Marja Liisa Hattula

Total mercury and methyl mercury contents in fish from lake Päijänne

Abstract The total mercury and methyl mercury contents of freshwater fish from Lake Paijanne, Finland, are studied. This is the second largest lake in Finland and has been quite heavily contaminated by mercury. The fish from the limnologically cleanest areas had the highest concentrations of mercury. Twelve species of fish (1774 analyses of total mercury and 157 of methyl mercury) were analysed during a four-year period. Total mercury was measured by flameless atomic absorption and by gas-liquid chromatography. The average mercury concentration for all fish was 0·65 mg/kg on a fresh weight basis, of which 98·7% was in a methylated form. The concentration of mercury in fish differed in different parts of the lake and also depended on the weight of the fish.

An evaluation of a model ecosystem with DDT.

The reproducibility, variability, and reliability of a simple aquatic-terrestrial model ecosystem experiment was tested withp,p′-DDT. The variation among the model replicates as well as within the units was studied by using hierarchal analysis of variance. The complete budget of the chemical was calculated and a theoretical transport model was constructed. The degradation and accumulation of DDT was followed by gas Chromatographic residue analysis, which showed good reproducibility of the experimental design. The degradation of DDT in the model was similar to that found in the field, but the determination of concentration factors was questionable. The material balance tables revealed that the soil and bottom substrates were the main contributors, which regulated the fate of the chemical in the model. The usefulness of the model is presented in this report.