UNIVERSITY OF GOTHENBURG
Department of Earth Sciences
Geovetarcentrum/Earth Science Centre
Heavy metal concentrations
as a relative age
marker in recent marine
sediment cores along
the Swedish west coast
Ardo Robijn
ISSN 1400-3821
Mailing address
Geovetarcentrum
S 405 30 Göteborg
Address
Geovetarcentrum
Guldhedsgatan 5A
B 608
Bachelor of Science thesis
Göteborg 2010
Telephone
031-786 19 56
Telefax
031-786 19 86
Geovetarcentrum
Göteborg University
S-405 30 Göteborg
SWEDEN
Abstract
Heavy metal concentrations in recent marine sediment cores can be used to establish a regional
chronology, because of the change in industrial and domestic chemical use over time. The aim of this
study is to identify age markers in heavy metal concentrations along the Swedish west coast. The data
used are archived 210Pb dated cores and new heavy metal analyses of parallel cores from five locations
along the west coast. The 210Pb ages are calculated according to the CRS model and the heavy metal
concentrations are analyzed by leaching of the sediments by the ‘Swedish standard’ method and ICPMS measurements. The heavy metal concentrations are compared with each other with the aid of the
210
Pb age model. The general trends in the results can be described by the rising of the concentrations
from low background values (before 1910) and a peak of concentrations during the 1970’s and 1980’s
from increased industrialization and domestic chemical use. This trend is in accordance with many
other locations as noted in Ridgeway and Price (1987). The top parts of the cores are marked by a
decrease in metal concentrations as a result of environmental protection policies. A peak in copper and
lead concentrations is identified as a possible relative age marker and corresponds to a date of c. 1970
The result of the Sannäs Fjord cores is greatly different from the rest of the cores, showing high
background concentrations to pre 1900 ages. The usage of 210Pb dating and the CRS model at the
Sannäs Fjord need to be evaluated to determine the source of the deviation from the rest of the cores in
this study.
Keywords: 210-Pb dating, CRS, heavy metal, chronology, chromium, copper, zinc, cadmium, lead,
recent marine sediments.
Sammanfattning
Tungmetallkoncentrationer i recenta marina sedimentkärnor kan användas för att skapa en regional
kronologi, eftersom användningen av kemikalier i industri och hushåll varierar med tiden. Syftet med
föreliggande studie är att identifiera åldersmarkörer i tungmetallkoncentrationerna längsmed den
svenska västkusten. De data som legat som grund för undersökningen är arkiverade 210Pb-daterade
kärnor samt nya tungmetallanalyser från parallellkärnor från fem lokaler längsmed västkusten. 210Pbåldrarna är beräknade enligt CRS metoden och tungmetallkoncentrationerna är analyserade genom
urlakning av sedimenten enligt ’Svensk standard’ metoden och ICP-MS analyser.
Tungmetallkoncentrationerna har jämförts med varandra genom 210Pb åldersmodellen.
Analysresultaten visar på en generell ökning i koncentrationerna från låga bakgrundsvärden (innan
1910) till en koncentrationstopp under 1970- och 1980- talen, troligen orsakad av ökad
industrialisering och användningen av kemikalier inom hushållen. Denna trend överensstämmer också
med flera andra områden som bl a beskrivs av Ridgeway och Price (1987). Den översta delen i
sedimentkärnorna karaktäriseras av en nedåtgående trend i tungmetallkoncentrationerna som är ett
resultat av de miljöskyddsåtgärder som förelegat under de senaste decennierna. En topp i koppar och
bly koncentrationerna tolkas som en möjlig åldersmarkör och överensstämmer med övrig datering till
ca år 1970. Analyserna av kärnorna i Sannäsfjorden skiljer sig från de övriga sedimentkärnorna som
undersökts. Dessa visar höga bakgrundsvärden för åldrar äldre än 1900. Därför måste 210Pb-datering
och CRS modellen i Sannäsfjorden utvärderas för att avgöra orsaken till avvikelsen från de övriga
sedimentkärnor i denna studie.
Nyckelord: 210-Pb datering, CRS, tungmetall, kronologi, krom, koppar, zink, kadmium, bly, recenta
marina sediment.
1
Contents
Abstract ................................................................................................................................................... 1
Sammanfattning....................................................................................................................................... 1
1 Introduction .......................................................................................................................................... 3
2 Study area ............................................................................................................................................. 3
2.1 Core locations ................................................................................................................................ 5
2.1.1 Havstens Fjord ........................................................................................................................ 5
2.1.2 Koljö Fjord ............................................................................................................................. 5
2.1.3 Gullmar Fjord ......................................................................................................................... 5
2.1.4 Sannäs Fjord ........................................................................................................................... 5
2.1.5 Dynekilen ............................................................................................................................... 5
3 Material and methods ........................................................................................................................... 5
3.1 Heavy metal analyses .................................................................................................................... 6
3.2 Swedish Environmental Protection Agency’s reference values .................................................... 7
3.3 210Pb dating method ....................................................................................................................... 7
3.4 Age model ..................................................................................................................................... 7
4 Results .................................................................................................................................................. 8
4.1 Havstens Fjord............................................................................................................................... 8
4.2 Koljö Fjord .................................................................................................................................... 8
4.3 Gullmar Fjord ................................................................................................................................ 9
4.4 Sannäs Fjord .................................................................................................................................. 9
4.4.1 SSK08 5E ............................................................................................................................... 9
4.4.2 SSK09 4,5B .......................................................................................................................... 10
4.5 Dynekilen .................................................................................................................................... 10
4.6 Accumulation rate ....................................................................................................................... 10
5 Discussion .......................................................................................................................................... 17
5.1 Relative dating markers ............................................................................................................... 17
5.2 Background levels in the Sannäs Fjord ....................................................................................... 18
5.3 Cadmium levels in the Koljö Fjord ............................................................................................. 18
6 Conclusions ........................................................................................................................................ 19
Acknowledgements ............................................................................................................................... 20
References ............................................................................................................................................. 20
Appendix A ...............................................................................................................................................
Appendix B ...............................................................................................................................................
2
1 Introduction
Absolute dating of recent marine sediment cores is of importance for detailed studies of the sediments,
although this can be an expensive procedure that requires specialized laboratory equipment. It would
therefore be convenient that trends in heavy metal concentrations could be used as a relative age
marker in these sediment cores. Heavy metals are often analyzed as part of environmental
investigations and to have an age model derived from the heavy metal concentrations can add
precision and quality to the interpretations and conclusions drawn from the cores. The aim of this
paper is to identify possible regional trends in the heavy metal concentrations in sediment cores from
five different localities along the Swedish west coast. This will be done with existing 210Pb dated cores
and new heavy metal analyses of parallel cores. The analysis of heavy metal traces in recent marine
sediments are previously done in the Kiel Bight and Gotland basin by Suess and Erlenkeuser (1975),
showing an increase in zinc flux from 1850 in the Kiel Bight and around 1930 the Gotland Basin. A
study in a Norwegian Fjord by Skei and Paus (1979) showed a onset of heavy metal concentrations
roundabout 1890. The method is also used in various other locations e.g. in Scotland by Ridgeway and
Price (1987) and a more recent example in Spain (Ligero et al, 2002).
2 Study area
The Bohus county coast is the northern part of Sweden’s west coast and boarders the Skagerrak arm of
the North Sea (Fig. 1). The area is characterized by an archipelago coast with deep fjords. The land
consists of bare hills of granitic bedrock and valleys filled with marine clays. These marine clays are
generally deposited after the retreat of the last glaciation which left the area c. 13Ka ago while the sea
level was c. 125 m elevated due to isostatic depressing of the land by the ice. Since the ice retreated an
isostatic rebound of the crust has exposed many of the previously submerged valleys. In the basins of
the fjords the sedimentation has been ongoing since the last glaciation and consists of organic rich
clays and silts.
The hydrography of the Skagerrak/Kattegat area is influenced by water from the Atlantic, North Sea
and Baltic Sea. The surface water consists of a low saline (c. 15-25 PSU) current, called the Baltic
current, which flows from the outlet of the Baltic to the north close to the Swedish coast. The Jutland
current has a salinity of c. 33-30 PSU and flows along the Danish west coast to the north. The Jutland
current continues across the Skagerrak, from Skagen in Denmark to the Swedish west coast, where it
combines with the Baltic current. This combined current has a typical salinity of 25-28 PSU and sets
to the north along the Bohus coast. Finally the current changes direction to follow the Norwegian coast
towards the west and out into the Norwegian Sea. From the pycnocline at c. 15-20 m below these
surface currents, in the Skagerrak, the normal saline (c. 32-35 PSU) and cold Atlantic water is situated
(Rodhe, 1996).
The Skagerrak has a mean depth of 210 m which is deep compared to the 49 m mean depth of the
North Sea. The deepest part of the Skagerrak, the Norwegian Trench, reaches over 700 m and is
connected to the Norwegian Sea with a sill depth of 270 m. The circulation in the bottom water is
cyclic and mainly driven by the wind stress form the North Sea, although the bottom topography with
the Norwegian Trench as the main feature plays a role in the circulations direction (Rodhe, 1996).
From the Skagerrak a bottom current flows southwards trough the Kattegat to the Baltic Sea.
3
Figure 1. Bathymetry map of the Skagerrak and Kattegat with a close up of the study area on the Swedish west
coast. The locations of the core sampling sites are marked with a red star.
4
The semidiurnal tide has an amplitude of c. 20 cm but the total sea level can vary over 1.5 m, which is
driven by air pressure (2 cm/mb) and wind transport (Svansson, 1975). Storm wave activity is limited
inside the fjords due to the protective topography of the fjord landscape.
Fjords are used in this study because the basins of the fjords provide good accumulation bottoms for
high resolution sediment cores.
2.1 Core locations
Sediment cores from five locations along the Bohus coast were used in this study.
2.1.1 Havstens Fjord
The Havstens Fjord is situated between the mainland and the islands of Orust and Tjörn (Fig. 1). The
sampling location is at N 58° 18.31', E 11° 44.75’ in 40 m deep water depth. The Havstens Fjord is
connected to the sea at the south with a 20 m sill depth. The net water circulation is northward through
the fjord and exits into the Koljö Fjord (Björk et al, 2000). Petrochemical industries are located on the
main land in the southern part of the fjord, in the Stenungsunds area, and an industrial boat yard was
located in Uddevalla until the mid 1986.
2.1.2 Koljö Fjord
The Koljö Fjord is an open ended fjord connected to the Havstens Fjord in the northeast, with a sill
depth of 12 m and connected to the open sea in the southwest through a narrow man made channel
with a sill depth of 8 meters(Filipsson et al, 2005). The core is collected at N 58° 13.62', E 11° 34.25’
at 43 m water depth (Fig. 1). The island of Orust to the south of the fjord is known for their famous
yachtbuilding and boatyards since a couple of hundred years ago (L. Bornmarlm , pers. comm., 2010)
2.1.3 Gullmar Fjord
The sample from the Gullmar Fjord was collected at N 58° 18.95', E 11° 32.36’ in the deepest basin of
the fjord at 113 m depth (Fig. 1). The fjord has a sill depth of 42 m and is in direct contact with the
open sea. The inner part of the fjord has received anthropogenic pollutants from sewage, a paper mill
and a sulfate mill until the late 1960s (Nordberg et al, 2000). And in Lysekil, in the outer part of the
fjord, sewage discharge and wastewater from herring canneries were released until the mid 1970’s
(Harland et al, 2005).
2.1.4 Sannäs Fjord
The Sannäs Fjord sampling sites are located at N 58° 44.9', E 11° 13.3’ in the deepest basin of the
inner part of the fjord at 25 and 30 m, behind the 8 m sill (Fig. 1). The fjord has no large scale
industries within its drainage area but it has received the waste water from the small village between
1967 and 1990 (Andersson, 2006).
2.1.5 Dynekilen
Dynekilen is the northernmost sampling site at N 59° 00.11', E 11° 11.86’ in 26 m water depth behind
a 13 m sill. North of Dynekilen is the entrance to the Ide Fjord, which endured heavy metal pollution
until the mid 1970’s (Apler, 2007).
3 Material and methods
The cores and data used in this study are taken from the archive of Prof. K. Nordberg. The sediment
cores are sampled between 1999 and 2009 using either a Multiple Corer Mark III-400 (Barnett et al,
1984) or a Gemini corer (Winterhalter, 2000), which both retrieve virtually undisturbed sediment
5
cores in soft, muddy sediments. The cores are immediately sub sampled in 1 or 2 cm thick slices
which are then weighed and freeze dried before further analysis.
The following sediment cores are previously dated using the 210Pb method (Fig. 2). The core from the
Koljö Fjord, K6A, is used in studies by Nordberg et al (2001), Filipsson and Nordberg (2004a) and
Filipsson et al (2005). The core H4A, taken in the Havstens Fjord, is used in Filipsson et al (2005) and
the core from the Gullmar Fjord, G01 113 A, is used in Filipsson and Nordberg (2004b). The dated
sediment core from Dynekilen, DI3002Ba, is still unpublished and in the Sannäs Fjord two 210Pb
datings are carried out in 2000 and 2002 which are both used in this study and are previously used by
Wattwil (2001) and Andersson (2006).
The heavy metal concentrations from the cores SSK08 5E and SSK09 4,5B, taken in the Sannäs Fjord
and G113 09 1, from the Gullmar Fjord, are previously analyzed and used in this study. For the Kojlö
Fjord, Havstens Fjord and Dynekilen, the parallel cores (K4C, H5A and DI3002A) of the dated cores
were selected using radiographs and are used for heavy metal analysis that is carried out for this study.
Figure 2. Summary of 210Pb dated sediment cores used in this study. Data from Prof. K. Nordberg.
3.1 Heavy metal analyses
The heavy metal analyses are performed at the Department of Earth Sciences, University of
Gothenburg, Sweden, except SSK08-5E which was analyzed at the Analycen laboratories in Luleå,
Sweden. The method of analysis follows the ‘Swedish standard’ (SS 028183) which is the common
method used for coastal research and monitoring programs (SEPA, 2000). Of the sample, 0.9 g is
homogenized in an agate mortar and 20 ml of 7M HNO3 is added to leach out the metals while heated
to 120 °C for 30 minutes. The liquid phase is separated and diluted for ICP-MS (Inductivety Coupled
Plasma Mass Spectrometer) analysis. Measurements for chromium, copper, zinc, cadmium and lead
6
(Cr, Cu, Zn, Cd and Pb) are made with the Agilent 7500 ICP-MS and the concentrations are
recalculated and expressed in mg/kg dw (dry weight).
3.2 Swedish Environmental Protection Agency’s reference values
The Swedish Environmental Protection Agency (SEPA) has issued reference values for metal
concentrations measured in marine sediments (SEPA, 2000). These values are based upon statistical
analysis of some hundred background values collected at 55 cm sediment depth, representing preindustrial levels as a natural background. The classification is divided in five classes of deviation from
the reference value (Table 1). The reference table will be used for comparing the results to national
values.
Table 1. Deviation classification according to Swedish Environmental Protection Agency (SEPA, 2000) All
values in mg/kg dry weight
Deviation
Class 1
Class 2
Class 3
Class 4
Class 5
Class:
None/
Slight
Significant
Large
Very large
Metal
Chromium (Cr)
Copper (Cu)
Zinc (Zn)
Cadmium (Cd)
Lead (Pb)
insignificant
< 40
40-48
48-60
60-72
> 72
< 15
15-30
30-49,5
49,5-79,5
> 79,5
< 85
85-127,5
127,5-204
204-357
> 357
< 0,2
0,2-0,5
0,5-1,2
1,5-3
>3
< 25
25-40
40-65
65-110
> 110
3.3 210Pb dating method
The 210Pb datings are performed as described by Nordberg et al (2001) in Risø, Denmark. For the
analysis 0.5-1 g of the sample is completely dissolved in hot HF/HNO3/HCl in the presence of 209Po as
a yield determinant for 210Po, the daughter isotope of 210Pb. The polonium isotopes are then plated on
polished nickel discs from dilute hydrochloric acid with ascorbic acid to complex the iron. Alpha
spectrometry is used for at least two days to measure the 209Po and 210Po concentrations and 226Ra is
counted using gamma spectrometry to determine the supported 210Pb levels. The mass of each sample
is compensated for its salt content and porosity.
The dates are calculated using the Constant Rate of Supply (CRS) model (Appleby and Oldfeild,
1978) for the top half of the core until unsupported lead values approach zero, the rest of the core is
calculated, assuming the same sedimentation rate as the top half, compensated for compaction
(Nordberg et al, 2001). This CRS model assumes a constant flux of 201Pb to the sediment surface,
while the flux of sediment can vary over time. The 210Pb has a half-life of 22.26 years suiting sediment
cores of 100 to 150 years. The error margin increases with depth, allowing for more precise dating in
the top of the sediment cores and assuming an error of ± 10 years at 100 years dated age (P. Roos,
pers. comm., 2010).
3.4 Age model
Correlating the dated sediment cores to the heavy metal analyzed cores is done by identifying similar
sequences on x-ray radiographs for The Koljö and Havstens Fjord, the depth differed less than one cm
throughout the cores because they were retrieved from the sea bed simultaneously. For Dynekilen no
radiographs where available but these cores were also parallel cores.
The heavy metal analyzed cores from the Gullmar Fjord and the Sannäs Fjord cores were taken c. 8
year later than the dated cores, which makes it necessary to adjust the dated timescale to fit the
collecting year of the heavy metal analyzed core. The estimated time scale is made by adding the time
7
lag between the two sampling dates to the 210Pb dated time scale to preserve the natural rate of
sedimentation and compaction of the specific sampling site.
4 Results
The results of the heavy metal analysis are compiled in figures 3 to 14 .The results are plotted versus
depth and age. The ages described in the results are influenced by errors, and caution should be taken
especially in the older ages, because the margin of error increases with depth.
4.1 Havstens Fjord
The heavy metal concentrations in the Havstens Fjord (core H5A, sampled 1999) are shown in figure
3. In figure 4 the heavy metal concentrations of H5A are plotted to the corresponding timescale of the
dated core H4A (sampled 1999).
Chromium (Cr) levels are between 40-45 mg/kg throughout the core, except for a dip at 20 cm core
depth and the top 5 cm of the core. The highest levels of Cr are found at 10-11 cm core depth and the
lowest concentrations at the surface sample. Copper (Cu) concentrations vary between the lowest
values of 20 mg/kg at the core bottom (49 cm) to 30 mg/kg at 12 cm. At 11 cm the concentrations
increases to 46 mg/kg but decrease gradually towards the surface of the core. Cadmium (Cd) has its
lowest values recorded in the lower (>30 cm) part of the core and the concentrations are less than 0.43
mg/kg below 10 cm core depth. Above 10 cm the concentrations increase to 0.70 mg/kg at 4-5 cm and
lower again to 0.37 mg/kg at the surface. Zinc (Zn) describes a similar trend as Cd, with a low at 99
mg/kg at 40 cm core depth and a maximum of 210 mg/kg at 8-9 cm. The lead (Pb) concentrations
describe two peaks, one at 10-11 cm of 52 mg/kg and one peak between 22 -27 cm of 45 mg/kg. The
lowest lead values are found at the core bottom, 22 mg/kg and from the peak at 10 cm the
concentrations decrease towards the sediment surface to 27 mg/kg.
A general trend for this core can be described with a narrow peak in Cu and Pb concentrations
correlating to 1967 and a broader peak in Cd and Zn concentrations during the 1970’s and 80’s. Also a
minor peak can be found in Cu, Zn, Cd and Pb from 25 down to 30 cm, it extends over time from c.
1910 and continues below the end of the graph at 1850.
4.2 Koljö Fjord
The heavy metal concentrations in the Koljö Fjord (core K4C, sampled 1999) are shown in figure 5. In
figure 6 the heavy metal concentrations of K4C are plotted to the corresponding timescale of the dated
core K6A (sampled 1999).
Chromium (Cr) concentrations fluctuate throughout the upper part of the core between the highest
levels at 15 cm (47 mg/kg) and the lowest value at the top of the core (27 mg/kg). The lower part of
the core varies between 30 and 40 mg/kg Cr. The concentration of copper (Cu) increases from the
lowest value at the core bottom (39 cm, 26 mg/kg) to the highest value (61 mg/kg) at 13 cm, which is
the first of two peaks. The second peak follows at 5 cm with a concentration of 60 mg/kg and
decreases towards the sediment surface down to 41 mg/kg. Zinc (Zn) concentrations also describe the
same two peaks at 13 and 5 cm (315 and 313 mg/kg respectively) and lower levels at the surface (188
mg/kg). The concentrations in the lower part of the core decrease gradually down to 96 mg/kg at the
bottom, but with a significant jump in the curve at 29 cm. Cadmium (Cd) concentrations are high
(1.5-2 mg/kg) from 29 to 3 cm, with a maximum of 2.20 mg/kg at 5 cm. The surface sample has a
somewhat lower concentration of 0.99 mg/kg as well as the samples below 30 cm (0.68-1.00 mg/kg).
The same jump at 29 cm, as seen in the Zn curve, is also noticeable in the Cd curve. The lead (Pb)
8
curve describes two peaks at 26 and 13 cm core depth at 59 and 64 mg/kg respectively. The lowest
values are found in the bottom of the core (27 mg/kg) as well as at the surface (32 mg/kg).
Obvious features in the Koljö Fjord core are the peaks at 5 and 13-15 cm visible to some extent in all
metals. The peak at 5 cm correlates to 1985 and the lower peak at 13-15 cm corresponds to the 1960’s.
The jump near the bottom at 30 cm (c. 1915-1925) is visible in Cu, Zn and Cd, but also in a lesser
degree in the Pb concentrations.
4.3 Gullmar Fjord
The heavy metal concentrations in the Gullmar Fjord (core Ga133 09 1, sampled 2009) are shown in
figure 7. In figure 8 the heavy metal concentrations of Ga133 09 1 are plotted to the corresponding
timescale of the dated core G01 113A (sampled 2001).
The chromium (Cr) concentrations are lowest at the surface (36 mg/kg) and consistently increase
down-core to a peak at 23 cm core depth. The second and highest peak (50 mg/kg) is at 39 cm.
Concentrations for copper (Cu) are also lowest at the surface (18 mg/kg), increasing down-core to 29
mg/kg at 23 cm. The lowest part of the core varies between 24 and28 mg/kg. Zinc (Zn) levels vary
from 105 mg/kg at the surface to 178 mg/kg at 23 and 39 cm core depth. There is little variation in the
cadmium (Cd) concentrations, the lowest Cd levels (0.10 mg/kg) are found at the surface and the
highest levels (0.30 mg/kg) at 23 cm. Lead (Pb) concentrations are also the lowest at the surface (28
mg/kg) and peak at 23 cm, and with a broad peak at 30-40 cm with the maximum concentrations of 53
mg/kg.
The lowest concentrations for all metals are found in the most recent sediments at the surface. The
peak at 23 cm correlates to c. 1970.
4.4 Sannäs Fjord
The heavy metal concentrations in the Sannäs Fjord (core SSK08 5E and SSK09 4,5B, sampled 2008
and 2009 respectively) are shown in figures 9 and 11. In figures 10 and 12 the heavy metal
concentrations of SSK08 5E and SSK09 4,5B are plotted to the corresponding timescale of the dated
cores ‘2000’ and ‘2002’ (sampled 2000 and 2002 respectively).
4.4.1 SSK08 5E
The lowest chromium (Cr) concentrations are measured at the surface sample at 39 mg/kg and the
highest levels are at 15 cm (55 mg/kg). In between these two points the concentrations fluctuate and
the bottom half of the core, below 15 cm, is fairly consistent in concentrations around 50 mg/kg with a
dip at 25 cm. The copper (Cu) levels vary between 30 and 40 mg/kg throughout the core, except for
the highest level of 45 mg/kg at 3 cm core depth and the lowest level of 28 mg/kg at the surface. Zinc
(Zn) levels are lowest at the surface (121 mg/kg) and rise to 198 mg/kg at the bottom (42 cm), with a
small peak at 3 and 15 cm and a dip at 25 cm. Cadmium (Cd) concentrations vary between the lowest
value of 0.47 mg/kg at the surface and the maximum value of 0.78 mg/kg at 3 cm. The Cd
concentrations curve shows peaks at 15 and 28-30 cm core depth. Lead (Pb) concentrations rise
throughout the core from the lowest value at the core surface (26 mg/kg) to the highest values of 50
mg/kg at 29 cm core depth. Peaks occur at 3 and 15 cm core depth.
The general trends in the SSK08 5E Sannäs Fjord core are the increase in concentrations down-core
and the peaks at 3 and 15 cm and a dip at 25 cm. These depths correspond to the years 2000, 1975 and
c. 1950 respectively.
9
4.4.2 SSK09 4,5B
The chromium (Cr) levels vary between the lowest concentrations at the surface and the highest at 25
cm core depth (40 and 55 mg/kg). The Cr concentrations show an increasing trend down core. The
copper (Cu) concentrations vary little between the lowest value of 30 mg/kg at 43 cm and the highest
level of 38 mg/kg at 25 cm. The zinc (Zn) concentrations are the lowest at the surface (129 mg/kg) and
the highest at 25 cm (195mg/kg). Cadmium (Cd) concentrations show two peaks, the highest of 0.73
mg/kg at 25 cm and the other peak is at 3 cm. The lowest levels are found at the surface (0.42 mg/kg)
and there are also low levels at 45 cm core depth. The lead (Pb) concentrations describe a gentle curve
from top to bottom, with the lowest value at the surface (32 mg/kg) and the highest value at 25 cm (52
mg/kg).
For all the metals there are declining trends in the top 4 cm (2003) with the lowest levels at the surface
(2009). Another trend that is found in all the metal concentrations is the peak at 25 cm core depth
which corresponds to a date around the mid 1950’s.
4.5 Dynekilen
The heavy metal concentrations in Dynekilen (core D3002A, sampled 2002) are shown in figure 13. In
figure 14 the heavy metal concentrations of D3002A are plotted to the corresponding timescale of the
dated core DI3002Ba (sampled 2002).
Chromium (Cr) concentrations are lowest at the surface (45 mg/kg) and from 2 to 16 cm the
concentrations describe a broad peak, with an extra peak at 14 cm (63 mg/kg). The bottom (43 cm)
half of the core varies little around 50 mg/kg. Copper (Cu) levels increase from the surface to the
highest concentration at 6 cm (53 mg/kg) from where they decline toward the lowest levels at the
bottom of the core (25 mg/kg). Zinc (Zn) concentrations describe a broad curve from top to bottom.
The highest concentration is found at 14 cm (249 mg/kg) and the lowest concentration at the bottom
(113 mg/kg). Cadmium (Cd) concentrations are 21 mg/kg both at the top and bottom of the core, in
between the concentrations rise to 41 mg/kg at 6 cm depth. Lead (Pb) also describes the same broad
curved trend with the highest concentration at 14 cm depth (75 mg/kg) and the lowest concentrations
at the bottom (29 mg/kg)
The heavy metal concentrations have all declined since 1991, which the upper values in all sediment
cores shows. The peak at 14 cm correlates to 1973 and at the bottom of the broad peak, which
occurred for all analyzed heavy metals, can be traced to c. 1950.
4.6 Accumulation rate
The accumulations are calculated from the top 20 cm of each dated core (Table 2). The results vary
from 2.9 mm/yr in the Havstens Fjord to 6.2 mm/yr in the Gullmar Fjord.
Table 2. Accumulation rate calculated on the top 20 cm of the cores.
K6A
4.1 mm/yr
H4A
2.9 mm/yr
G01 113A
6.2 mm/yr
Sannäs 2000
4.9 mm/yr
10
Sannäs 2002
5.5 mm/yr
DI3002Ba
4.9 mm/yr
Figure 3. Heavy metal concentrations from core H5A in the Havstens Fjord plotted against sediment
depth.
Figure 4. Heavy metal concentrations from core H5A in the Havstens Fjord plotted against 210Pb
dated age from the core H4A.
11
Figure 5. Heavy metal concentrations from core K4C in the Koljö Fjord plotted against sediment
depth. Note the different scale on the Cd concentrations bar.
Figure 6. Heavy metal concentrations from core K4C in the Koljö Fjord plotted against 210Pb dated
age from the core K6A. Note the different scale on the Cd concentrations bar.
12
Figure 7. Heavy metal concentrations from core Ga113 09 1 in the Gullmar Fjord plotted against
sediment depth.
Figure 8. Heavy metal concentrations from core Ga113 09 1 in the Gullmar Fjord plotted against
210
Pb dated age from the core G01 113A.
13
Figure 9. Heavy metal concentrations from core SSK08 5E in the Sannäs Fjord plotted against sediment depth.
Figure 10. Heavy metal concentrations from core SSK08 5E in the Sannäs Fjord plotted against 210Pb
dated age from the core Sannäs Fjord 2000.
14
Figure 11. Heavy metal concentrations from core SSK09 4,5B in the Sannäs Fjord plotted against
sediment depth.
Figure 12. Heavy metal concentrations from core SSK09 4,5B in the Sannäs Fjord plotted against
Pb dated age from the core Sannäs Fjord 2002.
210
15
Figure 13. Heavy metal concentrations from core DI3002A in Dynekilen plotted against sediment
depth.
Figure 14. Heavy metal concentrations from core DI3002A in Dynekilen plotted against 210Pb dated
age from the core DI3002Ba.
16
5 Discussion
The discussion is divided into three parts. The first part is concerning the usage of heavy metal
concentrations as a relative dating method, the second part discusses the discrepancy between the
heavy metal data and the dating in the Sannäs Fjord and the final part will assess the high cadmium
concentrations found in the Koljö Fjord.
The chromium concentrations are known to be mobile in the sediment between the surface and deeper
layers as mentioned in Cato (1997) and references therein. The Cr measurements will therefore be left
out from the interpretations and correlations in this study, but they are included in the diagrams to give
a complete summary of the analyses performed and they can be of value in future use of this data.
5.1 Relative dating markers
The general trends that are found in the cores from Koljö Fjord, Gullmar Fjord (only past 1950),
Dynekilen and Havstens Fjord (except lead concentrations) can be described by the rising of the
concentrations from low background values (before 1910). Furthermore peak of concentrations during
the 1970’s and 80’s from increased industrialization and domestic use of chemical products (e.g. paint,
batteries, wood impregnating and household chemicals). This trend is also observed in many other
locations worldwide as noted by Ridgeway and Price (1987), although the timing of the onset can
vary. The increase of environmental protection policies over the last few decades is visible in the
sediment as a decrease in metal concentrations in the top part of the cores.
One possible age marker can be found in the peaks in Pb and Cu concentrations found in all the cores
except for Sannäs Fjord (SSK09 4,5B). The peaks occur in a 6 year time interval in this data set. The
peak is recorded first in the southernmost fjords (Havstens Fjord and Koljö Fjord) in 1967, in the
Gullmar Fjord in 1969, at Dynekilen in 1974 and in 1975 in the Sannäs Fjord (Fig. 15). The time
difference for this occurrence is within the error of the dating method, meaning that it can be an
isochronous event. The decrease in concentrations near the top of the sediment core is not
simultaneous in the cores, and is therefore unsuitable as a direct age marker. Also in the bottom half of
the cores there are similarities in the curves, which are most clear at the oldest peak in the cores of the
Koljö Fjord, Havstens Fjord and Dynekilen. This peak occurs at c. 1900-1930, although the dating
method is more unreliable at this age, a similarity in shape is identifiable (Fig. 15).
The discussed marker peak is evident in most Cd and Zn curves as well except in the Havstens Fjord.
Several other peaks can occur at both younger and older ages in the cores which can makes
interpretation and relative dating imprecise. Although the features outlined in this study should be
sufficient to make a valid age estimate in for sediment cores from the study area. If a core is taken
from one of the sampling fjords, a direct correlation with the corresponding core in this study can give
a more precise age estimate.
The time of increase in concentrations near 1910 corresponds well to the dates observed by Suess and
Erlenkeuser (1975) that show an earlier onset in the Kiel Bight, but a later date in the Gotland Basin.
Also the onset of heavy metal concentrations in the Rana Fjord (Skei and Paus, 1979) show a similar
age of 1890±10.
17
Figure 15. Lead and copper concentrations plotted against the 210Pb dated timescale. The green line
marks the peak in concentrations that can possibly be used an age marker.
5.2 Background levels in the Sannäs Fjord
The general trends, as described above, with low background values from the time before increased
industrialization (1950 and 1910 in Koljö Fjord) are absent in both cores from the Sannäs Fjord. The
heavy metal record in the Sannäs Fjord describes an increase in concentrations towards the bottom of
the cores. These records could be interpreted as c. 50 year old sediments with a high sedimentation
rate as found in the Gullmar Fjord (Fig. 8), but the 210Pb datings (Fig. 2 and table 2) clearly suggest a
much lower sedimentation rate in the Sannäs. The concentrations in the bottom of the core are also
higher than concentrations found in the background values of the other cores. All the background
values at Koljö Fjord (except Cd, see next discussion) Havstens Fjord (except Pb) and Dynekilen are
within deviation Class 2 (slight deviation from reference value) of the reference values issued by the
SEPA (Table 1, SEPA, 2000), whereas the background values in the Sannäs Fjord are all in Class 3
(significant deviation from reference value).
It is unlikely for the heavy metal concentrations to describe a decreasing trend from the end of the
1800’s towards the present day given the industrial evolution and society’s development during the
time. The reason behind the anomaly can have different origins: these can be the dating method and
calculations, mobilization and re deposition of sediments or chemical processes in the sediments.
Different dating methods need to be used in this site to establish a 210Pb independent time scale to
evaluate the use of the 210Pb dating and the CRS model at the Sannäs Fjord sampling site.
5.3 Cadmium levels in the Koljö Fjord
The cadmium concentrations for the Koljö Fjord site are exceptionally high compared to the nearby
Havstens Fjord and the rest of the cores used in this study. Data from the Coastal Water Monitoring
Program of the Bohus coast (Cato, 2006) only shows high levels of Cd in surface sediments from Valö
(1,1 mg/kg dw in 2000) in Göteborgs southern archipelago. Very high Cd levels (over 10 mg/kg dw)
are recorded in sediments from the Ide Fjord, the most northern part of the Swedish west coast, but
these are only visible in the sediment record during the time of active pollution from c. 1960-1985
18
(Apler, 2007). The Cd concentrations in the Ide Fjord are < 0.4 mg/kg dw both before and after the
time of pollution, whereas the Koljö fjord Cd concentrations before 1900 also show high values (0.7-1
mg/kg dw).
The water exchange to the Koljö Fjord is mainly driven from the south, via the Havstens fjord (Björk
et al, 2000), making the Industrialized area around Uddevalla and Stenungsund (east shore of the
Havstens Fjord) possible sources of pollution. Regular surface sediment surveys, that have been done
in the Stenungsund area since 1981 (Cato, 2006), showed that all levels contained less than 1 mg/kg
dw Cd, in 1985 one site recorded 2.1 mg/kg dw, but the same site showed 0.16 mg/kg dw in 1995.
Together with the normal Cd concentrations in the Havstens Fjord it is considered unlikely for the
source to be the industry on the main land in Uddevalla and Stenungsund, although the industries can
still be contributing to the peak observed on top of the high background values. A peak in Cd
concentrations is recorded at the western end of the Koljö fjord, in a study of 6 sediment cores along
the profile of the Koljö Fjord system (Department of Earth Sciences, unpublished data). This implies
that the source of Cd should be local and persistent trough time to account for the high background
values in the sediments form before 1910.
The geochemical maps of the Swedish Geological Survey (Andersson, 2004) consist of systematic
analysis of silt-clay sized fractions of soil samples for a range of elements. The Cd map shows
concentrations between 0.03 and 0.10 mg/kg dw in the drainage areas to The Koljö, Havstens and By
Fjords, except for a small area northeast of the Koljö Fjord sampling site, where Cd concentrations are
0.10-0.17 mg/kg dw. If leaching of the the Cd concentrations on land is sufficient enough to take
account for the Cadmium recorded in the Koljö Fjord needs to be determined by a more detailed study
of land geochemistry and sediment records.
Cd is used as heat stabilizer in plastics and batteries (Cato, 1997). A source for the high levels of Cd
could be found in the numerous boatyards that exist on the island Orust located at the southern shore
of the Koljö Fjord sampling site. The boatbuilding industry has a long tradition on Orust, for at least
several hundred years. The yards started the production of plastic boats in the 1960’s (L. Bornmalm,
pers. comm., 2010). Because Cd and Zn behave similar Cd is present in many Zn rich products like
fertilizers (Cato, 1997). Zn levels are high in the upper part of the Koljö Fjord core which could be
caused by modern agriculture and can affect the Cd levels as well. Because Zn levels do drop whereas
Cd increases at c. 1890 the fertilizer does not answer the question about the pre 1900 levels of
cadmium. The boatbuilding industry is a likely candidate for the source of pollution, although the
amounts and application of Cd used during the 1800’s need to be looked at and a more detailed
research should be conducted to determine the source and spreading of Cd in the Koljö Fjord.
6 Conclusions
A peak in copper and lead concentrations is identified as a possible relative age marker in recent
marine sediments. The peak outlined corresponds to the dated sediment cores to roundabout 1970.
Questions about the 210Pb dating and the CRS model are outlined due to conflicting result in the heavy
metal concentrations on the Sannäs Fjord inner basin. This diverging result in the Sannäs Fjord
stresses the need for a different approach to confirm the results from this study.
The cadmium levels in the Koljö Fjord show high background levels and need further investigation to
determine the sources and spreading of Cd in the Koljö Fjord system.
19
Acknowledgements
I would like to thank my supervisor Prof. Kjell Nordberg for guiding me through this project and
taking time for my questions and thoughts. I would also like to thank Lennart Bornmalm for helping
me with preparations in the lab and giving me helpful comments. Owe Gustavsson and Johan
Hogmalm deserve thanks for helping me with the ICP-MS analyses and processing of the data. In
addition I would like to thank my opponent Linn Carlström Ödegaard for reading and improving my
final draft and Eelkje ten Kate for helping me with my English.
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21
Appendix A
CRS ages for the sediment cores used in this study, the age corresponds to the bottom of each sediment layer, the
sediment layers are 10 mm thick.
Core Depth
Koljö Fjord Havstens Fjord Gullmar Fjord Sannäs Fjord Sannäs Fjord Dynekilen
Bottom layer (cm) K6A
H4A
G01 113 A
2000
2002
D13002Ba
1
1997
1996.7
2000.4
1997.5
2001.4
2001.5
2
1995
1993.9
1999.6
1996.2
1999.7
2000.2
3
1992
1990.8
1998.7
1994.5
1998.2
1998.7
4
1989
1987.6
1997.4
1992.7
1996.6
1997.2
5
1986
1984.4
1996.1
1990.8
1994.9
1995.4
6
1984
1981.1
1994.9
1988.9
1992.9
1993.5
7
1981
1977.7
1993.5
1986.9
1990.9
1991.5
8
1978
1975.1
1991.9
1984.8
1989
1989.3
9
1976
1972
1990.3
1982.6
1986.7
1987.1
10
1974
1969.4
1988.6
1980.5
1984.9
1984.7
11
1972
1965.9
1987
1978.3
1983.3
1982.5
12
1970
1962.5
1985.1
1976.3
1981.5
1980.2
13
1966
1959.5
1983.1
1974.1
1979.9
1978.1
14
1964
1955.9
1981.2
1971.8
1978
1975.8
15
1961
1952.3
1979.4
1969.5
1975.9
1973.5
16
1959
1948.2
1977.5
1967.1
1973.6
1971.1
17
1956
1944
1974.8
1964.5
1971.5
1968.7
18
1953
1939
1972.8
1961.9
1969.3
1966.1
19
1951
1933.7
1970.4
1959.3
1967
1963.3
20
1948
1928.6
1968.3
1956.7
1964.8
1960.7
21
1946
1922.3
1966.5
1954
1963
1958.2
22
1943
1914
1964.9
1951.3
1960.5
1955.6
23
1940
1904.9
1963
1948.5
1957.9
1953
24
1936
1892
1960.6
1945.7
1955.3
1950.9
25
1933
1874.5
1958.2
1942.8
1952.7
1947.8
26
1930
1854
1956.2
1939.5
1949.3
1945
27
1927
1823.5
1953.9
1936.2
1946.3
1942
28
1924
1951.6
1932.9
1943
1938.8
29
1921
1948.6
1929.8
1939.1
1935.5
30
1917
1945.6
1926.8
1934.8
1932.2
31
1913
1942.8
1924
1930.7
1928.5
32
1909
1939.1
1920.9
1925.9
1925.2
33
1905
1936.5
1917.4
1920.7
1921.3
34
1902
1932.6
1914
1915.4
1917.3
35
1898
1910.3
1909.7
1913.5
36
1894
1906.6
1902.3
1909.3
37
1890
1903.1
1893.9
1904.6
38
1885
1899.2
1884.8
39
1881
1894.7
1873.1
40
1877
1890.2
1859.2
41
1872
1885
1837.2
42
1867
1879.4
43
1862
1873.2
44
1857
1865.8
45
1853
1856.9
46
1848
1845.1
47
1843
1828.4
48
1838
49
1833
50
1828
51
1823
52
1818
53
1813
Appendix B
Heavy metal concentrations for the cores used in this study. The sediment depth corresponds to the middle of the
sampled slice. Slices are 10 to 20 mm thick.
Havstens Fjord H5A
Sediment depth Cr /
Cu /
mid layer (cm)
53
65
0.5 35.05 25.55
2.5 38.19 29.69
4.5 38.79 30.63
6.5 40.14 32.18
8.5 43.21 34.89
10.5 44.05 47.00
12.5 42.21 27.13
14.5 43.21 25.42
16.5 40.29 22.82
18.5 40.58 23.05
20.5 38.32 23.49
22.75 42.07 24.97
25 43.24 24.22
27.25 41.49 24.15
28.5 41.80 22.34
30.5 42.85 21.60
34.5 42.67 19.98
36.5 42.08 19.78
38.5 40.92 19.97
40.5 41.21 19.21
42.5 40.81 20.11
44.5 41.44 20.89
46.5 42.66 21.03
48.5 41.92 20.26
Zn /
Cd /
Pb /
66
111
208
145.07
0.37 27.57
184.90
0.54 27.34
189.15
0.70 31.98
189.45
0.66 35.99
210.22
0.65 42.97
193.11
0.44 52.15
169.96
0.37 42.20
163.05
0.31 38.73
146.52
0.35 31.80
144.34
0.32 32.31
152.52
0.41 34.92
158.03
0.29 45.13
150.98
0.31 44.60
147.16
0.43 44.00
130.47
0.33 40.17
120.74
0.25 35.14
108.13
0.20 28.32
106.09
0.21 27.29
103.17
0.23 26.33
99.78
0.18 24.60
100.14
0.25 24.23
106.37
0.25 26.01
103.35
0.25 23.39
101.39
0.24 22.45
Koljö Fjord K4C
Sediment depth
mid layer (cm)
0.5
2.5
4.5
6.5
8.5
10.5
12.5
14.5
16.5
18.75
21.75
24.5
26.5
28.5
30.5
31.5
35.5
37.5
39.5
Zn /
Cd /
Pb /
66
111
208
187.51
0.99 31.64
250.96
1.38 39.85
314.90
2.20 48.34
240.08
1.61 40.28
262.33
1.52 53.18
281.98
1.80 55.00
312.69
1.91 63.79
245.02
1.51 47.82
230.88
1.51 46.93
223.87
1.60 42.07
206.77
1.76 44.47
205.52
1.42 48.95
191.95
1.72 58.61
195.16
1.35 51.32
117.54
0.68 41.88
116.99
0.88 40.01
106.20
0.99 32.02
101.45
0.96 29.79
96.29
0.83 26.76
Cr /
Cu /
53
65
29.66 41.04
37.15 54.56
38.27 59.62
30.52 45.05
39.58 51.87
36.15 55.22
41.83 60.67
47.07 42.25
36.49 40.21
35.10 37.32
31.23 33.67
34.47 34.66
38.30 35.02
37.63 34.11
36.28 26.17
37.63 27.93
37.61 28.53
36.40 28.58
33.97 26.10
Gullmar Fjord Ga 113 09 1
Sediment depth Cr /
Cu /
mid layer (cm)
53
65
0.5 35.67 19.76
1.5 39.44 24.47
2.5 39.90 23.35
3.5 40.44 24.74
5 40.39 24.27
7 41.25 24.25
9 41.84 24.69
11 41.41 25.31
13 42.83 25.02
15 43.32 25.56
17 44.71 25.54
19 45.11 27.41
23 48.10 29.49
27 45.08 29.39
31 45.41 26.69
35 47.20 28.28
39 49.81 28.03
43 48.96 27.10
47 47.86 25.93
51 47.98 27.02
55 45.77 24.40
Zn /
Cd /
Pb /
66
111
208
105.75
0.10 27.97
116.75
0.11 30.36
119.47
0.12 31.23
124.13
0.11 32.47
124.47
0.11 32.10
129.24
0.12 34.24
134.10
0.16 35.02
131.64
0.19 36.63
136.84
0.26 37.72
142.87
0.25 40.24
147.00
0.20 43.95
151.67
0.23 45.23
173.74
0.30 52.47
156.46
0.24 48.08
166.76
0.24 51.73
176.99
0.30 53.00
177.51
0.21 52.70
172.47
0.28 50.15
154.79
0.19 45.42
156.86
0.19 45.28
151.96
0.18 43.83
Sannäs Fjord SSK08-5E
Sediment depth Cr / Cu /
Zn /
Cd /
Pb /
mid layer (cm)
53
65
66
111
208
0.5 38.7
28.1
121 0.472
26.3
1.5 50.4
35.9
152 0.613
33.4
2.5 42.4
33.8
143 0.594
32
3.5 54.9
41.1
183 0.778
39.1
4.5 45.7
35.1
150 0.682
34.2
5.5 47.7
35.6
153
0.66
34
7.5 41.9
33.9
146 0.666
33.8
9.5
46
36.4
158 0.613
39.6
11.5 49.9
34.9
154
0.6
39.9
13.5 49.3
36
157 0.582
40.3
15.5 55.3
40
179
0.75
45.4
17.5 50.8
35.5
164 0.636
41.9
19.5 49.8
33.6
172 0.627
42.3
21
53
34.3
163 0.575
42.8
23 53.6
34.9
169 0.579
45.2
25 45.3
30.2
152 0.569
42.5
27 50.5
39.1
172 0.714
48.3
29 51.5
34.9
183 0.721
50.3
33 51.1
33.6
181
0.67
49.1
37 51.4
32.2
188
0.62
47.6
41 53.2
33.3
193 0.657
48.4
Sannäs Fjord SSK09-4,5B
Sediment depth Cr /
Cu /
mid layer (cm)
53
65
0.5 40.69 32.36
1.5 42.99 33.61
2.5 45.05 36.41
3.5 45.92 37.07
4.5 44.79 36.52
5.5 45.33 36.67
7.5 45.59 37.22
9.5 44.08 34.67
11.5 46.20 35.79
13.5 47.59 37.38
15.5 47.63 37.18
17.5 47.51 35.40
19.5 48.83 35.60
21.5 48.24 34.89
23.5 48.56 35.53
25.5 55.24 38.62
27.5 48.74 33.82
29.5 49.30 32.98
31.5 50.59 33.59
33.5 49.45 32.91
35.5 49.19 32.14
37.5 51.30 33.38
39.5 52.96 33.21
41.5 50.61 32.33
43.5 48.99 30.16
45.5 48.55 30.56
47.5 50.04 30.89
49.5 49.75 30.23
50.5 50.43 32.22
Zn /
Cd /
Pb /
66
111
208
129.19
0.42 31.67
134.34
0.51 32.03
145.99
0.59 33.99
152.74
0.71 35.07
147.28
0.61 34.62
149.93
0.60 35.22
151.75
0.62 35.49
148.43
0.59 36.36
155.25
0.58 41.07
160.14
0.63 41.62
161.12
0.66 42.47
162.18
0.62 43.81
171.01
0.65 46.98
170.01
0.63 46.98
175.00
0.66 47.98
195.61
0.73 52.04
174.79
0.62 49.38
177.82
0.55 49.89
186.99
0.62 49.83
184.15
0.61 48.68
182.50
0.61 48.16
184.35
0.60 48.62
181.44
0.54 48.17
174.77
0.50 47.02
165.96
0.47 45.35
165.31
0.44 44.58
169.94
0.49 45.11
168.48
0.51 42.55
174.78
0.52 42.98
Dynekilen DI3002A
Sediment depth Cr /
Cu /
mid layer (cm)
53
65
0.5 44.81 32.31
2.5 51.73 38.44
4.5 55.21 52.17
6.5 58.14 53.41
8.5 56.30 50.06
10.5 57.60 46.25
12.5 53.26 42.47
14.5 62.90 48.85
16.5 51.17 40.26
18.5 51.63 39.31
20.5 50.64 37.97
22.5 46.76 32.55
24.5 46.05 32.03
26.5 46.17 32.98
28.5 48.45 32.73
30.5 49.01 30.40
32.5 48.85 29.99
34.5 50.02 28.16
36.5 49.20 26.17
39.5 50.25 27.35
41.5 49.57 25.66
Zn /
Cd /
Pb /
66
111
208
132.58
0.21 36.12
163.66
0.24 46.36
181.69
0.36 50.78
198.75
0.42 56.09
198.55
0.41 57.83
213.53
0.42 63.26
208.36
0.39 63.32
249.01
0.42 74.95
206.38
0.34 64.13
203.93
0.36 63.29
193.88
0.31 60.37
174.11
0.27 54.86
169.28
0.27 53.45
165.50
0.25 52.58
159.32
0.24 54.32
152.15
0.22 55.46
143.68
0.23 56.63
135.73
0.25 48.71
122.51
0.24 37.37
119.26
0.22 32.12
112.73
0.21 29.01