Effect Of Precipitating Ca²⁺?Mg²⁺from The Aeration Zone On The Shallow Groundwater Hardness

Through the survey of hydrogeology conditions in Fuxin,the soil in northern urban areas is selected as research object.Taking ion Na⁺in sewage,ion H⁺in acid wastewater and ion NH₄⁺in agricultural fertilizer for example,indoor immersion and eluviation tests are used to analyze impact mechanisms of three cations on groundwater total hardness and to study their contributions to shallow groundwater hardness.The experiment aims at forecasting potential impacts on groundwater hardness and providing scientific basis for the increase of groundwater hardness.Immersion experiment results show that the hardness replacement influence of ion NH₄⁺is the largest.Ion H⁺is the second and ion Na⁺is the third.The maximum amount of replacement is 96.909mg/L,70.260 mg/L and 68.295mg/L respectively.Three cations can replace 92 percents of ion Ca²⁺and ion Mg²⁺of the soil in one hour.Therefore,in the event of heavy rainfall or irrigation up to one hour,ion Ca²⁺and ion Mg²⁺will be replaced in a short period.The reaction of ion Na⁺,H⁺,NH₄⁺and ion Ca²⁺,Mg²⁺in soil can be well explained to quasi-two dynamics model.Fitting equation is highly significant correlation and the correlation coefficient is as high as 99 percents.Eluviation experiment results show that the reaction rate of ion Na⁺,H⁺,NH₄⁺and ion Ca²⁺,Mg²⁺in soil is faster at the beginning of the eluviation,and ion Ca²⁺,Mg²⁺in eluviation liquid is bigger.Three kinds of eluviation liquid of ion Ca²⁺in soil exchange reaction rates are significantly faster than ion Mg²⁺.Eluviation time of NaCl solution is the largest,HCl solution is the second and NH₄Cl is the third.The eluviation time is 18h,24h and 32h respectively.The reaction of ion Na⁺and ion Ca²⁺,Mg²⁺in soil is the cation exchange.The reaction of ion H⁺and ion Ca²⁺,Mg²⁺in soil is the acid leaching effect.And the reaction of ion NH₄⁺and ion Ca²⁺,Mg²⁺in soil includes both cation exchange and acid leaching effect.