湖北网湖^(137)Cs、^(210)Pb计年与沉积速率研究

Study on ^(137)Cs and ^(210)Pb Dating and Sedimentation Rates of Wanghu Lake,Hubei Province

采用放射性核素137Cs和210Pb计年法测定百年来湖北网湖沉积物的年代,据此计算出网湖的沉积速率.结果表明:2种计年方法测得的沉积速率基本一致,以1954年和1963年为时标,137Cs测得的沉积速率分别为0.594cm·a-1和0.557cm·a-1.210Pb计年法CIC模式计算得到网湖平均沉积速率为0.56cm·a-1.CRS模式得到百年来网湖沉积速率变化较大,20世纪50年代以前,平均沉积速率为0.2cm·a-1左右;50年代至80年代中期,平均沉积速率上了一个台阶,约为0.4cm·a-1;80年代中期以后平均沉积速率攀升至约0.6cm·a-1,网湖沉积速率变化与湖区自然环境的改变和人类活动的影响密切相关。

A sediment core was collected from the centre of Wanghu Lake in Yangxin, Hubei province. Environmental ^137Cs and ^210Pb dating techniques were applied to determine recent sedimentation rates. The results showed the recent sedimentation rate of the sediment by the ^210Pb intensity and CIC model was 0.56 cm·a^-1 while it determined by ^137Cs were 0.594 cm·a^-1 and 0.557 cm·a^-1, respectively. The sedimentation rate was in agreement with the results of both methods. Base on the ^210Pb intensity and CRS model, time-depth correlation was established. It showed that three periods with sedimentation rate during the last century. A lower average sedimentation rate was about 0.2 cm·a^-1 before 1950, and it was increasing from 1950 to the mid-1980s, about 0.4 cm·a^-1, and after the mid-1980s the higher average sedimentation rate led to 0.6 cm·a^-1. The variations of sedimentation rate were in connection with flood of the Yangtze River and the Fushui River, as well as the intensity of human activities on the catchment.