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    巴丹吉林沙漠湖泊表层沉积物盐类矿物分布及对气候环境的指示

    Distribution pattern of saline minerals in surface sediments from lakes in the Badain Jaran desert and its implications for climate-environmental reconstruction

    • 摘要:研究目的】地下水补给是我国西北干旱地区湖泊的常见补给方式,尤其是在沙漠地区,了解该类型湖泊盐类矿物在湖泊中的沉积规律对于重建沙漠地区环境演化过程,探讨其对气候变化的响应具有重要的指示作用。【研究方法】本文以巴丹吉林沙漠南部地下水补给型湖泊为研究对象,分析了8个不同盐度的湖泊表层沉积物的矿物组合和分布特征。【研究结果】结果表明: 1)对于单个湖泊来说,多数湖泊盐类矿物沉积与具有径流补给的湖泊类似,即湖泊边缘碎屑矿物沉积较多,向湖泊内部盐类矿物沉积逐渐增多,且矿物类型由碳酸盐逐渐转为硫酸盐类和氯化物; 2)湖泊边缘沉积物的矿物组成更易受到湖泊水位、面积变化的影响,而靠近湖泊中心的沉积物可能受到水深和地下水补给的影响; 3)巴丹吉林沙漠地区浅水湖泊混合充分,不易受到湖水盐度、温度分层和底部淡水补给的影响,且盐类矿物总含量与湖水盐度具有较好的线性关系。【结论】沙漠地区地下水补给型湖泊沉积物中的盐类矿物组合和含量的变化能够很好地反映湖泊湖水盐度的变化。沙漠中湖泊对气候变化具有高度的敏感性,沙漠中湖泊的盐类矿物组合及含量的变化可以作为讨论全球变暖、沙漠化等环境问题的重要依据。

       

      Abstract: Objective It is of great significance to understand the distribution pattern of saline mineral deposits in lake basin for the reconstruction of palaeoenvironment and palaeohydrology. However, the studies on mineral distribution for groundwater recharged lake sediments are few, which hinders the climate-environmental reconstruction in arid area. MethodsThe Badain Jaran Desert, located in western Inner Mongolia in a hyper-arid area of China, is characterized by the coexistence of more than 110 perennial lakes and thousands of mega-dunes. More than 90% of the recharge of lakes between mega-dunes is from groundwater. In this study, we analyzed the mineral assemblage and distribution characteristics of the surface sediments of eight lakes with different salinity in the Badain Jaran Desert. ResultsThe results show that:1) For individual lakes, the distribution pattern of saline mineral deposits is similar to those of lakes with runoff recharge, that is, there are more detrital mineral deposits at the edge of the lake, and the saline mineral deposits gradually increase towards the lake interior, and the mineral types gradually change from carbonate to sulfate and chloride. 2) The mineral composition of the sediments near the lake edge is more easily affected by the variation of lake water level and area, while the sediments near the lake center may be affected by the water depth and the groundwater recharge. 3) The shallow lakes are well mixed and are not easily affected by the stratification of lake salinity and water temperature, and the replenishment of fresh water at the bottom. Moreover, the total content of salt minerals has a good linear relationship with the salinity of lake water. Conclusion The changes of saline mineral assemblage and its content in the lakes recharged by groundwater can well reflect the changes of lake salinity and can be used as a proxy of climate-environmental reconstruction in desert areas. The lakes in desert are highly sensitive to climate change. The changes of salt mineral assemblage and content in desert lakes can be used as an important basis for discussing environmental problems such as global warming and desertification.

       

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