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| Titel |
Scavenging ratios of polycyclic aromatic compounds in rain and snow in the Athabasca oil sands region |
| VerfasserIn |
L. Zhang, I. Cheng, D. Muir, J.-P. Charland |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 3 ; Nr. 15, no. 3 (2015-02-10), S.1421-1434 |
| Datensatznummer |
250119399
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| Publikation (Nr.) |
 copernicus.org/acp-15-1421-2015.pdf |
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| Zusammenfassung |
The Athabasca oil sands industry in northern Alberta, Canada, is a possible
source of polycyclic aromatic compounds (PACs). Monitored PACs, including
polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and
dibenzothiophenes (DBTs), in precipitation and in air at three near-source
sites in the Fort MacKay and Fort McMurray area during January 2011 to May
2012, were used to generate a database of scavenging ratios (Wt)
for PACs scavenged by both snow and rain. Higher concentrations in
precipitation and air were observed for alkylated PAHs and DBTs compared to
the other PACs. The sums of the median precipitation concentrations over the
period of data analyzed were 0.48 μ g L−1 for the 18 PAHs,
3.38 μ g L−1 for the 20 alkylated PAHs, and
0.94 μ g L−1 for the 5 DBTs. The sums of the median air
concentrations for parent PAHs, alkylated PAHs, and DBTs were 8.37, 67.26,
and 11.83 ng m−3, respectively.
Median Wt over the measurement period were 6100 – 1.1 ×
106 from snow scavenging and 350 – 2.3 × 105 from rain
scavenging depending on the PAC species. Median Wt for parent
PAHs were within the range of those observed at other urban and suburban
locations, but Wt for acenaphthylene in snow samples
were 2–7 times
higher compared to other urban and suburban locations. Wt for
some individual snow and rain samples exceeded literature values by a factor
of 10. Wt for benzo(a)pyrene, dibenz(a,h)anthracene, and
benzo(g,h,i)perylene in snow samples had reached 107, which is the
maximum for PAH snow scavenging ratios reported in the literature. From the
analysis of data subsets, Wt for particulate-phase dominant PACs
were 14–20 times greater than gas-phase dominant PACs in snow samples and
7–20 times greater than gas-phase dominant PACs in rain samples.
Wt from snow scavenging were ~ 9 times greater than from
rain scavenging for particulate-phase dominant PACs and 4–9.6 times greater
than from rain scavenging for gas-phase dominant PACs. Gas-particle fractions
of each PAC, particle size distributions of particulate-phase dominant PACs,
and the Henry's law constant of gas-phase dominant PACs explained, to a large
extent, the different Wt values among the different PACs and
precipitation types. The trend in Wt with increasing alkyl
substitutions may be attributed to their physico-chemical properties, such as
octanol–air and particle partition coefficients and subcooled
vapor pressure, which increases
gas-particle partitioning and, subsequently, the particulate mass fraction.
This study verified findings from a previous study of Wang et al. (2014) that
suggested that snow scavenging is more efficient than rain scavenging of
particles for equivalent precipitation amounts, and also provided new
knowledge of the scavenging of gas-phase PACs and alkylated PACs by snow and
rain. |
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