Downward Movement of Soil Organic Matter and Its Influence on Trace-Element Transport (210Pb, 137Cs) in the Soil

Data on depth distribution and 14 C content of soil organic carbon, and on soil CO 2 production in forest ecosystems are presented and discussed. Downward movement and turnover of soil organic matter is estimated from a box chain model. The downward transfer velocity of soil organic material depends on the litter material composition and on the annual rate of microbial decomposition. Depth distribution of 210 Pb and 137 Cs was measured. The identical transfer velocity of 210 Pb and soil organic material suggests that lead transport is due to movement of the organic material itself. Lead in organic-rich soils obviously is bound rather tightly to the organic carrier by ion exchange or organic complexing. 137 Cs migration depends on the turnover and downward movement of soil organic material. Results suggest that cesium is not transported only by the downward movement of solid organic matter, but, due to chemical exchange between the organic and hydrous phases, travels faster than organic matter.