太湖现代沉积物中磷的沉积通量及空间差异性

在水文状况、水质状况、生态类型均显著不同的三个太湖典型湖区, 利用^210Pb定年测定了近百年来沉积物及磷的沉积通量.结果发现, 三个湖区磷的沉积通量及其变化规律相差很大.发生蓝藻水华暴发的梅梁湾近百年来沉积物和磷的沉积通量都比较小, 只是在近十几年来才有明显增加的趋势; 太湖上游的夹浦沉积物沉积速率近百年来持续增加, 只有表层有所下降, 但表层12cm沉积物中磷的沉积通量却显著下降; 处于太湖下游草型化的胥口湾湖区, 在20世纪60年代以前沉积物沉积通量呈增加趋势, 之后呈下降趋势, 磷的沉积通量则呈振荡下降趋势.研究表明, 太湖沉积物中磷的累积通量具有明显的空间异质性.

PHOSPHORUS SEDIMENTATION FLUX AND ITS SPATIAL HETEROGENEITY IN TAIHU LAKE, CHINA

The accumulation of phosphorus is studied in recent sediments of Taihu Lake, a large (2338.1 km2) and shallow (mean depth 1.89 m) eutrophic freshwater lake in eastern China. Sediments dated back for nearly 100 years were core-sampled from three ecologically unique localities, including Meiliang Bay (a eutrophic area where Microcystis algae bloom occurs every summer since 1986), Jiapu (a turbid upper area of the lake with no algae bloom and macrophyte flourish), and Xukou Bay (the downstream of the lake that gradually become macrophytes-dominated). The sediment cores were studied with 210Pb and 137Cs and chemical analysis for determining the sedimentation flux and phosphorus accumulation flux in the lake. The results revealed large spatial heterogeneity in sediment accumulation rate and also the phosphorus accumulation rate. The phosphorus accumulation rate in Meiliang Bay is small before 1989, while it increased rapidly in the last dozen years. In Jiapu, however, the accumulation rate is very low in top 12cm (about 25 years) sediment. The sediment accumulation flux in Xukou Bay kept decreasing in recent 100 years, and so did the phosphorus flux. The results suggested that the recent phosphorus sedimentation flux in the lake is strongly location-dependent, reflecting the spatial differences in ecological type and hydrological condition in this large and shallow lake. To study the eutrophication in the lake, one should consider the spatial difference with proper strategy deployment.