太湖洑东流域陆地侵蚀与入湖物质通量的定量关系研究

在太湖流域选择了一个典型的半封闭洑东小流域，通过对该流域及入湖口区域沉积物的元素和同位素地球化学研究，建立了反映流域陆地侵蚀与入湖物质输入量之间的定量关系模型。研究结果表明:近40 a来洑东流域的入湖物质通量约为6074 t/a，与实际监测结果一致。根据流域土地利用类型和土壤侵蚀速率的分布，估算出流域土壤侵蚀总量为25670 t/a，说明侵蚀总量的237%进入湖泊，其余在河道或土地内部沉积下来。近40 a来太湖宜溧河湖交界区入湖物质通量〖WTBX〗（Q）与流域土壤侵蚀速率（E）和流域面积（A）的数学关系为：E=422Q/A。〖WTBZ〗结合湖泊沉积物来源分析结果，计算出流域内不同土地利用类型的平均土壤侵蚀速率，林地、茶园和水田的土壤侵蚀速率分别为1266、58355和17293 t/（km2·a）。该结果与¹³⁷Cs示踪法计算结果基本一致，表明利用湖泊沉积记录可以较好地反演流域不同土地类型土壤侵蚀量及其入湖营养通量的变化。

QUANTIFING THE RELATIONSHIP BETWEEN SOIL EROSION AND MATERIALFLUXES FROM THE FUDONG WATERSHED TO LAKE TAIHU

This paper focused on the Fudong watershed of Taihu Lake Basin.Based on analyzing the element and isotopic geochemistry of sediments within the watershed and estuary,the quantitative relationship between soil erosion and the material fluxes from Fudong watershed to Taihu Lake were established.The results showed that the average material flux from the Fudong watershed to Taihu Lake was 6074 t/a in recent forty years,which was consistent with actual monitor data.The total amount of soil erosion within Fudong watershed was 25670 t/a,which meaned that only 237 percent of eroded soil transferred into Taihu Lake and the others were deposited in the channels and fields.Therefore,the mathematical relationship among the material flux from watershed to lake〖WTBX〗 (Q)〖WTBZ〗,the watershed erosion rate〖WTBX〗 (E)〖WTBZ〗 and watershed area 〖WTBX〗(A)〖WTBZ〗 was:〖WTBX〗E〖WTBZ〗=422〖WTBX〗Q/A〖WTBZ〗.According to the analysis of source of lake sediments by using multi element fingerprinting method,the soil erosion rate distribution of different land use types in Fudong watershed were calculated.The average soil erosion rates of forest lands,tea plantations and paddy fields were 1266，58355  and 17293 t/（km2·a） respectively,which was consistent with the results by using 137Cs tracer technique.Our study proved that the soil erosion of different land use types and the nutrient flux of catchment could be reconstructed by using lake sediment records.〖