ENVIRONMENTAL-EFFECTS OF NATIONWIDE SELENIUM FERTILIZATION IN FINLAND

To study the possible pollution of natural waters by selenium added to agricultural fertilizers, water selenium concentrations were determin ed in lakes and ground water pools during the year 1992, when the enri chment of fertilizers by selenium had continued for 8 yr. Water sample s were preconcentrated by evaporating, and selenium concentrations wer e analyzed fluorometrically using the dye 2,3-diaminonaphthalene after wet digestion. In lake water samples from 13 lakes, no significant co rrelations were found between selenium and pH, chlorophyll A, total ni trogen, or phosphorus. Agriculturally affected and nonaffected lakes h ad no differences in their selenium concentrations. In the lakes that were surrounded by cultivated fields mean water selenium was 83.4 ng/L (range: 75.2-93.4 ng/L, n = 9). Correspondingly, in lakes situated in forests without agricultural surroundings, mean water selenium concen tration was 76.5 ng/L (range: 51.2-110 ng/L, n = 3). Only one lake in the close vicinity of a coal power plant had a high water selenium con centration (mean 272 ng/L). In ground water samples, there was a big v ariation in selenium levels between different pools, the levels varyin g between 33 and 260 ng/L. This variation may partly be explained by d ifferent selenium concentrations of the bedrock and sediments. However , simultaneous increase of total nitrogen, phosphorus, and selenium le vels in consecutive samples from some ground water pools indicates lea ching of selenium from the fertilizers into the ground water in certai n areas.