Background concentrations and extent of Cu, As, Co, and U contamination in Baltic Sea sediments

Abstract This study established background (pre-industrial) values of copper (Cu), arsenic (As), cobalt (Co), and uranium (U) in Baltic Sea sediments. The indicated background values could help identifying the spatial and temporal anthropogenic loads of these elements (metals and metalloids) in the Baltic Sea. In this study, 137 sediment samples were collected from cores obtained from 13 monitoring stations in the Gulf of Bothnia (Bothnian Bay and Sea) and the entire Baltic Proper. To understand the extent of contamination, we used direct and combined methods to define the geochemical background values as inputs for the geochemical index (Igeo) calculation. The obtained values were then compared with the background values established by the Swedish Environmental Protection Agency. From the direct method, Cu, Co, As, and U had background values of 39, 21.5, 12.4, and 6.3 mg kg−1 DW. Copper and U exhibited concentrations above the background values in surface sediment in the western and eastern Baltic Proper (maximum Igeo indicates moderate contamination). Arsenic was above background concentrations in the Baltic Sea and highest in the Gulf of Bothnia (maximum Igeo indicates strong contamination). Cobalt concentrations were within the range of background values (no contamination).