Profiles of Hg, Cd, Cu, Pb and Zn, PCDDs, PCDFs and dL-PCB-s in the bottom boundary layer of some North-Estonian coastal areas

Abstract

The hazardous substances listed in the EU Water Framework Directive (Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy) as priority and priority hazardous substances, HELCOM substances of specific concern to the Baltic Sea and some other pollutants which our team deemed potentially problematic for the Baltic Sea were analyzed in the botom boundary layer (BBL) in some coastal areas of the Gulf of Finland (GOF). All of the substances under observation are persistent, toxic, bioaccumulative and, because of these properties, are hazardous to the water environment. Chemical analyses indicated that the content of the most toxic HELCOM metals - Hg, Cd and Pb was very low at most stations, but considerable amounts of Zn and Cu were found at some stations. The highest concentrations of PCDD/Fs (WHO-TEQ 2005 value up to 6 ng/kg d.m.) and dl-PCB-s were found in some deeper areas of Tallinn Bay and Muuga Bay. Based on the circumstance that the maximum concentrations of all investigated metals and compounds were found in lower layers of sediments (6-15 cm) it may be concluded that the environmental status of the catchments and also of the sea has improved considerably during the last decades. The results on the content of toxic metals in Estonian sediment samples are in good agreement with those obtained by other investigators of the Baltic Sea and the Gulf of Finland. It seems that the environmental status of the near bottom water and bottom surface sediment is quite good in the North-Estonian coastal sea area.