Study On The Chemical Characteristics And Evolution Of Groundwater In The Tailai Basin

The Tailai basin is an important industrial area in Shandong province.It is well-developed in agricultural,industrial and densely populated.With the development of social economy,the contradiction between the supply and demand of water resources is becoming more and more prominent,and the influence of human activities on the groundwater system is becoming more and more significant,which seriously threatens the sustainable development of the region.Based on the systematic analysis of the geological and hydrogeological background of the Tailai basin,this paper has studyed the chemical feature and evolution of the groundwater in the Taylai basin by means of mathematical statistics,ratio of ions,isotope analysis and hydrogeochemical simulation to provide the scientific evidence for the sustainable development and utilization of regional groundwater resources.Researche has shown that the groundwater chemical types in the study area were mainly state of HCO3-Ca,HCO3-Ca·Mg,HCO3·SO4-Ca,HCO3·Ca·Mg,SO4-Ca·Mg.The cations of groundwater are mainly Ca2+,Mg2+,Na+,and the mainly anions are HCO3-,SO42-,NO3-and Cl-,and the coefficient of variation TDS,pH,Ca2+,Mg2+ and HCO3-are smaller in the groundwater.with a large variation coefficient of Na+,SO42-,Cl-and NO3-.The overall distribution of major ions(HCo3-,SO42-,Cl-,NO3-)and TDS space in groundwater is as follows:the total amount of recharge areas with higher elevations is small,and the discharge area along the groundwater run off path to the middle of the basin gradually increases,that is,with the Taian-Laiwu line as the central axis,presenting south,it shows high-altitude low-value areas on both sides of the south and north,the higher they are,the higher it is to the Tailai plain.The chemical components of groundwater are less affected by evaporation-concentration and atmospheric precipitation,while water-rock reactions are the controlling factor of water chemical ions.The dissolution of carbonate rocks and sulphate rock,such as calcite(CaCO3)and dolomite(CaMg(CO3)2),gypsum(CaSO4·2H2O),etc.This is the main source of Ca2+,Mg2+,SO42-and HCO3-in groundwater.The main source of groundwater recharge is atmospheric precipitation,and it is influenced by evaporation in the process of receiving recharge,and the groundwater is mainly mixed water of modem atmospheric precipitation.The typical profile evolution process can be summarized as the evolution of calcite from undersaturated state to saturated or oversaturated state;dolomite,gypsum and rock salt are basically dissolved in undersaturated state;cation exchange occurs takes place along the direction of groundwater runoff,and CO2 is in dissolving state and participates in water-rock-gas action.