Sandimirov S. Screening studies of POP levels in bottom sediments from selected lakes in the Paz watercourse / In State of the environment in the Norwegian, Finnish and Russian border area. The Finnish Environment. Finland, Jyvaskyla: Kopijyva Oy. 2007, №6.

Screening studies of PO P levels in bottom sediments from selected lakes in the Paz watercourse and some studies in the Canadian Arctic. The levels detected in the Paz-watercourse are lower than the levels in sediments from Ellasjoen from Bjornoya (740 pg/g dw) and from Great Lakes in the Canada (500 - 3100 pg/g dw) (Song et al., 2004, 2005). In Ellasjoen a dated sediment core the levels are increasing rapidly the last years (Evenset et al., 2006). <u -Q E3с со го ч-J со S9 S8 55 S4 S7 56 S3 S2 S1 □ PBDE # 28 □ PBDE # 47 □ PBDE # 99 □ PBDE # 100 □ PBDE # 153 □ PBDE # 154 □ PBDE # 183 0 % 10 % 20 % 30 % 40 % 50 % 60 % 70 % Relative concentration, % of zPBDE 80 % 90 % 100 % Figure 10. Contributions o fPBDE congeners to total PBDE concentration in bottom sediments. 5.4.5. Polychlorinated dibenzo-para-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) Neither dioxins nor furans are produced commercially because they have no known use. These are by-products resulting from the production o f other chemicals. Dioxins may also be released into the environment through the production o f pesticides and other chlorinated substances. Furans are a major contaminant formed during production o f PCBs. Both dioxins and furans are produced in a variety o f incineration reactions, and during the synthesis and use o f a variety of chemical products. Dioxins and furans have been detected in emissions from the incineration of coal, peat and wood, as well as from the incineration o f wastes and in emission from smelters. Dioxins and furans are two groups o f planar tricyclic compounds that have very similar chemical structures and properties. They may contain between 1 and 8 chlorine atoms; dioxins have 75 possible positional isomers and furans have 135 positional isomers. They are generally very persistent and lipophilic. The most toxic compound is 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD. The toxicity o f other dioxins and chemicals like PCBs that act like dioxin are measured in relation to TCDD. O f the 210 dioxins and furans, 17 contribute most significantly to the toxicity o f complex o f mixtures. In order to facilitate a comparison o f mixtures, International Toxicity Equivalency Factors (TEFs) have been assigned to individual dioxins and furans based on a comparison o f toxicity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The IARC has determined that 2,3,7,8-TCDD can cause human cancer. Table 8 summarise o f the results of PCDD/F analyses. Geograpical distribution o f total dioxin concentration found in sediment samples from the sites investigated is presented in Figure 10 . Rapport APN- 514.3665.01 22