Soil solution and stream water chemistry in a forested catchment I: Dynamics

Soil solution and stream water chemistry were studied during two years in a catchment in Bispgården in central Sweden (63°07′N, 16°70′E). Soil samples and soil solution were collected in a slope at two distances (10 and 80 m) from a stream. The aims were to examine interactions between recharge (podzol) and discharge (arenosol) areas and to investigate the relations between soil solution and stream water chemistry. The parent material was similar within the catchment, but the content of C and N were higher in the discharge area most likely due to the difference in hydrological conditions compared to the recharge area. Exchangeable cations and base saturation were higher in the discharge area than in the recharge area, which may be due to the higher content of C. The concentrations in soil solution of H, DOC, NO3, SO4, Al, Si, Ca and K were also higher in the discharge area compared to the recharge area which was probably caused by transportation of elements in soil and retention due to the increased content of C. During snow melt, the concentrations in soil solution of DOC, SO4, Al, Si, Ca and K were low due to dilution and low biological activity. The concentrations were then increasing during the seasons as an effect of biological activity and mineral weathering. NO3 concentration in soil solution was found in higher concentrations during snow melting and was then diminishing during summer likely as a result of biological uptake. After a dry period followed by an intensive rain in August 2003, the stream water chemistry was markedly altered for a few days. The concentrations of H, DOC SO4, Al and Ca were increased and the concentration of Si was decreased in the stream water. It therefore appeared that the stream water mirrored the upper soil horizons in the discharge area during high flows, while reflecting the lower soil horizons and ground water during low flows.