%0 Journal Article
%T 137Cs DATING BY ANNUAL DISTINGUISH FOR RECENT SEDIMENTATION:SAMPLES FROM ERHAI LAKE AND HONGFENG LAKE<br>现代沉积年分辨的137Cs计年──以云南洱海和贵州红枫湖为例
%A Wan Guojiang
%A <br>万国江
%J 第四纪研究
%D 1999
%I 
%X Accurate dating of lake sediments is the basis of establishing precise geochemical cycle model and revealing regional pollution history and global environmental changes. The fallout radionuclide 137Cs is an efficient tracer for lake sedimentation and watershed erosion. 137CS vertical profiles have been successfully used for comparing sedimentation rates. However, it is very difficult to use the 137CS dating technique for determining low sedimentation rate (< 1cm / a) because of sampling problem, so it is necessary to improve on the differentiation level of sampling and determining. In the NOrth Hemisphere, the 1954 and 1964 bine markers of 137CS can be used for dating sediments, but the 137CS-activity peak of sediment horizon in the 1954 is too low to be distinginshed.The sampling equipment, which don' t disturb the sedimentS with the precision of sample separation as good as 0.1cm, were used to collect samples in Erhai Lake and Hongfeng Lake in 1997 and 1988. 137CS vertical profiles in sedimentS show three Peaks; the highest peak corresponds to the fallout accumulation in sediment horizon of the year 1964, the other tWo correspond to the global fallout delivery of 1975 and the leakage of the Chernobyl reactor of 1986. The three Peaks indicate the order of the 137CS accumulation in lake sedimentS, so they can be used as new bine markers. The discrepancy betWeen the 137CS vertical distribution characteristics and the deposihonal fluxes is probably caused by the 137CS diffusion in eariydiagenesis process, hilt the 137CS diffusion can' t change the location of 137CS peaks. Sediment accumulation rates, which are calculded according to the 1964, 1975, and 1986 bine markers respechvely, show good consistency. TIs reveals the possibility and reliability of the 1975 and 1986bine markers. The average sedimentation rate of Erhai Lake is 0.047 ± 0.0029 / (cm2.a) which agrees with the result of the 210pb method, and that of Hongfeng Lake is0.17 t 0.01g / (cm2. a) which is consistent with the observahon result since theestablishment of HOngfeng Lake. The 137CS achvity of the sediment horizon in 1964for Erhai Lake is 46.4Bq / kg and that of Hongfeng Lake is 145Bq / kg. Because thesedimentahon accumulahon rate of Hongfeng Lake is hoe bines of that of Erhai Lake,the '3'Cs ashvity of the sediment horizon in 1964 for Hongfeng Lake is 10 bines ofthat for Erhai Lake. 99.4% of 137CS inventory is distributed in sedimentS older than1985 for Hongfeng Lake and 19.4% of that is distributed in sedimentS younger than1986 for Erhai Lake, which indicates larger 137CS diffusion capacity in sedimentS ofErhai Lake than in Hongfeng Lake.
%K ~(137)Cs
%K sediment dating
%K Erhai Lake
%K Hongfeng Lake<br>沉积物计年
%K 洱海
%K 红枫湖
%K 云南
%K 铯137
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=621CF755B1A341E5&jid=EA07051745CDC8D89D5F01A3A4CFE6A9&aid=EA211525A4D563DAD747A7E7101BC30E&yid=B914830F5B1D1078&vid=2A8D03AD8076A2E3&iid=CA4FD0336C81A37A&sid=B9704B40A4225A24&eid=E203FB1A272C9DD2&journal_id=1001-7410&journal_name=第四纪研究&referenced_num=64&reference_num=20