Biogeochemistry of Lead-210 and Polonium-210 in Fresh Waters and Sediments

摘要

The objective was to investigate the behavior of toxic metals in lakes and streams using the naturally occurring radioactive metals lead-210 and polonium-210 as tracers. The radionuclides were measured as a function of position and time in a Massachusetts lake, its sediments and pore waters, and associated streams. A mass balance for the epilimnion showed that lead-210 direct uptake by bottom sediments was inconsequential. Below the epilimnion, a steep temperature/density gradient limited vertical transport. Anoxic conditions caused remobilization of iron and lead-210, which reprecipitated at the oxycline and returned to the bottom via settling. Below the oxycline, lead-210 and iron distributions resulted from constant release from anoxic sediments and dilution in the water column. Sediment lead-210 distributions were caused by sedimentation and Fickian transport.