地下水化学组分对酸雨的滞后响应--以云冈石窟上层滞水为例

Lagged Response of Groundwater Hydrochemical Components to Acid Rain--A Study on Perched Groundwater in the Yungang Grottoes

酸雨入渗显著改变了某些地区的地下水水质,但关于地下水化学组分对酸雨响应过程的研究少有报道。以山西云冈石窟景区为研究区,通过对比酸雨、河水和地下水20年时间尺度的水化学组分变化,揭示了酸雨如何控制不同类型地下水的水化学演化过程。结果表明:2003年以来云冈石窟山体的饱和带地下水中SO_(4)^(2-)浓度未发生明显变化,其较高浓度的SO_(4)^(2-)来源为地下水区域尺度水循环过程中的水-岩反应;2003年和2012年二窟泉水中SO_(4)^(2-)浓度较低,但近几年其SO_(4)^(2-)浓度大幅度上升,分析成因为历史上的酸雨于近几年到达二窟泉,酸雨与砂岩的水-岩作用也引起了二窟泉水中其他阳离子浓度的明显上升;2003年以来石窟顶部上层滞水水质无明显变化,指示了历史上的酸雨至今尚未通过非饱和带下渗至上层滞水对应层位,证明石窟顶部粉土层具有良好的阻水作用。通过研究二窟泉水和石窟山体上层滞水对酸雨的响应关系,加深了对云冈石窟山体不同部位地下水来源的认识,对云冈石窟水害治理具有重要意义。

Infiltration of acid rain has significantly changed the groundwater quality in some areas,but there are few reports on the response process of groundwater chemical components to acid rain.Taking the Yungang Grottoes in Shanxi as the study area,by comparing the chemical components changes of acid rain,river water and groundwater over the past 20 years time scale,this paper reveals how acid rain controls the hydrochemical evolution process of different types of groundwater.The results show that the SO_4^(2-)concentration of groundwater in the saturated zone has not changed significantly since 2003,and the high concentration of SO_4^(2-)is derived from the water-rock reaction during the regional scale water circulation of groundwater.In 2003 and 2012,the concentration of SO_4^(2-)in the Cave NO.2 spring is relatively low,but in recent years,the concentration of SO_4^(2-)has increased significantly.It is assumped that the historical acid rain has reached Cave NO.2 spring in recent years,and the water-rock interaction between acid rain and sandstone also causes the concentration of other cations in Cave NO.2 spring to increase significantly.The water quality of perched groundwater overlying the grottoes has not changed significantly since 2003,indicating that the acid rain has not penetrated to perched groundwater through the unsaturated zone,which proves that the silt overlying the sandstone has a very low permeability.By studying the responses of Cave NO.2 spring water and perched groundwater of grotto mountain to acid rain,this study deepens understanding of the sources of groundwater in different parts of the rock mass of the Yungang Grottoes,which is of great significance for the control of water disaster in the Yungang Grottoes.