Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

IF value: 5.414
IF5.414
IF 5-year value: 5.958
IF 5-year
5.958
CiteScore value: 9.7
CiteScore
9.7
SNIP value: 1.517
SNIP1.517
IPP value: 5.61
IPP5.61
SJR value: 2.601
SJR2.601
Scimago H <br class='widget-line-break'>index value: 191
Scimago H
index
191
h5-index value: 89
h5-index89
Volume 15, issue 3
Atmos. Chem. Phys., 15, 1421–1434, 2015
https://doi.org/10.5194/acp-15-1421-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 15, 1421–1434, 2015
https://doi.org/10.5194/acp-15-1421-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 10 Feb 2015

Research article | 10 Feb 2015

Scavenging ratios of polycyclic aromatic compounds in rain and snow in the Athabasca oil sands region

L. Zhang1, I. Cheng2, D. Muir3, and J.-P. Charland4 L. Zhang et al.
  • 1Air Quality Research Division, Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, M3H 5T4, Canada
  • 2Independent Researcher, 5785 Yonge Street, Toronto, Ontario, M2M 4J2, Canada
  • 3Aquatic Contaminants Research Division, Science and Technology Branch, Environment Canada, 867 Lakeshore Road, Burlington, Ontario, L7R 4A6, Canada
  • 4Air Quality Research Division, Science and Technology Branch, Environment Canada, 335 River Rd. S., Ottawa, Ontario, K1A 0H3, Canada

Abstract. 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.

Publications Copernicus
Download
Short summary
This study analyzed air and precipitation concentrations of 43 polycyclic aromatic compounds (PACs) collected in the Athabasca oil sands region. A database has been built for the parameter scavenging ratio, which is defined as the ratio of the concentration of PACs in precipitation to that in air. A better understanding of the potential differences between gas and particulate scavenging and between snow and rain scavenging has been achieved.
This study analyzed air and precipitation concentrations of 43 polycyclic aromatic compounds...
Citation
Altmetrics
Final-revised paper
Preprint