【作者】 孙亚乔；

【导师】 钱会；

【作者基本信息】 长安大学 ， 地质工程， 2007， 博士

【摘要】 目前,粉煤灰对地下水环境影响的研究主要集中于粉煤灰浸出液对地下水环境影响的现状评价和预测上,对于粉煤灰浸出的化学特征和浸出液与不同介质相互作用的反应机理研究较少。本文以灞桥电厂灰场的粉煤灰为研究对象,通过室内实验和地球化学模拟,分析粉煤灰的浸出特征,揭示浸出液与不同介质相互作用机理。全文以浸出液的水—岩作用机理研究为主要目标,从粉煤灰浸出、浸出液的单相混合、浸出液的多相混合和浸出液的土柱实验四个角度出发,对粉煤灰浸出液及其与不同介质的水文地球化学作用进行系统研究,得出如下结论:1.通过粉煤灰浸出模拟实验,研究不同液固比和不同反应时间条件下粉煤灰的浸出特征,研究结果表明:由于粉煤灰中碱性氧化物CaO水解,粉煤灰浸出液为碱性溶液;随着液固比的增大,浸出液中Na⁺、Cl^-、Ca²⁺、SO₄^2-浓度呈现急剧下降的趋势,并迅速趋于稳定;在pH值高的粉煤灰浸出液中,Al³⁺主要以Al（OH）₄^-形式存在、SiO₂主要以H₃SiO₄^-的形式存在。在灰—水系统中,矿物NaCl、石膏、方解石和白云石的溶解/沉淀量随液固比的增大而逐渐变小;在时间和液固比的影响下,硅铝酸盐的溶解量随着反应时间的延长逐渐上升,随着液固比的增大逐渐减少。不同矿物的溶解/沉淀作用直接影响浸出液水化学组分的形成。2.浸出液与不同介质相互作用的实验结果表明,粉砂、亚砂土和黄土三种不同介质的混合溶液水化学特征各不相同,以粉砂为介质的多相混合溶液中主要水化学类型是SO₄-Ca和HCO₃-Ca型,以亚砂土为介质的多相混合溶液中主要水化学类型是SO₄-Ca·Mg和SO₄-Ca型,以黄土为介质的多相混合溶液中主要水化学类型是SO₄-Mg·Ca和HCO₃-Mg·Ca型。液固比对以粉砂为介质混合溶液中Na⁺浓度影响最大,对以亚砂土为介质的多相混合溶液中Ca²⁺、Mg²⁺、SO₄^2-浓度影响最大,对以黄土为介质的多相混合溶液中Cl^-浓度影响最大;对以亚砂土为介质的混合溶液中Na⁺、Cl^-浓度影响最小,对以黄土为介质的混合溶液中Ca²⁺、Mg²⁺、SO₄^2-浓度影响最小。3.以PHREEQC为模拟手段进行地球化学模拟,深入研究不同条件下水—岩作用过程中的化学反应。模拟结果表明:①在单相混合溶液中,随着混合比例增大,NaCl、石膏、方解石和白云石的饱和指数逐渐下降,由于混合过程中受到pH变化的影响,溶液中CO₃^2-活度降低较大,使方解石和白云石的饱和指数降低。②在多相混合溶液中,不同混合溶液与粉砂（或亚砂土）混合过程中水化学组分的演变,从初始溶液到最终溶液是经历NaCl、石膏、CO₂、白云石、钾长石溶解作用,方解石、玉髓、伊利石沉淀作用及CaX₂/NaX阳离子交换作用之后形成的;不同混合溶液与黄土混合过程中水化学组分的演变,从初始溶液到最终溶液是经历NaCl、石膏、CO₂、白云石、钠长石溶解作用,方解石、玉髓、伊利石沉淀作用及CaX₂/NaX阳离子交换作用之后形成的。③不同介质与不同溶液混合时,NaCl溶解量高低次序为:黄土＞粉砂＞亚砂土,NaCl溶解直接影响不同混合溶液中CI^-浓度高低;石膏溶解量的高低次序为:亚砂土＞粉砂＞黄土;石膏的溶解直接影响不同混合溶液中SO₄^2-浓度高低;方解石沉淀量高低次序为:黄土＞亚砂土＞粉砂;白云石溶解量的高低次序为:黄土＞亚砂土＞粉砂,白云石的溶解直接影响不同混合溶液中Mg²⁺浓度的高低;阳离子交换作用使Ca²⁺由固相进入液相的次序为:黄土＞亚砂土＞粉砂,从而使Na⁺由液相进入固相的次序为:黄土＞亚砂土＞粉砂;硅酸盐和硅铝酸盐不等量的溶解/沉淀作用影响着溶液中K⁺、Al³⁺、SiO₂浓度的高低。4.最后,通过亚砂土柱实验研究和模拟结果分析得出,在土柱渗滤过程中,粉煤灰浸出液比自来水对亚砂土中的矿物具有更强的溶滤作用,使粉煤灰浸出液渗滤土柱的渗透系数高于自来水渗滤土柱的渗透系数,矿物的溶解量也高于后者。更多还原

【Abstract】 A large amount of studies of the fly ash leachate is pertaining to the effects on groundwater environment present evaluation and prediction;however,only relatively few studies have attempted to predicting the chemical properties of leachate and the reaction mechanism in leachate-mediator interaction.Experimental and hydrogeochemical simulation focused on analyzing the chemical characteristic of fly ash leachate derived from the fly ash in Baqiao coal-fired power plant and explains the reaction mechanism in water-rock interaction of the leachate.Under the guidance of reaction mechanism in water-rock interaction of leachate,from the characteristic of leachate,the single-phase mixing,polyphase mixing and column experiment,the author discusses the hydrogeochemistry about the leachate with different meidiator.Through those work,some important conclusions can be drawn,as follows:（1）From leaching experiment,the author analyzes the chemical properties of leachate evolving over different solid/liquid ratio and time.It is shown the leachate is highly alkaline solution for the CaO dissolution.The concentrations of Na⁺、Cl^-、Ca²⁺、SO₄^2- is decreasing and being in stable quickly with solid/liquid ratio increasing.The dominant solution species of Al³⁺,SiO₂ is Al（OH）₄^-,H₃SiO₄^- in high pH.In flyash-water system,as the liquid/solid ratio increased,the dissolution/precipitation of halite,gypsum,calcite and dolomite decrease.As the reaction time increased,the dissolution of aluminosilicate increase;and as the liquid/solid increased,the dissolution of aluminosilicate decrease.The combined effects of these reactions result in the chemical characteristics.（2）The experiment of leachate water-rock interaction indicates the chemical characteristic that the mixing solution of silty sand,sandy loam,loess is different.The major chemical styles of silty sand mixing solution show SO₄-Ca and HCO₃-Ca,the major chemical styles of sandy loam mixing solution show SO₄-Ca·Mg and SO₄-Ca,and the major chemical styles of the loess mixing solution show SO₄-Mg·Ca and HCO₃-Mg·Ca.The liquid/solid ratio have the maximun influence on concentration of Na⁺ in silty sand mixing solution,the concentration of Ca²⁺,Mg²⁺,SO₄^2- in sandy loam mixing solution,and the concentration of Cl^- in loess mixing solution.The liquid/solid ratio has the minimum influence on concentration of Na⁺,Cl^- in sandy loam mixing solution,and the concentration of Ca²⁺,Mg²⁺, SO₄^2- in mixing solution. （3）The geochemical modeling approach was used to predict the chemical reaction in water-rock interaction of leachate to the water composition by the PHREEQC software.The simulations lead to following conclusions:①In single-phase mixing solution,the saturations of halite,gypsum,dolomite and calcite are decreasing with mixing ratio rising.The activities of CO₃^2- decreased as a function of pH, so the saturation of calcite and dolomite decrease.②In polyphase mixing solution,the evolution of chemical components,in mixing procedure of silty sand with solution,undergo the dissolution of halite,gypsum,CO₂, dolomite and k-feldspar,the precipitation of calcite,chalcedony,illite and cation exchange. The evolution of chemical component,in mixing procedure of loess with solution,undergo the dissolution of halite,gypsum,CO₂,dolomite and k-feldspar,the precipitation of calcite, chalcedony,illite,and cation exchange.③As the solutions mix with silty sand,sandy loam,loess individually,the dissolution amount order of halite is loess＞silty sand＞sandy loam,the halite dissolution influence the concentration of Cl^- in solution.The dissolution amount order of gypsum is sandy loam＞silty sandy＞loess,the gypsum dissolution influence the concentration of SO₄^2- in solution.The precipitation amount order of calcite is loess＞sandy loam＞silty sand.The dissolution amount order of dolomite is loess＞sand loam＞silty sand,the dissolution of dolomite influence the concentration of Mg²⁺ in solution.The cation exchanges make the Ca²⁺ into the solution from solid,make the Na⁺ into solid from solution,the exchange amount order is loess＞sandy loam＞silty sand.Under the combined effects of dissolution/precipitation of silicate and aluminosilicate,the concentration of Al³⁺ and SiO₂ is variation.（4） Finally,from the column experiment and geochemical simulation,the author puts up the leachate can dissolution more mineral than main-water,so permeability coefficient of the column filtration by leachate is bigger than by main-water,and the mineral dissolution capacity as so.更多还原