TRACE-METAL BUDGET, TRANSPORT, MODIFICATION AND SINK IN THE TRANSITION AREA BETWEEN THE ODER AND PEENE RIVERS AND THE SOUTHERN POMERANIAN BIGHT

Concentrations of Cd, Pb, Cu, Zn, Co, Ni, Fe, Mn and Hg in the dissolv ed phase, in particles and in surface sediments (<63 mu m) were analys ed during four transects, between January and October 1995 in the Pome ranian Eight. Additional samples were also taken once in the inner coa stal Oder Lagoons in August 1996. Modification processes influenced by seasonal variations were observed for the redox relevant manganese. H ighest Mn(diss) and han(SPM) values were determined in summer, when th e decomposition of organic material resulted in, a change of condition s, from oxic to anoxic, in surface sediments of the Oder Lagoon. A lat eral wind induced transport of dissolved manganese through the river o utlets resulted in higher Mn(diss) and Mn(SPM) contents in the souther n Pomeranian Eight. The distribution of Cd(diss) was linked to phytopl ankton growth. A mean Cel(diss) removal from the water column of 50% w as calculated during shimmer 1955, Tn addition, the cadmium inflow wit h river discharge waters into the Pomeranian Eight was lower in June 1 995, because most of the Cd(diss) had been eliminated during phytoplan kton growth in the highly productive waters of the Oder Lagoon. Gradie nts between the Oder Lagoon and the river mouth of the Peenestrom show ed, that only a very small net percentage of river transported trace m etals entered the Pomeranian Eight in August 1996. Most of the Pb (98. 4%), Cd (90.6%), Cu (79.7%), Zn (94.9%), Co (83.4%), Ni (68.3%) and Fe (93.6%) was retained in the inner coastal lagoons. In this connection the percentage of metals in the particulate phase is of greatest sign ificance. In August 1996, approx. Fe (80%), Mn (70%), Cd, Bb, Zn (45%) , Co (40%), Cu, Ni (35%) are associated with particles in the inner co astal lagoons, while at the stations in the Pomeranian Eight this prop ortion decreased drastically, due to factor 50 lower particle contents . Maximum anthropogenic enrichment factors (EF) of 15-30 (Cd), 10-17 ( Pb) and 5-10 (Zn) were found in the surface sediment fraction <63 mu m in the western part of the Pomeranian Eight. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.