Atlantic Ocean between the Arctic and Antarctica: the air-sea equilibrium of Hexachlorocyclohexane (HCHs)

Investigations were carried out to give evidence of POPs transport from the northern hemisphere to the southern. Investigations were carried out along transects from northern regions to the polar or sub-polar regions to reconstruct the trends in concentrations of POPs and to emphasize the potential contribution from the more anthropized regions. Transport processes were assessed on the base of concentration gradient and using the isomeric composition of some POPs. Hexachlorocyclohexanes (HCHs) were determined simultaneously in air and seawater during two cruises across the Atlantic Ocean between the Arctic Ocean (Ny-Alesund/Svalbard, 79°N; 12°E) and the Antarctic Continent (Neumayer Station/Ekstroem Ice Shelf, 70d°S; 8.2°W) in 1999/2000 (Lakaschus et al., 2002). The concentrations of α-HCH and γ-HCH in air and surface waters of the Arctic exceeded those in Antarctica by 1-2 orders of magnitude. Average concentrations in surface seawater between 75°N and 80°N were 315±184 pg L-1 and 137±49 pg L-1 for α-HCH and γ-HCH respectively. In the sea region of the southern fronts (50°S) the mean concentrations were 3.9 pg l-1 and 0.8 pg l-1 α-HCH and γ-HCH respectively. Between Cape Town and Neumayer Station the average gaseous concentrations of α-HCH and γ-HCH were 1.1 pg m-3 and 1.4 pg m-3 and decreased further to 0.36 ± 0.03 pg m-3 and 0.15 ± 0.04 pg m-3 on the Ekstroem IceShelf at Neumayer Station. By comparison of results obtained from archived samples taken in 1987/1997 and those from 1999, a systematic decrease of α-HCH was observed at all sampling locations. However, it must be emphasized that a different trend was observed for γ-HCH. In particular, the level of γ-HCH in surface seawater as a function of the time was constant in the tropical Atlantic region and the authors concluded that the tropical Atlantic acts as a sink for γ-HCH at present time.