| 用137Cs计年法确定湖泊沉积物沉积速率研究进展 |
| |
| 引用本文： | 张燕,潘少明,彭补拙.用137Cs计年法确定湖泊沉积物沉积速率研究进展[J].地球科学进展,2005,20(6):671-678. |
| |
| 作者姓名： | 张燕 潘少明 彭补拙 |
| |
| 作者单位： | 南京大学城市与资源学系,江苏,南京,210093 |
| |
| 基金项目： | 国家重点基础研究发展计划(973计划);国家自然科学基金 |
| |
| 摘 要： | 137Cs计年法利用137Cs固有的理化和沉降特性，在湖泊沉积物的137Cs垂直分布与大气137Cs沉降间确立对应关系，找出有异常137Cs含量的沉积层作为时标，但需注意137Cs从水体表面至湖底的时间和粘粒含量对各层137Cs含量的影响，并用其它方法校验时标的可靠性。再求取不同时标层间的年均沉积厚度，或因克服了压实效应而更能反映真实沉积速率的年均沉积通量，且结合GIS等手段进一步估算湖泊各区域的沉积总量；还可延伸研究湖泊内源污染负荷及相关环境演变和湖泊演化。但是，沉积柱样的分割厚度取多少才能既满足计年精度要求又不使工作量过大，137Cs的大气沉降时间与进入沉积物时间还与泥沙的陆地迁移时间有关，沉积物中究竟是否发生137Cs下渗及其机理等都还是此法应用中有待解决的问题。
|
| 关 键 词： | 137Cs计年 沉积通量 滞后 下渗 |
| 文章编号： | 1001-8166(2005)06-0671-08 |
| 收稿时间： | 2004-09-14 |
| 修稿时间： | 2004年9月14日 |
AN OVERVIEW ON THE EVALUATION OF SEDIMENT ACCUMULATION RATE OF LAKE BY 137Cs DATING |
| |
| ZHANG Yan,PAN Shao-ming,PENG Bu-zhuo.AN OVERVIEW ON THE EVALUATION OF SEDIMENT ACCUMULATION RATE OF LAKE BY 137Cs DATING[J].Advance in Earth Sciences,2005,20(6):671-678. |
| |
| Authors: | ZHANG Yan PAN Shao-ming PENG Bu-zhuo |
| |
| Institution: | Department of Urban and Resources Sciences, Nanjing University, Nanjing 210093, China |
| |
| Abstract: | The vertical distribution of 137Cs in sediment profiles is present in accordance with the record of 137Cs fallout variations in the atmosphere. Therefore,137Cs can be used to infer a geochronology for sediment profiles and sediment accumulation rates can be estimated by measuring vertical distribution of 137Cs in sediment profiles. But some factors must be taken into account for dating horizon in sediment profiles more accurate and precise. The time lag between the time of atmospheric deposition of 137Cs and the time of deposition of 137Cs to sediment profiles should be calculated. For some sediment profiles 137Cs concentration per unit of clay should be explained. In order to prove the accurate of 137Cs dating, sediment accumulation rates estimated by 137Cs dating should also be compared with that measured at same site by other methods, such as standard sediment survey method,210Pb dating, sedimentary lamination, pollen and so on. Then with several depositional horizons marked by 137Cs the depth (cm) or the mass (g/cm2) of sediment for different time periods can be calculated. And it can be made to compare sediment accumulation rate in depth (sediment accumulation rate) and in mass (sediment flux) for different time periods. Because of compaction effect on sediment the sediment flux can well and truly reflect sedimentation rate. Based on the sediment flux and the area of lake bed measured by GIS, the annual gross accumulation of sediment can be calculated and internal load of pollutants in the lake sediment, lake evolution and environment changes of the lake basin can be studied further. Therefore, 137Cs dating has been extensively used for evaluation of sediment accumulation rate of lake, estuary, and ocean. However, there are still some problems under resolve. Firstly, how thickness of sampling should be divided up to meet both the needs of 137Cs dating precision and the propriety of measurement work. Secondly, attention should be paid to the lag time between 137Cs deposition in atmosphere and in sediment relates to the transport time from soil loss in field to lake. Thirdly, it should be also carefully taken into account whether diffusion and infiltration movement of 137Cs in sediment profiles occurred and what their mechanisms are. |
| |
| Keywords: | 137Cs dating Sediment accumulation rate Lag time Infiltration |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
| 点击此处可从《地球科学进展》浏览原始摘要信息 |
| 点击此处可从《地球科学进展》下载免费的PDF全文 |
|
