淋洗剂乙二胺四乙酸对重金属污染土工程特性的影响

以重金属铅（Pb2+）污染土和淋洗剂乙二胺四乙酸（EDTA）为研究对象,通过批次试验研究了不同浓度EDTA的淋洗对Pb2+污染土的渗透特性、持水特性、压缩特性、抗剪强度等工程特性的影响,为淋洗修复后土壤的二次利用提供参数支持。基于矿物成分、孔隙结构等微观试验,揭示了土壤工程特性变化的内在机制。研究结果表明,当淋洗剂EDTA浓度从0增加到0.15 mol/L,经淋洗修复后的污染土壤pH值从7.94下降到5.12,渗透系数降低超过一个数量级,黏聚力降低50%以上,而内摩擦角增大,持水性能提高,孔隙比从0.81下降到了0.76。微观试验的结果表明,随着淋洗剂浓度的增大,土壤中的蒙脱石、钠长石和伊利石矿物含量减少,石英矿物含量增加,其中蒙脱石含量从7.87%下降到了0.07%,而石英矿物含量增加了11.09%;淋洗后土壤单位质量进汞量由0.22 ml/g降低到0.15 ml/g,土壤总孔隙体积减少。重金属污染土淋洗修复工程在考虑重金属去除率及经济性指标的同时,还应考虑淋洗剂对土壤工程特性的弱化。     

水泥固化重金属污染土的强度特性试验研究

土体受到重金属离子污染后,会引起土的工程性质的改变,重金属离子的渗出也会给周围环境带来严重的危害。在国外,目前常采用水泥固化技术来处治重金属污染土;而在我国,这方面的研究成果还很少。主要通过系统的室内试验和理论分析,研究了在不同污染物掺量、污染物类型、水泥掺量以及养护龄期条件下固化污染土的强度特性。试验结果表明,金属污染物的存在会导致土体无侧限抗压强度较小幅度的降低,但随着水泥掺入量及养护龄期的增加,土体强度会有显著提高。试验结果还发现,不同的污染物类型及掺入量对固化污染土强度存在不同的影响,NaCl能促进水泥固化土早期强度的提高,而CuCl2和AlCl3则会阻碍水泥与土的固化反应。     

非饱和黄土渗透性规律的土柱试验研究

黄土边坡的变形破坏一般与地表水入渗导致的地下水位上升有关。然而,现场观测发现黄土地区地表水入渗深度有限,降雨的湿润峰一般在2m以内。自湿润峰以下至地下水位之间很长一段的含水率是不变的,那么地表水是如何补给地下水的,一直存在争议。为此,本文利用甘肃正宁县地区的Q3黄土重塑样进行非饱和渗透特性的土柱试验。在一个4m高的玻璃桶内制备土样,土柱上按一定间距插入水分计探头,在顶部按每天1000mL水量均匀渗入水,测得给定时间沿土柱的含水率剖面。结果发现,随着补给时间的延长,湿润峰下移,湿润峰经过的上半土柱含水率几乎不变,当湿润峰到达土柱底部时,形成潜水位,这和现场观察的现象一致。这说明在地表活动带以下,饱和带以上,虽然土的含水率不变,但存在着稳定非饱和渗流,这是黄土地区地下水的唯一补给方式。     

考虑温度电动淋洗法去除污染软土中铬试验研究

针对铬污染软土,自行设计了电动淋洗试验装置,开展了铬污染软土室内土柱淋洗试验,分析了试验过程中电流、电解质溶液pH的变化以及淋洗液种类、外加电压、温度对重金属铬去除特性的影响。结果表明:电动淋洗试验可以有效去除土壤中的重金属铬;相对于单一淋洗试验,用10 V电压强化淋洗试验显著提高了重金属铬去除效果,淋洗液为十二烷基苯磺酸钠（SDS）时Cr（VI）和Cr（总）去除效率是单一淋洗法的2.79,3.12倍。当电压为10 V,温度升高至45 ℃时,淋洗液为柠檬酸（CA）和草酸（OA）的各组试验表明Cr（Ⅵ）与Cr（总）去除率均相应提高;而淋洗液为十二烷基苯磺酸钠时的试验组中Cr（VI）去除率提高了5.84%,Cr（总）去除率降低了4.25%,表明升高温度使部分Cr（VI）还原成不易迁移的Cr（III）;淋洗液为草酸的试验组中升高温度时Cr（Ⅵ）与Cr（总）去除率最高,分别达到了82.08%、77.57%,分别相应提高了27.65%、26.01%。电动淋洗试验后,铬污染软土土粒结构变得更紧密,土粒之间的孔隙减小且被填充的更加密实。     

粉土p-y曲线的试验研究

进行了浸水黄河粉土中模型钢管桩的水平静力荷载试验,对试验弯矩用6阶多项式进行拟合,推得了黄河粉土的p-y曲线,并与API建议砂土和软黏土p-y曲线进行了比较。根据粉土试验p-y曲线,提出了黄河粉土p-y曲线的理论表达式,用此理论p-y曲线进行了水平荷载下模型桩的数值分析,并与试验测试弯矩进行了比较。研究结果表明：粉土的黏聚力对p-y曲线有很大的影响,忽略粉土黏聚力的抗力作用将导致桩基水平承载力的设计偏于保守;基于理论粉土p-y的模型桩的数值结果与试验弯矩值吻合得较好。     

黄河口不同强度粉土液化特性的试验研究

研制真空压缩装置以制备不同强度的粉土土样,并进行动三轴试验,测试不同强度粉土的液化特性。建立了土的强度与动剪应力比的关系,确立孔压增长模型及其参数,探讨土的强度和动应力对液化的影响。结果表明,（1）真空压缩装置制备土样过程中,土体超孔压在24 h内基本消散完毕,28 d贯入阻力达300～400 N,不排水抗剪强度达8 kPa,达到黄河口软弱土的强度;（2）土的强度与动剪应力比基本呈线性关系,且土的强度越高,孔压增长曲线越呈现上凸趋势,破坏时的孔压比也越大;（3）指数模型能够较好模拟黄河口粉土孔压增长情况,其中参数a和b分别位于0.77～5.63和0.17～4.65之间;对于孔压比上限,参数a, b分别为0.92和4.65;孔压比下限,参数a, b分别为1.25和0.89。     

Cu(Ⅱ)污染作用下膨胀土的胀缩时程效应研究

为探讨Cu(Ⅱ)对膨胀土胀缩特性的影响,针对初始状态相同的膨胀土试样,采用浓度为2.5 g·L-1、5.0 g·L-1、10.0 g·L-1的CuSO4溶液以及去离子水进行处理,开展一系列重金属Cu(Ⅱ)污染作用下的胀缩性试验,并运用Does Response模型对胀缩时程曲线进行描述;利用马尔文激光粒度测试,分析了污...     

粉土改良膨胀土的路用性能与现场试验

为探究粉土对膨胀土的改良效果,对不同粉土占比改良膨胀土进行了胀缩特性、路用性能和微观结构测试。研究表明：掺入粉土改变了膨胀土土体颗粒成分及结构,抑制了膨胀土的胀缩潜势;随着粉土颗粒的增加,膨胀土的密实度和无侧限抗压强度均先增大后减小,最大干密度在粉土占比为40%时达到1.889 g/cm³,无侧限抗压强度在粉土占比为10%时最大,加州承载比(CBR)值持续显著提高,回弹模量呈下降趋势,均满足规范要求;验证了粉土改良膨胀土的可行性,确定了最佳配合比为粉土掺量40%。为便于现场施工,并考虑现场拌和均匀程度,先掺入3%低剂量石灰对膨胀土进行“砂化”,降低膨胀土黏性使其破碎。在此基础上,采用粉土掺量40%对膨胀土进行改良后用于高速公路路堤填筑,并开展了现场压实度、CBR值、弯沉值等测试。现场试验结果表明：现场填筑联合改良试验段和单一石灰改良对照段整体压实质量良好,但试验段压实度易受粉土均匀程度影响而降低;试验段路基CBR值和路基弯沉与对照段相当,粉土改良有效弥补了相对于对照段减少的2%石灰所提供的强度。     

Unbiased identification of nonlinear sorption characteristics by soil column breakthrough experiments

Accurate identification of interactions of reactive solutes with porous media constituents is necessary for reliable risk assessment studies and the development of efficient sanitation strategies. Standard parameter estimation procedures bear a number of unsolved problems with respect to uniqueness and identifiability. This paper presents a new approach for the identification of nonlinear interaction parameters of column outflow experiments. The procedure requires no a priori assumptions on the shape of the underlying interaction process functions. Employing experimental data sets on cadmium and anthracene breakthrough as case studies, possible applications of the new approach will be shown, and its features will be discussed. Error analysis based on singular value decomposition of the sensitivity matrix quantifies the identification error. Identification procedures without a priori shape information are superior to fixed parametrizations in diagnostic investigations, especially in cases without reliable a priori knowledge on the sorptive interactions.     

Removal of heavy metals from a contaminated soil using organic chelating acids

Changes in heavy metal speciation and uptake by maize in a soil before and after washing with chelating organic acids, citric acid, tartaric acid and ethylenediaminetetraacetic acid were assessed. A sandy loam was collected from the vicinity of the Benue industrial layout, Makurdi, Nigeria and spiked with a quinternary mixture of nickel, copper, zinc, cadmium and lead nitrates to achieve higher levels of contamination. Batch soil washing experiments performed on 1.0 g portions of the spiked soil using 0.05 M chelating agents at a solid:liquid ratio of 1:25 showed that washing efficiencies varied in the order: ethylenediaminetetraacetic acid> citric acid> tartaric acid with metal extraction yields typically following the sequence, copper> nickel> zinc> cadmium> lead. Sequential extractions proposed by the European Communities Bureau of Reference method used to assess the redistribution of heavy metal forms in the soil showed that apparent metal mobilities were reduced upon soil washing. Citric acid removed most of the metals hitherto associated with the exchangeable and reducible fractions; tartaric acid, the exchangeable metal pools; and ethylenediaminetetraacetic acid, the non-residual metal pools. Heavy metal assay of harvested biomass of maize grown on unwashed and washed soil samples indicated that metal transfer coefficients, decreased in the order of treatment: ethylenediaminetetraacetic acid <citric acid <tartaric acid <unwashed soil. Ethylenediaminetetraacetic acid and citric acid appeared to offer greater potentials as chelating agents to use in remediating the high permeability soil. Tartaric acid, however, is recommended in events of moderate contamination.     

氨基膨润土对铜镍镉污染土壤的钝化修复研究

采集土壤,加入铜、镍和镉制成重金属污染土壤。以四乙烯五胺改性膨润土和膨润土原土作为修复剂,通过模拟酸雨和混合提取剂提取有效态重金属,评价膨润土和氨基膨润土对土壤中铜、镍、镉的钝化效果。结果表明:p H=3. 5的模拟酸雨对各污染土壤中重金属离子的提取率均在0. 1%以下。混合提取剂对污染土壤中有效态金属的提取能力比模拟酸雨强很多。添加膨润土原土和氨基膨润土均能钝化土壤中的铜、镍和镉,氨基膨润土上嫁接的氨基对金属有络合作用,因而比膨润土原土对铜、镍和镉具有更强的钝化能力。综合评价表明氨基膨润土是一种对铜、镍和镉污染土壤具有应用前景的钝化修复材料。     

Stabilization of fuel oil contaminated soil—A case study

Fuel oil contamination brings adverse effect on basic geotechnical properties of foundation soil. The present study pertains to one such case, from the petrochemical complex near Vadodara City in Gujarat State, India. Here, the fuel oil contaminated soil samples exhibit drastic changes in their geotechnical parameters. Noteworthy among such deleterious changes are: decrease in maximum dry density (–4%), cohesion (–66%), angle of internal friction (–23%) and unconfined compressive strength (UCS) (–35%) and increase in liquid limit (+11%). An attempt has been made to stabilize the contaminated soil using various additives viz., lime, fly ash and cement independently as well as an admixture of different combinations. It is apparent from the test results that the stabilization agents improved the geo-technical properties of the soil by way of cation exchange, agglomeration, and pozzuolanic actions. The best results were observed when a combination of 10% lime, 5% fly ash and 5% cement was added to the contaminated soil. The improvement in unconfined compressive strength (UCS), cohesion and angle of internal friction can be attributed to neo-formations such as Calcium Silicate Hydrates (CSH, CSH-1) that coats and binds the soil particles. Formation of stable complex between oil and metallic cations, results in reduction of leachableoil.     

污染土壤石油生物降解与调控效应研究

为考察修复过程中土壤石油降解效应,选用中国北方某油田区现场的原油污染土壤,进行了投加除油菌、调节氮磷营养含量和水分含量等强化措施的修复试验。经过180d修复,结果表明,土壤石油污染物去除率达70·6%,去除速率达0·15g·kg-1·d-1,与自然条件相比,石油污染物半衰期由929d减少为103d。饱和烃去除率占总石油去除的75%以上,主要为十八烷、二十七烷、二十九烷、三十一烷与三十四烷。初期投菌对石油污染土壤的生物修复具有快速启动作用,但后期多次投菌对生物修复的促进作用不明显。对氮磷营养水平的适当调节有利于生物修复进行,本试验中对除油菌生长和石油去除最有利的有效态碳氮比为C∶N=100∶1~50∶1。在石油去除过程中,土壤石油去除速率的变化与除油菌数量变化趋势基本一致,表明微生态环境调控对于污染土壤中的石油降解具有显著的促进作用。     

Utilization of a new soil stabilizer for silt subgrade

Silt cannot satisfy the requirements of highway construction because of its low strength. A new stabilizing agent (SEU-2) was developed to improve the mechanical performance and applicability of silt in road. Laboratory tests, including unconfined compression and shrinkage tests, were performed. Test results show that the new stabilizing agent can significantly increase the strength and the water stability, and decrease the shrinkage strain of silt. Field tests were also carried out and the results indicated that the new stabilizing agent could effectively improve the entire stiffness of subgrade. From the point of view in mechanics and applicability in road, adding 4% new stabilizing agent is an economic and reasonable method to stabilize the silt. The stabilized silt has high early strength, small shrinkage deformation, and high entire stiffness. It can satisfy the requirements of highway subgrades.     

土壤pH对镉存在形态影响的模拟实验研究

通过模拟实验,研究了土壤pH对水稻土、紫色土和黄壤的水溶态、可交换态、碳酸盐态、铁锰氧化态、有机结合态和残渣态Cd含量的影响。结果表明:在中碱性条件下,水溶态Cd质量分数比值小于3%,但pH<6.5时,水溶态Cd含量随着pH 减小迅速增加, pH 为4. 57 时,水稻土水溶态Cd 质量分数比值最高达48 39%;可交换态Cd含量在碱性条件下,随着土壤pH值增大迅速下降,在酸性区域内,可交换态Cd含量随pH增加呈上升趋势;碳酸盐态和铁锰氧化态Cd含量随土壤pH增大而增加;有机结合态Cd含量随土壤pH增加而增大,但变化幅度不大。对Cd污染的土壤进行治理时,控制土壤pH大于6.5以及增施有机肥等是减少Cd对生态系统危害的关键。     

Cd-As复合污染农田土壤修复材料的筛选

Cd和As两种污染物的离子电荷不同,化学性质迥异,因此Cd和As复合型重金属污染的土壤修复难度大。某地农田土壤呈弱碱性,因受老旧废弃垃圾填埋场的影响变为弱酸性,土壤样品中Cd和As均超标,有效态含量高,水稻样品超标率＞15.4%。实验室小试证明:生石灰可以降低Cd的活性,升高As的有效态,综合修复效果差;活性炭和矿物“微胶囊”因其吸附机制可同时降低Cd和As的有效态含量;活性炭钝化Cd的短期效应相与矿物“微胶囊”相当,钝化As的短期效应相比矿物“微胶囊”有一定的优势;矿物“微胶囊”的长期钝化效应最好,2年观察周期后活性炭效果归零,而矿物“微胶囊”效果稳定持续,有效态去除率最终可达90%。3种材料修复Cd和As复合污染型耕地土壤的综合性能筛选结果为矿物“微胶囊”（优）＞活性炭＞生石灰（差）。     

粉土循环累积应变和残余动模量的试验研究

粉土地基上建造的铁路或公路在交通荷载作用下易产生各种病害,导致基础设施不能正常工作。为研究交通循环荷载作用下粉土的累积变形和动力性能,针对钱塘江粉土开展一系列的循环三轴试验,探讨土体物理条件（相对压实度、含水率）和应力特征（频率、围压、动应力比）等对粉土累积轴向应变、动模量和阻尼比等的影响。试验结果表明,钱塘江粉土的临界动应力比约为0.11,当轴向动应力小于临界动应力时,粉土的动模量变化很小,相应的累积轴向应变也很小;当动应力超过临界动应力后,土样的动模量快速下降,残余动模量约为初始弹性模量的20%,同时,动模量和阻尼比随着累积轴向应变（或名义振次）的发展变化显著。粉土的动模量和阻尼比在归一化后可得到统一规律：在轴向应变（或名义振次）小于一定值时,动模量几乎不变,而后呈指数形式衰减,最终趋于稳定值;粉土阻尼比随着轴向应变（或名义振次）的发展呈指数关系增长。     

实验室与田间条件下骨炭粉与海藻肥对镉污染土壤修复效果评价

本研究基于小麦、玉米、高粱籽粒及烟草烟叶镉(Cd)消减率、修复边际效率及土壤中Cd有效态含量的变化等对比了实验室与田间条件下骨炭粉与海藻肥对Cd污染农田土壤的修复效果。研究结果表明：骨炭粉与海藻肥使玉米、小麦、高粱和烟草对Cd的吸收、转运均有显著(P<0.05)降低作用;在田间条件下,骨炭粉与海藻肥对不同作物籽粒或烟叶的Cd消减率为16.2%~39.8%,可增加作物产量12.3%~38.6%。钝化剂对不同作物增产效果有一定差异,对小麦籽粒增产作用最为有效。研究发现添加钝化剂改变了Cd在土壤团聚体中的分布,使得Cd在大粒径团聚体中负载量增加,并且与对照相比,显著提高土壤pH(提高0.43~0.77),降低土壤Cd的有效性,有利于控制Cd在土壤植物系统中的迁移。总体而言,不同钝化剂的Cd污染土壤修复边际效率为3.99%~14.74%,同海藻肥相比,骨炭粉的修复边际效率较高。不同钝化剂在盆栽实验的修复效果优于田间实验的效果,可能是因为相比于田间实验,盆栽实验条件下根系的作用范围有限,钝化剂的作用效果较高。