On the other hand, cadmium concentrations in the sediments have been increasing continuously during the past 100 years as a result of agricultural effluent being discharged into the pond. The reported concentrations of dissolved zinc and cadmium in Nozha Hydrodrome are low when compared with natural levels: this is an indication of the good quality of its water and provides evidence that both metals are trapped

in the solid phase (sediment and particulate matter). Unless major changes in the physicochemical properties (especially pH) of the water take place, cadmium and zinc do not at present pose a serious environmental threat to the Nozha Hydrodrome ecosystem. “
“Long-range atmospheric transport and chemical condensation reactions are responsible for Cyclopamine concentration the widespread distribution of compounds such as poly- cyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) in the Arctic (e.g. Halsall et al. 2001, Wania & Su 2004). In the European sector of the Arctic, regional sources of pollutants such as metallurgical smelters and military installations operating along the Norwegian and Russian coasts

add to supplies from global emissions sources (Savinov et al. 2003, Carroll et al. 2008a). Marine sediments are the final sink for volatile persistent organic pollutants (POPs) entering the Arctic (Wania & Su 2004). Marine sediments acquire XL184 purchase their contaminant composition through direct particle deposition (Ab Razak et al. 1996) and by transfer from seawater to the bottom surface sediments during downwelling events. For example, in the Norwegian Sea the PCB flux via settling particles was 320 kg yr−1 compared to a direct removal flux to surface sediment deposits of 870 kg

yr−1 in the North Atlantic VAV2 (Lohmann et al. 2006). Sea ice transport also facilitates the transfer of contaminants from industrialized areas of the Siberian coast to other locations in the Arctic (Pfirman et al. 1995, 1997, Pavlov et al. 2004). Estimates prepared by the Arctic Monitoring and Assessment Program (AMAP) report that approximately 45% of PCBs reaching Svalbard are by air transport, 30% by ocean currents and 25% by sea ice transport (AMAP 2004). Sediment accumulation is an important process governing the storage of contaminant-laden sediments on the sea floor. However, contaminant distribution and composition are further affected by post-depositional processes. Sediment mixing may affect the down-core concentration and composition of contaminants, causing chemicals to spread further down the sediment column. In high energy and/or high benthic infauna density environments, resuspension events may result in contaminant reintroduction to the water column (Thibodeaux & Bierman 2003, Carroll & Lerche 2003). Moreover, polychlorinated biphenyls can be degraded by both anaerobic and aerobic bacteria.