TREATMENT OF MERCURY CONTAMINATED FISH BY SELENIUM ADDITION

Treatment of Hg contaminated fish by addition of Se (the Boliden SRM-method) has been shown to be an effective mean to reduce the Hg concentration of pike and perch. The fullscale tests in eleven lakes in Sweden have confirmed the earlier results in lake Oltertjarn in Sweden. The 1 yr old perch in the treated lakes shows a reduction in the mean Hg concentration. The Hg concentration in tissue varied between 0.04 and 0.29 mg kg-1 in the different lakes before treatment. After treatment the Hg concentration decreased to 0.02 to 0.07 mg kg-1. The reduction in perch was as much as 60% for the three lakes with lower background concentration in pike (less than 0.7 mg kg-1) and as high as 85% for eight lakes with higher concentrations. In pike with Hg concentration at or above 1 mg kg-1 it was reduced by 22% after only 1 yr and by 28% after 2 yr of treatment. Experience gained in these tests verifies the importance of adjusting the dose and addition period to the lake. Good circulation in the lake is essential during addition.