RECENT FIFTY-YEAR SEDIMENTARY RECORD OF HEAVY METAL POLLUTION IN THE FUXIAN LAKE
近50年来抚仙湖重金属污染的沉积记录*

The concentration of heavy metals in lake sediments has been an indicator of contamination level of water and can record the history of pollution. Fuxian Lake, the third deepest lake in China, has a long history of residence. Its water quality has been largely affected by industrialization, agricultural cultivation, and deforestation, particularly in recent 20 years. However, few studies have reported its environmental problems. This paper focused on the change of heavy metal concentration in sediments from the heavily polluted northern region (the FB core) and the less polluted middle area (the FZ core) of the Fuxian Lake respectively. Based on the analyses of 137 Cs activities and heavy metal (Cu, Ni, Ti, Cr, V, Pb, Cd and Zn) concentration-depth profiles from the cores, the sources and pollution history of heavy metals were investigated. The geo-accumulation index (Igeo) has been used to assess their contamination levels. 137 Cs dating showed that the mean sedimentation rates is 2.0~2.8mm/a in northern lake. Before the 1980s, the main sources of heavy metals(Cu, Ni, Ti, V, Pb, Cd and Zn)are natural. After the 1980s, despite being influenced by human activities, heavy metals (Cu, Ni, Ti, V, Pb, Cd and Zn) in middle lake as well as Cu, Ni, Ti and V in northern lake are still originated mainly from the nature, but the sources of Pb, Zn and Cd in northern lake are influenced by anthropogenic activities. The geo-accumulation indices (Igeo) revealed that Pb and Zn in northern lake were considered as "unpolluted to moderately polluted" (Igeo<1); Cd was "strongly polluted" (3