环境地球化学国家重点实验室知识库

Dissolved organic carbon (DOC) can be considered fine indicators of soil quality that influence soil function in specific ways and are very sensitive to changes in soil management practices. In this study, the contents and isotopic compositions of dissolved organic carbon (delta C-13(DOC)) in soils were analyzed at different topographic positions on two typical slopes in a karst area to evaluate the source and fate of DOC in the soil from these regions. The results show that DOC contents of the two slopes were mainly affected by soil organic matter (SUM) input, topography, and soil quality. DOC contents at each topographic location on the two slopes decrease with increasing soil depth. The delta C-13(DOC) of the shrubby slope surface soils varied from -15.1% to -22.1%, and are consistent with SUM delta C-13 and local vegetation. The delta C-13(DOC) C of the grassy slope surface soils ranged from -20.0% to -20.9%, similar to isotopic compositions of soil organic carbon. (delta C-13(SOC)), but are inconsistent with present-day vegetation. The delta 13C(DOC) varied significantly with depth at each topographic location. Thus, the dependence of delta C-13(DOC) in soil profiles on depth reflects the migration and transformation of DOC in soils.