Assessing metal contaminants in Antarctic soils using diffusive gradients in thin-films.

Abstract

Metal contaminants in Antarctic soils are typically found around research stations which are concentrated in ice-free coastal areas. The risk of these contaminants to the Antarctic environment is not well understood, given Antarctica s unique organisms and climate. This study assessed the use of diffusive gradients in thin-films (DGT), a passive sampler that measures fluxes of labile metals from soils to porewaters, in Antarctic soils. DGT-labile measurements were compared to three chemical extractants of increasing strength including high-purity water, dilute acid (1\xa0M HCl), and concentrated acids (3:1 v/v HNO3:HCl), to understand differences in contaminant geochemistry that may affect environmental risk. One site had high lead concentrations measured with dilute (114\xa0±\xa04\xa0mg\xa0kg-1) and concentrated (150\xa0±\xa010\xa0mg\xa0kg-1) acids, while DGT-labile concentrations were below the method detection limit (0.5\xa0μg\xa0L-1), indicating that the lead species has low solubility or lability. Another site had low concentrations of zinc measured by dilute (36.2\xa0±\xa00.5\xa0mg\xa0kg-1) or concentrated (76\xa0±\xa06\xa0mg\xa0kg-1) acid extracts, but had high DGT-labile concentrations (350\xa0±\xa080\xa0μg\xa0L-1). This reflects an active source of zinc supplied from soil to pore water over time. Copper was found to be acid extractable, water-soluble, and DGT-labile, with DGT-labile concentrations of up to 12\xa0μg\xa0L-1. Despite the soil and metal-specific geochemical differences, any of the extracts could be used with statistical clustering techniques to identify differences in sites with elevated metal concentrations. This study shows that the DGT-method can identify contaminated sites comparably to chemical extracts but provides environmentally relevant measurements of metal contaminant lability in Antarctic soils.