Evaluation of biogeochemical sulfur transformations in forest soils by chemical and isotope data

The fate of simulated wet sulfur deposition was investigated in a lysimeter experiment in which 30 forest soil cores were irrigated with ³⁴S-enriched sulfate. Sulfur balance was determined from an inventory of concentrations and isotope compositions of sulfate in sequential seepage water samples and different forms of soil sulfur at the beginning and end of the experiment. The ability of the soils to retain the irrigation sulfate varied dependent upon their geogenic and/or pedogenic chemical properties. After 89 weeks, the maximum integrated throughput of labelled irrigation sulfate was only 22%. Depending on soil type and irrigation treatment, from 36 to 74% of the retained sulfur was bound inorganically while the remainder was immobilized as organic sulfur. -Authors