藏南羊卓雍错近代沉积物碳酸盐氧同位素特征及其环境意义  

ENVIRONMENTAL SIGNIFICANCE OF STABLE ISOTOPE COMPOSITION OF CARBONATES FROM A SEDIMENT CORE AT LAKE YAMZHO YUMCO ON THE SOUTHERN TIBETAN PLATEAU OVER THE PAST 30 YEARS

作　　者：盛叶子 沈吉 孙伟伟[2] SHENG Yezi;SHEN Ji;SUN Weiwei(School of Geography and Ocean Science,Nanjing University,Nanjing 210023,Jiangsu;State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Science,Nanjing 210008,Jiangsu)

机构地区：[1]南京大学地理与海洋科学学院,江苏南京210023 [2]中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室,江苏南京210008

出　　处：《第四纪研究》2022年第6期1624-1632,共9页Quaternary Sciences

基　　金：科技部第二次青藏高原综合科学考察研究项目(批准号:2019QZKK0202);中国科学院(B类)战略性先导科技专项项目(批准号:XDB40000000)共同资助。

摘　　要：20世纪80年代以来气候变暖加剧,青藏高原冰川物质负平衡趋势增强,导致众多湖泊水位上升,但位于藏南地区的羊卓雍错,湖泊水位近年来却呈现出显著的波动下降趋势。本研究通过对羊卓雍错YZYC2沉积岩芯(长23 cm)进行Pb活度测定,建立沉积物的年代序列;分析公元1989年以来沉积物全样碳酸盐含量及其氧同位素组成,并结合现代气象及水文观测数据,揭示羊卓雍错沉积物碳酸盐氧同位素(δ^(18)O)的环境意义及其对气候变化的响应过程与机制。结果表明,YZYC2岩芯碳酸盐矿物以自生成因的文石为主,其含量变化范围为23.3%~39.7%,δ^(18)O值变化范围为-4.7‰~-3.2‰。沉积物碳酸盐δ^(18)O值总体呈波动上升趋势,较好地记录了近30年来羊卓雍错湖泊水位变化。1989~2019年羊卓雍错水位变化总体由降水与蒸发共同作用下的湖区有效湿度变化主导,同时也可能受到羊湖电站运行的影响。Since the 1980 s, the climate has intensified warming and the negative balance trend of most glaciers in the Qinghai-Tibetan Plateau has strengthened, with most lakes expanding. However, the water level of Lake Yamzho Yumco(28° 16′~29° 11′N, 90° 21′~91° 05′E) in the southern plateau has shown a significant decline in the recent years. Due to the lack of studies on the environment of Lake Yamzho Yumco recorded by sedimentary cores, the response of its water balance and hydrochemical changes to long-term climate changes needs to be further explored. Here we selected the sediment of Lake Yamzho Yumco(YZYC2), which was dated byPb activities, to analyze its carbonate content and the value of δ^(18)O during 1989~2019 A.D. The gravity core(YZYC2)was taken at a water depth of 30 m in Lake Yamzho Yumco at a GPS location of 28° 56′2.6″N, 90° 40′34.4″E in August 2020. The core was 23 cm in length and 23 sedimentary samples were obtained. The results showed that the content of carbonate minerals in YZYC2 fiercely fluctuated during 1989~2019 A.D., varying from 23.3% to 39.7%, and the average value was 32.8%;the values of δ^(18)O increased generally, varying from-4.7‰~-3.2‰, and the average value was-4.2‰. In addition, the carbonate minerals in YZYC2 were mainly authigenic carbonate(mostly composed of aragonite and calcite), and its carbonate δ^(18)O could precisely reflect the changes of water level over the past 30 years. Compared with modern meteorological and hydrological observation data, the water level fluctuation of Lake Yamzho Yumco in 1989~2019 A.D. was mainly caused by the change of effective humidity(the combined influence of precipitation and evaporation), while isotopic fractionation results from regional warming and glacial meltwater had little effect. Besides, the decreasing trend of water level from 2013 A.D. to 2015 A.D. may be affected by the operation of the hydropower station built by the lake.

关 键 词：羊卓雍错 湖相碳酸盐 稳定同位素 气候变化 水位变化 

分 类 号：P597.2[天文地球—地球化学] P467[天文地球—地质学]