Atmospheric Environment xxx (2013) 1e8
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Atmospheric Environment
journal homepage: www.elsevier.com/locate/atmosenv
Anthropogenic sources of VOC in a football stadium: Assessing human
emissions in the atmosphere
Patrick R. Veres, Peter Faber, Frank Drewnick, Jos Lelieveld, Jonathan Williams*
Max Planck Institute for Chemistry, 55128 Mainz, Germany
h i g h l i g h t s
VOC and CO2 were measured using PTR-MS-TOF during a football match.
The human emission ratios of VOC are extrapolated to the global scale.
Ethanol was found to be the dominant gas phase VOC during a football match.
VOC tracers of smoking, drinking and skin oxidation by ozone were observed.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 December 2012
Received in revised form
17 April 2013
Accepted 7 May 2013
Measurements of gas-phase volatile organic compounds (VOCs), aerosol composition, carbon dioxide
(CO2), and ozone (O3) were made inside Coface Arena in Mainz, Germany (49 590 300 N, 8 130 2700 E) during a
football match on April 20 2012. The VOC measurements were performed with a proton-transferreaction time-of-flight mass spectrometer (PTR-TOF-MS). Observed VOCs could be classified into
several distinct source categories including (1) human respiration/breath, (2) ozonolysis of skin oils, and
(3) cigarette smoke/combustion. In this work, we present a detailed discussion on the scale and potential
impacts of VOCs emitted as a result of these sources and their contributions on local and larger scales.
Human emissions of VOCs have a negligible contribution to the global atmospheric budget (w1% or less)
for all those quantified in this study. However, fluxes as high as 0.02 g m2 h1 and 2 104 g m2 h1,
for ethanol and acetone respectively are observed, suggesting the potential for significant impact on local
air chemistry and perhaps regional scales. This study suggests that even in outdoor environments, situations exist where VOCs emitted as a result of human presence and activity are an important
component of local air chemistry.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Football
Soccer
PTR-MS
VOC
Stadium
Breath
Skin
1. Introduction
Since the dawn of civilization, people have been gathering en
masse to watch various sporting and theatrical events. From the
gladiatorial contests, plays and the public spectacles of the Roman
coliseum to the more contemporary FIFA World Cup tournament,
tens of thousands of people have been gathering in search of
entertainment and camaraderie. For football (otherwise known as
soccer) crowds in excess of 200,000 have been recorded for a single
match at the Macarana stadium in Brazil. In Germany, where this
study was conducted, some 1224 Bundesliga (German Football
league) matches are played each season at 35 stadiums, all with a
capacity for over 25,000 spectators. In addition to sporting events,
* Corresponding author.
E-mail address: [email protected] (J. Williams).
concerts, demonstrations, fetes, fairs and festivals all serve to
congregate large crowds of people into a relatively confined space
thereby allowing direct human emissions via skin, breath, and activities such as smoking to significantly alter the local atmosphere.
The impact of humans on the atmosphere has focused on contributions from a particular physical action (e.g. burning biomass) or
man-made creation (e.g. the car), collectively anthropogenic sources. Global atmospheric budgets have been compiled to quantify
various anthropogenic emission sources such as traffic emissions,
industrial activity, deforestation (Bo et al., 2008; Piccot et al., 1992).
Few studies have focused on the human being as a respiratory
source or a reactive surface for the generation and removal of atmospheric trace gases. Human impact on air quality has been previously examined, particularly in enclosed spaces such as offices
(Wisthaler and Weschler, 2010) and aircraft cabins (Weschler et al.,
2007; Wisthaler et al., 2005). Other practitioners have independently determined VOCs in human breath in order to develop
1352-2310/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.atmosenv.2013.05.076
Please cite this article in press as: Veres, P.R., et al., Anthropogenic sources of VOC in a football stadium: Assessing human emissions in the
atmosphere, Atmospheric Environment (2013), http://dx.doi.org/10.1016/j.atmosenv.2013.05.076
2
P.R. Veres et al. / Atmospheric Environment xxx (2013) 1e8
2. Experimental section
measurement location indicated by a yellow star. Throughout the
measurement period the stadium remained largely empty with the
exception of a Bundesliga football match between Mainz 05 vs. VfL
Wolfsburg, on April 20, 2012. During the evening of the football
match on April 20 the official attendance was approximately 31,000.
A single inlet from which all instruments sub-sampled was
positioned at a height of approximately 12 m above ground level in
an entryway located between a full vertical break in the seating
areas on the downwind portion of the stadium. Seventeen food
outlets were located around the outer ring of the stadium, at
ground level, underneath the seating areas. Each station was
equipped with grills for cooking, deep fat fryers, and alcoholic and
non-alcoholic beverages.
An evening match was selected (8:30 pm local time, UTC þ2) so
that the extent of turbulent induced ventilation of the stadium is
minimized. The evening game reduces the complicating effects of
photochemical sources, traffic emissions, and photo-induced
biogenic emissions. Measurements from a nearby meteorological
station, Fig. 1 yellow star, measured nighttime wind speeds of
approximately 1 m s1. Coface arena is a “state of the art” stadium
located on the edge of the city within a generally agricultural area
(see Fig. 1). Conditions during the evening game were considered
optimal for studying the emissions and chemistry within the
football stadium while providing a minimal amount of mixing with
VOC sources external to the stadium.
2.1. Field site
2.2. Instrumentation
A suite of instruments was deployed and operated in the
northeast corner of the Coface Arena (49 590 300 N, 8 130 2700 E) in
Mainz Germany from the afternoon of April 20 until midday April
23. An aerial view of the stadium is shown in Fig. 1 with the
VOC measurements were performed using a commercial PTRTOF-MS instrument from Ionicon Analytik GmbH (Innsbruck,
Austria). The PTR-TOF-MS was configured with a mass resolution of
approximately 3700 m/Dm. Mass spectra were collected ranging
medical applications (Beauchamp, 2011). A review of VOCs in breath
suggests that while it is unlikely that humans are a significant source
on a regional and global scale, breath emissions are important indoor sources of VOCs (Fenske and Paulson, 1999). The strong, diverse
and rapidly changing flux emissions expected during a football
match provide an ideal test bed for recently developed instrumentation as well as an opportunity to uncover atmospheric chemical
processes in a hitherto unexplored environment.
Here we describe simultaneous, high time resolution measurements of ambient mixing ratios of VOCs using proton-transferreaction time-of-flight mass spectrometry (PTR-TOF-MS) and a
Li-COR CO2 analyzer. Measurements were performed inside the
Coface Arena in Mainz, Germany (49 590 300 N, 8 130 2700 E) from April
20 to April 23, 2012 during which the Mainz 05 vs. VfL Wolfsburg
Bundesliga football match was played on the evening of April 20,
2012 resulting in a 0:0 draw. Co-located real-time measurements of
aerosol using a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) will be discussed in a companion paper
(Faber et al., 2013). Measurements within the football stadium
during the match presents an interesting test of the human impact
on outdoor air quality. To our knowledge, the extent of atmospheric
impact that these large crowds pose has yet to be studied and
therefore remains largely unknown.
Fig. 1. An aerial photograph of Coface Arena taken from the southwest direction with the location of the instrumentation and the inlet, yellow star, and the location of the Max
Planck Institute for Chemistry where the external meteorological data were collected from the rooftop, red star, indicated. The stadium is largely surrounded by agricultural land
with the Johannes Gutenberg University to the Northeast. (Photo Copyright Coface Deutschland AG). (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
Please cite this article in press as: Veres, P.R., et al., Anthropogenic sources of VOC in a football stadium: Assessing human emissions in the
atmosphere, Atmospheric Environment (2013), http://dx.doi.org/10.1016/j.atmosenv.2013.05.076
P.R. Veres et al. / Atmospheric Environment xxx (2013) 1e8
from m/z 10e500. The instrument was operated with a drift voltage
of 600 V and a drift pressure of 2.20 mbar (E/N 140 Td). Internal
mass calibration of the PTR-TOF-MS was performed by permeating
1,3,5-trichlorobenzene into a 1 mm section of 1.58 mm o.d. Teflon
tubing used in the inlet flow system controlled to 60 C. Post
acquisition data analysis was performed according to procedures
described elsewhere (Mueller et al., 2011, 2010; Titzmann et al.,
2010). VOC concentrations are reported in parts-per-billion by
volume (ppbv). Standards for isoprene, acetone, acetonitrile, benzene, and toluene were purchased as pressurized gas bottle standards (Apel-Riemer Environmental) while ethanol, diacetyl,
6-methyl-5-hepten-2-one (6-MHO), and decanal were dynamically produced using the mobile oxidation carbon calibration system (MOCCS) technique described elsewhere (Veres et al., 2010).
CO2 was measured at 1 Hz using a Li-COR Li-7000 system. Ozone
measurements were determined by the absorption of ultraviolet
3
light (254 nm) with a time resolution of 1 min using the Airpointer
gas measurement system (Recordum Messtechnik GmbH, Austria).
Two meteorological stations were used to monitor conditions inside and external to the stadium, indicated by stars in Fig. 1. A highresolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS)
was also deployed for the measurement of aerosol properties.
Instrumental details and a discussion of observed organic particulate matter using Positive Matrix Factorization (PMF) can be found
elsewhere (Faber et al., 2013).
3. Results and discussion
The top panel of Fig. 2 shows a time series of the enhancement
of CO2 mixing ratio above background levels for the entire measurement period. Ambient CO2 background (395 ppmv) has been
subtracted from the ambient measurements. In the absence of a
100
Ambient CO2 Enhancement above 395 ppmv background
Approximated Stadium Background
Football Game Contribution
CO2, ppbv
80
60
40
20
0
Isoprene, ppbv
4
Isoprene, Ambient
Isoprene, Stadium Background
Isoprene, Football Game Contribution
3
2
1
0
Ethanol, ppbv
400
Ethanol, Ambient
Ethanol, Stadium Background
Ethanol, Football Game Contribution
300
200
100
0
Acetone, ppbv
5
Acetone, Ambient
Acetone, Stadium Background
Acetone, Football Game Contribution
4
3
2
1
0
12:00 AM
4/21/12
12:00 PM
12:00 AM
4/22/12
Date and Time
12:00 PM
12:00 AM
4/23/12
Fig. 2. Time series of enhanced CO2, isoprene, ethanol, and acetone for the entire duration of measurements made within the football stadium. All gas phase species presented in
this manuscript are significantly elevated during the football match (April 20 2012, 8:30 pm local time) in comparison to the remainder of the measurement period. Background
levels not related to the football match are approximated by applying a smoothing spline to the measured data in the absence of the football match (red trace). The difference in the
ambient measurement and the stadium background yields the enhancement in VOCs as a direct result of the football match. (For interpretation of the references to colour in this
figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: Veres, P.R., et al., Anthropogenic sources of VOC in a football stadium: Assessing human emissions in the
atmosphere, Atmospheric Environment (2013), http://dx.doi.org/10.1016/j.atmosenv.2013.05.076
P.R. Veres et al. / Atmospheric Environment xxx (2013) 1e8
Table 1
Summary of emission ratios relative to CO2 ðERCO2 Þ for the breathing and smoking
sources, percent contribution of smoking sources to ambient measured breath and
ozonolysis products, and global annual emission estimates from humans compared
to previously published global budgets including all known sources where possible.
Analyte
Cigarette
source (%)
Breath emissions
Ethanol
<1
Acetone
17 (7)
Isoprene
55 (18)
Ozonolysis products
6-MHO
3 (1)
Decanal
<1
Cigarette emission
Isoprene
Acetone
6-MHO
Acetonitrile
Benzene
Diacetyl
Toluene
ER CO2 a
4.3 (0.5)
0.042 (0.004)
0.020 (0.005)
ER CO2 a
0.01 (0.001)
0.0018 (0.0016)
ER CO2 f
5.0 (0.6)
0.5 (0.3)
0.02 (0.01)
2.1 (0.3)
0.5 (0.1)
1.4 (0.2)
0.7 (0.1)
Source
(Tg yr1)
Global budget
(Tg yr1)
0.39b
0.12
0.06
146d
535e
42
c
0.05
0.02
a
Units are given in (ppbv)(ppmv CO2 emitted in breath)1, 1s errors in
parenthesis.
b
Breath source corrected for average global alcohol consumption and natural
emission.
c
Kirstine and Galbally, 2012.
d
Fischer et al., 2012.
e
Guenther et al., 2012.
f
Units are given in (ppbv cigarette factor)(ppmv CO2 emitted in cigarette
smoke)1, 1s errors in parenthesis.
Ethanol, ppbv
120
100
400
80
300
60
200
40
100
20
0
0
Ozonolysis Products
100
6-MHO, ppbv
1.0
80
0.8
60
0.6
0.4
40
0.2
20
0.0
2.0
0
Smoking/Combustion
100
1.5
80
60
1.0
40
0.5
20
CO2 Enhancement, ppmv
The upper panel of Fig. 3 shows a time profile of the game time
CO2 (shaded grey) from the time just prior to the steady arrival of
spectators (indicated with the dotted line, w6:30 pm) through the
Human Respiration/Breath
CO2
CO2 Enhancement, ppmv
3.1. Human respiration
500
CO2 Enhancement, ppmv
football match, concentrations of CO2 build up inside the stadium in
the late afternoon and throughout the night. The most likely
emission source of CO2 inside the stadium is nighttime respiration
of the grass and other biogenic sources external to the stadium
causing a net flux of CO2 to the atmosphere (Hiller et al., 2011). The
red trace in Fig. 2 is an approximation of the background CO2 levels
in the absence of the football event. The difference of the ambient
measurements and this background approximation gives the
approximate game time contribution to measured CO2 (CO2 football source). The scatter around zero of the non-game time CO2
gives a measure of the uncertainty associated with this method of
background subtraction (20% of game time measured CO2). In
addition to CO2, several VOCs were significantly elevated, greater
than two-fold increase, during the match with respect to the
remainder of the measurement period. Table 1 summarizes the
observed VOC measurements. VOCs were background corrected
using the method described for CO2, the results of this correction
are presented in Fig. 2 for various examples.
The remainder of this paper focuses on emission sources and
corresponding temporal variations of the VOCs observed
throughout the football match. Observed VOCs have been categorized into three source groups: (1) human respiration/breath, (2)
ozonolysis of skin oils, and (3) cigarette smoke/combustion. Fig. 3
shows an example time series from each of these source groups.
An explanation of each assignment and discussion of the most
abundant VOCs will be provided in detail in the following sections.
Some VOCs appear to be emitted by a single source type; however,
multiple emission sources may be involved. In this case, an
approximate source contribution is estimated and included in
Table 1. A discussion of this analysis will be given in later sections.
Acetonitrile, ppbv
4
0
6:00 PM
4/20/12
8:00 PM
10:00 PM
12:00 AM
4/21/12
Date and Time
Fig. 3. Representative VOCs from the three emissions sources identified in the football
stadium: Human respiration/breath (upper), ozonolysis products (middle), and
smoking/combustion (lower). The top panel shows a time series of the stadium source
of CO2 and ethanol. The dotted line indicates the time at which the stadium was
steadily beginning to fill with fans, and the shaded areas (green) represent the first and
second half of the football match with a break for halftime. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of
this article.)
late evening after the stadium had cleared (w12:00 am). The green
shaded regions identify the first and second halves of the game
with the halftime break in between. It is clear from the timing of
the enhancements in CO2 above the observed background levels
(w395 ppmv) that the observed increase is directly related to the
arrival and departure of people to and from the stadium. The most
likely source of CO2 within the stadium during this time period is
human respiration. The contribution of cigarette smoking to CO2
has been determined to be negligible (<2%) and will be discussed in
detail later in Section 3.3.
The upper panel of Fig. 3 shows a comparison of the football
match source of CO2 to measured ethanol. In most urban influenced
ambient air studies of VOCs, the most abundant species are acetone
(0.1e2 ppbv), methanol (0.5e2 ppbv), and aromatics (Gros et al.,
2011); however, these “typical” ambient VOCs are dwarfed by the
mixing ratio of ethanol. The availability of alcoholic beverages in the
Please cite this article in press as: Veres, P.R., et al., Anthropogenic sources of VOC in a football stadium: Assessing human emissions in the
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P.R. Veres et al. / Atmospheric Environment xxx (2013) 1e8
VTidal
dB
MVOC
L
dt
22:4 mol
(1)
where %CO2 is the average CO2 in exhaled air in units of ppmv (4%
CO2 ¼ 4 104 ppmv, (Pleil and Lindstrom, 1995), Vtidal is the average
volume of a lung (0.5 L), dB/dt is an average breathing rate
(15 breaths min1 (Sherwood, 2006; Tortora and Anagnostakos,
1990), and MVOC is the molecular mass of the VOC. ERCO2 is the
average of the ratio of the breath-related VOC to the CO2 contribution
from breath observed during the three-hour period encompassing
the match. It is important to note that by using ratios of VOCs to CO2
enhancement this calculation is independent of the number of fans
in attendance. Multiplying the result of Equation (1), [VOC]annual by 7
billion (the approximate global population) we arrive at an approximation of human breath contribution to the global atmospheric VOC
budget. The results of this calculation are summarized in Table 1 and
compared to known total global budgets where available.
The ethanol source derived using this methodology (10.2 Tg yr1)
is overestimated, as alcohol consumption during the match is higher
than the global average. To better illustrate this we can calculate the
average blood alcohol content (%BAC) using this measured ethanol
to CO2 emission ratio. A direct relationship between ethanol concentrations in breath and %BAC has previously been established
(Jones and Andersson, 2003). Using this relationship, the average %
BAC for a fan in attendance at the football match between kickoff and
the end of the match was determined to be 0.028%, a level that leads
to loss of judgement, relaxation, slight body warmth and an altered
mood (CDC, 2011). Fig. 4 shows a time series of ethanol and calculated %BAC throughout the duration of the football match.
In an attempt to better quantify the bias in our calculated
emission source, we can use reported global alcohol consumption
data for comparison. In 2011 World Health Organization (WHO)
reports that the global yearly average adult per capita consumption
of alcohol is 7.89 L (WHO, 2011). This equates to an average consumption rate of 0.9 mL h1, roughly a %BAC of 0.001, over 25 times
lower than that observed throughout the match. The figures provided by the World Health Organization apply only to the global
population over the age of fifteen, 75% (Agency, 2008), therefore,
correcting our initial ethanol source estimate (10.2 Tg yr1) by a
0.74 population factor and adjusting downward by a %BAC factor of
0.036, the ratio of the WHO %BAC to %BAC in the football stadium,
yields an approximate global ethanol source from human exhalation of 0.27 Tg yr1. To this approximation, we must add ethanol
emitted naturally in breath not directly related to consumption of
alcohol. Using the average mixing ratios observed in Fenske and
Paulson (1999), we calculate ERCO2 as 0.043 that translates into
an annual human ethanol emission of 0.12 Tg yr1. A summation of
120
Ethanol
CO2
%BAC
500
100
400
0.08
BAC, %
80
60
0.06
40
0.04
20
0
0.02
7:00 PM
4/20/12
8:00 PM
9:00 PM
10:00 PM
300
Ethanol. ppbv
½VOCannual ¼ ERCO2 %CO2 0.10
CO2 Breath, ppmv
stadium, lack of other plausible sources, and strong correlation with
CO2 suggests that the dominant source of ethanol is via emission
from exhalation. Direct evaporation of ethanol and CO2 from alcoholic beverages is also a plausible source to the stadium atmosphere.
While the CO2 source from beer would be several orders of magnitude smaller than CO2 from breath, it is difficult to approximate the
source of ethanol from spillage and direct evaporation from beer to
any reasonable degree. Therefore we consider any calculations
involving ethanol from breath an upper limit. Observed acetone can
be primarily assigned to emission from human breath, though a
secondary acetone source from cigarette smoking has been
approximated as 15e20% of the measured ambient acetone. Details
of the source factor analysis used are presented in Section 3.3.
Emission ratios of VOC to CO2 (ERCO2 , in units of ppbv VOC per
ppmv CO2) can be used to extrapolate the average annual per capita
contribution of a VOC to the atmosphere with the following
approximation:
5
200
100
0
11:00 PM
Date and Time
Fig. 4. Time series of ethanol (blue), CO2 from breath (grey), and blood alcohol content
(%BAC, black) calculated from ethanol and CO2 measurements throughout the football
match. (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
these two factors, ethanol in breath from consumption of alcohol
and ethanol naturally emitted in breath, we arrive at a global
ethanol budget from human breath of 0.39 Tg yr1.
The most recent estimates of the global ethanol budget range
from 22 to 56 Tg yr1, the largest contribution is from terrestrial
plants with a mean flux estimated as 6.3 105 g m2 h1 (Kirstine
and Galbally, 2012). The annual contribution of human breath is an
insignificant fraction (w1%) of the global ethanol budget; however,
the average flux of ethanol over the three-hour period encompassing the match is 0.02 g m2 h1, higher than other known
natural emission rates. This large flux suggests that breath emissions of ethanol can be important on a local scale during events
where a high density of people and consumption of alcohol are
present.
ERCO2 for acetone was found to be 0.043 (0.12 Tg yr1) during the
football match. Emission of acetone from breath is insignificant in
comparison to the estimated global budget of acetone of
143 Tg yr1 (Fischer et al., 2012). The acetone flux from the football
stadium (2 104 g m2 h1) is on the order of the flux expected
from forest plants (2.4 104 g m2 h1) (Guenther et al., 2012).
Therefore, particularly in densely populated urban areas, acetone
emission from human breath is potentially a non-negligible source
of atmospheric acetone on a local scale.
Ethanol and acetone are expected to increase the rate of production of PAN via the following chemistry. Ethanol will likely react
via proton abstraction reactions with hydroxyl radicals (OH). The
dominant product of the oxidation of ethanol is acetaldehyde
(Carter et al., 1979; Grosjean, 1997), which is subsequently removed
from the atmosphere by photolysis and reaction with OH (Atkinson,
1986, 1990) in the presence of NO2 leading to the formation of
peroxyacetyl nitrate (PAN). Additionally, atmospheric oxidation of
acetone to PAN significantly contributes to the global PAN budget
(Singh et al., 1995, 1994). PAN is a strong lachrymator and key
component of photochemical smog. Therefore downwind from the
football stadium, PAN formation rates are expected to be elevated
as a result of the considerable fluxes of both ethanol and acetone.
3.2. Ozonolysis of skin oils
Recent work has shown the potential for the production of
secondary oxidation products via surface ozonolysis reactions
with human skin oils in enclosed environments (Tamas et al., 2006;
Weschler et al., 2007; Wisthaler et al., 2005; Wisthaler and Weschler,
2010). Additional studies have observed similar reactions on surfaces
Please cite this article in press as: Veres, P.R., et al., Anthropogenic sources of VOC in a football stadium: Assessing human emissions in the
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P.R. Veres et al. / Atmospheric Environment xxx (2013) 1e8
that have come in contact with skin oils directly as well as oil soaked
clothing (Coleman et al., 2008). Humans have been identified as a
potential ozone sink as well as a source for secondary environmental
pollutants based on measurements of these ozonolysis reactions
(Coleman et al., 2008; Pandrangi and Morrison, 2008; Rim et al.,
2009; Tamas et al., 2006; Weschler et al., 2007). Products of this
ozonolysis chemistry have been previously measured in an outdoor
setting; however, they attributed the observed products to reactions
with oils observed on the surface of plants (Ciccioli et al., 1993;
Fruekilde et al., 1998; Matsunaga et al., 2004). Inside the football
stadium, these secondary oxidation products were observed in
measurable quantities likely as a result of the aforementioned ozonolysis reactions on the surface of human skin and oil soaked
clothing or surfaces.
Fig. 5 shows a time series of observed ozone, decanal, 6-MHO
and CO2 during the football match. Decanal is the most abundant
product formed from ozonolysis of the unsaturated fatty acids in
human skin lipids (Nicolaid, 1974). Fig. 5 shows that ozone begins to
deplete upon the arrival of spectators while both 6-MHO and
decanal are produced. In addition to decanal, several other compounds were observed where production can be attributed to these
ozonolysis reactions. These results agree well with previous measurements that identify decanal and 6-MHO among the most
dominant volatile products from the ozone skin interaction
(Fruekilde et al., 1998; Wells et al., 2008; Wisthaler and Weschler,
2010). We do not mean to suggest that all of the O3 loss observed
in the stadium is a direct result of these ozonolysis reactions; we
acknowledge that reactions with additional VOCs and surface
deposition additionally contribute directly to ozone loss.
Due to the degree of correlation between decanal, 6-MHO and
CO2, ERCO2 can be calculated using the approach described in Section
3.1. We acknowledge that the relationship between CO2 and the
ozone oxidation products is non-causal; however, in this case we are
utilizing CO2 as a scalar that represents population, population being the causal relationship. ERCO2 remains constant throughout the
duration of measurements therefore we conclude that the reaction
is independent of the density of people and can be extrapolated to
the global population. If we assume that O3 is available in all
geographical locations populated with humans, we can calculate
maximum global production rates of these ozonolysis products by
scaling to global CO2 emission from humans. The results of this
approximation are included in Table 1. It is necessary that we
consider this a maximum production as the reaction rate is expected
to be proportional to the concentration of ozone, which is not
equally distributed in populated areas.
3.3. Combustion emissions
Fig. 6 shows a time series of acetonitrile and diacetyl. Acetonitrile, a known emission from combustion sources (Arijs and
Brasseur, 1986; Holzinger et al., 1999; Lobert et al., 1990) including
cigarette smoke (Campbell et al., 1963; Houeto et al., 1997), serves as
a tracer for smoking within the stadium. Of note is the large spike in
cigarette related emissions that occurs at half time when the rate of
smoking in the stadium increases. These species correlate well with
a cigarette smoking organic aerosol (CSOA) tracer, shown in Fig. 6,
observed in the PMF analysis of the aerosol measurements reported
in the companion paper to this manuscript (Faber et al., 2013). The
concentrations of the two most abundant carbonyls observed in the
stadium, acetaldehyde and diacetyl, ranged from several hundred
pptv to 4 ppbv and from below the detection limit to 0.8 ppbv
respectively in the football stadium. These results are in agreement
with a study of toxic carbonyl compounds in cigarette smoke, where
acetaldehyde and diacetyl were observed to be among the most
abundant carbonyl compounds emitted in cigarette smoke (Fujioka
and Shibamoto, 2006).
Mixing ratios of benzene and toluene were also elevated in the
stadium as a result of cigarette smoking with concentrations ranging
from about 200 pptv to 500 pptv. The benzene to toluene ratio
observed remained fairly constant at 0.84 0.24 ppbv ppbv1 (1s
standard deviation) throughout the football match. This is in agreement with previous results reporting an average emission ratio of
benzene to toluene in cigarette smoke of 0.86 0.07 ppbv ppbv1
(Darrall et al., 1998). This agreement suggests that we are in fact
capturing emission ratios in cigarette smoke in the absence of significant air mass ageing that would cause the ratio to increase.
Considering the magnitude of the impact of smoking on the
stadium atmosphere, it is necessary to examine the contribution of
cigarette smoke to the measured CO2. An independent study
determined an approximate emission ratio of CO2 to toluene in
cigarettes smoke of 1.41 ppmv ppbv1 (Liu et al., 2010). Using the
measured football source of toluene, the contribution of cigarette
1.4
0.8
25
1.2
0.8
0.4
0.6
0.4
Diacetyl, ppbv
Acetonitrile, ppbv
20
0.6
1.0
15
10
0.2
5
0.2
0.0
Cigarette Smoking Organic Aerosol PMF, a.u.
Acetonitrile
Diacetyl
Cigarette PMF
0
0.0
Fig. 5. Ozone (red), decanal (blue), and 6-MHO (green) measured in the stadium.
Decanal and 6-MHO are likely ozonolysis products of fatty acids and oils excreted from
human skin (Fruekilde et al., 1998; Wells et al., 2008; Wisthaler and Weschler, 2010).
The combined activities of the football match are responsible for titrating observed
ozone by approximately 20% a likely combination of ozonolysis reactions with VOCs,
skin oils, and increased surface deposition. (For interpretation of the references to
colour in this figure legend, the reader is referred to the web version of this article.)
6:00 PM
4/20/12
9:00 PM
12:00 AM
4/21/12
Date and Time
Fig. 6. Acetonitrile (red) and diacetyl (pink) measured with PTR-TOF-MS. These VOCs
are well correlated with an aerosol derived cigarette smoking organic aerosol PMF
factor (blue) (Faber et al., 2013). (For interpretation of the references to colour in this
figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: Veres, P.R., et al., Anthropogenic sources of VOC in a football stadium: Assessing human emissions in the
atmosphere, Atmospheric Environment (2013), http://dx.doi.org/10.1016/j.atmosenv.2013.05.076
P.R. Veres et al. / Atmospheric Environment xxx (2013) 1e8
smoking to the football source of CO2 reaches a maximum at half
time of 1.5%. We conclude that in comparison to CO2 produced via
exhalation, the contribution from cigarette combustion is
insignificant.
The measured isoprene mixing ratio ranged from approximately
100 pptv to over 4 ppbv during the football match. The emission
ratio of isoprene relative to toluene observed in the football stadium is 12.2 1.8. The average emission ratio observed in the
Darrall et al., 1998 study is 7.84 1.38 for cigarette emissions. One
possible explanation of the observed disagreement in the isoprene
to toluene ratio is the presence of a significant additional source of
isoprene within the stadium. Isoprene is a well-known component
of exhaled human breath (Gelmont et al., 1981) and as such we
initially expected the respiratory source to be the dominant source
of isoprene present in the stadium. We can approximate the
contribution from these sources (smoking and breath) by defining
the stadium source of isoprene, [Isop]Stadium, as a linear combination of the two isoprene sources:
½IsopStadium ¼ ½IsopCigarettes þ ½IsopBreath
(2)
where [Isop]Cigarettes is the concentration of isoprene from cigarettes and [Isop]Breath is the contribution from human breath. If we
define [Isop]Cigarettes in terms of toluene and rearrange Equation (3)
we arrive at the following definition for [Isop]Breath:
½IsopBreath ¼ ½IsopStadium ERTol ½TolStadium
(3)
where ERTol is the emission ratio of isoprene to toluene found in
cigarettes, and [Tol]Stadium is the stadium source of toluene. We
7
determine a value of 7.1 for ERTol such that the correlation of [Isop]Breath to CO2, and [Isop]Cigarettes to acetonitrile has been optimized.
Contrary to our initial estimate, the breath corrected cigarette
emission ratio, ERTol ¼ 7.1, is in good agreement with the results of
the Darrall et al., 1998 study, 7.84. The results of this analysis, the
two calculated isoprene source factors, are shown in Fig. 7. This
type of analysis has been performed for all other VOCs presented in
this study. The results of this factorization are presented in Table 1
as the percent contribution of the cigarette-smoking source to
measured stadium concentrations.
Using the calculated source factors, ERCO2 for isoprene in breath
is determined to be 0.016 0.004. Using maximum observed
isoprene in breath reported in the Fenske and Paulson, 1999 study
(w600 ppbv), ERCO2 for isoprene in breath can be calculated as
0.015. This agreement supports our application of this analysis for
the separation of the smoking and breath contributions to additional VOCs measured in this study. Using ERCO2 for isoprene in
breath (0.016) we approximate the emission of isoprene from human breath as 0.06 Tg yr1, a negligible contribution to the global
isoprene budget of 535 Tg yr1 (Guenther et al., 2012). Nevertheless, emitted isoprene could contribute to additional ozone formation downwind from the stadium over the city where the
chemistry is not expected to be NOx limited.
4. Conclusions
Typical ambient VOC patterns are markedly changed during the
football match. Many VOCs including ethanol, acetone, acetonitrile,
decanal and 6-MHO were all significantly higher than normal
levels. Given that football matches generally take place in urban
environments we should consider the probable fate of emissions
resulting from these dense gatherings. PTR-TOF-MS is an ideal
measurement technique for the accurate monitoring of these
rapidly changing VOC mixing ratios observed in the football stadium with detection limits on the order of 10e100 pptv on a 1 min
timescale for the VOCs considered in this study.
These measurements draw attention to the magnitude of various
direct and largely unavoidable atmospheric impacts human beings
have on our immediate environment. The results presented here are
not limited to the atmospheric environment at football matches in
Germany; however, can be extrapolated to any large-scale gatherings
of people. While there is no evidence at this time to support any
claims of a direct health concern or significant global impact, the large
fluxes of VOCs observed in the stadium suggest a considerable impact
on the local atmosphere, internal as well as external to the stadium.
Concentrations of the species reported in this study are directly
dependent on population density, extent of atmospheric isolation (i.e.
indoor versus outdoors), and social activity. It is necessary that we
remain aware of these human VOC sources in the future as a result of
continual growth in global population and density.
Acknowledgements
Fig. 7. Isoprene measured in the stadium can largely be attributed to two sources (1)
emission from cigarette smoke and (2) isoprene in human breath. Using measured
acetonitrile (not shown), CO2 in breath (grey), and toluene (not shown) both isoprene
sources can be approximated and are shown for the cigarette source factor (blue) and
breath source (green). Approximated contribution of CO2 from cigarette smoke is
shown for comparison (red). This analysis was carried out for all VOCs presented
within this work. (For interpretation of the references to colour in this figure legend,
the reader is referred to the web version of this article.)
The authors thank the 1. FSV Mainz 05 football club, especially
the staff of the Coface Arena for providing the measurement site and
support. In particular, we would like to thank Herr Matthias Britz for
coordinating our visit and serving as our contact with all stadium
affairs. Thomas Klüpfel and Thomas Böttger are acknowledged for
their technical support in helping to set up the instrumentation.
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atmosphere, Atmospheric Environment (2013), http://dx.doi.org/10.1016/j.atmosenv.2013.05.076