Advances in Earth Science ›› 2005, Vol. 20 ›› Issue (6): 671-678. doi: 10.11867/j.issn.1001-8166.2005.06.0671

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ZHANG Yan; PAN Shaoming; PENG Buzhuo   

  1. Department of Urban and Resources Sciences, Nanjing University, Nanjing 210093, China
  • Received:2004-09-14 Revised:2005-02-16 Online:2005-06-25 Published:2005-06-25

ZHANG Yan;PAN Shaoming;PENG Buzhuo. AN OVERVIEW ON THE EVALUATION OF SEDIMENT ACCUMULATION RATE OF LAKE BY 137Cs DATING[J]. Advances in Earth Science, 2005, 20(6): 671-678.

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.

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