Arsenic, antimony, and germanium biogeochemistry in the Baltic Sea

Abstract

Arsenic, antimony, and germanium species concentrations have been determined from fivehydrographic stations along the central axis of the Baltic Sea from the Bornholm Basin to theGulf of Finland. Arsenic and antimony concentrations are lower than in the open oceans and inmost rivers. In the oxic waters, the pentavalent species of As and Sb predominate, while in theanoxic basins, the distribution shifts to the trivalent species and possibly some sulfo-complexes.Methylated arsenic species make up a large fraction of dissolved As in the surface waters, andmethylated species of As, Sb, and Ge are detectable throughout the water column. Germanicacid concentrations are about ten times higher than in the ocean and much higher than can beaccounted for by Ruvial input. The vertical distributions of arsenic, antimony, and germaniumwithin the Baltic Sea are controlled by biogeochemical cycling, involving biogenic uptake, particulate scavenging and partial regeneration. A mass balance including river and atmosphericinputs, exchange with the Atlantic through the Belt Sea, and removal by sediment depositionsuggests that anthropogenic inputs make a significant contribution to the budgets of all threeelements, with atmospheric fluxes dominating the input of Ge to the Baltic.