贵州省西南部麦岗水库沉积物的^(137)Cs和^(210)Pb测年与沉积速率研究  

^(137)Cs and ^(210)Pb Dating and Inference of Sedimentation Rate for Maigang Reservoir in Southwest Guizhou Province

作　　者：李春梅[1] 王红亚[1] 

机构地区：[1]北京大学城市与环境学院资源环境地理系地表过程与模拟教育部重点实验室,北京100871

出　　处：《水土保持通报》2010年第2期215-219,共5页Bulletin of Soil and Water Conservation

基　　金：国家重点基础研究发展计划(973)项目"长江流域环境与水资源演化规律"(2003CB415201);科技部基础性工作专项课题(2007FY140800-1)

摘　　要：对贵州省西南部麦岗水库沉积物柱芯MG4-2,采用210Pb和137Cs法进行了测年与现代沉积速率研究。结果表明,该柱芯中存在这3个明显的137Cs蓄积峰,对应1964,1975,1986年3个计年时标。运用210Pb的恒定补给速率(CRS)模式计算得到的年代,总体上与137Cs法的结果吻合较好,但存在一定的偏差,特别是与1964年的计年时标的偏差较大,这可能是因为沉积物柱芯受到了一些人为扰动所致。两种核素测定的平均沉积速率在数值上有一定的偏差,但都反映了麦岗水库沉积物近几十年以来经历了从慢到快再到慢的沉积过程,初步推测,沉积速率的这种变化与人类活动有一定的关系。两种计年方法结合,相互印证,使计年和沉积速率的研究更为准确。^137Cs and ^210pb techniques are used to date a sediment core （MG4-2） retrieved from Maigang Reservoir in Ziyun County, Southwest Guizhou and infer its sedimentation rates. Three distinctive ^137Cs peaks are identified in this core, which are ascribed to the abundant fallouts occurring in 1964, 1975, and1986. The ^210 Pb ages calculated with CRS model are generally coincident to the ages inferred with ^137 Cs activities. However, there are also some discrepancies in the dates derived from the two methods. In particular, the age calculated with ^210Pb for the depth with an age of 1964 inferred with ^137Cs activities is remarkably different from the ^137Cs age. Although the sedimentation rates derived with the two methods are different, both of them indicate a quite similar trend of changes in accumulation in the reservoir during the last decades. Sedimentation was rather slow in the earlier stage, then was fast in the middle stage, and finally slowed down again in the later stage. Such variations in sedimentation rate in MG4-2 may be due to the human being activities in the catchment of Maigang Reservoir. Simultaneous uses of ^137Cs and 210 Pb methods may allow cross-checks of the results derived with the two methods and thus lead more reliable and accurate chronology and sedimentation rate.

关 键 词：^137Cs法 ^210PB 测年 沉积速率 麦岗水库 

分 类 号：S157[农业科学—土壤学] S124[农业科学—农业基础科学]