Atmospheric Pb and Cd input into the Baltic Sea: a new estimate based on measurements

Bulk deposition samples were collected during a summer (1997) and a winter (1998) measurement campaign at four coastal stations along the southern Bal tic Sea coast and on the Island of Gotland. The data were used to construct Pb and Cd deposition fields over the Baltic Sea. A weak gradient with decr easing deposition rates from the southwest towards the east and north was o btained for Pb. In the case of Cd, the spatial distribution pattern was cha racterized by an extreme deposition maximum at the Polish station on the He l Peninsula. The total atmospheric input of Pb and Cd into the Baltic Sea w as 550 and 33 t/year, respectively, and exceeds the riverine input by appro ximately about 50%. Previous measurement-based estimates were higher by a f actor 2-3 and indicate a decrease of the atmospheric deposition during the past 10-15 years. The comparison with modelled deposition data yielded part ly large differences and was impaired by the fact that 1990 emission invent ories were used whereas our measurements were performed in 1997/1998. Relating our deposition estimate and the Pb/Cd input by rivers to the mean concentrations in Baltic Sea water, residence times of 0.29 and 3.6 years w ere obtained for Pb and Cd, respectively. (C) 2000 Elsevier Science B.V. Al l rights reserved.