to minimize the use of intermediate vessels. Contact with metal surfaces was avoided
and contact time with air was minimized.
The headspace in the vials was kept as small as possible and the vials were capped as soon as
possible. Vials were stored at room temperature away from light sources. Samples were stored
for their entire lifetimes in the amber headspace vials. At no time were any of the vials opened
before measurement. Only samples with seals intact were measured and those that showed signs
of leakage were discarded.
The lifetime of samples from sampling to laboratory analysis was kept as short as possible, with
an average lifetime of 45 to 50 days.
The document that accompanied each sampling kit and the detailed sampling protocol is
included in Appendix B. Typical sample kits and packaging are shown in Appendix C.
4.2
Sample Custody and Information Management
Great care was taken to ensure the integrity of the samples. All samples were documented
with full chains of custody at all points in their life cycle. Initial chains of custody were
generated by the refinery personnel who collected the samples. The samples were sealed with a
custody sticker (see Appendix C) and sent to an intermediary laboratory at Ottawa University.
To protect the commercial information about the refinery, the intermediary stripped off any
identifying information except the sampling data and preassigned crude oil code (shown in
Table 3), repackaged the samples, and initiated a new “ID-blind” chain of custody form. The
form from the refineries was archived by the sample manager at Ottawa University and one
sample was retained for analysis. See Section 5.1 for a description of the method.
14
The “ID-blind” samples were then transferred to Environment Canada with the hand-off
documented on the new chain of custody form started by the intermediary at Ottawa University.
Environment Canada retained three vials (if all were unbroken) for archival purposes and for
measuring density and sulphur content as described in Section 5.3. The final two vials were
shipped to CEBAM Analytical for analysis under seal of custody as outlined in Section 5.2.
A flowchart of sample management is shown in Figure 7.
Refiner
6 Vials
Original Chain of Custody
Ottawa
University
1 vial
[THg]
(CVAA)
1 vial
Density &
Sulphur
5 Vials
Id-Blinded Chain of Custody
Environment
Canada
2 Vials
Id-Blinded Chain of Custody
CEBAM
Analytical
2 vials
1 vial
1 vial
Figure 7
Archive
[THg]
(CVAFS)
Archive
Sample Management and Documentation
Environment Canada also provided coded samples to both Ottawa University and CEBAM
Analytical Laboratories. These consisted of blind challenge samples for both labs. An “IDBlind” chain of custody record was started by Environment Canada and sent out to accompany
the challenge samples. Examples of the refineries’ Chain of Custody Record and the ID-Blind
form are provided in Appendix D.
15
5.
Laboratory Measurement
Samples were sent to two laboratories, one at Ottawa University in Ottawa, Ontario
Canada, to be measured using cold-vapour atomic absorption and the other to CEBAM
Analytical Laboratories of Seattle, Washington in the U.S. This laboratory was also used for
primary analysis in the parallel U.S. EPA/API/NPRA study.
5.1
Ottawa University: Cold Vapour Atomic Absorption
The method for analyzing total mercury concentrations in crude oil and other petroleum
hydrocarbons was developed by Ottawa University for the present study. It is based on the
SP-3D, a high-temperature combustion analyzer from Nippon Instrument Corporation (NIC).
The analytical method used is a modification of the standard method provided in the NIC
operating manual. The method used here is similar to U.S. EPA Method 7473 (U.S. EPA, 1998),
but was adapted for a hydrocarbon matrix.
5.1.1
Method Summary
Samples were ultrasonicated in the original sample vials for 30 minutes to ensure
homogeneity. An aliquot of approximately 100 μL of oil was weighed out into a sample boat.
Samples were combusted in the sample boat along with appropriate additives. Additive M
consists of equal amounts of calcium hydroxide and sodium carbonate and was used to control
halides that might interfere with the instrument and the reading. Additive B is made of aluminum
oxide which absorbs the combustion gas and slowly releases it for decomposition.
To ensure that the additives were mercury-free, crucibles of each additive were retained in a
muffle furnace maintained at a constant 700°C. During the course of the analysis, the additives
were interchanged between each sample run and allowed to cool down for 15 minutes before use.
Samples were analyzed sequentially with the two additives in the order B-S-B-M with B
standing for additive B, S for sample, and M for additive M.
Combustion and sample decomposition took place using the manufacturer’s recommended mode
for heavy naphtha, crude oil, lubricating oil, and other viscous oils. In this mode, the sample was
first combusted at 350°C for 10 minutes in the combustion tube followed by decomposition of
the produced gas for 6 minutes at 700°C in the decomposition furnace. Sample decomposition
took place in a high-temperature combustion tube. A catalyst was used to accelerate the process.
The gaseous decomposition product was scrubbed in a pH-7 phosphate buffer to remove acid
gases and moisture. The sample was then cooled and dehumidified. The mercury gas sample was
collected into a gold trap. Other gaseous products exited through the exhaust filter and carbon
trap. Mercury on this first gold trap was desorbed and collected on a second gold trap to provide
a cleaner sample with less interference.
The second gold trap was then heated and the released mercury transported in a carrier gas to the
detector using cold vapour atomic absorption (CVAA).
16
5.1.2
Quality Control
Calibration standards were prepared from 1000 ppm of mercurous chloride (Hg2Cl2)
stock solution obtained from the instrument manufacturer (Nippon Instrument Corporation,
Japan). A working standard solution of 50 ppb was serially diluted from the stock solution, with
0.001% L-cysteine added to minimize loss to the container walls or volatilization of the mercury.
A calibration curve was obtained by dispensing 100, 200, 300, and 400 μL of working standard
onto clean, ceramic boats used specifically for standards and analyzing to check recoveries.
The instrument was calibrated using a machine blank reading and concentrations of 4 standard
mercury solutions in the range of the samples to be measured were run at the start of each day. It
was required that the coefficient of variation (r2) exceed 0.999 to obtain an acceptable calibration
curve.
Blanks were analyzed both before and after each sample. Blank values were consistently below
0.01 ng of mercury.
A certified standard reference material (Conostan Division, ConocoPhillips Specialty Products
Inc., U.S.) was run at least once a day. Acceptable recoveries were at least 95% of the standard
value. Check standards and blanks were run every 5 samples. Samples spiked with a standard
mercury material were also run on a regular basis to determine matrix recoveries.
Samples were analyzed in triplicate and reported as means and standard deviations.
5.2
CEBAM Analytical: Cold Vapour Atomic Fluorescence Spectrometry
This method was performed at CEBAM Analytical Inc. of Seattle, Washington. It is
based on combustion/trap/cold vapour-atomic fluorescence spectroscopy (CVAFS) and has been
evolving since the early 1990s. This method was most recently published in Liang et al., (2003).
It consists of a unique, purpose-built mercury cold vapour trap, followed by analysis on a
commercial atomic fluorescence spectrometer.
5.2.1
Method Summary
Samples were homogenized by immersion in an ultrasonic bath for 1 hour. The
temperature of the bath was controlled so as not to exceed 30°C, with cold water added as
needed.
For oil samples with a lower viscosity, aliquots were pipetted directly into the combustion tube.
For more viscous samples, 0.5 to 0.8 mL of the oil was removed from the sample vial through
the septum by syringe (without opening the vial), diluted to approximately 3 volumes with
dichloromethane, and capped tightly. The diluted samples were then homogenized again and
treated exactly the same as the less viscous samples.
After homogenization, an aliquot of oil (or viscous oil solution) was removed through the vial
septum with a pre-conditioned metal needle. The oil was then immediately introduced into the
sample introduction segment of the combustion column. The carrier gas, ultra-high purity air at
320 L/min, was then connected to the sample port of the combustion column.
The combustion/trap system is composed of a combustion column, a scrub bottle, and a soda
lime trap (Liang et al., 1996). The combustion column is a quartz tube, 30 cm long, 6 mm ID,
and 8 mm OD, packed with glass wool. The tube is divided into two independent heating zones,
17
one for sample introduction and the other for combustion. The sample introduction segment is
about 4 cm long and was heated from room temperature to 800°C after the sample was
introduced, then allowed to cool after sample decomposition for 1 to 2 minutes. The combustion
segment was maintained at 800°C during the analysis.
After combustion, vapour was blown through a scrub bottle containing distilled, deionized water
and a pair of soda lime traps and finally collected on a custom-made, gold-coated sand trap (25
mm long, 4.0 mm ID, and quartz). The carrier gas was allowed to sweep the sample into the
gold-coated sand trap for 4 to 5 minutes from sample injection. The trap was then removed for
analysis on a Brooks Rand Model III atomic fluorescence spectrometer (Brooks Rand Trace
Metals Analysis and Products, U.S.) as described in Liang et al. (1993).
5.2.2
Quality Control
Calibration standards of methyl mercury (MeHg) were prepared by serial dilution with
dichloromethane from a stock solution of methylmercury (CH3HgCl) (Johnson Matthey, U.S.) in
isopropanol. Initial calibration aliquots typically contained 50, 100, 150, and 200 pg of mercury,
with a nominal 0-pg blank also included. Calibration verification standards, run with each set of
samples, were the mid-level calibration standard and a method blank. Calibration repeatabilities
were required to be less than 25%. Calibration standards were prepared often to ensure accurate
concentrations.
Before any analysis, the system was blanked for 5 minutes with only the pure carrier gas, i.e., no
sample was introduced into the injection port. It was required that the baseline mercury level of
the system be less than 2 pg.
Before analyzing each set of samples, a reference oil of known concentration (developed at
CEBAM) was run before and after sample analysis in duplicate to ensure that instrument
recoveries were within acceptable limits.
Three method blank samples consisting of pure dichloromethane were run before and after
sample analysis. Method blanks were required to have total mercury contents less than 0.1 ng of
mercury/mL of dichloromethane.
For each set of 10 samples (or less), duplicate matrix spikes were also analyzed using one sample
chosen at random. Matrix spike recovery was required to be 75% to 125%, with the duplicates
having a relative percent difference (RPD) of less than 25%.
All samples were analyzed in duplicate. All duplicates were required to have RPDs of less than
25%. Results were reported as duplicate values, means, and RPDs.
5.3
Environment Canada: Density and Sulphur Content
Environment Canada’s Oil Research Laboratory at the Environmental Science and
Technology Centre in Ottawa, Ontario measured the density and sulphur content of each crude
oil in the study. The analytical procedures were based on ASTM standard methods and were
required to meet the reproducibility and repeatability of the appropriate method.
18
5.3.1
Method for Determining Density and API Gravity
The density of an oil sample, in g/mL, was measured using an Anton Paar DMA 48
digital density meter (Anton Paar, U.S.A.) following ASTM Method D5002 (ASTM, 1999a).
Measurements were performed at 20.0°C. The instrument is calibrated using air and distilled,
deionized water at 0.0°C and 20.0°C. Method and operator performance is monitored by periodic
measurement of a check standard of p-xylene at 15.0°C. A method control chart is kept of these
measurements.
Densities are corrected for sample viscosity, as specified by the instrument manufacturer.
Measurements are repeated in triplicate and the mean reported as the density.
5.3.2
Method for Determining Sulphur Content
The mass fraction of total sulphur in oil is determined using X-ray fluorescence, closely
following ASTM Method D4294 (ASTM, 1999b).
The X-ray fluorescence spectrometer is calibrated using a duplicate series of 6 sulphur-in-oil
standards (National Institute of Standards and Technology, U.S.A.). A calibration chart is
prepared from the 12 standard measurements. Single-element standards are used to calibrate and
remove chlorine interference in the sulphur signal. Instrument and operator performance is
monitored by a triplicate measurement of a check standard consisting of a well characterized
historical standard of crude oil. Check standard measurements are tracked on a quality control
chart and used to estimate the uncertainty in measurement.
Approximately 3 mL (+/- 0.1 mL) of oil was measured out into 31-mm HDPE XRF cells and
sealed with 0.25 mm thick mylar film. The sealed cells are measured on a Spectro Titan XRF
spectrometer (SPECTRO Analytical Instruments, Germany).
5.4
PS Analytical: Confirmation Laboratory Testing
PS Analytical of Kent in the United Kingdom was used as a confirmation laboratory for a
select number of samples.
5.4.1
Method Summary
In order to obtain a representative homogeneous sample aliquot, the samples were placed
in an ultrasonic bath for 15 minutes before aliquots were removed for preparation. The samples
were prepared by heating in aqua regia at 120°C for 2 hours. Once cooled, an aliquot of the
aqueous phase was removed, diluted, and analyzed using vapour generation atomic fluorescence
spectrometry. All the samples were prepared in duplicate on two consecutive days and each
solution was then analyzed in duplicate, i.e., n=4. Expanded uncertainties were reported for all
measurements.
Blank solutions were prepared and analyzed along with the samples, as were samples of
Conostan mercury in base oil (prepared at 20 ng g-1), which were used to validate the
measurements.
19
6
Quality Assurance and Quality Management
The data quality objective for the present work is to provide a defensible and statistically
reasonable estimate of the volume-weighted mean and standard deviations of mercury
concentrations in crude oils refined in Canada. Several steps were taken during the sampling
design and measurement phases of this project to support this goal.
6.1
Analysis Requirements
The laboratories were required to meet several objectives in order for their results to be
considered appropriate for use in the present work. In addition, several parameters related to the
study design and the sample list had to be judged acceptable to ensure general applicability of the
results. Method detection limits (MDLs) were required to be below those of the range of
measured concentrations. Detection limits were determined for both techniques by analyzing
element-blank oil samples provided by Conostan Division, ConocoPhillips Specialty Products
Inc., U.S. For both laboratories, method blank measurements were below 0.1 ng of mercury/g of
oil.
Accuracies were required to be 100% ± 15%, i.e., standard recoveries should average between
85% and 115%. Accuracies were determined by performing internal quality controls on check
standard and spike recoveries, but also by presenting blind challenge samples to each laboratory.
Challenge samples were prepared in the following ways: a certified mercury standard (Conostan,
U.S.) was spiked into an element-blank oil; the certified standard was also spiked into a crude oil
(Alberta sweet mixed blend); and standard-addition recoveries were calculated. See Sections
6.2.2 and 6.3.2 for results.
Precision was monitored for each measurement by analyzing each sample in duplicate (CEBAM
Analytical) or triplicate (University of Ottawa). The relative percent difference (RPD) between
measurements was not to exceed 20%. Pooled replicate analysis was also used to determine the
relative standard deviation of all measurements. See Sections 6.2.3 and 6.3.3. Reproducibility
between laboratories was not to exceed 15% on average. See Section 6.4 for additional
information.
As discussed in Section 3, the samples taken were considered to be representative of the
Canadian oil market in 2002, based on coverage of 71% of the total oil refined in Canada by
volume. The samples were representative in terms of the origin of each major oil, each refinery
region, and of each type of refinery input. This was deemed broad enough to easily approximate
the volume of Canadian refined oil. Practical considerations of availability and logistics did not
significantly affect the coverage of the sample list.
Most oil types were sampled three times (some types were only available to be sampled once see Table 3). Absolute variances were calculated for each oil type. To minimize the absolute
variances, the following procedure was used to calculate the number of resamples necessary for
each oil type.
The average concentration of total mercury in all types of crude oil is computed as:
[THg ]Vol = ∑ [THg ]i Vi
where
∑V
i
[THg]i is the mean concentration of total mercury in crude type I, and
20
(1)
Vi is the volume of refinery usage in 2002.
For each type of oil, [THg]i is initially estimated by three measurements. From these
measurements, the average triplicate-measured concentration [THg(3)]i and the variance, σ(3)i2,
are computed.
The average concentration of all the types of crude oil (for three measurements), [THg (3)]is
computed. The total number of samples to be taken in the study, n, is decided. In this study,
n = 109. To minimize the variance in the weighted-average concentration, [THg ]Vol , the number
of samples per type of crude i is then computed as:
ni = n
[∑V ]σ (3)
∑ (V [∑V ]σ (3) )
Vi
j
i
j
i
j
j
(2)
Thus, to minimize the overall study variance, a further ni-3 samples should be taken for each
type of crude oil (where ni-3 > 0).
Note that this criterion was used only as a guide to further sampling, not as a rule. Practical
considerations such as sample availability and time limitations required some reductions in the
number and selection of samples taken over the course of the study.
Both laboratories were required to be accredited by a recognized standards body. The Ottawa
University Laboratory participates in the Canadian Association of Environmental and Analytical
Laboratories (CAEAL) round-robin proficiency testing and is accredited for mercury analysis in
coal by that body. CEBAM Analytical participates in mercury proficiency testing administered
by the National Institute of Standards and Technology/National Voluntary Laboratory
Accreditation Program (NIST/NVLAP) and the U.S. EPA and maintains good standing under
both programs. Certifications for both laboratories were deemed to be acceptable.
6.2
Quality Assurance for Ottawa University Laboratory
6.2.1 Internal Quality Control
As described in Section 5.1., the Ottawa University laboratory’s control parameters
consisted of running blanks every five samples and preparing control standards in a mineral oil
base from a known standard, both supplied by Conostan. In all cases, the reported blank values
were below the stated detection limits and the reported recoveries of their control standards
exceeded 90% but were less than 110%. Both these parameters met the study objectives for
internal quality control.
Increasing standard deviation with measurement can be a problem if the standard deviation
increases more than a linear increase in the measurement. To test if this was a concern, the
relative standard deviation was plotted against concentration. This test at the Ottawa University
laboratory is presented in the top graph in Figure 8. While the absolute standard deviation in
measured mercury concentration may increase with increasing concentration, it is apparent that it
is considerably less than linear. Measurements carried out at the Ottawa University laboratory
have smaller RSDs on average at higher concentrations than near the detection limit. This is
considered an acceptable result for this laboratory.
21
Note also that no results were reported below the method detection limit of 0.1 ng/g of oil.
Blanks were checked regularly to ensure that low values were properly determined.
6.2.2
Challenge Samples
The analytical results for Ottawa University’s challenge samples are shown in Figure 9
and Table 4. These results include recoveries from a certified pure mineral oil base (Conostan,
U.S.) and spike-addition recoveries in an Environment Canada reference oil (Alberta Sweet
Mixed Blend, Reference Pour #4), a light, sweet crude oil similar to the more common Federated
crude oil. The total mercury concentration of this oil was determined in advance by the Ottawa
University laboratory.
All samples were considered in aggregate when estimating the recovery, bias, and expanded
uncertainty. The sample “Heavy Oil #5-01” prepared by CEBAM Analytical is routinely used by
this lab as a check standard in their regular measurements.
Recoveries show a bias of -14% and a relative standard deviation in recoveries of 7%. The bias
value is close to the target maximum of 15% (absolute), but both values satisfy the objectives for
each parameter.
The linear correlation between the measured and the nominal values for the Ottawa University
laboratory can be seen in Figure 9. For clarity, the value for Heavy Oil #5-01 is not shown in the
figure. The error bars plotted for the measured values are the reported standard deviations listed
in Table 4. As seen in the figure, there is a very strong linear relationship between the method
results and nominal values, as shown by both the slope of the graph being very close to 1 and the
coefficient of correlation, r2, also being very close to unity. The evidence of bias is also clear,
however, with the intercept of the linear fit being displaced down to almost -2. While very linear
and producing a 1:1 response, the Ottawa University laboratory values appear to slightly overreport the measured value of mercury.
6.2.3
Results of Pooled Replicates
As an alternative method for determining the relative variance in the data, rather than
relying on a relatively small number of challenge samples, the pooled relative standard deviation
of all replicates for all samples measured by Ottawa University (measured in triplicate) was
calculated. The Ottawa University laboratory reported 117 triplicate measurements of total
mercury concentration [THg]. Assuming that the relative variances are all similar, the pooled
relative standard deviation can be computed for the entire dataset using the equation:
sr , p =
where:
[(∑ (n − 1)s [THg ] ) ∑ (n − 1)]
i
2
i
1/ 2
−2
i
i
(3)
sr,p is the pooled relative standard deviation,
ni is the number of points in each data set (3 in this case),
si is the standard deviation of data set i, and
[THg ] i is its mean.
The pooled relative standard deviation (n = 343) for the Ottawa University data set is 0.077 or
7.7%. Using a coverage factor of k = 2, the expanded uncertainty for the pooled RSD is 15%.
22
3.0
σ[Hg] (ng/g oil) (n=3)
2.5
2.0
1.5
1.0
0.5
0.0
0
10
20
30
40
50
Ottawa University [Hg] (ng/g)
1.2
RPD*[Hg] (ng/mL) n=2
1.0
0.8
0.6
0.4
0.2
0.0
0
2
4
6
8
Cebam Analytical [Hg] (ng/mL)
Figure 8
Absolute Standard Deviation Plotted against Measured Mercury
Concentration for the Ottawa University Laboratory (top) and Absolute
Difference Plotted against Mercury Concentration for CEBAM Analytical
(bottom)
23
Ottawa University Measured [Hg] (ng/g oil)
14
Meas= 1.002 Nom -1.901
r ²=0.9999
12
10
8
6
4
2
0
0
2
4
6
8
10
12
14
Nominal [Hg] (ng/g)
Figure 9
Measured Concentration of Total Mercury Plotted against Nominal Values
for Ottawa University Laboratory Challenge Samples
Table 4
Results of Challenge Samples for Ottawa University Laboratory
Sample Matrix
Nominal Value Ottawa U
Ottawa U
Recovery
(ng/g oil)
Mean (n = 3)
SD (n = 3)
(ng/g oil)
(ng/g oil)
Mineral Oil
Mineral Oil
Mineral Oil
HEAVY OIL # 5-01
ASMB#4
ASMB#4
ASMB#4
ASMB#4
5.577
11.058
11.268
275.000
13.000
13.023
8.109
8.597
4.88
0.23
9.77
0.25
9.82
0.08
273.72
13.59
10.69
0.46
10.48
0.25
6.53
0.22
6.90
0.18
Mean
Bias
Standard Deviation
Observations
Coverage Factor (n = 7, 95.45%)
Expanded Uncertainty
24
87.5%
88.4%
87.1%
99.5%
82.2%
80.5%
80.5%
80.3%
85.8%
-14.2%
7%
8
2.43
16%
6.2.4
Estimated Uncertainties in the Results from Ottawa University Laboratory
The two estimates of expanded uncertainty agree remarkably well considering the large
differences in size of the datasets. From both results, the relative uncertainty of measurement in
the results from the Ottawa University laboratory is estimated to be 15%.
6.3
Quality Assurance for CEBAM Analytical
6.3.1 Internal Quality Control
As described for the Ottawa University laboratory in Section 6.2.3, CEBAM Analytical
used three types of quality control. A reference check was run before each set of standards,
method blanks were run before and after each sample analysis, and a duplicate matrix spike was
analyzed using one of the samples chosen at random. It was required that all recoveries be
between 75% and 125%.
As with the results from the Ottawa University laboratory, it is useful to determine whether the
variation in repeat measurement increases as the value of mercury concentration increases. Since
CEBAM Analytical was contracted to provide duplicate rather than triplicate measurements, the
absolute differences (RPD×[THg]) are plotted against the measured mercury concentrations.
From Figure 8, it can be seen that the absolute difference values do not greatly increase with
increasing mercury concentration.
As with the Ottawa University laboratory, CEBAM Analytical reported no results below their
method detection limit of 0.1 ng/mL of oil. They also checked blanks regularly to ensure that low
values were determined properly.
6.3.2
Challenge Samples
The analytical results for the challenge samples at CEBAM Analytical are shown in
Table 5. The calculated values include both recoveries from a certified pure mineral oil base
(Conostan, U.S.) and standard addition recoveries in the Environment Canada reference oil
(Alberta Sweet Mixed Blend #4).
The sample “MeHgCl” was prepared by the Ottawa University laboratory by mass from a
Conostan U.S. mercury standard in an aqueous medium.
It is immediately apparent from Table 5 that there was a systematic difference between the
recoveries in the mineral oil, aqueous, and ASMB #4 matrices. This difference is probably due to
uncertainty in the concentration of the ASMB #4 reference oil. This concentration was
determined by duplicate measurements of four samples spaced months apart in the sampling
schedule. The same procedure was used for the Ottawa University ASMB #4 measurements. The
ASMB #4 matrix recoveries thus include measurement uncertainties both in the reference oil and
in the spiked samples. Because of the differences between the two sets of samples, they have
been considered separately for the purposes of bias and uncertainty estimations.
Recoveries show biases of -14% for the mineral oil matrix and +15% for the crude oil matrix.
These are within the objectives for both, although the span high and low is 30%. Relative
standard deviations for both matrices are within the sampling design objectives.
25
Table 5
Results of Challenge Samples for CEBAM Analytical
Sample
Matrix
Nominal Value
(ng/g oil)
Mineral Oil
Mineral Oil
Mineral Oil
Mineral Oil
Mineral Oil
4.143
5.944
5.728
57.794
59.091
CEBAM
Mean (n = 2)
(ng/mL oil)
3.13
4.28
4.36
43.90
44.64
CEBAM
RPD (%)
-6.7
0.2
-2.3
0.1
-3.8
CEBAM
(ng/g oil)
3.60
4.92
5.02
50.55
51.40
Mean
Bias
Standard Deviation
Observations
Coverage Factor (n = 4, 95.45%)
Expanded Uncertainty
Recovery
87.0%
82.8%
87.6%
87.5%
87.0%
86.4%
-13.6%
2%
5
2.87
6%
MeHgCl
50.000
50.33
-3.7
50.33
100.7%
ASMB #4
ASMB #4
ASMB #4
ASMB #4
ASMB #4
ASMB #4
ASMB #4
ASMB #4
10.065
9.975
10.237
10.063
10.783
10.124
13.023
7.697
7.03
8.68
9.23
9.41
10.67
9.85
13.57
8.03
3.7
-1.8
-6.1
0.5
3.7
-3.6
-3.0
-0.4
8.35
10.31
10.97
11.18
12.68
11.70
16.13
9.54
83.0%
103.4%
107.2%
111.1%
117.6%
115.6%
123.8%
124.0%
114.7%
14.7%
8%
7
2.52
20%
Mean
Bias
Standard Deviation
Observations
Coverage Factor (n = 6, 95.45%)
Expanded Uncertainty
The nominal and reported values for the CEBAM Analytical challenge samples are compared in
Figure 10. For the mineral oil matrix samples, CEBAM Analytical reported results almost
identical to those of Ottawa University except that the slope is somewhat smaller. Response does
appear to be very linear over the measurement range for the mineral oil matrix samples. The
spike recoveries from the reference crude oil cover a narrower range and thus the fit equation is
not as certain as that for the mineral oil matrix samples. The spike recoveries are linear over the
range examined and very consistently reproduce the same recoveries. It is apparent from Figure
10 that the ASMB #4 samples are displaced vertically from the mineral oil matrix line,
supporting the hypothesis that the difference between the two data sets is an uncertainty in the
total mercury concentration of the base ASMB crude oil.
26
60
CEBAM Analytical Measured [Hg] (ng/g oil)
MeHgCl
(Aqueous)
50
40
30
Mineral Oil Matrix
Meas=0.87Nom-0.09
R2=1.00
ASMB#4 Matrix
Meas=1.28Nom-1.41
R2=0.87
20
10
0
0
10
20
30
40
50
60
Nominal [Hg] (ng/g)
Figure 10
Measured Concentration of Total Mercury Plotted against Nominal Values
for CEBAM Analytical Challenge Samples
Even if the absolute recoveries are in question, the repeatability of both data sets is well within
the study design objectives of 15% for standard deviations of repeat measurements. Expanded
uncertainties were found to be 6% for the mineral oil data set and 20% for the ASMB crude oil
matrix set.
6.3.3
Results of Pooled Replicates
The duplicate measurements for each sample were used to compute a pooled relative
standard deviation. The general equation for multiple replicates is shown in equation 3, Section
6.2.3. For duplicate measurements, equation 3 simplifies to:
sr , p =
where
[∑ (a − b / [THg ]) 2n]
2
1/ 2
=
[∑ RPD
2
2n
]
1/ 2
a and b are the duplicate measurements,
[THg ] is their average, n is the number of pairs, and
RPD is the relative percent difference (as a fraction).
27
(4)
For the CEBAM Analytical pool of duplicates (n = 260), the pooled, relative standard deviation
is 5.2%. Again, assuming a coverage factor of 2, the relative expanded uncertainty for the
CEBAM Analytical results is approximately 10%.
6.3.4
Estimated Uncertainty in CEBAM Analytical Results
The relative expanded uncertainties of measurement for the CEBAM Analytical data sets
are 6% from the mineral oil, 20% from the ASMB #4 spike recovery data, and 10% from the
pooled replicate data. While the mineral oil recovery data set agrees very well with the pooled
replicate estimate, the ASMB #4 spike recovery data set does have a larger uncertainty estimate.
Given the small size of the two recovery data sets (n = 5 for the mineral oil and n = 7 for the
ASMB #4) and the large size of the pooled replicate data set (n = 260), it seems reasonable,
however, to use the larger pooled replicate value. For the individual measurements reported by
CEBAM Analytical, it was assumed that the relative uncertainty is approximately 10%.
6.4
Inter-laboratory Differences: Ottawa University and CEBAM Analytical
The relationship between the measurements performed at Ottawa University and
CEBAM Analytical for each oil sample is shown in Figure 11. The horizontal ranges represent
the RSD reported by Ottawa University for each sample type; the vertical ranges show the RPD
reported by CEBAM Analytical. The graph at the top of the figure shows the entire data set and
the graph at the bottom shows those ranging from 0 to 20 ppbw. A strong linear relationship can
be observed between the two sets of measurements, although there is scatter between both
measurements. The 0.89 value of the coefficient of correlation reflects this observation.
The slope of the correlation shows that Ottawa University reported values approximately 15%
higher than those of CEBAM Analytical. This is consistent with the challenge sample results
discussed in Sections 6.2.2 and 6.3.2. Ottawa University reported values almost equal to the
nominal values, while CEBAM Analytical showed a trend of under-reporting. At no more than
approximately 15%, however, these differences appear to be relatively minor. This is within the
range of the uncertainties calculated earlier.
Another way of examining the relationships of the datasets is to compute the double-tailed
Student’s t-values for the two data sets. Assuming a hypothesis of zero difference between the
datasets, i.e., that they are identical and an alpha of 0.05, that is at 95% confidence, the Student’s
t-test gives a statistic of -0.63, a P(T<=t) (two-tail) of 0.53, and a t-critical (two-tail) of 1.97. The
mean of the Ottawa University data set is higher than that of the CEBAM Analytical dataset, but
the t-statistic falls well below the critical t-value for a significant difference. Based on this
calculation, it is more than 95% likely that the two data sets are statistically similar.
28
50
CEBAM Analytical [Hg] (ng/g oil)
CA = 1.1623 OU - 0.0076
r2 = 0.8900
40
30
20
10
0
0
10
20
30
40
50
Ottawa University [Hg] (ng/g oil)
CEBAM Analytical [Hg] (ng/g oil)
20
15
10
5
0
0
5
10
15
20
Ottawa University [Hg] (ng/g oil)
Figure 11
Measured Total Mercury Concentration for 109 Samples of Crude Oil,
Ottawa University Plotted against CEBAM Analytical - Top shows entire data
set, bottom shows range from 0 to 20 ppbw.
29
6.5
Inter-laboratory Differences: PS Analytical
As an additional check on the analyses conducted by both CEBAM Analytical and
Ottawa University, approximately 10% of the sample set was sent to PS Analytical in Kent, UK.
The results for all three labs are shown in Table 6. An attempt was made to choose samples with
a wide range of values that covered the full range of concentrations seen in the study.
Table 6
Results for Ottawa University, CEBAM Analytical, and PS Analytical
Sample ID Sample Date Ottawa U
CEBAM
PS Analytical PS Analytical
(ng/g oil)
(ng/g oil)
(ng/g oil)
Uncertainty
CCCN43
CCEP24
CCCN43
CCCN51
CCCN65
CCCN36
CCEP30
CCCN38
CCAF43
CCCN66
CCCN67
CCEP32
CCEP33
23-Jun-04
10-Jun-04
12-Jul-04
4-Jul-04
26-Jul-04
12-Aug-04
24-Jul-04
23-Sep-04
9-Dec-04
13-Dec-04
29-Nov-04
3-Dec-04
4-Dec-04
6.50
1.03
7.57
0.73
0.19
0.94
2.53
0.57
16.45
0.23
38.24
13.38
3.53
6.26
0.91
5.02
0.55
0.25
3.00
2.57
1.22
12.44
0.78
43.60
18.80
4.33
3.64
< 0.30
2.47
< 0.30
< 0.30
1.26
0.95
<0.30
14.7
< 0.30
47.68
20.25
1.99
0.79
0.1
0.02
0.08
1.3
4.28
2.19
0.08
The results from Ottawa University and CEBAM Analytical are plotted against the
corresponding results from PS Analytical (PSA) in Figure 12. In both cases, 0.15 ppbw or one
half the method detection limit was estimated for the below-detection-limit values reported by
PS Analytical. Both graphs show a strong linear relationship between the data from PSA and the
data from the other two laboratories. The slopes for both graphs are more than 1, indicating that
the PSA measurements for total mercury concentration may be consistently less than those of the
other two laboratories.
Double-tailed Student’s t-tests were computed for both the Ottawa University-PSA and CEBAM
Analytical-PSA pairs of data. Assuming differences of 0 and with 24 degrees of freedom, the tstatistics were found to be -0.028 for OU-PSA and 0.092 for CA-PSA. For a 95% probability of
being identical, the t-statistics should be in the range -2.06 to +2.06. There does not appear to be
any significant difference between the PSA data and that of either of the other two laboratories.
30
50
PSA [Hg] (ng/g oil)
40
30
PSA = 1.24 OU - 1.61
r2 = 0.96
20
10
0
0
10
20
30
40
50
Ottawa University [Hg] (ng/g oil)
50
PSA [Hg] (ng/g oil)
40
30
PSA = 1.13 CA - 1.46
r2 = 0.992
20
10
0
0
10
20
30
40
50
CEBAM Analytical [Hg] (ng/g oil)
Figure 12
Results from Ottawa University (top) and CEBAM Analytical
(bottom) Plotted against PS Analytical Results
31
7
7.1
Total Mercury Concentrations
Sample Data
The data for each sample taken over the course of the study are given in Table 7, listed
according to sample code and date. Measurements for each sample are: density (±0.0005),
sulphur content by weight (±0.05%), mean result of mercury concentrations (n = 3) from Ottawa
University (OU [THg]), the relative standard deviation (RSD) of the three Ottawa University
measurements, the CEBAM Analytical mean result of mercury concentrations (n = 2),
(CA[THg]), and the relative percent difference (RPD) between the two measured values for
CEBAM Analytical.
As CEBAM Analytical reported their results in ng/mL of oil, in this table their results have been
converted from mass/(unit volume oil) units to mass/(unit mass oil) units by the corresponding
average densities measured by Environment Canada.
[THg ](ng / g ) = [THg ](ng / mL) ρ ( g / mL)
(5)
A result from CEBAM Analytical is not available for one sample, CCCN36 sampled on 12-Jul04. This is indicated by NM in Table 7. This sample was damaged in transit and a replacement or
archive sample was not available. As CCCN36 was found to have very low values for total
mercury concentration, a fourth replacement sample was deemed unnecessary.
Table 7
Sample
ID
CCAF43
CCAF43
CCAF43
CCAF43
CCAF43
CCAF43
CCAF45
CCAF45
CCAF45
CCCN30
CCCN30
CCCN30
CCCN30
CCCN32
CCCN32
CCCN32
CCCN33
CCCN33
CCCN33
CCCN36
CCCN36
CCCN36
CCCN36
Sample Data
Sampling
Density
Date
(g/mL)
Sulphur
(%w/w)
9-Dec-04
17-Dec-04
25-Dec-04
31-May-05
8-Jun-05
20-Jun-05
12-Jul-04
11-Aug-04
4-Aug-04
13-Jan-05
14-Jan-05
13-Jan-05
14-Jan-05
5-May-04
29-Jun-04
22-Jul-04
25-Jun-04
29-Jun-04
1-Jul-04
12-Jul-04
10-Aug-04
11-Aug-04
12-Aug-04
0.12
0.12
0.12
0.11
0.10
0.11
0.31
0.20
0.16
0.5621
0.5635
0.4707
0.5522
0.3809
0.5754
0.4606
0.255
0.244
0.2175
0.1
0.4
0.1
0.2
0.7940
0.7940
0.7948
0.7943
0.7943
0.7948
0.8044
0.7341
0.7315
0.8155
0.8160
0.8160
0.8161
0.8425
0.8414
0.8448
0.8183
0.8184
0.8196
0.7530
0.6804
0.6797
0.6805
32
OU
[THg]
ng/g oil
16.5
16.4
11.8
7.6
4.5
5.1
2.8
1.3
1.3
1.2
0.6
1.2
0.9
1.1
1.3
0.9
0.6
0.7
0.7
1.2
0.8
1.1
0.9
OU
RSD
(%)
1.8%
3.4%
1.5%
5.6%
2.0%
3.3%
8.9%
2.2%
0.9%
1.6%
5.8%
7.5%
10.7%
12.9%
8.8%
1.9%
10.7%
7.6%
3.9%
7.6%
2.8%
7.4%
CA
[THg]
ng/g oil
12.4
19.7
16.0
14.4
9.8
10.3
2.4
2.2
0.9
1.4
1.2
1.4
1.1
1.0
0.9
0.6
1.1
1.2
1.6
NM
1.6
1.1
3.0
CA
RPD
(%)
2.4
-0.4
-1.3
-1.4
-9.9
-6.1
3.2
7.2
-9.2
8.9
0.6
-7.6
-4.6
7.3
0.8
-4.9
5.9
7.0
-10.0
5.1
-4.4
-4.9
Sample
ID
Sampling
Date
Density
(g/mL)
Sulphur
(%w/w)
CCCN37
CCCN37
CCCN37
CCCN38
CCCN38
CCCN38
CCCN39
CCCN39
CCCN39
CCCN40
CCCN42
CCCN42
CCCN42
CCCN43
CCCN43
CCCN43
CCCN43
CCCN43
CCCN43
CCCN49
CCCN49
CCCN49
CCCN50
CCCN50
CCCN50
CCCN51
CCCN51
CCCN51
CCCN53
CCCN53
CCCN53
CCCN60
CCCN60
CCCN60
CCCN62
CCCN62
CCCN62
CCCN62
CCCN62
CCCN62
CCCN64
CCCN64
CCCN64
CCCN65
CCCN65
22-Jun-04
25-Jun-04
13-Jul-04
16-Jun-04
13-Jul-04
23-Sep-04
1-Aug-04
25-Sep-04
12-Oct-04
18-Jun-04
18-Jul-04
30-Aug-04
1-Oct-04
23-Jun-04
30-Jun-04
12-Jul-04
17-Nov-04
6-Jan-05
15-Feb-05
25-Nov-04
21-Feb-05
3-Mar-05
29-Nov-04
6-Dec-04
13-Dec-04
23-Jun-04
28-Jun-04
4-Jul-04
17-Jun-04
21-Jul-04
26-Aug-04
21-Jun-04
26-Jun-04
9-Jul-04
17-Jun-04
13-Jul-04
28-Sep-04
30-May-05
2-Jun-05
8-Jun-05
16-Jun-04
13-Jul-04
23-Sep-04
22-Jun-04
14-Jul-04
0.8468
0.8472
0.8415
0.8323
0.8199
0.8264
0.8413
0.8310
0.8295
0.8208
0.9258
0.9349
0.9277
0.9216
0.8348
0.9250
0.9232
0.9206
0.9180
0.8500
0.8567
0.8570
0.8604
0.8584
0.8593
0.8487
0.8469
0.8476
0.9283
0.9323
0.9277
0.8273
0.8292
0.8290
0.8225
0.8218
0.8209
0.8217
0.8217
0.8217
0.8302
0.8295
0.8304
0.8272
0.8283
0.8
0.8
0.6
0.6
0.3
0.6
0.5
0.5
0.5
0.6
3.0
3.2
3.1
3.4
0.8
3.6
3.7
3.6
3.7
0.2
0.2
0.2
1.0
0.9
1.0
1.3
1.3
1.3
3.1
3.0
3.2
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.6
0.4
0.4
0.5
0.4
0.5
33
OU
[THg]
ng/g oil
1.6
1.6
1.2
0.8
0.5
0.6
1.6
1.9
1.6
0.8
1.6
2.4
2.0
6.5
1.5
7.6
8.9
7.0
8.3
0.4
0.3
0.6
0.5
0.4
0.4
0.8
1.2
0.7
1.1
1.1
1.4
2.9
3.1
2.2
6.3
2.9
1.8
2.8
1.3
3.6
3.0
2.3
4.0
0.6
0.3
OU
RSD
(%)
5.7%
4.5%
3.5%
10.2%
5.9%
12.3%
2.7%
9.7%
7.5%
3.7%
1.8%
5.9%
5.5%
9.1%
6.7%
8.0%
2.1%
1.3%
3.3%
4.3%
19.4%
4.0%
2.0%
5.9%
2.8%
9.7%
11.9%
11.5%
4.7%
2.8%
4.3%
5.5%
4.6%
7.2%
6.0%
8.8%
2.9%
19.5%
7.9%
4.2%
3.8%
8.0%
9.9%
8.5%
13.0%
CA
[THg]
ng/g oil
1.6
0.8
0.9
0.6
0.5
1.2
1.9
2.0
1.9
0.5
1.6
1.7
1.5
6.3
1.0
5.0
9.8
8.2
10.7
0.6
0.4
0.3
0.7
0.9
0.6
0.6
0.3
0.6
0.9
0.7
1.9
1.8
1.1
1.1
1.6
2.1
1.2
3.6
6.6
7.6
1.0
2.0
1.7
0.4
0.5
CA
RPD
(%)
7.0
5.7
0.0
-5.4
3.2
13.9
8.6
-3.8
3.4
2.6
9.2
9.1
9.2
7.0
5.2
19.5
-2.4
-3.9
-3.0
6.5
-8.0
-3.5
8.1
-2.4
0.0
11.3
-6.9
21.3
-2.3
18.2
8.7
-11.8
9.4
-7.5
5.8
-11.8
-4.9
7.1
-0.4
-0.5
9.9
11.5
-11.5
0.0
0.0
Sample
ID
Sampling
Date
Density
(g/mL)
Sulphur
(%w/w)
CCCN65
CCCN66
CCCN66
CCCN66
CCCN67
CCCN67
CCCN67
CCCN67
CCCN67
CCCN67
CCCN67
CCCN71
CCCN71
CCCN71
CCEP22
CCEP24
CCEP24
CCEP24
CCEP29
CCEP29
CCEP29
CCEP30
CCEP30
CCEP30
CCEP30
CCEP30
CCEP30
CCEP32
CCEP32
CCEP32
CCEP32
CCEP33
CCEP33
CCEP33
CCME56
CCME56
CCME56
CCSA38
CCSA38
CCSA38
CCUS105
26-Jul-04
29-Nov-04
6-Dec-04
13-Dec-04
29-Nov-04
6-Dec-04
16-Jul-05
26-Jul-05
27-Jun-05
4-Jul-05
11-Jul-05
3-Mar-05
11-Mar-05
20-Mar-05
7-Jun-04
10-Jun-04
23-Apr-05
23-Apr-05
26-May-04
17-Jun-04
14-Jul-04
31-May-04
5-Jul-04
24-Jul-04
21-Nov-05
21-Nov-05
21-Nov-05
3-Dec-04
29-Mar-05
2-Apr-05
5-Jun-05
4-Dec-04
11-Dec-04
21-Dec-04
10-May-04
2-Aug-04
1-Oct-04
20-Jul-04
20-Jul-04
20-Jul-04
24-Sep-04
0.8268
0.8559
0.8559
0.8559
0.8691
0.8690
0.8691
0.8690
0.8661
0.8665
0.8667
0.8596
0.8769
0.8628
0.8546
0.8502
0.8502
0.8502
0.8781
0.8765
0.8715
0.8284
0.8291
0.8280
0.8288
0.8290
0.8293
0.7961
0.7961
0.7961
0.7961
0.9064
0.9068
0.8991
0.8656
0.8713
0.8646
0.8750
0.8749
0.8749
0.8265
0.4
0.2
0.2
0.2
0.1
0.1
0.1
0.1
0.1
0.2
0.1
0.4
0.3
0.3
0.4
1.1
1.0
1.1
0.3
0.3
0.3
0.4
0.4
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0.6
0.6
NM.
2.5
2.8
2.6
0.5
1.0
1.2
0.6
34
OU
[THg]
ng/g oil
0.2
0.4
0.2
0.2
38.2
0.1
1.4
0.1
2.4
1.0
1.3
0.8
1.6
1.5
1.7
1.0
1.2
1.1
1.7
1.1
0.7
3.4
1.8
2.5
1.8
1.5
1.9
13.4
5.3
6.4
6.5
3.5
0.7
1.6
0.7
0.5
0.6
1.6
1.8
1.9
2.0
OU
RSD
(%)
15.8%
10.3%
12.4%
14.2%
4.2%
4.0%
7.2%
4.0%
3.7%
2.1%
27.2%
4.7%
6.4%
8.5%
7.8%
11.2%
6.4%
9.0%
3.3%
15.0%
10.6%
2.4%
6.6%
7.5%
5.7%
0.6%
3.2%
6.4%
2.5%
11.8%
37.6%
7.0%
4.8%
9.0%
15.4%
8.7%
7.3%
7.7%
3.9%
8.7%
2.4%
CA
[THg]
ng/g oil
0.3
0.5
0.4
0.8
43.6
1.6
1.6
0.6
1.0
1.0
0.9
0.3
0.4
1.4
1.1
0.9
0.7
0.8
0.9
0.8
0.5
2.3
1.5
2.6
2.0
2.1
2.3
18.8
11.4
14.7
11.8
4.3
1.6
1.6
0.5
1.2
0.5
1.3
1.3
2.0
1.5
CA
RPD
(%)
18.2
11.1
2.9
13.3
2.3
15.1
0.0
-5.1
0.0
3.4
-3.7
0.0
-5.8
3.6
-1.4
12.2
2.0
-8.5
-14.3
7.0
3.1
6.6
10.2
0.1
-3.6
0.0
3.9
1.1
-7.1
2.3
-4.0
2.0
8.3
4.3
10.2
-0.5
-6.2
11.0
-9.7
3.4
3.8
One hundred and nine (109) samples were measured over the course of the study. The samples
show considerable variability, ranging from 0.1 to 38.2 ng of mercury/g of oil for the Ottawa
University measurements and 0.2 to 43.6 ng of mercury/g of oil for the CEBAM Analytical
results.
While Ottawa University reported one measurement at the method detection limit (for a
CCCN67 sample), no samples were reported below the detection limit for either laboratory. A
detection limit of 0.1 ng of mercury/g of oil was sufficient to provide quantitative results for
every measurement for all the types of oil measured in the study.
7.2
Correlation of Density and Sulphur Content with Mercury Concentration
The possible relationships of total mercury concentration in crude oil to both density and
total sulphur content (by weight) are shown in Figures 13 and 14 respectively.
As can be seen from Figure 13, there does not appear to be a simple or dominant relationship
between the oil density and the total mercury concentration. A wide range of oils is represented,
from light condensates (density 0.68) to heavy crude types (density 0.94). The vertical
distribution of concentrations at a density of 0.78 to 0.79 is composed of measurements of two
light crudes from Africa: CCAF43 and CCAF45 (see data in Table 7). With the exception of
these two oils, the densities are distributed almost equally for the entire range of measurements
of total mercury concentration. The density of crude oil does not appear to have a strong
correlation with its total mercury content.
As seen in Figure 14, any relationship between sulphur content and total mercury concentration
is likewise small and does not dominate the mercury chemistry in this set of crude oils. The
measured oils consist of sweet crudes, with less than approximately 1% sulphur and sour crudes,
with more than 2% sulphur. For the 28 sweet crude oils, the highest total mercury concentrations
were measured for the oils with the lowest sulphur content (<0.2% sulphur). For the 4 sour crude
oils, CCCN42, CCCN43, CCCN53, and CCME56, there may be a positive correlation between
increasing sulphur and mercury levels, but there are too few data points in the present study to
draw definitive conclusions. These two features are suggestive of several possible mercury
chemistries in crude oil: a sweet-crude configuration when the mercury compounds do not
contain sulphur and a sour-crude chemistry with a possible sulphur-mercury association.
7.3
Averaged Crude Oil Data
The mean density, sulphur content, and total mercury concentration for both the Ottawa
University (OU) and CEBAM Analytical (CA) laboratories for each sample type are given in
Table 8. Note that the RSD values given for each total mercury concentration are those
calculated from the variances of the values for each oil code in Table 7, i.e., they reflect the
standard deviation between the individual measurements for each type of oil only.
In Table 9, one set of values has been removed from the averages. The values for CCCN67
sampled on 29-Nov-04 (given in Table 8) have been omitted from the calculation due to the wide
variation between the sampling on this date and all other samples of this crude oil. The outlier is
well beyond the mean +3σ level considering all other samples of this type. An investigation of
the sampling details on the chain of custody records indicated nothing unusual for this oil and the
high value appears to be a true high concentration based on testing at three laboratories.
Nevertheless, it is reasonable to believe that the statistical rejection of this data point is valid and
that the average of the remaining values is the best representation of the average value for crude
35
oil type CCCN67. With 109 individual samples taken, it is not unreasonable to find one sample
outside the 99%/3σ limit of average measurement. All other sample values shown in Table 8
were used to compute the averages shown in Table 9.
50
45
40
[THg] (ng/g oil)
35
30
Ottawa U
CEBAM
25
20
15
10
5
0
0.6500
0.7000
0.7500
0.8000
0.8500
0.9000
0.9500
Density (g/mL) at 20C
Figure 13
Total Mercury Concentration [THg] and Density of Oil
50
45
40
[THg] (ng/g oil)
35
Ottawa U
CEBAM
30
25
20
15
10
5
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
% Sulphur (w/w)
Figure 14
Total Mercury Concentration [THg] and Sulphur Content of Oil
36
Table 8
Averaged Crude Oil Data
Sample ID Density
Sulphur
OU [THg]
(g/mL)
(%w/w)
(ng/g)
CCAF43
0.7944
0.1
10.3
CCAF45
0.7567
0.2
1.8
CCCN30
0.8159
0.5
1.0
CCCN32
0.8429
0.5
1.1
CCCN33
0.8188
0.2
0.7
CCCN36
0.6984
0.2
1.0
CCCN37
0.8452
0.7
1.5
CCCN38
0.8262
0.5
0.6
CCCN39
0.8339
0.5
1.7
CCCN40
0.8208
0.6
0.8
CCCN42
0.9295
3.1
2.0
CCCN43
0.9072
3.1
6.6
CCCN49
0.8546
0.2
0.4
CCCN50
0.8594
1.0
0.4
CCCN51
0.8477
1.3
0.9
CCCN53
0.9294
3.1
1.2
CCCN60
0.8285
0.5
2.7
CCCN62
0.8217
0.5
3.1
CCCN64
0.8300
0.5
3.1
CCCN65
0.8274
0.4
0.4
CCCN66
0.8559
0.2
0.3
CCCN67
0.8679
0.1
1.1
CCCN71
0.8664
0.3
1.4
CCEP22
0.8546
0.4
1.7
CCEP24
0.8502
1.1
1.1
CCEP29
0.8754
0.3
1.2
CCEP30
0.8288
0.4
2.2
CCEP32
0.7961
0.2
7.9
CCEP33
0.9041
0.6
1.9
CCME56
0.8672
2.6
0.6
CCSA38
0.8749
0.9
1.8
CCUS105
0.8265
0.6
2.0
* Only one sample of this oil was available.
7.4
OU RSD
(%)
CA [THg]
(ng/g)
5.4
0.8
0.3
0.2
0.1
0.2
0.3
0.1
0.1
*
0.4
2.7
0.2
0.1
0.3
0.2
0.5
1.8
0.9
0.2
0.1
0.9
0.4
*
0.1
0.5
0.7
0.2
1.5
0.1
0.2*
*
13.8
1.8
1.3
0.8
1.3
1.9
1.1
0.8
1.9
0.5
1.6
6.8
0.4
0.7
0.5
1.2
1.3
3.8
1.6
0.4
0.6
1.1
0.7
1.1
0.8
0.7
2.1
14.2
2.5
0.7
1.5
1.5
CA
RPD
(%)
3.8
0.8
0.2
0.2
0.3
1.0
0.4
0.4
0.1
*
0.1
3.6
0.1
0.1
0.1
0.6
0.4
2.7
0.5
0.1
0.2
0.4
0.6
*
0.1
0.2
0.4
3.4
1.6
0.4
0.4*
*
Mean and Median Total Mercury Concentration
Several simple statistics computed from the data in Table 8 are shown in Table 9. There
is very good agreement between the laboratories for both the arithmetic means and medians, well
within the measurement uncertainties calculated in Section 6.
37
Table 9
Arithmetic Mean and Median Total Mercury in Oil Concentrations
Ottawa University CEBAM Analytical Lab Average
(ng/g oil)
(ng/g oil)
(ng/g oil)
Arithmetic Mean
2.0
2.2
2.1
( [THg ] )
Median
1.2
1.2
1.2
Minimum
Maximum
Standard Deviation
0.3
10.3
2.3
0.4
12.2
3.4
The distribution of total mercury concentrations in each type of crude oil for both laboratories
from Table 8 is plotted in roughly ascending order in Figure 15. The black bars show the labaverage arithmetic mean and median, which can be found in the right-hand column of Table 9.
[THg] (ng/g oil)
It can be seen from Figure 15 that the different “average” values that can be computed for total
mercury concentration in crude oil vary significantly. This is due to the extremely non-uniform
range of concentrations of mercury in oil. The total mercury concentrations in most types of oil
measured in this study is below 2.1 ppbw (25 of 32 for Ottawa University, and 26 of 32 for
CEBAM Analytical) and a few oils have a concentration above 5 ppbw (3 for both laboratories).
Based on these results, a simple arithmetic mean is not a good measure of the “average” value of
crude oil processed in Canada for the types of oil measured in the present work, as it is distorted
by a very few types of oil with concentrations much higher than the mean.
16
14
12
10
8
6
4
2
0
CEBAM Analytical
Mean [Thg] (2.1 ppb)
Median [THg] (1.2 ppb)
Ottawa University
Figure 15
Distribution of Total Mercury Concentration by Type of Oil
38
8
Data Analysis
8.1
Volume-weighted Averages of Total Mercury Concentrations
To simulate an “average” concentration of total mercury in oil that best reflects the refinery
usage Canada, production volume-weighted averages have been computed using Equation 1 in
Section 6.1. Weighted averages have been calculated for both the Ottawa University (OU) results
and the CEBAM Analytical (CA) results, which are shown in Table 10. As well as a national
average for all crude oil used in the country for all oil origins, weighted averages have also been
computed for oil origin (East, West and Foreign) and refinery location (Quebec and Atlantic,
Ontario, and Western Canada). Finally, volume-weighted averages have also been calculated for
synthetic crude oils derived from Alberta oil sands production using the data for oil types
CCCN43, CCCN66, and CCCN67. The production volumes as well as the oil origins, refinery
locations and the samples included in the averages can be found in Table 3. Measured mercury
concentrations were taken from Table 8. All averages, for both laboratories are shown in Table
10.
These weighted averages are compared in figure 16. It can be seen that the two labs are in
agreement in every case within the estimated 95% uncertainty limits. Both laboratories give
statistically indistinguishable results results, the averages of the two sets of data will result in a
more representative estimate of the mercury levels in the crude oils. The average total mercury
concentrations are shown in Table 10 with estimated uncertainties. Note that the relative
uncertainty for the combined laboratory average concentration is approximately 20% in all cases.
Table 10
In Study
Weighted Total Mercury Concentrations
CA
Average
2002
% PV
OU
Mercury
Production Volume Canada [THg ]Vol
[THg ]Vol
Concentration
(m3/yr)
2002
(ng/g oil) (ng/g oil)
in Oil
(ng/g oil)
74,714,601
71.3% 2.5 ± 0.4 2.8 ± 0.3
2.6 ± 0.5
Crude Oil Origin
Canada East
Canada West
Foreign
5,592,842
40,934,020
28,187,739
5.3%
39.1%
26.9%
1.2 ± 0.2
1.6 ± 0.3
3.9 ± 0.6
1.0 ± 0.1
1.5 ± 0.1
5.0 ± 0.5
1.1 ± 0.2
1.6 ± 0.3
4.5 ± 0.8
Refinery District
QC & Atlantic
Ontario
Western Canada
22,340,627
27,624,777
24,749,204
21.3%
26.4%
23.6%
4.0 ± 0.6
2.1 ± 0.3
1.4 ± 0.2
5.1 ± 0.5
2.1 ± 0.2
1.4 ± 0.1
4.5 ± 0.8
2.1 ± 0.4
1.4 ± 0.3
Synthetic Crude Oils
13,617,885
13.0%
2.1 ± 0.3
2.2 ± 0.2
2.2 ± 0.4
39
10
Ottawa University Laboratory
CEBAM Analytical
[THg]Vol
8
6
4
2
Figure 16
Sy
Cr nthet
ude ic
Oil
s
Qu
Atl ebec
ant &
ic
On
tar
io
We
Ca stern
nad
a
Fo
rei
gn
We
st
Ea
st
Ca
Av nadia
era n
ge
0
Comparison of Volume-Weighted Average Total Mercury Concentrations
[THg] in Crude Oil
It is useful to compare the results listed in Table 10 with the historical values discussed in
Section 2 and shown in Figure 1. Figure 1 is reproduced in Figure 17 with the historical literature
ranges on the left compared to the current results on the right. The black circles in Figure 17 plot
the average values or in the case of some of the literature results, recommended values, for total
mercury concentration, while the vertical lines represent the minimum and maximum observed
values for each study or category. Note that the vertical scale in Figure 17 is logarithmic.
It can be seen in Figure 17 that the average total mercury concentrations measured in the present
work, reported in Table 10, are orders of magnitude lower than several of the historical results.
In particular, it appears that the estimate of 3,500 ppbw (Brooks, 1989) used by the U.S. EPA as
the value for estimating mercury budgets is much too high (U.S. EPA, 1997). On the other hand,
more recent studies and reviews including those of Liang et al. (2000) and Morris (2000), and the
10 ppbw value recommended in the review by Wilhelm (2001) are all within the ranges observed
in the present work.
40
100000
100000
10000
10000
1000
1000
100
100
Region of
Origin
Refinery
District
[THg] (ppb)
10
10
1
1
0.1
Literature Ranges
(see Figure 1)
Western Synthetic
National Canada Foreign QC and
Crude
East
Atlantic
Canada
Oils
Canada
Ontario
West
0.1
Figure 17
Measured Total Mercury Concentration [THg] Compared to Historical
Ranges of Mercury
It is important to note, however, that while in the more recent literature these values are within
the range of mercury concentrations observed in this work, in most cases these authors report
values that are several times higher than the weighted averages measured in this study. Several
factors may account for this.
Firstly, as can be seen in Table 10, Canadian crude oils have lower concentrations of total
mercury than those from non-Canadian sources. This can also be seen indirectly in the averages
based on refinery districts. Refineries in the Quebec and Atlantic regions process mostly crude
oils of foreign origin. Processed oils from this region have the highest average concentrations of
total mercury. In contrast, refineries in western Canada process crude oils almost exclusively
from western Canada. This refinery district has the lowest average mercury level in its crude oil
input stream.Oils produced in eastern Canada, which come primarily from offshore
Newfoundland, have some of the lowest mercury concentrations found in this study. As these
oils were not yet in wide use in Canadian refineries in 2002, however, they do not significantly
affect the volume-weighted average mercury concentrations.
Secondly, the historical values have been biased high because instrumental detection limits were
higher than the methods used in the present work. In several cases, the “low values” for the
historical ranges (Figure 1) are the method detection limits. As it was therefore not possible to
determine low concentrations for these studies, the reported averages are higher. It should be
41
noted that in the present work no sample was found to be below the method detection limit for
either laboratory.
Finally, many of the previous studies were limited in their selection of oils. It can be very
difficult to arrange for sampling of a set of oils that are representative of use patterns at
refineries. Many authors were able to study only a limited set of oils and no literature studies
attempt to weight the reported averages by refinery or commercial use. Many of the oils used in
past studies were not selected for the purpose of estimating a broad average. Authors often
deliberately selected oils with high mercury concentrations in order to measure “pathological”
cases. In the present study, however, care has been taken to sample accurately in order to reflect
the actual use of crude oils by refineries. This should lead to a more accurate and lower estimate
of the broader volume-weighted average for mercury concentrations in crude oil.
42
8.2
Total Mass of Mercury in Crude Oil refined in Canada
The total mass of mercury in crude oil was calculated by multiplying the individual oil total
mercury concentrations [THg ]i by the corresponding production volume (PVi) and the individual
oil densities ρi:
Mass = ∑ [THg ]i × PVi × ρ i
(6)
i
Where [THg ]i and ρi are taken from Table 8, and PVi is taken from Table 3. Estimated
uncertainties in the mercury mass were computed by multiplying the relative estimated
uncertainties, shown in Table 10, from Sections 6.2.4 and 6.3.4 for the Ottawa University results
and CEBAM Analytical values respectively.
Similar to the volume weighted sub-averages in section 8.1, total masses of mercury were also
computed for each geographic origin and for region of refiners from the data in Table 8, with
groupings and volumes taken from Table 3. Note that these mercury masses are calculated only
for the oil volumes included in the study. The total and partial amounts of mercury in crude oil
refined in Canada in 2002 are shown in Table 11 in kilograms.
Table 11
Mass of Mercury in Crude Oil*
Mercury Mass
In Oil Refined
(kg Hg/yr)
227 ± 30
Canada 2002
Production District
Canada East
7.0 ± 1.4
Canada West
77 ± 15
Foreign
143 ± 26
Refinery District
QC & Atlantic
115 ± 21
Ontario
71 ± 13
Western Canada
41 ± 8
Alberta Tar Sands Product
Synthetic Crude Oils
37 ± 7
*Production Volume Weighted for 2002
43
8.3
Total Mercury in Crude Oil in the Context of Canadian Emissions
Releases of mercury to the environment in Canada from industrial sources must be
reported to the National Pollutant Release Inventory (NPRI) program. The NPRI is managed by
Environment Canada and tracks 323 classes of substances. The total emissions from each class
are compiled from the NPRI database every calendar year. Mercury and its compounds are
considered as a single pollutant class by the NPRI. The NPRI totals for mercury for 2002 are
shown in Table 12 and compared to the total mercury in crude oils processed in Canada, taken
from Table 11. These results are also plotted in Figure 18.
Table 12
Total Mercury Emissions in 2002 Compared to Mercury in Processed
Crude Oils
Total Emissions
Mercury in Mercury in Oil from all Mercury
Crude Oil
Total Emissions
Sources (kg/year)
(kg/year)
(%)
NPRI: QC & Atlantic
1,338
115.4
8.6%
NPRI: Ontario
1,483
70.5
4.8%
NPRI: Western Canada
4,354
41.3
1.4%
National NPRI Total
5,837
227.2
3.9%
Estimated Total Canadian
Anthropogenic Emissions
6,340
3.6%
Assuming the worst case, the release of all the mercury in crude oil refined in Canada to the
environment, the percentage of the total mercury emissions budget that could be attributed to the
refined oils is shown in Table 12. While the Quebec and Atlantic region has the lowest total
emissions from all sources, it also has the highest total mercury in crude oil refined in that
region. This can be attributed to the high mercury content of the oils refined in Quebec and the
Maritimes coming from foreign sources. By contrast, western Canada has the lowest total
amount of mercury in processed crudes and refines almost exclusively domestic Canadian
crudes.
While the NPRI database includes most of the industrial and institutional releases of mercury,
some sources, including small commercial and residential sources, are not required to report
emissions. The Pollution Data Branch of Environment Canada estimates emissions from all of
these non-NPRI sources. Their estimate for all anthropogenic emissions of mercury in Canada
for the year 2002 was 6,340 kg as shown in Table 12.
The trends shown in the data in Table 12 are also shown in Figure 18. While the total mercury in
refined crude oil is lowest in the western district and highest in Quebec and the Atlantic regions,
the total mercury emissions reported by the NPRI show the opposite trend. While the
percentages of mercury in crude oil to total emissions differ by an order of magnitude in Table
12, it can be seen in Figure 18 that these differences are caused mainly by the relatively large
emissions of mercury in western Canada.
44
7000
6000
All sources including NPRI
NPRI Sources Only
Emissions of Hg (kg/year)
5000
4000
3000
2000
1000
Total NPRI
Refined Oil Total
0
Canadian Total
Figure 18
Western
Canada
Ontario Quebec &
Atlantic Regions
Total Canadian Mercury Emissions in 2002 Compared to Mercury in
Refined Crude Oils
45
From the average mercury concentration of 2.6 ng/g (from Table 12) and an average oil density
of 0.8477 g/mL (from Table 8), the total amount of mercury in all crude oil processed in Canada
from 2002 to 2005 can be estimated using equation 6 in Section 8.1. The amounts for each year
are shown in Table 13. Note that the variations from year-to-year in the estimated total mercury
are within the uncertainty of the estimated total mercury values of approximately ±30 kg/year.
Table 13
Mercury in Crude Oil Processed in Canada from 2002 to 2005
Estimated Total
Year
Volume of Crude Oil
Mercury (kg/year)
Processed (1000 m3)*
2002
104,719
227
2003
106,742
231
2004
110,908
240
2005
107,420
233
*Source: Statistics Canada, 2006
9
Conclusions and Recommendations
During this study, 32 types of oil were sampled and 109 individual oil samples were
measured. The crude oils were selected for type based on the list of oils processed by
participating refineries in Canada in 2002. The oils were chosen based on geographical origin
(western Canada, eastern Canada, and foreign), the district in which the refineries were located
(western Canada, Ontario, and Quebec and Atlantic Canada), by oil type (condensate, crude, and
synthetic crude), and their availability for sampling. The oils sampled covered 71% of all oil (by
volume refined) in Canada in 2002. The samples measured were chosen from a list of 103 types
of crude oil representing more than 88% of crude oil processed in Canada. It is assumed that the
results for all 10 reporting refineries (103 types of crude oil, 88% by volume) can be extrapolated
to 100% of the refined volume of crude oil in 2002 for all 19 refineries reporting to the NPRI in
that year.
The average total mercury concentration in crude oil weighted by volume used in the Canadian
refining sector in 2002 is 2.6 ± 0.5 ng/g of oil or parts per billion by weight (ppbw) at 95%
confidence. In general, Canadian crude oils have lower concentrations of total mercury (1.2 to
1.6 ± 0.3 ppbw) than crude oils from outside Canada (4.5 ± 0.8 ppbw). As a result, the average
mercury concentrations in the input streams of Quebec and Atlantic refineries were the highest in
the country (4.5 ± 0.8 ppbw) because of their reliance on foreign inputs. In contrast, refineries in
Ontario and western Canada used crude oils that were on average lower in total mercury
concentrations: 2.1 ± 0.4 ppbw and 1.4 ± 0.3 ppbw, respectively. Finally, it was found that three
“synthetic” crude oils manufactured from bitumen from the Alberta tars sands had an average
total mercury concentration of 2.2 ± 0.4 ppbw (weighted by refined volumes).
Each sample was measured by two laboratories, one using cold-vapour/atomic absorption
(CVAA) and the other using cold-vapour atomic fluorescence spectrometry (CVAFS). Both
laboratories met or exceeded the following quality objectives over the entire study: accuracies of
± 15% based on spike recoveries and precisions of ± 20% based on pooled replicates. The
estimated relative uncertainties of measurement were 16% for CVAA and 10% for the CVAFS
techniques at 95.45% (2σ) confidence. The detection limit of both methods was 0.1 ppbw. All
samples measured were at or above 0.1 ppbw. No oil sample reported in the present work was
found to be below this detection limit.
46
These average total mercury concentrations are significantly lower than those reported in the
literature. Reviewers have reported values from 3,500 ppbw (Brooks, 1989) to 10 ppbw
(Wilhelm, 2001). In the present work, values of 0.3 to 15 ppbw were observed for the 32 types of
oil sampled. The arithmetic mean of all values, i.e., not weighted by refinery-usage volume, was
found to be 2.1 ppbw. The median (50th percentile) total mercury concentration was 1.2 ppbw.
The distribution of concentrations skewed low - most oils had low total mercury concentrations
with the mean being brought up by a very few oils with higher concentrations (above 5 ppbw).
The differences between the range of concentrations measured in this work and those reported by
other authors can be explained by the following three factors.
1.
Canadian crude oils make up approximately half by volume of all the crude oils used by
Canadian refineries. The total mercury levels of these Canadian oils are lower than oils
from the rest of the world and thus tend to bring down the averages.
2.
Improvements in detection limits allow lower concentrations to be quantified and
included in the averages.
3.
Previous studies focused in part on oils with very high concentrations of mercury. It is
difficult to obtain representative average concentrations of total mercury from these
datasets.
The density and sulphur content of each oil sample were also measured. No correlation could be
found between density and total mercury concentration. Mercury levels in crude oil vary
independently of their density. The case for sulphur was more ambiguous. The oils sampled
consisted of sweet (<1.5% sulphur) and sour (>2.5% sulphur). High mercury concentrations were
found in some of the very sweetest (low sulphur) oil samples. In addition, observations of the
sour crude oils suggested a trend, with very sour crude oils (5% sulphur) having moderate
mercury concentrations (5 ppbw).
The Canadian refinery sector processed 104,719,128 m3 of crude oil in total in 2002. Multiplying
this volume by the production-weighted average of 2.6 ± 0.5 ppbw, it is estimated that a total of
227 ± 30 kg of mercury was contained in all of the oil refined in Canada in 2002. In comparison,
a total of 5,837 kg of mercury emissions were reported to Environment Canada’s National
Pollutant Release Inventory (NPRI) in 2002. Assuming the worst case that all of the mercury in
the crude oil processed in Canada is released to the environment, the petroleum-refining sector
and all associated downstream activities could constitute 3.9% of the 2002 annual total release of
mercury reported to the NPRI. In 2002, the total emissions to the Canadian environment
estimated from typical use were 6,340 kg. This value for total emissions includes non-NPRI
reporting sources, such as the residential sector. The petroleum-refining sector could then
constitute 3.6% of that total.
The potential mercury emissions that could originate from the refining of crude oil vary greatly
from region to region. Because of their use of foreign crude oils, the refineries in Quebec and
Atlantic regions could have emitted as much as 115 kg of mercury in 2002. Refineries in Ontario
could have been responsible for approximately 70 kg and those in western Canada could have
accounted for as little as 41 kg. These variations are almost entirely caused by the use of oil from
different sources. Note that almost equal amounts of crude oil were refined in all three regions in
2002.
47
9.1
•
•
•
•
•
•
•
•
•
•
Main Findings
The main findings of this study are summarized here.
More than 100 types and 104.7 million m3 of crude oil were processed in Canada in 2002,
approximately half of which originated from Canada and the other half from foreign
countries.
The average concentration of total mercury weighted by refined volumes in Canadian
crude oil (2002 data) is 2.6 ± 0.5 ng/g of oil.
The observed range of mercury concentrations in oil was 0.1 to 50 ng/g of oil.
This average concentration and range of values are significantly lower than those
reported in the literature.
No strong correlations were found between total mercury concentration and either the
density or total sulphur content of the crude oil. Sulphur content of the various types of
crude oil ranged from 0.1% to 3.1% w/w. The average density was calculated at
0.8477 g/mL.
In 2002, Canadian refineries processed crude oil containing a total of 227 ± 30 kg of
mercury.
If all of this mercury had been emitted to the environment, it would have made up 3.6%
of the total anthropogenic air emissions, including both NPRI and non-NPRI sources, in
2002.
There are significant regional differences in the levels of mercury in crude oil. Oils from
eastern Canada contain less mercury (<1 ppbw) than oils from western Canada
(<2 ppbw). Products from the tar sands have among the highest levels of all crude oils
produced in Canada. The mercury levels in foreign crude oils can be ten times or more
than those in domestic crude oils.
Because of their usage patterns, refineries on Canada’s east coast process crude oils with
higher levels of mercury than those used in Ontario or western Canada. Refineries in
Quebec and the Atlantic provinces thus have a higher potential for mercury emissions
than those in other parts of the country.
The study results represent the crude oil processing pattern for the 10 participating
refineries in 2002. These refineries make up 88% by volume of the refining sector. If the
usage of crude oil for refining changes significantly, the study results will no longer
apply.
This study has produced an estimate for total mercury concentration in crude oil and potential
emissions of mercury to the environment from refinery inputs based on real-world usage data.
These data, which represent the concentrations and total mercury in the crude oil refinery input
stream, can be used with for estimating emissions from the petroleum sector and activities
associated with its outputs, including heating with petroleum fuel; road, ship, and diesel rail
transportation; and petroleum-fueled power generation.
It should be emphasized, however, that these estimates account only for the mercury contained in
the crude oil used by the refineries. The actual disposition of mercury in the refining process is
not well understood at the present time. It is still largely unknown how much mercury is
removed by the refineries during processing and how it fractionates into each type of refined
product, e.g., gasoline, diesel, marine fuel oils, and asphalts. The mercury lost to the air from
crude oil between extraction and its arrival at the refinery has also not been included in this
study.
48
While it seems that the overall worst-case estimate of possible contributions of crude oil to the
total anthropogenic emissions of mercury is quite low, it is useful to remember that total mercury
emissions have fallen swiftly in the past two decades and continue to fall. With petroleum
products becoming an increasingly important source of fuel and with petroleum extraction and
refining setting record volumes every year, it will become even more important to assess
potential mercury emissions from the oil and gas sector each year.
9.2
Recommendations
The value of 2.6 ± 0.5 ng of mercury/g oil (ppbw) can be used as an estimate of the
average total mercury concentration in Canadian crude oil weighted by refined volumes. Using
this average mercury concentration, the total amount of mercury in crude oil processed in
Canada is estimated to be 227 kg in 2002, 231 kg in 2003, 240 kg in 2004, and 233 kg in 2005,
based on the total amount of crude oil refined in Canada in those years.
The pattern of processing crude oil reported here was that for 2002. In this year, eight types of
crude oil accounted for 30% of the Canadian processing volume but contained more than 80% of
all the mercury in crude oil processed in Canada. These eight crude oils originated from western
Canada, Europe, and Africa. However, the processing pattern of crude oil in Canada has changed
slightly each year. In future, if crude oil use deviates significantly from the usage pattern
evaluated in this work, the results of this study will need to be re-evaluated.
The total amount of mercury in all crude oil processed in Canada in 2002 (227 ± 30 kg) can be
used as an estimate of the upper limit of potential mercury emissions from the petroleum-refining
sector. This includes both potential mercury emissions from all refined petroleum products and
all potential mercury releases from refineries. This study targeted only that mercury contained in
the crude oil received by the refinery. Actual emissions from refineries were not measured. In
addition, mercury released from upstream oil, gas extraction, and handling and transport to
refineries should not be included in this estimate. Mercury from other refinery inputs, such as
natural gas, may also affect this estimate.
The value for the total amount of mercury in the inputs of crude oil refineries can also be used as
an estimate of the upper limit of mercury in refined fuels. Atmospheric mercury emissions from
the exhaust of on-road motor vehicles as a result of combustion of refined petroleum products is
estimated to be no more than 227 ± 30 kg/yr. Using this worst-case estimate, the maximum
potential anthropogenic atmospheric emissions of mercury from the combustion of refined fuel
would be 3.6% of the total Canadian total (6,340 kg of mercury) in 2002. Note that the actual
disposition of mercury in each stream of petroleum products, including gasoline and diesel fuels
used to power on-road motor vehicles, was not measured in the present study.
49
10
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Atomic Fluorescence Spectrometry”, RMZ-Materials & Geoenvironment, 51:1885-1889, 2004.
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Hitchon, B. and R.H. Filby, “Geochemical Studies - Trace Elements in Alberta Crude Oils”,
Alberta Research Council for Alberta Energy and Utilities Board and Alberta Geological Survey,
Alberta, Canada, Open File Report 1983-02, 1983.
Kelly, R.W., S.E. Long, J.L. Mann, “Distribution of Mercury in SRM Crude Oils and Refined
Products by Isotope Dilution Cold Vapour ICP-MS using Closed-system Combustion”, Anal.
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Trans-Boundary Air Issues Branch, Hazardous Air Pollutants Program, Environment Canada,
Richmond, BC, 2000.
Liang L. and N.S. Bloom, “Determination of Total Mercury by Single-stage Gold Amalgamation
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Liang, L., M. Horvat, and P. Danilchik, “A Novel Analytical Method for Determination of
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50
Liang, L., S. Lazoff, M. Horvat, E. Swain, and J. Gilkeson, “Determination of Mercury in Crude
Oil by In-situ Thermal Decomposition using a Simple Lab-built System”, Fresenius' J. Anal.
Chem., 367 (8):8, 2000.
Liang, L., M. Horvat, V. Fajon, N. Prosenc, J. Li, and P. Pang, “Comparison of Improved
Combustion/Trap Technique to Wet Extraction Methods for Determination of Mercury in Crude
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Crude Oils”, in Proceedings of the SPE/EPA Exploration & Production Environmental
Conference, SPE Paper No. 52725, 1999.
Morris, R., “New TRI Reporting Rules on Mercury”, presented at the National Petroleum
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NPRI (National Pollutant Release Inventory), “NRPI National Overview 2000, Appendix D National Atmospheric Releases of Mercury”,
http://www.ec.gc.ca/pdb/npri/2002Highlights/NPRI2000Overview/appendixd_e.cfm, 2000.
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ICP-MS”, Analyst, 122:1229, 1997.
Shah, K.R., R.H. Filby, and W.A. Haller, “Determination of Trace Elements in Petroleum by
Neutron Activation Analysis”, J Radioanal. Chem., 6:413-422, 1970
Shafawi, A., L. Ebdon, M. Foulkes, P. Stockwell, and W. Corns, “Determination of Total
Mercury in Hydrocarbons and Natural Gas Condensate by Atomic Fluorescence Spectrometry”,
Analyst, 124:185, 1999.
Spiric, Z., “Innovative Approach to the Mercury Control during Natural Gas Processing”,
Proceedings of the ETCE 2001 Engineering Technology Conference on Energy, Feb. 5-7, pp. 14, 2001.
Statistics Canada, “The Supply and Disposition of Refined Petroleum Products in Canada”,
Statistics Canada, Catalogue No. 45-004-XIB, 100 p., Ottawa, ON, 2006.
Sunderland, E.M., and G.L. Chmura, “The History of Mercury Emissions from
Fuel Combustion in Maritime Canada”, Environmental Pollution, 110:297-306, 2000.
Tao, H., T. Murakami, M. Tominagaa, and A. Miyazakia, “Mercury Speciation in Natural Gas
Condensate by Gas Chromatography Inductively Coupled Plasma Mass Spectrometry”, J. Anal.
At. Spectrom., 13:1085-1093, 1998.
U.S. EPA (Environmental Protection Agency), “Method 7473, Mercury in Solids and Solutions
by Thermal Decomposition, Amalgamation, and Atomic Absorption Spectrometry”, 1998.
51
U.S. EPA (Environmental Protection Agency), “Mercury Study Report to Congress”,
EPA/452/R-97/003 (NTIS PB98-124738), Office of Air Quality Planning and Standards,
Research Triangle Park, NC and Office of Research and Development, Washington, DC, 1997.
U.S. EPA (Environmental Protection Agency), “Specifications and Guidance for ContaminantFree Sample Containers”, Office of Solid Waste and Emergency Response, EPA 540/R-93/051,
Washington, DC, 1992.
Wilhelm, S.M., “Design Mercury Removal Systems for Liquid Hydrocarbons”, Hydrocarbon
Processing, April, pp. 61-71, 1999.
Wilhelm, S.M. “An Estimate of Mercury Emissions to the Atmosphere from Petroleum”,
Environ. Sci. Tech., 35(24):4704-4710, 2001a.
Wilhelm, S.M., “Mercury in Petroleum and Natural Gas: Estimation of Emissions from
Production, Processing, and Combustion”, for U.S. Environmental Protection Agency, Office of
Research and Development, EPA-600/R-01/066, Washington, DC, 2001b.
Wilhelm, S.M. and N. Bloom, “Mercury in Petroleum”, Fuel Processing Technology, 63:1-27,
2000.
Wilhelm, S.M. and D. Kirchgessner, “Mercury in U.S. Crude Oil: A Study by U.S. EPA, API
and NPRA”, SPE/EPA/DOE Exploration and Production Environmental Conference, Society of
Petroleum Engineers Paper 80573, San Antonia, TX, 2003.
Wilhelm, M., L. Liang, D. Cussen, and D. Kirchgessner, “Mercury in Crude Oil Processes in the
United States (2004)”, Env. Sci. & Technol., (in press).
52
53
Appendix A Crude Oils and Refined Volumes Processed by Reporting Refineries in 2002
Crude Oil
Code
Origin of
Crude Oil
Location of
Refinery
Volume
by
Location
(m3/yr)
Canada Total (2002)
Canadian Study Total
Combined Canadian and U.S. Study Total
Major Types of Crude Oils (Volume > 1%)
Ontario & Western
CCCN67a Canada West
Canada
Ontario
Western Canada
CCEP30
Europe
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCCN65
Canada West
Western Canada
CCAF43
Africa
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCEP33
Europe
QC/Atlantic
CCCN32
Canada East
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCME57
Middle East
QC/Atlantic
CCCN64
Canada West
Western Canada
CCCN51
Canada West
Ontario
Ontario & Western
b
CCCN43
Canada West
Canada
Ontario
Western Canada
CCCN38
Canada West
Western Canada
CCCN62
Canada West
Western Canada
CCEP29
Europe
QC/Atlantic
CCEP32
Europe
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCCN42
Canada West
Ontario
CCCN66a Canada West
Western Canada
CCEP22
Europe
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCCN53
Canada West
Ontario
CCUS105 United States
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCME56
Middle East
QC/Atlantic
CCCN60
Canada West
Ontario
CCEP24
Europe
QC/Atlantic
CCCN71
Canada West
Ontario
Volume
Processed
in 2002
(m3/year)
Fraction
2002
Total (%)
Sampled
in this
Study
Sampled in
U.S. EPA/
API Study
104,719,128
74,714,601
71.35%
82,735,621
79.01%
8,760,725
8.37%
YES
6,095,688
5.82%
YES
YES
5,819,171
5,645,287
5.56%
5.39%
YES
YES
YES
YES
4,297,500
3,738,838
4.10%
3.57%
YES
YES
YES
YES
3,696,238
3,346,093
3,331,872
3.53%
3.20%
3.18%
YES
YES
YES
YES
YES
2,806,402
2.68%
YES
YES
2,586,216
2,494,699
2,194,478
2,171,157
2.47%
2.38%
2.10%
2.07%
YES
YES
YES
YES
YES
2,068,005
2,050,758
1,894,392
1.97%
1.96%
1.81%
YES
YES
YES
YES
1,862,063
1,618,401
1.78%
1.55%
YES
YES
YES
YES
1,416,160
1,371,238
1,209,664
1,170,900
1.35%
1.31%
1.16%
1.12%
YES
YES
YES
YES
YES
YES
YES
3,391,951
5,368,774
1,446,040
4,649,648
5,533,481
111,816
2,130,429
1,608,409
1,918,218
888,184
YES
YES
1,015,774
1,155,383
346,324
1,548,068
1,129,454
488,944
54
Crude Oil
Code
CCCN37
CCCN50
CCAF46
Origin of
Crude Oil
Canada East
Canada West
Africa
Location of
Refinery
Ontario & QC/Atlantic
QC/Atlantic
Ontario
Western Canada
QC/Atlantic
Minor Types of Crude Oil (Volume < 1%)
CCCN30
Canada West
Western Canada
CCCN41
Canada West
Western Canada
CCMX15 Mexico
QC/Atlantic
CCCN54
Canada West
Ontario
South
QC/Atlantic
CCSA36
America
CCCN49
Canada West
Ontario
CCEP34
Europe
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCEP23
Europe
Ontario
South
QC/Atlantic
CCSA38
America
CCCN36c Canada East
Ontario
CCAF41
Africa
QC/Atlantic
CCAF45c Africa
Ontario
CCEP21
Europe
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCUS102 USA
Ontario
CCCN48
Canada West
Ontario
CCCN39
Canada West
Ontario
CCCN59
Canada West
Ontario
CCCN55
Canada West
Ontario
CCCN75
Canada West
Western Canada
CCCN31
Canada East
Ontario
CCAF44
Africa
Ontario & QC/Atlantic
QC/Atlantic
Ontario
South
QC/Atlantic
CCSA34
America
CCCN40
Canada West
Western Canada
CCMX17 Mexico
QC/Atlantic
CCEP28
Europe
Ontario & QC/Atlantic
QC/Atlantic
Ontario
CCCN52
Canada West
Ontario
CCMX16 Mexico
QC/Atlantic
South
CCSA30
QC/Atlantic
America
CCUS104 USA
Ontario
Volume
by
Location
(m3/yr)
Volume
Processed
in 2002
(m3/year)
Fraction
2002
Total (%)
Sampled
in this
Study
Sampled in
U.S. EPA/
API Study
1,142,046
1.09%
YES
YES
1,083,517
1,059,383
1.03%
1.01%
YES
YES
YES
798,232
791,533
731,798
719,824
0.76%
0.76%
0.70%
0.69%
716,092
0.68%
611,571
596,892
595,257
0.58%
0.57%
0.00%
0.00%
0.57%
YES
538,738
0.51%
YES
536,416
526,101
511,017
490,971
0.51%
0.50%
0.49%
0.47%
YES
483,729
462,814
458,998
456,520
426,898
421,076
390,826
330,396
0.46%
0.44%
0.44%
0.44%
0.41%
0.40%
0.37%
0.32%
330,128
0.32%
313,560
313,483
297,287
0.30%
0.30%
0.28%
247,440
206,617
0.24%
0.20%
188,499
0.18%
177,296
0.17%
1,082,585
59,461
295,371
301,521
YES
YES
YES
YES
YES
431,523
59,448
YES
YES
189,073
141,323
YES
YES
237,813
59,474
55
YES
Crude Oil
Code
CCCN33
CCEP25
CCCN72
CCME59
CCCN79
CCAF42
CCEP31
CCEP27
CCCN45
CCUS106
CCCN69
CCEP35
CCEP26
CCSA32
CCCN74
CCME55
CCSA35
CCME54
CCSA37
CCCN46
CCEP37
CCCN58
CCSA33
CCAS11
CCUS107
CCSA31
CCCN68
CCCN73
CCCN34
CCCN77
CCCN35
CCME58
CCCN47
CCUS103
CCCN44
CCCN70
CCCN78
CCCN56
CCMX18
Origin of
Crude Oil
Canada East
Europe
Canada West
Middle East
Canada West
Africa
Europe
Europe
Canada West
USA
Canada West
Europe
Europe
South
America
Canada West
Middle East
South
America
Middle East
South
America
Canada West
Europe
Canada West
South
America
Asia
USA
South
America
Canada West
Canada West
Canada East
Canada West
Canada East
Middle East
Canada West
USA
Canada West
Canada West
Canada West
Canada West
Mexico
Location of
Refinery
Ontario
Ontario & QC/Atlantic
QC/Atlantic
Ontario
Ontario
QC/Atlantic
Western Canada
Ontario & QC/Atlantic
QC/Atlantic
Ontario
QC/Atlantic
QC/Atlantic
Ontario
Ontario
Ontario
QC/Atlantic
QC/Atlantic
Volume
by
Location
(m3/yr)
Volume
Processed
in 2002
(m3/year)
175,542
171,142
Fraction
2002
Total (%)
Sampled
in this
Study
Sampled in
U.S. EPA/
API Study
167,600
160,464
182,623
148,611
0.17%
0.16%
0.00%
0.00%
0.16%
0.15%
0.17%
0.14%
144,855
142,223
139,023
135,658
113,300
109,231
106,888
0.14%
0.14%
0.13%
0.13%
0.11%
0.10%
0.10%
YES
YES
QC/Atlantic
103,889
0.10%
YES
Ontario
QC/Atlantic
102,100
86,957
0.10%
0.08%
YES
QC/Atlantic
84,083
0.08%
QC/Atlantic
83,242
0.08%
QC/Atlantic
82,584
0.08%
Ontario
Ontario
Ontario
76,791
75,209
58,942
0.07%
0.07%
0.06%
QC/Atlantic
54,506
0.05%
Ontario
Ontario
52,365
51,988
0.05%
0.05%
QC/Atlantic
48,940
0.05%
Ontario
Ontario
Ontario
Western Canada
QC/Atlantic
QC/Atlantic
Ontario
Ontario
Ontario
Ontario
Western Canada
QC/Atlantic
QC/Atlantic
44,916
40,100
33,895
33,458
31,653
28,890
25,896
23,611
21,010
19,700
19,097
18,590
18,514
0.04%
0.04%
0.03%
0.03%
0.03%
0.03%
0.02%
0.02%
0.02%
0.02%
0.02%
0.02%
0.02%
171,138
4
YES
YES
127,711
20,900
56
YES
YES
YES
YES
YES
YES
YES
YES
Crude Oil
Code
Origin of
Crude Oil
CCUS100
CCUS108
CCCN80
CCEP36
CCCN61
CCUS101
CCMX14
CCCN76
CCCN63
USA
USA
Canada West
Europe
Canada West
USA
Mexico
Canada West
Canada West
Location of
Refinery
Volume
by
Location
(m3/yr)
Ontario
Ontario
Western Canada
Ontario
Ontario
Ontario
QC/Atlantic
Western Canada
Western Canada
Volume
Processed
in 2002
(m3/year)
16,000
13,100
11,093
9,800
9,758
3,486
1,260
781
126
a
Synthetic Crude Oil (upgraded bitumen): CCCN66 and CCCN67
non-upgraded oil sands bitumen: CCCN43
c
Gas Condensates: CCAF45 and CCCN36
b
57
Fraction
2002
Total (%)
0.02%
0.01%
0.01%
0.01%
0.01%
0.00%
0.00%
0.00%
0.00%
Sampled
in this
Study
Sampled in
U.S. EPA/
API Study
YES
YES
Appendix B Sampling Protocol
This document was included in every sampling kit provided to the refineries.
Mercury has many forms in oil. Elemental mercury and organic mercury compounds are very
volatile and evaporate readily. Inorganic forms of mercury can form sediments that sink in oil.
Some mercury compounds absorb on metal surfaces. When sampling the oil, the sampling
personnel must make every effort to:
• thoroughly mix the oil;
• minimize the contact of the oil and the sample with air; and
• use only glass containers if possible and minimize all contact with metal.
A single “sample” consists of 6 vials of oil sampled from the same batch of oil, one immediately
after another. A crude oil type should be sampled (6 vials collected) three or more times. As far
as possible, each sample (of 6 vials) should be taken from a different shipment or batch of oil. As
far as possible, oils should be sampled soon after receipt by the refinery, ideally directly from the
incoming pipeline or the tanker, and preferably not from long-term storage tanks.
Oil samples are only to be identified by the 7-digit code (e.g., CCCNxxx) assigned by CPPI. No
identifying marks should be made on the sample vials, except those described below.
Sampling Procedure
The sampling kit provided includes 6 glass bottles with septa caps (pre-cleaned, 40-mL
EPA/VOA clear glass vials, caps with Teflon septa), bottle labels, a chain-of-custody form,
return packaging, and a shipping label. The bottles are ready for use. No preparation is
necessary. A single sample is considered to be the 6 replicate sample vials.
• As far as possible, this procedure should be performed by a single individual.
• Before sampling, ensure that the oil is as well mixed as practicable.
• During sampling operations, minimize sample contact with metal surfaces, as is practical.
Glass-sampling equipment is preferred.
• Samples should be taken as close and as soon as practical to the point of entry of the
crude oil into the refinery. When sampling from a pipeline, take samples as close as
possible to the point of entry of the pipeline into a refinery. When sampling from a
tanker, grab samples are preferred, taken from the bulk of the oil, away from the vessel
walls. Autosamplers or grab samples are the preferred sampling methods. Other sampling
techniques are acceptable, but should be noted on the chain-of-custody form.
• Sampling directly into the supplied vials is preferred. Intermediate transfers should be
minimized. Glass or PTFE transfer equipment is preferred.
• When sampling, minimize contact with the air: reduce open-air transit times and cap the
vials as soon as possible.
• Minimize headspace in the sample vials. Fill the vials as full as possible.
• All six vials should be filled together, in a single batch. Use the same grab sample, if
possible, or sample from the same location in the oil.
• Cap samples immediately, ensuring a good seal.
• After samples have reached the ambient temperature, check that vial caps are sealed
tightly.
• Clean vials and affix the supplied labels.
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•
Ensure each label has the following information:
- Crude oil code assigned by CPPI to the sampled oil (e.g., CCCN01)
- Sampling date in the form MM/DD/YY (e.g., 03/24/04 for March 24, 2004)
- A letter from A to F, where A was the first vial collected, F the last.
- Complete the chain of custody form including:
- Crude oil code
- Sampling date in the form MM/DD/YY (e.g. 03/24/04 for March 24, 2004)
- Sampling location (pipeline/tanker/other)
- Notes on collection process, including sample mixing, sampling method (grab
samples, auto sampler, etc.), intermediate transfer stages, etc.
- Ensure that caps are tight on vials.
- Seal each vial in the supplied plastic bag with supplied chain-of-custody seals and
sign and date seals.
- Pack bagged vials into the shipping container.
- Label the shipping container with the oil code and the sampling date on the supplied
label.
- Package the shipping container with the supplied materials and ship to the sample
manager at the address below. DO NOT REFRIGERATE SAMPLES. Store samples
at between 15°C and 25°C. Samples must be shipped within two days of sampling.
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Appendix C Sampling Kits, Packing Materials, and Documentation
Sampling Kit - Vials and Packing Materials – This shows the typical sample kits, packaging,
and forms and labels that are provided for each sample of oil.
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Documentation for Sampling Kits - Clockwise from bottom left, Vial Labels, Sampling
Protocol (see Section 4.1), Chain of Custody form (see Section 4.2), return mailing label, and
custody seal for the return packaging.
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Appendix D Chain of Custody Forms
The following is the Chain of Custody form sent to refineries to be completed by sampling
personnel.
CHAIN OF CUSTODY RECORD
Mercury in Crude Oil Project (2004)
Project Partners: Environment Canada, CPPI, NA Refinery
SAMPLE CODE:
SAMPLING DATE (MM/DD/YY):
SAMPLING LOCATION:
DETAILS:
___ Pipeline
___ Tanker
___ Other
SAMPLING CONDITIONS: Method (grab, autosampler, other), Intermediate Containers (size, material,
headspace), Mixing, Other Special Conditions
OIL TEMPERATURE (when sampled):
SAMPLED BY:
DATA RECORDED BY:
SAMPLE
DATE
COLLECTED
TIME
COLLECTED
A
B
C
D
E
F
CONDITION OF SAMPLES ON RECEIPT:
None
ITEMS
RELINQUISHED BY
ANALYSIS
REQUIRED
THg
THg
THg
THg
THg
THg
MATRIX
LAB
ID
REMARKS
Oil
Oil
Oil
Oil
Oil
Oil
Custody Seals Intact: ___Yes ___ No ___
DATE/TIME
Notes:
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RECEIVED BY
DATE/TIME
The following is the Chain of Custody form sent by Ottawa University to the Environment
Canada laboratory and to CEBAM Analytical.
CHAIN OF CUSTODY RECORD (ID BLIND)
Mercury in Crude Oil Project (2004)
To be sent on to EC/CEBAM
Project Partners: Environment Canada, CPPI, NA Refinery
SAMPLE CODE:
SAMPLING DATE (MM/DD/YY):
RECORD STARTED BY:
Condition of Samples on Receipt:
None
ITEMS
RELINQUISHED BY
Custody Seal Intact: ___Yes ___ No ___
DATE/TIME
NOTES:
63
RECEIVED BY
DATE/TIME