三亚市原生环境水文地质问题与防治对策

Hydrogeological problems of primary environment and countermeasures in Sanya city

根据研究区的环境地质综合调查工作,查明了三亚市存在的原生环境水文地质问题有地下水酸化与地下水咸化。区内pH值介于5.5~6.5的弱酸性水主要分布于河流冲积层孔隙水及花岗岩风化裂隙水。地下水酸化主要受表层土壤酸化、含水介质上部覆盖层和碳酸的水解等影响。地下咸水区范围分布面积约为21.76 km^(2),地下水类型属松散-半固结岩类孔隙承压水,地下水矿化度为1.289~5.368 g/L,属于微咸水-咸水。3条高密度电法测线测量成果揭示咸淡水界面深入陆地50 m以上和钻孔揭示地下咸水水头压力普遍在4 m标高以上,认为地下水咸化与现代海水入侵无关。同时,咸水区内的钠氯系数(γNa^(+)/γCl^(-))介于0.4~0.78,平均值为0.58,推测该咸水属于古封存型咸水。最后探讨了上述环境地质问题的防治措施,为三亚市地下水资源保护与开发利用提供地学支撑。

Based on the comprehensive investigation of environmental geology in the study area,groundwater acidification and groundwater salinization are identified of the hydrogeological problems of primary environment in Sanya city.Weakly acidic water with pH value ranging from 5.5 to 6.5 were mainly distributed in the pore water of river alluvium and granite weathering fissure water.Groundwater acidification were mainly affected by acidification of the surface soil,the overburden of aqueous medium and the hydrolysis of carbonic acid.The distribution area of saline groundwater was about 21.76 km^(2).The groundwater type attach to unconsolidated and semi-consolidated rock type pore confined water.The groundwater salinity ranges from 1.289 g/L to 5.368 g/L,belonging to brackish water to salt water.The three high-density electrical measurement revealed that the interface of salt and fresh water was more than 50 m from coastline to land and the borehole revealed that the head pressure of saline groundwater was generally above 4 m elevation.Therefore,it was believed that the salinization of groundwater had nothing to do with the invasion of modern seawater.At the same time,the coefficient of sodium and chlorine(γNa^(+)/γCl^(-)) in the saline groundwater ranged from 0.4 to 0.78,with an average value of 0.58,suggesting that the saline groundwater belonged to the Paleo-sealed salt water.Finally,the prevention and control measures of the above problems are discussed to provide geoscience support for the protection and exploitation of groundwater resources in Sanya City.