不同地质背景下河流水化学特征及影响因素研究:以广西大溶江、灵渠流域为例

2013年5月至2014年4月,对漓江上游两个具不同地质背景的地表河流域进行一个完整水文年的观测和采样,探讨河流水化学的季节性变化特征和主要影响因素.结果表明,无论是碳酸盐岩占一半的灵渠流域,还是仅占9%的大溶江流域,其水化学类型均为Ca-HCO_3型,HCO_3~-和Ca~(2+)是主要的阴阳离子.河水的主要离子浓度整体表现为冬高夏低的特征,主要受流量变化的影响.Ca~(2+)、Mg~(2+)、HCO_3~-主要源自流域内碳酸对碳酸盐岩的风化溶解,同时存在硫酸风化碳酸盐岩和硅酸盐岩风化的贡献.此外,相较于灵渠,大溶江流域上游具较强侵蚀性外源水对下游碳酸盐岩的侵蚀,增加了碳酸盐岩风化对河流水化学的贡献.而K~+、Na~+、Cl~-、NO_3~-、SO_4~(2-)主要受大气降水和人类活动的影响,相较而言,灵渠流域受人类活动影响更为显著.

Hydrochemical Characteristics and Influencing Factors in Different Geological Background: A Case Study in Darongjiang and Lingqu Basin, Guangxi, China

The observation and sampling were carried out in May 2013 to April 2014 in a hydrological year for two river basins with different geological background in upstream of Li river basin. The seasonal variations of river water chemistry and its main influencing factors were discussed in this paper. The results showed that the hydrochemistry types of both Darongjiang basin with 9% of carbonates and Lingqu basin with nearly 50% of carbonates in area belonged to Ca-HCO₃ type. Ca²⁺ and HCO₃^- were the main cations and anions. The main ion concentrations were higher in winter and lower in summer, affected by the change of the flow. Ca²⁺, Mg²⁺, HCO₃^- were mainly sourced from the weathering of carbonates by carbonic acid. The weathering of carbonates by sulfuric acid and the weathering of silicate rocks also had contribution to the river water chemistry. In addition, comparing to the Lingqu basin, the contribution of the weathering of carbonates was much more than the percent of carbonates area, because the carbonate rocks were eroded by the allogenic water. On the other hand, K⁺, Na⁺, Cl^-, NO₃^-, SO₄^2- were mainly affected by the atmospheric precipitation and human activities. Comparing to the Darongjiang Basin, the effects of human activities on the changes of K⁺, Na⁺, Cl^-, NO₃^-, SO₄^2- were more significant in Lingqu Basin.