结合粒度和137Cs对小流域水库沉积物的定年——以黔中-湖泊科学.PDFVIP

J. Lake Sci.(湖泊科学), 2008, 20(3): 306-314 . E-mail: jlakes@ ©2008 by Journal of Lake Sciences 结合粒度和137Cs 对小流域水库沉积物的定年——以黔中喀斯特地区 克酬水库为例* 王文博, 蔡运龙, 王红亚 (北京大学资源与环境地理系, 地表过程分析与模拟教育部重点实验室, 北京 100871) 摘 要: 对取自黔中喀斯特地区克酬水库 32cm 长沉积物柱样进行 137Cs 比活度以及粒度测定, 结合气象站点降雨数据进行比对分 析, 对沉积物不同层位的年代进行了划分, 并以此结合质量深度推算了 1960-2004 年间该水库的沉积速率. 结合实例分析了 137Cs 沉降、运移和沉积, 改进了仅依靠 137Cs 峰值定年方法, 认为在流域面积较小、137Cs 比活度测试绝对数值较小的流域, 降水和其他 条件造成的土壤侵蚀程度差异可能是造成土壤中 137Cs 进入湖泊沉积物多少的更主要原因, 并表现为沉积物中 137Cs 不同层位的差异. 关键词: 137Cs 定年; 喀斯特小流域; 水库沉积物; 粒度 Dating by sediment grain size and 137Cs in small reservoir: a case study of Kechou reservoir, in Karst area of central Guizhou Province WANG Wenbo, CAI Yunlong WANG Hongya (Key Laboratory for Earth Surface Processes , Ministry of Education , Department of Resources Environment and Geography, Peking University, Beijing 100871, P.R.China) Abstract : A 32cm long sediment-core was sampled from Kechou reservoir located in Karst area of central Guizhou Province. According to study on grain size pattern and 137Cs dating in the profile, comparing with precipitation records, we determined the sediment ages in different depth of this core. Using the cumulative mass depth, we also calculated the deposit rates in different stages from 1960 to 2004. We improved the traditional 137Cs dating method which only relied on the position of peaks in profile. By analyzing the 137Cs depositing transportation and sedimentation, we found that the absolute values of 137Cs in the certain small catchment often appear in the low level. We believe that the soil erosion, which was caused by precipitation and other reasons, should intensively affect the amount of 137Cs depositing from soil to the sediment in reservoir. That should be