MERCURY CONCENTRATIONS IN AN AQUATIC ECOSYSTEM DURING 20 YEARS FOLLOWING ABATEMENT THE POLLUTION SOURCE

Phenyl Hg was widely used as a slimicide in Finnish pulp industry until the end of 1967. The use of Hg caused a significant increase of Hg levels in fish in several areas. High concentrations were measured in Lake Kirkkojarvi in Hameenkyro, SW Finland. Vast amounts of Hg are still present in the lake sediments. Since 1968 uncontaminated fibres have partly covered the contaminated layers. Since 1971 Hg has been monitored in fish, sediments and aquatic plants in the water course downstream from the pulp and paper factory. The Hg concentration of a 1-kg pike (Esox lucius) has decreased from 1.5-mu-g g-1 in the years 1971-74 to 0.8-mu-g g-1 in 1990.