INFLUENCE OF BIOTURBATING ANIMALS ON FLUX OF CADMIUM INTO ESTUARINE SEDIMENT

The role of bioturbation in downward transport of cadmium from the wat er phase into a sandy marine sediment was investigated in a series of laboratory experiments, where dissolved Cd-109 was added to overlying water in sediment cores with and without bioturbating animals. The pol ychaetes Nereis diversicolor and Arenicola marina and the crustacean C orophium volutator initially stimulated the downward transport of wate r-phase cadmium into uncontaminated sediments by a factor of 1.5-2 com pared to control sediments without benthic macrofauna. N. diversicolor and A. marina transferred cadmium to > 4 and 13 cm depth in the sedim ent, respectively, whereas in the presence of C. volutator no cadmium was detectable below 1.5-2 cm. Cadmium transported to the deeper layer s in N. diversicolor bioturbated sediments was primarily adsorbed to t he 0-3-mm radial zone around burrows. It is suggested that the higher downward transport of cadmium from the water-column into sediments wit h infaunal burrows is driven by adsorption to metal oxides (iron and m anganese) and to the mucus cement in burrow linings combined with the increased area of oxidized sediment-water interfaces. In the case of A . marina, percolation of irrigated water through the reduced head-shaf t sediment may cause cadmium adsorption to sulfides as well. (C) 1998 Elsevier Science Ltd All rights reserved.