摘要
人类核事件形成的^(137)Cs蓄积峰作为一种重要的时标,被广泛应用于湖泊沉积物计年。在云南地区的湖泊沉积剖面中,除1963年^(137)Cs最大蓄积峰外,1975年和1986年蓄积峰存在与否,其成因及时标意义一直存在争议。本文选取滇西腾冲青海湖为研究对象,通过构建^(137)Cs沉积模型,利用重建的区域^(137)Cs大气沉降数据定量化拟合出^(137)Cs的沉积分布曲线,结合210 Pb_(ex)年代、Pu同位素分析结果及前人对区域其他湖泊的研究结果,对沉积物剖面中各^(137)Cs蓄积峰的年代、成因及其影响因素进行深入解析,进而识别其对应的时标特征。结果表明,腾冲青海湖沉积剖面中1963和1986年^(137)Cs峰主要由大气沉降的^(137)Cs蓄积形成,大气沉降量的贡献比例为77%~80%和51%~62%,分别对应1963年全球大气沉降高峰和1986年切尔诺贝利核事故沉降峰,具有明确的时标特征。腾冲青海湖沉积剖面中1975年^(137)Cs峰主要由流域输入的^(137)Cs蓄积形成,流域输入量的贡献比例高达80%~88%;由于流域输入成因的1975年^(137)Cs蓄积峰不具有明显的时标特征,因此不能作为时标应用。在云南地区,1963年^(137)Cs最大蓄积峰的时标特征明确,是湖泊沉积物计年的可靠时标;1986年蓄积峰的时标特征可识别,可作为该区域沉积物计年的辅助时标。
The^(137)Cs accumulation peaks recorded in lake sediments resulted from human nuclear activities have been served as important time markers and widely applied in modern sediment dating.In the lake sediment profiles collected in the Yunnan area,except for the common appeared main^(137)Cs accumulation peaks of 1963,whether there were sub-peaks of^(137)Cs corresponding to the year 1986 and/or 1975,the reasons for the formation of those so-called sub-peaks as well as whether they can be time markers were still controversial.In this study,Lake Qinghai in Tengchong,a natural volcanic lake located in western Yunnan,was selected as the major research object.By modeling the vertical distributions of^(137)Cs in sediment cores based on the reconstructed regional atmospheric deposition data of^(137)Cs,combined with the results of the^(210)Pb_(ex)age data and the distribution of plutonium isotopes,as well as the previous researches on other lakes in the region,the possible corresponded ages of the main accumulation peaks and sub-peaks of^(137)Cs in sediment profiles and their formation reasons as well as the influencing factors were comprehensively discussed,and the corresponded time markers of^(137)Cs in the region were further identified.The results indicated that the^(137)Cs peaks of 1963 and 1986 in sediment profiles of Lake Qinghai in Tengchong were respectively corresponded to the deposition of the global fallout from the nuclear weapon tests in 1963 and the regional fallout from the 1986 Chernobyl Nuclear Accident(CNA),with the contributions of 77%-80%and 51%-62%,respectively,showing the clear time-mark characteristics.While the^(137)Cs peak of 1975 in the sediment profiles was predominantly contributed by the catchment-derived^(137)Cs with the proportion of 80%-88%,implying that this peak could not serve as a time marker corresponding to the regional fallout from the Chinese nuclear tests in 1975.This study suggested that in the Yunnan Plateau region,the maximum peak of^(137)Cs provides a reliable time marker in 1963,and the sub-peak contributed from the 1986 CNA can also be identified as the time marker of the year 1986 for the modern sediment dating in the region.
作者
郭海婷
吴孟孟
潘少明
徐仪红
李启凡
康都
Guo Haiting;Wu Mengmeng;Pan Shaoming;Xu Yihong;Li Qifan;Kang Du(The Key Laboratory of Coastal and Island Development of Ministry of Education,School of Geography and Ocean Science,Nanjing University,Nanjing 210023,P.R.China;The Key Laboratory of Earth Surface Processes and Regional Response in the Yangtze Huaihe River Basin,School of Geography and Tourism,Anhui Normal University,Wuhu 241000,P.R.China;Tengchong Beihai Wetland Provincial Nature Reserve Management Bureau,Baoshan 679100,P.R.China)
出处
《湖泊科学》
北大核心
2025年第3期1081-1090,I0037-I0039,共13页
Journal of Lake Sciences
基金
国家重点研发计划项目(2016YFA0600502)
国家自然科学基金项目(41877449)联合资助
