CHARACTERIZATION OF LAKE-LADOGA SEDIMENTS .2. TOXIC-CHEMICALS

Chemical contamination of Lake Ladoga was studied by analyzing 12 sedi ment samples collected at various parts of the lake for polyaromatic h ydrocarbons, chlorobenzenes, organochloropesticides and heavy metals. The results were also used to explain the negative effects of these se diments observed earlier in bioassays with a midge Chironomus riparius (Ristola et al. 1995). Concentrations of analyzed chemicals were most ly typical to lakes which are considered as unpolluted. Only the conce ntrations of PAH were somewhat elevated in the sediment collected near River Volkhov inlet in the southern pat of the lake. Adverse effects on midges could, however, not be explained by chemical contamination.