Sulfur cycling in an experimentally acidified seepage lake
Recent interest in sulfur biogeochemistry of softwater lakes has been generated by the need to understand lake acidification processes. This study examines sulfur biogeochemistry in an experimentally acidified seepage lake in northern Wisconsin. For the pre-acidified lake, direct atmospheric deposition to the lake surface accounted for 93\% of total input; seepage inflows and leaf litter accounted for the remaining 7\%. Half of the input sulfur was retained by in-lake processes, and seston deposition was the dominant sulfate sink. Even though 70-80\% of sediment trap sulfur was recycled, seston-derived sulfur accounts for 70\% of sulfur accumulation in cores. Dissimilatory reduction in surficial sediments accounted for 30\% of net S retention i n the preacidified lake and reduction rates appear to be increasing in the acidified basin. Laboratory experiments with 35-S show that sulfur diagenesis is more complex than shown by the conventional model and that organic-inorganic transformations of sulfur in sediments are important diagenetic processes.
American Chemical Society
New Orleans, LA