粉煤灰、粘土、膨润土等对Zn2+的吸附试验研究

研究了粉煤灰、粘土、膨润土等从溶液中去除有毒金属离子Zn2+的吸附过程。动态试验显示吸附过程是快速的。吸附试验结果表明,粉煤灰、膨润土对Zn2+的吸附能力相当,但远大于粘土、粉质粘土。平衡吸附模型充分说明,在高浓度下Zn2+在粉煤灰、粘土、粉质粘土上的吸附符合Langmuir等温线。试验结果亦表明,随着吸附剂中Zn2+含量的增加,粉煤灰等吸附剂对Zn2+吸附的百分率均呈减小的趋势。     

宁南西吉含水层沉积物的氟释放特征

宁南西吉存在范围较大的高氟地下水区,属于高氟水重灾区.以宁南含水层沉积物为研究对象开展室内实验,探讨了pH、Ca2+、Na+、HCO3-和Ca2+/OH-协同作用对沉积物中氟释放的影响及定量关系.结果表明,相对于HCO3-,pH值对F-释放的促进作用更高,相对增量为10％～50％.低Ca2+/ Na+比提高了沉积物所释放F-的活度,有利于地下水中F-的聚集.不同岩性对pH值的缓冲能力不同,从而决定F-的释放.整体而言,粉质粘土、泥岩和粘土F-释放的浓度相对其他岩性要高.泥岩和粉质粘土的F-释放受pH影响较大.沉积物中Al、Fe、Mn、Si组分含量、总F-浓度与不同条件下淋滤出的F-浓度也具备较好的相关性.沉积物的F-含量对地下水中F-聚集有较大的影响.     

陕西省渭河扩建电厂粉煤灰处理场土壤对Cr（Ⅵ）的吸附作用

粉煤灰处理区的环境地质调查表明:由于受地面排放的粉煤灰的影响,地下水中Cr（Ⅵ）浓度高出背景值4⁵倍.野外现场试验对Cr（Ⅵ）监测结果显示:在2m厚的灰体底部,下渗水中的Cr（Ⅵ）浓度已高达0.701ppm,超标14倍.很明显,Cr（Ⅵ）是粉煤灰中的主要污染质之一.老灰场的环境地质调查还发现:土壤对Cr（Ⅵ）的迁移有很大的阻滞作用.作者对此进行一系列野外及室内试验来研究粉煤灰中Cr（Ⅵ）的解吸,迁移及其与土壤之间的相互作用和有关的化学机理,并且评价了渭河扩建电厂新灰场区土壤包气带对粉煤灰中Cr（Ⅵ）的净化能力.     

辽宁省典型地区高氟地下水的分布特征及成因分析

在前人研究的基础上,通过水文地质调查、综合物探法、水化学及水质检测方法,探测辽宁省典型地区水化学特征,分析了水化学特征与地下水氟离子的含量关系;不同地貌单元地下水氟离子含量分布不同;主要从高氟地下水形成的物质基础,水文地质环境对氟离子变化的制约,粘性土层是富集氟离子最好场所等方面分析辽宁高氟地下水的形成原因,通过研究了解到高氟地下水一般存在于潜水的上部及粘土层中,这一研究为今后寻找低氟水源提供前期有力资料奠定基础。     

凹凸棒粘土的除氟作用研究

凹凸棒粘土主要由坡缕石组成，后者为发育有一系列孔道的层链状硅酸盐矿物，具有很强的吸附能力，凹凸棒粘土的吸氟作用实验表明，其吸氟量随着溶液中氟离子浓度的提高而增加，在酸性含氟溶液中，凹凸棒粘土对溶液中氟的吸附量及溶液的降氟率都明显增加，而在碱性含氟溶液中，凹凸棒粘土对溶液中氟的吸附能力则大大降低，甚至不吸附。     

沉积物岩性及水化学性质对水土界面氟迁移行为的影响

水土界面氟的迁移对高氟地下水的形成具有重要影响。以大同盆地典型氟中毒区为例,分析了不同岩性沉积物中的氟质量分数和形态分布特征,并通过室内静态实验,探究了水溶液的pH值、Ca2+、HCO-3以及H2PO-4质量浓度对水土界面氟迁移的影响。研究结果表明,沉积物中不同形态氟按含量由高到低的顺序依次为:残余态氟铁锰氧化态氟水溶态氟有机束缚态氟离子交换态氟;各形态氟在不同岩性沉积物中含量大小均表现为:黏土粉质黏土粉砂;在沉积物中,黏土矿物和方解石是主要的固氟矿物成分。溶液的pH值、Ca2+、HCO-3以及H2PO-4质量浓度与氟在沉积物表面的吸附-解吸和沉淀-溶解平衡密切相关,沉积物对氟的吸附量随溶液pH值和HCO-3质量浓度增大而降低,随Ca2+和H2PO-4质量浓度增大而增大。     

露天堆放粉煤灰对地下水的污染研究

中国是煤炭资源非常丰富的国家,大多数火力发电厂均以煤炭为其电力生产的基本燃料,而其副产品粉煤灰则露天 露天堆放。粉煤灰中含有的大量重金属和放射性元素是潜在的污染源,尤其是对水环境的污染。文中选取一位于安徽淮北 的火力发电厂的储灰场,对其周边地表及地下水进行野外采样和分析,并取该灰场粉煤灰进行元素含量、矿物成分的分析 及室内淋滤实验。结果表明粉煤灰堆放场周边 12 个取样点的地下水水样中 NO3-,Cr6+,Se 含量超标,其中超标最严重的 Se 的超标率占检测水样的 58.3%,最大浓度值达到III类标准的 6.6 倍。进一步应用主成分分析和聚类分析方法对研究区地下水 离子进行水源分析,发现地下水化学成分主要有 3 个来源:天然背景下,很少受人为影响的水源,其贡献率为 53.32%;第 二个来源反映了处于径流区或排泄区的地下水源并受到一定程度人为因素的影响,其贡献率为 17.37%;第三个来源反映了 粉煤灰对地下水的污染,其贡献率为 14.96%。聚类分析的结果进一步验证了粉煤灰场污染地下水中的空间分布特征:即离 灰场越近,埋深越浅受污染的风险就越大。主成分分析和聚类分析法的应用为今后开展灰场对周围地下水影响的研究,确 定地下水是否受到污染及污染来源 , 提供了一条有效途径。     

滨海地区不同质地土壤对垃圾渗滤液中氨氮的吸附作用

为了探讨粉砂、粉质粘土、粉土对垃圾渗滤液中NH4+-N的吸附作用,在室内做了吸附实验,实验结果表明,三种土样吸附NH4+-N的等温吸附曲线均符合Langmuir模式,且最大吸附量分别为粉砂1.3 034 ms/g,粉质粘土1.109 mg/g,粉土0.3 439 mS/S.不同土样吸附NH4+-N的能力差异较大,三种土样的吸附顺序为:粉砂>粉质粘土>粉土;三种土样的迟滞因子分别为粉砂27.939,粉质粘土21.782,粉土18.257,说明粉砂和粉质粘土的防污能力较粉土强.     

污染场地六价铬迁移转化机制与数值模拟研究

随着全球工业化迅猛发展,土壤和地下水六价铬污染日益严重。基于某铁合金厂铬渣场地现场调查与采样分析,开展铬渣场地土样吸附、渗透和弥散试验,研究六价铬在粉质黏土土样中的吸附特性和迁移规律,建立考虑对流-弥散-吸附的六价铬迁移三维动力学模型,结合数值软件获取污染源位于场地上、下游时地下水中六价铬迁移分布特征,并揭示弥散度?和分配系数 对六价铬时空分布的影响。试验结果表明,粉质黏土对六价铬吸附符合Langmuir等温吸附模型,最大吸附量为466.6 mg/kg;蒸馏水和160 mg/L 六价铬溶液入渗下粉质黏土渗透系数约为6.5×10–7～6.7×10–7 cm/s,1 000 mg/L六价铬溶液的渗透系数增大至4.4×10–6 cm/s;粉质黏土水动力弥散系数D为1.4×10–4 m2/d,计算得到阻滞因子 为4.2～10。数值模拟结果表明,场地下游受到六价铬污染时,即使不考虑分子扩散作用,上游仍有被污染的风险,污染程度取决于含水层的弥散度;考虑含水层对六价铬吸附时,土体分配系数越大,六价铬污染羽分布范围越小,在预测地下水中六价铬浓度分布时应重点考虑六价铬吸附等转化过程。     

包气带土层对氮素污染地下水的防护能力试验研究

包气带土层能够有效滞留和吸附污染物,是阻隔污染物进入地下水的重要屏障。通过对北京市典型地区包气带土体进行土柱淋溶试验,研究包气带土层对氮素污染地下水的防护能力,实验结果显示,包气带土层对氮素的截污性能具有明显的分段性。粘质粉土对氮素污染地下水具有较强的截留和防护能力,粉砂截留和防护能力相对较差。经计算粘质粉土和粉砂对再生水的净化能力分别为83.3%、29.1%。包气带土层颗粒粒径愈大,污染物浓度高,水动力条件好,包气带土层的防护能力愈差。     

Feasibility of using fly ash,lime, and bentonite to neutralize acidity of pore fluids

Acidic groundwater resulting from the poorly planned use of acid sulfate soils has become a major environmental issue in coastal Australia over the last several years. Use of permeable reactive barriers (PRBs) designed to generate alkalinity by promoting sulfate reduction has recently become popular as an alternative solution to this problem. However, recent studies have also revealed that the long-term performance of such PRBs can be significantly undermined by chemical precipitation and clogging of pore space, which would decrease the buffer capacity and hydraulic conductivity of the reactive material. This study seeks to explore the feasibility of using bentonite in addition to lime and fly ash to form mixtures with a high buffer capacity and permeability that would enable groundwater flow through PRBs over a substantial period of time. A series of laboratory experiments, including buffer capacity and leaching tests, were performed on different mixtures of fly ash with lime and bentonite using acidic fluids of low pH. It was found that the ability of such mixtures to neutralize acidic fluids was mostly controlled by the content of lime. Laboratory data also showed that an addition of bentonite to lime—fly ash mixtures could decrease the buffer capacity of soil. Compaction tests indicated that the presence of bentonite would increase the dry density of mixtures at the optimum moisture content. A series of hydraulic conductivity tests were carried out to study changes in the coefficient of permeability of lime—fly ash mixtures with different contents of bentonite permeated with acidic liquids. The obtained results revealed that the coefficient of permeability of the specimens tended to increase over a period of time, likely due to the changes in the diffuse double layer of bentonite particles.     

掺土粉煤灰的工程性质试验研究

粉煤灰是火电厂燃煤的副产品,如何处理利用是国内外十分关注的问题。目前,解决这一问题的途径很多,利用粉煤灰进行筑坝或作为基础填筑材料是比较有效的消纳方法。粉煤灰是一种轻质、多孔松散体,在许多方面具有比较优越的工程性能,但因为纯的粉煤灰缺少必要的凝聚力,对水的反映较为敏感,从而对工程的安全运行造成不利影响。在粉煤灰中掺合不同量的黏土有望改善粉煤灰的工程性能,对不同掺土量粉煤灰力学特性的研究有助于更好促进粉煤灰的工程应用。以咸阳渭河电厂粉煤灰为研究对象,对其掺入不同比例的黄土掺合形成掺土粉煤灰,通过击实试验、压缩试验、直剪试验和三轴试验等研究不同掺土量下粉煤灰的工程特性,得到不同掺土量对粉煤灰变形及强度特性的影响规律,为在工程中有效利用粉煤灰,改善其工程性质提供参考。     

粉煤灰和二灰对桂林红黏土力学性质的影响

为了研究粉煤灰和二灰掺量及养护时间对桂林红黏土的改良效果,进行了直剪试验、固结试验以及电镜扫描试验。试验结果表明,粉煤灰的掺入提高了红黏土的抗剪强度,但超过一定量（18%粉煤灰掺量）反而会降低红黏土黏聚力,各掺量粉煤灰红黏土随养护龄期的延长,抗剪强度呈先增后缓趋势。二灰改良红黏土,在早期强度剧增,且强度随养护时间增长而大幅增加,一定龄期内,二灰红黏土黏聚力随二灰掺量呈先增后减趋势。粉煤灰和二灰的掺入均增大了红黏土的压缩模量,且随养护时间的延长而逐渐增大。红黏土中随粉煤灰、石灰的加入,发生一系列物理化学反应,从微观结构分析得知土中孔隙减少,结构性较素红黏土好。     

Development of synthetic soil mixture for experimental shaking table tests on building frames resting on soft soils

In this study, a synthetic soil mixture has been developed and proposed for experimental soil-structure interaction shaking table tests on building frames with shallow foundations resting on soft soil deposits. The proposed mix provides adequate undrained shear strength to mobilise the required shallow foundation bearing capacity underneath the structural model while meeting both criteria of dynamic similarity between the model and the prototype to model soft soils in shaking table tests. To find the most appropriate mixture, different mixes with different proportions of mix components were examined in the soils laboratory. Performing bender element tests, the shear wave velocity of the soil specimens was acquired at different cure ages and the results were examined and compared. Based on the test results, a synthetic clay mixture consisting of kaolinite clay, bentonite, fly ash, lime and water has been proposed for experimental shaking table tests.     

Reduction of Expansive Index,Swelling and Compression Behavior of Kaolinite and Bentonite Clay with Sand and Class C Fly Ash

Swelling behavior of expansive soil has always created problems in the field of geotechnical engineering. Generally, the method used to assess the swelling potential of expansive soil from its plasticity index, shrinkage limit and colloidal content. Alternative way to evaluate swelling behavior is from its expansive index (EI) and swelling pressure value. The present study investigates the reduction of EI and swelling pressure for kaolinite and bentonite clay when mixed with various percentages of Ottawa sand and Class C fly ash. The percentages of Ottawa sand and Class C fly ash used were 0–50 % by weight. The results show that there is a significant reduction in the swelling properties of expansive soil with the addition of Ottawa sand and Class C fly ash. The reduction in EI ranged approximately from 10 to 50 and 4 to 49 % for kaolinite and bentonite clay, respectively. Also the maximum swelling pressure of kaolinite and bentonite clay decreased approximately 93 and 64 %, respectively with the addition of various percentages of Ottawa sand and Class C fly ash. Standard index properties test viz., liquid limit, plastic limit and linear shrinkage test were conducted to see the characteristics of expansive soil when mixed with less expansive sand and fly ash. Also, for these expansive soils one dimensional consolidation test have been conducted with sand and fly ash mixtures and the results were compared with pure kaolinite and bentonite clay.     

Heave Studies on Fly Ash-Stabilised Expansive Clay Liners

Clay liners or compacted earthen barriers are important barrier materials used for preventing contaminant transport through soils. A low hydraulic conductivity (k) is a significant parameter that governs the design and construction of clay liners. Compacted expansive clays, which are montmorillonite clays, also have a very low hydraulic conductivity (k). When expansive clays are blended with fly ash, an industrial waste, the hydraulic conductivity (k) further reduces as the ash-clay blends result in increased dry densities at increased fly ash contents. Hence, fly ash-stabilised expansive clay can also be proposed as a unique clay liner material. As expansive clays undergo heave when they come into contact with water, it is necessary to study the heave behaviour of fly ash-stabilised expansive clay liners. This paper presents heave studies on fly ash-stabilised expansive clay liners. Fly ash in different contents by dry weight of the expansive clay was added to the clay, and the ash-clay blend was compacted as a liner overlying a natural field soil layer. Compacted lateritic clay was used for simulating the natural field soil into which contaminants migrate. Calcium chloride (CaCl₂) solution of varying concentration (5, 10, 20, 50, 100 and 500 mM) was used as the permeating fluid in the heave studies. The rate of heave and the amount of heave of the fly ash-stabilised expansive clay liners were monitored. Deionised water (DIW) was also used as inundating fluid for comparative study. Heave (mm) decreased with increase in solute concentration for all fly ash contents. For a given solute concentration, heave decreased up to a fly ash content of 20 % and thereafter it increased when the fly ash content was increased to 30 %. Heave of the fly ash-stabilised expansive clay liners was correlated with their permeability, liquid limit (LL) and free swell index (FSI) pertaining to the respective fly ash content and CaCl₂ concentration.     

1,2-二氯乙烷和1,2-二氯丙烷在某污染场地包气带的吸附-解吸特性

1,2-二氯乙烷(1,2-DCA)和1,2-二氯丙烷(1,2-DCP)是某污染场地地下水中检出最高的挥发性有机污染物。文中采用批试验方法,研究污染场地包气带中三种不同深度土壤样品对1,2-DCA和1,2-DCP的吸附-解吸特性。结果表明:土壤中有机质决定其吸附行为,三种土壤对1,2-DCA和1,2-DCP的吸附符合Henry线性等温方程,分配系数在20.49～22.43L.kg-1,1,2-DCA和1,2-DCP在三种土壤中分别具有相似的吸附能力;同一土壤中两种目标污染物的吸附能力为Kd(1,2-DCA)>Kd(1,2-DCP),但差别不大。1,2-DCA和1,2-DCP在三种土壤中的解吸可用Freundlich等温方程拟合,解吸的难易程度与土壤中黏粒含量相关,黏粒含量越高,目标污染物的解吸越困难,第三层(地下4.9～5.1m)土壤的防污能力较强;两种污染物在三种土壤中的解吸都存在明显的滞后效应,1,2-DCP的滞后指数比1,2-DCA的大。     

软土深层搅拌桩的水泥土抗腐蚀性室内试验

结合深港西部通道填海区深层搅拌桩在滨海地下水环境中施工的需要,对水泥土在自来水、地下水、海水及Na2SO4溶液环境下的抗腐蚀性进行了室内研究,研究表明以纯水泥为固化剂的水泥土在腐蚀性地下水环境中的抗腐蚀性能较差,增加矿渣、粉煤灰的含量,能增强水泥土抗腐蚀性;分析了固化剂中矿渣、粉煤灰掺入量对水泥土抗压强度及抗腐蚀性的影响规律,即固化剂掺入比不变的情况下,用矿渣、粉煤灰替代部分水泥能大幅度提高水泥土的抗压强度,同时改善其抗腐蚀性;得出了抗腐蚀性能良好的水泥土配方,即矿渣、粉煤灰的质量占固化剂的40%～60%,可供同类工程借鉴.     

德兴铜矿地区土壤的基本特征及其对重金属元素的吸附研究

本文首先分析了江西德兴铜矿区周围土壤的微量元素和矿物组成特征,结果显示该地区重金属元素富集,且表层土中重金属元素含量与粘土矿物相对含量变化具有较好的一致性。室内土柱淋滤实验结果表明,当总淋滤时间为451 h时,土壤对Pb²⁺的总吸附量为2 584.75 mg/kg,淋滤实验的前半期存在多种竞争吸附机制,后半期土壤对Pb²⁺的吸附基本达到动态平衡。淋滤后土壤矿物的相对质量分数发生了改变,粘土矿物有所减少。粘土矿物在不同土壤层对Pb²⁺的吸附能力也各异。