Changing sources and environmental factors reduce the rates of decline of organochlorine pesticides in the Arctic atmosphere

Abstract

Abstract. An extensive database of organochlorine (OC) pesticide concentrations measured at the Norwegian Arctic monitoring station at Ny-Ålesund, Svalbard, 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 interannual trends. Although a simple comparison of annual mean concentrations (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(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][2004][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/cischlordane (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.

Step changes in persistent organic pollutants over the Arctic and their implications

“…2). This increasing trend Kalney et al, 1996) and sea ice extent (July-September, 10 7 km 2 ) anomalies from 1981 to 2012, averaged over the Arctic as the departures from 1979 to 2010 mean, manipulated from NSIDC data (Clark, et al, 1999). has been attributed to changes in source types and the presence of impurities in currently used pesticides as well as sea ice retreat (Hung et al, 2010;Becker et al, 2012). However, no step change point for HCB in our statistical analysis was detected, though this substance exhibited a clear increasing trend in the mid-2000s at the Zeppelin site.…”

“…The both temporal and spatial patterns of POPs in arctic air have been attributed to various processes driven by climate-induced changes in the arctic environment, such as reduced ice cover, increasing air and seawater temperatures, and biomass burning in boreal regions (Hung et al, 2010;Ma et al, 2011;Becker et al, 2012). Since the step changes in POPs are unlikely to be associated with interannual cli-mate variability (e.g., NAO, ENSO) and biomass burning (which should affect primarily the seasonal or interannual alteration in POPs), these step changes were anticipated to be fluctuations in the long-term trend in POP time series.…”

“…The statistically significant step change point years for PCBs in the present study appeared to coincide with those years during which arctic sea ice exhibited marked decline. Since sea ice melting is a crucial factor for controlling the environmental fate of POPs in the Arctic under a warming climate (Becker et al, 2012;Grannas et al, 2013) and the associations between the step changes in ambient atmospheric concentrations and sea ice concentrations, it is worthwhile to elucidate the response of POPs to arctic warming and sea ice fluctuation and melting. We simulated perturbed air concentration (pg m −3 ) of PCB 28, 153, and α-HCH subject to water-air and ice-air exchange processes from 1995 to 2012 using the perturbation model Ma et al, 2011).…”

“…Increasing concentrations of hexachlorobenzene (HCB) and many polychlorinated biphenyl (PCB) congeners were also observed in arctic air from the mid-2000s at the Zeppelin Mountain Air Monitoring Station, Svalbard/Norway (78 • 55 N, 11 • 56 E), and the Alert station, Canada (82 • 30 N, 62 • 19 W), resulting in the lack of statistically significant trends of these chemicals in the Arctic since the late 1990s (Hung et al, 2010). While the increasing trends of HCB and PCBs in the 2000s in the Arctic have been attributed partly to their revolatilization from their arctic repertories in ocean, ice, and snow due to arctic warming and sea ice retreat (Hung et al, 2010;Ma et al, 2011;Becker et al, 2012), this hypothesis was not supported sufficiently by statistical evidence.…”

Three years (2008–2010) of measurements of atmospheric concentrations of organochlorine pesticides (OCPs) at Station Nord, North-East Greenland

“…25 The high values may arise from transport episodes associated with regional sources or events such as boreal forest res, which can release POPs previously deposited on the soil surface to the atmosphere. 26 The seasonal proles of p,p 0 -DDT measured at Station Nord showed a clear peak in June followed by a rapid decrease in July-August.…”