Articles | Volume 15, issue 3
Atmos. Chem. Phys., 15, 1411–1420, 2015
Atmos. Chem. Phys., 15, 1411–1420, 2015

Research article 09 Feb 2015

Research article | 09 Feb 2015

Annual cycles of organochlorine pesticide enantiomers in Arctic air suggest changing sources and pathways

T. F. Bidleman1,2, L. M. Jantunen2, H. Hung3, J. Ma4, G. A. Stern5, B. Rosenberg6, and J. Racine7 T. F. Bidleman et al.
  • 1Department of Chemistry, Umeå University, 901 87 Umeå, Sweden
  • 2Air Quality Processes Research Section, Environment Canada, 6248 Eighth Line, Egbert, ON, L0L 1N0, Canada
  • 3Air Quality Processes Research Section, Environment Canada, 4905 Dufferin St., Toronto, ON, M3H 5T4, Canada
  • 4Key Laboratory of Western China's Environmental System, Ministry of Education, College of Earth and Environment Sciences, Lanzhou University, Lanzhou, China
  • 5Centre for Earth Observation Science, University of Manitoba, 474 Wallace Building, 125 Dysard Road, Winnipeg, MB, R3T 2N2, Canada
  • 6Freshwater Institute, Department of Fisheries and Oceans, University of Manitoba, 501 University Crescent, Winnipeg, MB, R3T 2N6, Canada
  • 7Air Quality Modelling Application Section, Canadian Meteorological Centre, 2121 Trans-Canada Highway, Dorval, QC, H9P 1J3, Canada

Abstract. Air samples collected during 1994–2000 at the Canadian Arctic air monitoring station Alert (82°30' N, 62°20' W) were analysed by enantiospecific gas chromatography–mass spectrometry for α-hexachlorocyclohexane (α-HCH), trans-chlordane (TC) and cis-chlordane (CC). Results were expressed as enantiomer fractions (EF = peak areas of (+)/[(+) + (−)] enantiomers), where EFs = 0.5, < 0.5 and > 0.5 indicate racemic composition, and preferential depletion of (+) and (−) enantiomers, respectively. Long-term average EFs were close to racemic values for α -HCH (0.504 ± 0.004, n = 197) and CC (0.505 ± 0.004, n = 162), and deviated farther from racemic for TC (0.470 ± 0.013, n = 165). Digital filtration analysis revealed annual cycles of lower α-HCH EFs in summer–fall and higher EFs in winter–spring. These cycles suggest volatilization of partially degraded α-HCH with EF < 0.5 from open water and advection to Alert during the warm season, and background transport of α-HCH with EF > 0.5 during the cold season. The contribution of sea-volatilized α-HCH was only 11% at Alert, vs. 32% at Resolute Bay (74.68° N, 94.90° W) in 1999. EFs of TC also followed annual cycles of lower and higher values in the warm and cold seasons. These were in phase with low and high cycles of the TC/CC ratio (expressed as FTC = TC/(TC+CC)), which suggests greater contribution of microbially "weathered" TC in summer–fall versus winter–spring. CC was closer to racemic than TC and displayed seasonal cycles only in 1997–1998. EF profiles are likely to change with rising contribution of secondary emission sources, weathering of residues in the environment, and loss of ice cover in the Arctic. Enantiomer-specific analysis could provide added forensic capability to air monitoring programs.

Short summary
Canadian Arctic air samples were analysed for enantiomers (mirror-image isomers) of pesticides α-hexachlorocyclohexane (α-HCH), trans-chlordane (TC) and cis-chlordane (CC). Annual cycles of enantiomer proportions suggested greater emission of microbially degraded residues from water and soil in warm vs. cold seasons. Enantiomer profiles may change in the future with rising contributions from secondary sources, monitoring them could increase the forensic capability in air monitoring programs.
Final-revised paper