1950年以来青藏高原兹格塘错碳酸盐稳定碳同位素变化及其原因  

Variation of δ^(13)C value in authigenic carbonates from Zigetang Co,Tibetan Plateau since 1950 AD

作　　者：类延斌[1,2] 张虎才[1] 李世杰[1] 杨伦庆[1,2] 姚书春[1] 李春海[1] 雷国良[1] 张文翔[1] 

机构地区：[1]中国科学院南京地理与湖泊研究所湖泊与环境国家重点室,南京210008 [2]中国科学院研究生院,北京100049

出　　处：《湖泊科学》2010年第1期143-150,共8页Journal of Lake Sciences

基　　金：国家自然科学基金项目(40871096);中国科学院重要方向项目(KZCX2-YW-338)联合资助

摘　　要：兹格塘错是青藏高原中部一个典型的半混合型咸水湖泊。本文在^(210)Pb和^(137)Cs定年的基础上,研究了兹格塘错重力岩芯(ZGTC A-1)小于38.5μm细颗粒组分碳酸盐稳定碳同位素1950年以来的变化及其影响因素。对冬夏季湖水水化学特征的分析表明,夏季湖水溶解CO_2呈逸出状态,冬季湖水钙离子浓度是夏季湖水的10倍,据此可以得出兹格塘错碳酸盐矿物主要在夏季沉淀。通过与那曲气象站气象记录对比发现,1950年以来A-1岩芯碳酸盐碳同位素变化与年均温度有很好的相关性,表现出年均温度高时碳同位素偏重,而年均温度低时碳同位素偏轻的特征。兹格塘错1950年以来自生碳酸盐碳同位素的变化是由湖区及水体碳循环(如碳酸盐沉淀,有机质的沉淀与分解,有机碳和无机碳的转化等)的变化引起的,但各种因素的相互作用非常复杂。碳酸盐含量也与温度有关,温度越高,碳酸盐含量越高,同时降水量与碳酸盐含量也存在明显的相关关系。1950年以来有机质含量与温度呈反相关,可能与湖泊生产力的下降有关。Zigetang Co, located on the central Tibetan Plateau, is a meromictic saline lake. A 96-cm-long core （ZGTC A-1 ） was taken from Zigetang Co （the water depth 25m） in summer 2006. The age of the upper 9.25cm （since 1890AD） of the core was got through CIC model of ^210Pb. The δ^13C during the past 60 years had good correlation with the average temperature in Naqu Station, which indicated that it was mainly controlled by average temperature in a year. When the annual mean temperature was higher, the δ^13C value in the sediment became heavier and vice versa. In Zigetang Co, the main factor controlling the 813C was the CO2 exchange between lake water and atmosphere. Seasonal variation of Ca^2 ＋ and dissolved inorganic carbon （DIC） indicated that the calcium carbonate （ mainly composed of calcite and aragonite） mainly precipitated in summer. The dissolved CO2 in the lake water escaped into the atmosphere due to the relatively high temperature in summer. When the average temperature in a year was higher, the escape of CO2 into the atmosphere became larger due to the shorter frozen time on the lake surface in winter and higher water temperature in summer, which induced the δ^13C of the dissolved inorganic carbon in the lake water was more positive, so do the δ^13C in carbonates.

关 键 词：兹格塘错 细粒碳酸盐 无机碳同位素 现代过程 青藏高原 

分 类 号：P597[天文地球—地球化学]