岩石风化对三峡库区农业小流域水化学特征的影响

Impact of rock weathering on water chemical characteristic in a typical small agricultural watershed of Three Gorges reservoir areas

通过对三峡库区典型农业小流域-重庆涪陵王家沟小流域为期一年的水质系统监测,明确了流域主要离子组成,分析了小流域的水化学特征和主要离子来源.结果表明,该流域水化学类型为Cl-—Ca2+型;大多数离子的含量随采样点、季节、水体类型的不同而有显著性差异;Gibbs图、阴阳离子三角图分析结果表明,该流域水体离子组成受岩石风化的影响比较显著,且阴离子可能主要来自于岩盐溶解和碳酸盐的风化,而岩盐溶解也是控制流域阳离子的主要机制,硅酸盐矿物的风化侵蚀作用也存在一定影响;主成分分析得出对该流域水体离子组成影响最大的可能是碳酸盐(其中H2CO3风化碳酸盐岩过程比H2SO4风化作用更为显著),其次是岩盐、硅酸盐,农业活动和居民生活也有一定影响.

One year’s systematic monitoring on the water quality in a typical agricultural watershed in the Three Gorges reservoir areas-Wangjiagou small watershed,located in Fuling,Chongqing,hade been conducted,for understanding its water chemical charateristics as influenced by rock weathering process.The results showed that water quality could be classified as Cl-—Ca2＋type,and the contents of most ions varied with different sampling points,seasons and water bodies.Gibbs and triangular diagrams analyses revealed that the water compositions in the watershed were significantly impacted by rock weathering process.The anions in the water bodies mainly derived from the dissolution of evaporites and carbonate weathering,while the cation compositions were mainly under the control of the later process together with the weathering and erosion of silicate minerals to some extent.Further,principal component analyses suggested that the impacts of rock weathering on the water ion compositions in the studied watershed followed a sequence of carbonate〉 evaporates〉 silicate minerals,and the carbonate weathering process was subjected to H2CO3 rather than H2SO4.In addition,agricultural and domestic activities could also show some impacts on water characteristics.