Air-Seawater Exchange of Organochlorine Pesticides in the Southern Ocean between Australia and Antarctica

Abstract

This study contributes new data on the spatial variability of persistent organic pollutants in the Indian–Pacific sector of the Southern Ocean and represents the first empirical data obtained from this region in 25 years. Paired high-volume atmospheric and seawater samples were collected along a transect between Australia and Antarctica to investigate the latitudinal dependence of the occurrence and distribution of legacy organochlorine pesticides (OCPs) and the current use pesticide chlorpyrifos in the Southern Ocean. Dissolved ΣHCH and dieldrin concentrations decreased linearly with increasing latitude from 7.7 to 3.0 and from 1.0 to 0.6 pg·L–1, respectively. There was no consistent trend observed in the latitudinal profile of atmospheric samples; however, some compounds (such as dieldrin) showed reduced concentrations from 7.5–3.4 to 2.7–0.65 pg·m–3 at the highest latitudes south of the Polar Front. Chlorpyrifos was found in samples from this area for the first time. Estimated air–seawater fugacity ratios and fluxes indicate a current net deposition between −3600 and −900, −6400 and −400, and −1400 and −200 (pg·m–2·d–1) for γ-HCH, dieldrin, and chlorpyrifos, respectively. These findings suggest that, under current climatic conditions, the Southern Ocean reservoir in the Indian–Pacific sector serves as an environmental sink rather than a source of OCPs to the atmosphere.