Further Evidence for a Drastic Decline of Potentially Hazardous Trace Metals in Baltic Sea Surface Waters

Abstract We present results of a Baltic Sea surface water study on selected dissolved trace metals ( 0.4 μm ) in which we compare our ‘historical’ data of 1982 with measurements obtained from samples collected in 1995 in the same area. The methods of collection, storage and analysis followed the same procedures with the exception of Zn. Between 1982 and 1995, significant concentration decreases have been observed for Pb (≈73%), Cd (≈66%), Zn (≈23%), Cu (≈19%) and Ni (≈18%) in the Baltic proper. Concentration decreases of 5–6% yr −1 for Cd and Pb, and 1.4–1.8% yr −1 for Ni, Cu and Zn have been observed in the Bornhom and Gotland Seas. We attribute these changes to reduced input from river, waste waters, and atmospheric deposition. The study also reveals that short-term or seasonal variations in the concentrations of these elements are small in Baltic surface waters. In contrast, strong seasonal variations of Mn are observed in open Baltic surface waters.