SEASONAL VARIABILITY OF TOTAL AND EASILY LEACHABLE ELEMENT CONTENTS IN TOPSOILS (0-5 CM) FROM 8 CATCHMENTS IN THE EUROPEAN ARCTIC (FINLAND,NORWAY AND RUSSIA)

Frozen topsoil samples (0-5cm) were collected during March/April 1994 in eight Arctic catchments in northern Europe (4 in Russia, 3 in Finla nd, 1 in Norway at varying distances and wind directions from the emis sions of the Russian nickel ore mining, roasting and smelting industry on the Kola Peninsula. Between 14 and 25 sites were sampled in catchm ent basins ranging in size from 12 to 35 km(2). Sampling was repeated in spring immediately after the snow melted, in summer and in autumn t o study seasonal variability and the fate of elements when the snow me lts. The <2mm fraction of air-dried topsoils was analysed for total (a qua regia extraction) and easily leachable (in 1 M ammonium acetate, b uffered at pH 4.5) element concentrations using ICP-AES and GFAAS for up to 35 elements. Results for selected elements ale presented here. S oil organic matter can be shown to be the controlling factor determini ng element contents and fate. In catchments close to the Russian nicke l industry, the topsoils have low carbon and nitrogen contents. Using both extraction methods most elements reach maximum concentrations in winter; lowest concentrations are observed in midsummer. Soil organic matter and elements associated with it are thus leached out of the soi ls together with soluble elements when the snow melts. This process co ntinues in summer. Elements will enrich surface waters, the lower laye rs of podzol profiles, or reach the groundwater, The use of the two ex tractions described provides a simple method to study the mobilities a nd pathways of elements in the topsoils during the arctic year. Using the proportions of easily leachable to total concentration, a good est imation of the status of the topsoil in the study area can be given. ( C) 1997 Elsevier Science Ltd.