青藏高原拉萨河流域水化学时空变化特征控制因素研究

Study on the Spatiotemporal Pattern and Controlling Factors of River Water Hydro-Chemical Characteristics in the Lhasa River Basin,Tibet Plateau

根据丰、枯水期采集的拉萨河河水、地下水、降水以及冰川水样品,提取采样点子流域面积、地形、岩性以及冰川面积占比等流域特征因子。采用Piper图、Gibbs图分析河流水化学受岩石风化的控制作用;采用主成分分析和相关性分析方法,分析河流水化学主成分及其与子流域特征因子之间的关系。结果表明:拉萨河河水为HCO_(3)-Ca型水,主要受碳酸盐岩风化控制,蒸发盐岩溶解影响次之,丰水期河水水化学还受降水、冰川融水补给影响。河水水化学特征总体呈现为,随着子流域面积增加、海拔降低,水岩作用增强,碳酸盐岩风化作用增强,蒸发盐岩溶解作用减弱。而枯水期的冰川影响区,由于采样点控制面积大且枯水期地下水补给较强,蒸发盐岩影响作用随碳酸盐岩溶解增强而加强。研究结果为揭示高寒山区河水水化学特征的控制因素及区域规律研究提供科学依据。

Based on the samples of river water,groundwater,precipitation,and glacier meltwater collected from Lhasa River basin during the dry and wet seasons,the characteristics of sub-basins,such as area,topography,lithology,and glacier coverage for the sampling sites,were extracted.The Piper diagram and Gibbs diagram were used to analyze the controls of river hydro-chemical characteristics by rock chemical weathering,and methods of principal component analysis and correlation analysis were used to reveal the relationship between the main chemical components of river water and the landscape factors of sub-basins.The results show that the hydro-chemical type of river water is mostly HCO_(3)-Ca,which is mainly affected by the weathering of carbonate rock and the dissolution of evaporative rock.During the wet season,the hydro-chemical characteristics of the river water are also affected by precipitation and glacial meltwater.Generally,the contents of chemical compositions of the river water change with landscape characteristics.With the increase of sub-basin area and the decrease of altitude,the water-rock interaction and carbonate weathering are enhanced,while the dissolution of the evaporative rock is weakened.During the dry period and in glacierized sub-basins,the influence of evaporite on the chemical compositions of the river water is of great significance due to the large areas of sub-basins and the strong groundwater recharge.The study provides a scientific basis for revealing the controlling factors and regional patterns of the chemical characteristics of river water in cold and high-altitude areas.