桂林覆盖型岩溶区土壤溶液对碳酸盐岩的溶蚀能力探讨  

Discussion of the soil solution corrosion of carbonates in the covered karst area of Guilin

作　　者：闫志为[1,2] 曾召田[3] 刘辉利[1,2] 王羽辉 李水新[1,2] 周国清[4] 周小红[5] 

机构地区：[1]桂林理工大学环境科学与工程学院,广西桂林541004 [2]广西矿冶与环境科学实验中心,广西桂林541004 [3]桂林理工大学土木与建筑工程学院,广西桂林541004 [4]桂林理工大学测绘地理信息学院,广西桂林541004 [5]中国地质科学院岩溶地质研究所,广西桂林541004

出　　处：《水文地质工程地质》2015年第2期132-139,155,共9页Hydrogeology & Engineering Geology

基　　金：国家自然科学基金(41162011);广西高等学校高水平创新团队及卓越学者计划

摘　　要：在桂林覆盖型岩溶区6处包气带土层中,通过钻探定深采集土样34组,进行土工实验,测定其密度、孔隙比、饱和度、塑性指数等物理指标。以浸提法（土水质量比1∶5）提取土壤溶液,测定其p H值和HCO^-3、CO3^2-、Cl^-、SO4^2-、Ca^2＋、Mg^2＋、Na^＋、K^＋等离子含量。其中,对B1、X7两孔采集的24组土样,采用PHREEQC软件将浸提原液模拟浓缩至接近于天然土不同饱和度的含水量,根据浓缩结果分别计算方解石、白云石饱和指数,判别土壤溶液在给定各含水量条件下对碳酸盐岩的溶蚀能力。主要认识如下：①土壤p H值为4.35~7.08,多较低,大部分为酸性土和强酸性土。紧靠石灰岩面的土p H值较大。②土壤溶液中Ca^2＋、Mg^2＋等各种离子含量均很低。受人类活动影响,B1、X7两钻孔表现除浅部Ca^2＋、SO4^2-、HCO^-3含量高、深部低,其它几种离子则表现出含量较少且上、下基本一致甚至向下略有微量升高的特征。③人类活动区浅部土层中Ca^2＋、Mg^2＋、Na^＋、SO4^2-、Cl^-含量均明显高于人类活动较少区。④靠近石灰岩面的土壤溶液中Ca^2＋含量高。在距离下伏灰岩面几米以远的包气带土层中Ca^2＋等含量很少。⑤不同浓度土壤溶液的SIC、SID与桂林周边碎屑岩裂隙水接近,均为负值,且其绝对值较大,表明对方解石、白云石具有较强溶蚀能力;且SID均明显小于SIC;由于同离子效应,随着浓缩程度提高SIC、SID逐渐升高,但仍为较小负值。⑥与桂林漓江水、漓江两岸第四系孔隙水、岩溶地下水相比,不管是土样浸提原液还是按不同比例浓缩后土壤溶液的SIC、SID均明显更低,单纯从溶解作用考虑,其对方解石、白云石的溶蚀能力更强。桂林黏性土土壤溶液SIC、SID低、溶蚀作用强主要是由于桂林地区长期湿润多雨的气候条件造成较低土壤p H值和低Ca^2＋、Mg^2＋等离子含量以及土壤中高CO2分压所致In the Guilin karst area,34 groups of soil samples in six soil strata of the aeration zone are collected by drilling to the certain depth. The density, porosity, saturation, plasticity index and other physical indicators of the soil are determined with soil test methods. The soil solution is extracted by leaching（ soil andwater ratio is 1∶ 5）,its p H value and the ion contents including HCO^-3,CO3^2-,Cl^-,SO4^2-,Ca^2＋,Mg^2＋,Na^＋,K^＋are determined. For 24 groups of the soil samples collected from holes B1 and X7,the leaching soil solution is concentrated close to the moisture content of different saturation in natural soil using the PHREEQC procedure simulation. The saturation index of calcite and dolomite are calculated respectively,and the corrosion ability of the soil solution to carbonates under diffetent moisture content is distinguished. The results show that： ①most of the soils are acid and strongly acid with lower p H values ranging from 4. 35 to 7. 08,and the soil p H value is the highest near the limestone surface. ② The concentrations of ion such as Ca^2＋and Mg^2＋are low. In holes B1 and X7,because of the influence of human activities,the contents of Ca^2＋、SO4^2-and HCO^-3are high in the shallow part but low in the deep part. For other ions,the contents are low and consistent in the upper and the lower parts,and even have a slight rise according to the depth. ③The contents of Ca^2＋,Mg^2＋,Na^＋,SO4^2-and Cl^-in the shallow strata affected by human activities are significantly higher than those in the other area. ④The soil solution near the limestone surface has high contents of Ca^2＋,but in the aeration zone strata a few meters far from the underlying limestone surface,the contents of Ca^2＋are low.⑤The SICand SIDof the soil solution of different concentrations are close to those of the fissure water in clastic rock around the Guilin area,which are negative and with high absolute value and has strong corrosion ability to calcite and dolomite. The SIDis significan

关 键 词：桂林 岩溶区 土壤溶液 碳酸盐岩 溶蚀能力 

分 类 号：P642.25[天文地球—工程地质学]