Water chemistry in a forested catchment as influenced by biogeochemical transformations in riparian soils

Transformations of nitrate and sulfate were investigated with respect to st reamwater quality in a forested headwater catchment in the Black Forest (SW Germany). Analyses of seepage collected with ceramic cups in the waterlogg ed riparian zone provide evidence for a distinct removal of nitrate due to reduction processes. This is in accordance with results from a laboratory e xperiment. Solutions enriched with nitrate were percolated through soil col umns from a histic gleysol. Apparently, nitrate removal results from denitr ification, whereas in the dynamics of sulfate various processes appear to b e superimposed. In total, the reduction processes observed are favoured by higher temperatures as well as by longer times of contact with the solid ph ase. The effects on other hydrochemical parameters (notably pH-value and ac id neutralizing capacity) are discussed.