Recent Environmental Change Inferred from GrainSize Records in Fuxian Lake, Yunnan Province

Key words: 
• radionuclide dating (210Pb and 137Cs) /
• grainsize

Abstract: 210Pb and 137Cs were used to analyze for the Fuxian Lake sediment core. 210Pb (CRS) dating result showed a little deviation from 137Cs dating, and two reasons were investigated. According to the feature of Fuxian Lake, we analyzed the grain size characteristics and obtained the content of the core, which contained 36% of clay, 44% of fine sand and 18% of coarse sand. By calculation, the different grainsize parameters were also obtained, the mean grain diameter () was between 6.48 and 7.92, the standard deviation (So) was between 1.27 and 1.42, and the skewness (SKD) was between 0.18 and 0.04. Based on radionuclide dating and grainsize distribution characteristics in the sediment core, we concluded a sedimentary environment in Fuxian Lake had been greatly changed since 1878, which can be marked off four stages: natural evolution stage, manmade disturbances stage, manmade transformation stage, and recent treatment stage. Human activities of historical period had played a very important role in changing the environment of the Lake. 