MIGRATION OF NUTRIENTS, PESTICIDES AND HEAVY-METALS IN FRACTURED CLAYEY TILL

This study of fractured clayey till shows that the hydraulic activity of groundwater flow and the migration of pollutants from an orchard and from arable land are by far the most intensive in the upper 10 m of the till. In this zone dual porosity is developed as a result of desiccation and glacial jointing. Rapid leaching in the macropore structure is indicated by the distribution of tritium and chloride and by the vertical migration of the pesticides atrazine and simazine through 5-6 m of clayey till over ten years. Additional colloidal transport of DDT, DDE and DDD is indicated by preferential migration of clay minerals and DDE in fractures. In the upper 3-4 m of the weathered zone the distribution of authigenic Fe(III) minerals and root fragments in the macropore structure indicates a potential for denitrification under water-saturated conditions during autumn and winter. Mercury, copper and arsenic seem to be immobile in spite of the high levels of these metals detected in the topsoil of the orchard.