ORGANIC CHLORINE COMPOUNDS IN LAKE-SEDIMENTS .6. 2 BOTTOM SITES OF LAKE LADOGA NEAR PULP-MILLS

Chloride, total and extractable organically bound chlorine, chlorohydr ocarbons, polychlorodibenzo-p-dioxins (PCDD) and polychlorodibenzofura ns (PCDF) were measured in dated bottom sediment layers of two sites o f the northern Lake Ladoga near pulp mills. Concentrations and annual depositions of pulp chlorobleaching products in Ladoga sediments were significantly lower than those in pulp mill recipient bottoms in Centr al Finland. However, typical chlorobleaching traces bound chlorophenol ics, chlorocymenes and chlororetenes were readily identified. HCBz, HC Hs and chlordanes occurred at low background levels like in Central Fi nland. In contrary, depositions of the DDT residues (4-16 mug m-2 a-1) and PCBs (7-19 mug m-2 a-1) at Ladoga were higher than the background levels in Finland (1 and 2 mug m-2 a-1, respectively). PCB isomer pat tern in Ladoga indicated a Russian origin. PCDD and PCDF were at low b ackground levels. Their isomer patterns deviated from those of pulp mi ll effluent or common background.