Atmos. Chem. Phys. Discuss., 9, 515-540, 2009
© Author(s) 2009. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Changing sources and environmental factors reduce the rates of decline of organochlorine pesticides in the Arctic Atmosphere
S. Becker1, C. J. Halsall1, W. Tych1, R. Kallenborn2,3, M. Schlabach2, and S. Manø2
1Lancaster Environment Centre, Lancaster University, Lancaster, UK
2Norwegian Institute for Air Research (NILU), Kjeller, Norway
3The University Centre in Svalbard (UNIS), Longyearbyen, Svalbard, Norway

Abstract. An extensive database of organochlorine (OC) pesticide concentrations measured at the Norwegian Arctic Monitoring Station was analysed to assess longer-term trends in the Arctic atmosphere. Dynamic Harmonic Regression (DHR) is employed to investigate the seasonal and cyclical behaviour of chlordanes, DDTs and hexachlorobenzene (HCB), and to isolate underlying inter-annual trends. Although a simple comparison of annual mean concentrations (1994–2005) suggest a decline for all of the OCs investigated, the longer-term trends identified by DHR only show a significant decline for p,p'-DDT. Indeed, HCB shows an increase from 2003–2005. This is thought to be due to changes in source types and the presence of impurities in current use pesticides, together with retreating sea ice affecting air-water exchange. Changes in source types were revealed by using isomeric ratios for the chlordanes and DDTs. Declining trends in ratios of trans-chlordane/cis-chlordane (TC/CC) indicate a shift from primary sources, to more ''weathered'' secondary sources, whereas an increasing trend in o,p'-DDT/p,p'-DDT ratios indicate a shift from use of technical DDT to dicofol. Continued monitoring of these OC pesticides is required to fully understand the influence of a changing climate on the behaviour and environmental cycling of these chemicals in the Arctic as well as possible impacts from ''new'' sources.

Citation: Becker, S., Halsall, C. J., Tych, W., Kallenborn, R., Schlabach, M., and Manø, S.: Changing sources and environmental factors reduce the rates of decline of organochlorine pesticides in the Arctic Atmosphere, Atmos. Chem. Phys. Discuss., 9, 515-540, doi:10.5194/acpd-9-515-2009, 2009.
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