Temporal variation (2011–2014) of atmospheric OCPs at King George Island, west Antarctica

Abstract

A three-year sampling campaign (Jan 2011–Jan 2014) was conducted on organochlorine pesticides (OCPs) using high-volume air sampling nearby the Chinese Great Wall Station, west Antarctica. The concentrations of ∑23OCPs ranged between 5.87 and 27.9 pg m−3 (mean 14.3 ± 5.4 pg m−3), and no temporal trend was observed over the entire sampling period. However, the dominant compound, hexachlorobezene (HCB) (71% on average of ∑23OCPs), exhibited a seasonal variation with higher levels in the austral winter. Gas-particle partitioning of OCPs was explored based on KOA absorption model, steady-state model and Junge–Pankow adsorption model. LogKP showed significantly negative correlations with logPL0 of OCPs (p < 0.01, the slope is −0.30) and TSP values in the samples (p < 0.01), suggesting absorption by the organic matter as the dominant sorption process and TSP as an important factor influencing gas-particle partitioning of OCPs in this remote environment. The chiral signature indicated a commonly nonracemic residue of α-HCH and o,p’-DDT in the Antarctic air. The deviation from racemic (DFR) of o,p’-DDT showed a strongly negative dependence on its concentration (p < 0.01), properly suggesting more fresh input of o,p’-DDT after 2011. Preferential depletion of (+) α-HCH was observed mainly in gas phase, indicating the influence of re-volatilization of chiral compounds from source areas and/or ocean on their enantiomeric composition in remote air. Source apportionment demonstrated that long range atmospheric transport (LRAT) was the main transport pathway of OCPs, while nonracemic residues of HCHs and DDTs indicated a contribution of secondary source emission, i.e. seawater-air exchange, to their occurrence in west Antarctica.