2022年汉江流域中游“汛期反枯”背景下的区域地下水化学特征

Hydro-chemistry characteristics of regional groundwaterin the context of “flood season drought” in the middlereaches of the Hanjiang River basin in 2022

2022年6月份,长江流域由于大气环流异常等因素而爆发大面积的严重干旱,产生了“汛期反枯”的异常现象,这种现象一直持续到当年冬季。汉江是长江第一大支流,选取汉江中游襄阳段岸线带周边地下水为研究对象开展研究,采用多元统计分析、Piper三线图、主成分分析、Gibbs图等方法对该地区地下水水化学特征及动态变化进行分析。结果表明:研究区地下水水化学类型主要为低矿化度偏碱性水,地下水组分中的阳离子以Ca^(2+)和Na^(+)为主,阴离子以HCO_(3)^(-)为主,9月地下水pH偏高,地下水咸度有所下降;6月汉江流域襄阳段周边的地下水类型主要为HCO_(3)·SO_(4)-Ca·Mg型,9月地下水存在向HCO_(3)-Na型转化的趋势,离子浓度变化大多是整体变化,可能与周边含水层的侧向补给有关;地下水水化学特征受到周边碳酸盐岩和硅酸盐岩风化溶解共同控制,靠近下游区域的地下水阳离子交替吸附作用较强,受到干旱少雨的影响,导致该区域阳离子吸附作用明显减弱。

In June 2022,a large-scale severe drought broke out in the Yangtze River Basin due to abnormal atmospheric circulation and other factors,resulting in the abnormal phenomenon of"flood season anti-drought",which continued until the winter of that year.As the largest tributary of the Yangtze River,the Hanjiang river was studied by selecting the groundwater around the banks of the Xiangyang section of the middle reaches of the Hanjiang river as the research object,and analyzing the chemical characteristics and dynamic changes of groundwater in the area by using multiple statistical analysis,Piper three-line diagram,principal component analysis,Gibbs plot and other methods.The results showed that the chemical types of groundwater in the study area were mainly alkaline water with low salinity,The cations in the groundwater components are mainly Ca^(2+) and Na^(+),and the anions are mainly HCO_(3)^(-).In September,the groundwater pH was high,and the groundwater salinity decreased.In June,the shallow groundwater types around the Xiangyang section of the Hanjiang river Basin were mainly HCO_(3)·SO_(4)-Ca·Mg type,and there was a trend of groundwater conversion to HCO_(3)^(-)Na type water in September,The change of ion concentration is mostly the overall change,which may be related to the lateral recharge of the surrounding aquifer.The hydro-chemical characteristics of groundwater are controlled by the weathering and dissolution of surrounding carbonate rocks and silicate rocks.The cation exchange adsorption of groundwater near the downstream area is strong,which is affected by drought and less rain,resulting in a significant weakening of cation adsorption in this area.