Atmospheric deposition of semivolatile organic pollutants in European high mountains: Sources, settling and chemical degradation

Highlights: • Toxic semivolatile organic compounds are deposited in remote European mountains. • Regional sources of PAHs and endosulfans were observed in Eastern and Southern sites. • PCBs, HCHs and PBDEs deposition reflect baseline contributions from distant sources. • Wet deposition dominates PAHs, HCHs and HCB removal from the atmosphere. • Reaction with OH and direct photolysis strongly influence PAHs and PBDEs deposition. Bulk atmospheric deposition samples, including wet and dry deposition, were collected during 2004–2006 in four high mountain European lakes: Skalnate Pleso (Tatra mountains, Slovakia), Gossenköllesee (Alps, Austria), Redon (Pyrenees, Spain), and Lochnagar (Grampian Mountains, Scotland). Samples were analysed for polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), endosulfans, and polybromodiphenyl ethers (PBDEs). The deposition of PCBs, HCHs, and low brominated BDEs reflected baseline contributions from long range atmospheric transport. This was also the case for PAHs in Redon and Gossenköllesee, endosulfans in Lochnagar and Gossenköllesee and HCB in these three lakes. However, Skalnate received PAHs, endosulfans, and HCB from regional sources as it was the case for endosulfans in Redon. The distinct origin of these pollutants was reflected in the relative composition of some metabolites such as the proportion of endosulfan sulfate vs α- and β-endosulfans or the relative composition of BDE47 and BDE99. Wet deposition was the main process for atmospheric removal of PAHs, HCHs, and HCB. In addition, warm season revolatilization from soils and melting snow with subsequent condensation at low temperature were significant for volatile PAHs, HCB, low chlorinated PCBs, and endosulfans. Reaction with OH radicals was not a significant loss process of HCHs and HCB in remote areas, dominated by wet deposition, whereas PCBs and PAHs were significantly removed by both wet deposition and OH radical oxidation, the latter dominating in the highest altitude sites. Photolysis was the main atmospheric removal process of PBDEs, dominating over atmospheric deposition and OH depletion in all sites.