Currently used pesticides, hexachlorobenzene and hexachlorocyclohexanes in the air and seawater of the German Bight (North Sea)
AbstractSurface seawater and air samples collected from the German Bight (North Sea) in March, May and July 2010 were analysed for hexachlorobenzene (HCB) and hexachlorocyclohexanes (HCHs), five currently used pesticides (CUPs) (trifluralin, endosulfan, chlorpyrifos, dacthal and quintozene) and pentachloroanisole (metabolite). Volatilisation from local surfaces was considered to be the main source of these chemicals to the air (excluding trifluralin). Long-range transport from Western Europe partly contributed to the higher air concentrations observed in July whereas riverine input was the main source for HCHs and pentachloroanisole in seawater in March. Air–sea gas exchange of HCB and α-HCH in the German Bight was found to be near equilibrium, probably reflecting the past use of these chemicals, their wide dispersal in the environment and lack of contemporary use. Deposition of target compounds from the air to seawater was observed to be much higher in July compared with depositional fluxes for March and May, except for chlorpyrifos (with volatilisation fluxes in all sampling periods: ~25 ng m–2 day–1). Concentrations of trifluralin in seawater appear to have decreased since its restriction of use in European Union member states, with net volatilisation from seawater observed in March (flux: 6.3 ± 7.2 ng m–2 day–1). With the exception of chlorpyrifos, our results indicate that volatilisation from local sources combined with long-range transport from Western Europe and subsequent deposition are important pathways for these compounds to German Bight seawater during summer periods.