STRUCTURE AND CONTENT OF POLLUTANTS IN TEMPORAL SURFACE SEDIMENTS IN SMALL WATERSHEDS

Formation of gel-like surface sediments has been observed during sprin g and autumn in small watersheds in boreal areas with pH <5.7 and conc entrations of humic substances above 3 mg L(-1). This structure effici ently accumulates dissolved, colloidal and particulate constituents. T he gel consists of ferric (hydr)oxides and fulvic acid and has high vi able counts of bacteria (notably Gallionella spp.) as well as fungal h yphae. The solid/solution distribution (log K-d; l kg(-1)) for trace m etals (Cd, Cu, Pb, V, Zn) ranges from 4 to 6.5 which indicate an effic ient accumulation during periods with gel. The concentrations of adsor bable organic halogens in the gel were not different from forest soils in general.