摘要
The water quality of Dianchi Lake declines quickly and the eutrophication is getting serious. To identify the internal pollution load of Dianchi Lake it is necessary to evaluate its sediment accumulation. Sedimentation rates of Dianchi Lake are determined by ^137Cs dating. However, ^137Cs vertical distribution in sediment cores of Dianchi Lake has special characteristics because Dianchi Lake is located on the southeast of the Qinghai-Tibet Plateau, the Kunming quasi-stationary front is over the borders of Yunnan and Guizhou where the specific precipitation is distributed. Besides 1954, 1963 and 1986 ^137Cs marks can be determined in sediment cores, a ^137Cs mark of 1976 representing the major period of ^137Cs released from China unclear test can be determined and used for an auxiliary dating mark. Meanwhile Dianchi Lake is divided into seven sections based on the water depth, basin topography, hydrological features and supplies of silt and the lakebed area of each section is calculated. The mean annual sedimentation rates for seven sections are 0.0810, 0.1352, 0.1457, 0.1333, 0.0904, 0.1267 and 0.1023 g/cm^2 a in 1963-2003, respectively. The gross sediment accumulation of the lake is 26.18×10^4 t/a in recent 17 years and 39.86×10^4t/a in recent 50 years.
The water quality of Dianchi Lake declines quickly and the eutrophication is getting serious. To identify the internal pollution load of Dianchi Lake it is necessary to evaluate its sediment accumulation. Sedimentation rates of Dianchi Lake are determined by ^137Cs dating. However, ^137Cs vertical distribution in sediment cores of Dianchi Lake has special characteristics because Dianchi Lake is located on the southeast of the Qinghai-Tibet Plateau, the Kunming quasi-stationary front is over the borders of Yunnan and Guizhou where the specific precipitation is distributed. Besides 1954, 1963 and 1986 ^137Cs marks can be determined in sediment cores, a ^137Cs mark of 1976 representing the major period of ^137Cs released from China unclear test can be determined and used for an auxiliary dating mark. Meanwhile Dianchi Lake is divided into seven sections based on the water depth, basin topography, hydrological features and supplies of silt and the lakebed area of each section is calculated. The mean annual sedimentation rates for seven sections are 0.0810, 0.1352, 0.1457, 0.1333, 0.0904, 0.1267 and 0.1023 g/cm^2 a in 1963-2003, respectively. The gross sediment accumulation of the lake is 26.18×10^4 t/a in recent 17 years and 39.86×10^4t/a in recent 50 years.
基金
National Natural Science Foundation of China, No.40771186
The Key Project of the State Key Laboratory of Soil Sustainable Agriculture,Nanjing Institute of Soil Sciences,Chinese Academy of Sciences,No.5022505
