非均匀电动力学修复技术对土壤性质的影响

非均匀电动力学技术是正在发展中的环境修复技术，其特点之一是不破坏原有的环境系统。通过小型实验研究了非均匀电动力学及其运行方式对土壤性质的影响，分析了非均匀电动力学的作用机理和影响因素，同时研究了非均匀电动力学系统的能耗和运行特征。实验结果表明，采用合适的运行方式和运行参数，可以最大限度地保护土壤原有的特征，降低能量消耗，具有潜在的应用前景。     

重金属污染土壤电动力学修复技术

电动力学修复技术是把电极插入受污染的土壤并通入直流电 ,发生土壤孔隙水和带电离子的迁移。土壤中的污染物质在外加电扬作用下发生定向移动并在电极附近累积 ,抽出处理从而被除去。新兴的电动力学原位修复技术去除土壤重金属污染正越来越多地被各国研究人员接受。一系列实验规模的研究和技术已日渐成熟 ,其中Lasagna技术和Electro klean技术已在美国肯塔基州和路易斯安那州等地进行了原位修复     

电动力学技术强化原位生物修复研究进展

介绍了利用电动力学技术强化土壤及地下水原位生物修复的原理和最新进展。电动力学强化的基本原理是利用电渗析、电迁移和电泳等电动力学效应加速污染环境中有机污染物和微生物运动,注入营养物、电子受体或活性微生物,或者利用电极反应和电流热效应为地下生物降解创造有利条件。研究表明．电动力学技术能有效地强化原位生物修复,而且该技术不破环生态环境．安装和操作简单,成本低廉．有广泛的应用前景。     

重金属污染土壤电动力学修复技术

电动力学修复技术是把电极插入受污染的土壤并通人直流电，发生土壤孔隙水和带电离子的迁移。土壤中的污染物质在外加电扬作用下发生定向移动并在电极附近累积，抽出处理从而被除去。新兴的电动力学原位修复技术去除土壤重金属污染正越来越多地被各国研究人员接受。一系列实验规模的研究和技术已日渐成熟，其中Lasagna技术和E-lectro-klean技术已在美国肯塔基州和路易斯安那州等地进行了原位修复。     

EDTA强化电动力学修复重金属复合污染土壤

在自制的电动力学装置中,研究多种重金属复合污染土壤的电动力学修复,通过在阴极添加络合剂EDTA来提高修复效率。实验结果表明,EDTA的引入提高了修复过程中的电流值,且EDTA与重金属的络合提高了污染物向电极液的迁移效率,从而强化了电动力学修复效果。在设定的浓度(0、0.01、0.02、0.05和0.1 mol/L)中,0.1 mol/L的EDTA具有最佳的修复效率。在此实验条件下,污染土壤中的总铜、总铅和总镉的去除率分别为90.2%、68.1%和95.1%。电动力学修复后,对土壤重金属进行化学形态分析,发现电动力学修复显著改变了土壤重金属存在形态,修复后土壤中的铜、铅、镉主要以较稳定的有机态和残余态形式存在,显著降低了对周边生物和环境的毒害。     

利用电动力学方法向土壤注入无机盐研究

研究了利用电动力学向土壤注入无机盐过程中,电极运行方式、电压和注入时间对营养盐分布的影响。结果表明,采取变换电场方向的运行方式,更有利于电场中营养盐的均匀分布。通过电动注入的方式,可以在较短时间(24～36h)内向土壤中有效引入硫酸盐,且随着时间的延长,硫酸根在土壤中的浓度不断提高。由于电场可导致不同氮形式间的转化,引起含氮营养盐有效形态的流失,因此电动注入硝酸盐的时间不宜过长,在72 h内为佳。同时,由于硝酸根迁移速度较快,因此为保证硝酸盐在土壤中的浓度,0.5 V/cm电压梯度的效果较好。     

镉污染胶东棕壤的电动力学修复研究

在Cd污染的胶东棕壤土体两端加以1 V/cm的直流电压梯度进行电动力学修复.考察了电动力学修复过程中阴阳极电解液pH、电渗流量和电流密度的变化,并将处理后的土体分6段进行了分析,主要参数为pH、电导率、土壤中Cd的浓度及其形态分析.结果表明,经过445.0 h的电动力学修复,阳极附近3段土壤中Cd的去除率分别达到98.19%、97.01%和96.24%;阴极附近3段土壤中出现了Cd富集现象,且pH为5.88的土壤段Cd的富集率最高.     

土壤电动修复中菲迁移的数值模拟

针对菲污染土壤修复建模的问题,通过对电动力学作用下菲污染土壤的迁移现象的室内模拟实验,确定了影响菲迁移的电渗流、电迁移、对流和弥散4个主要过程,建立了电动力学作用下菲在污染土壤中的迁移模型;运用COMSOL Multiphysics 5.3软件结合迁移模型的各项方程和选取的参数对菲的迁移过程进行了模拟计算。结果表明:当孔隙率分别为0.33、0.38、0.43和0.48时,菲的最大迁移率分别为31.89%、34.78%、37.97%和41.74%;当电压从0.5 V·cm~(-1)增加至2 V·cm~(-1)的过程中,电渗流通量增大,最大迁移率可达到44.35%;修复区域的浓度均呈"碗状"分布,模拟计算得到在中间靠近阳极区域的菲的浓度达到最小值2.14 mol·m~(-3),迁移率最大为38%。模拟计算的菲迁移分布结果与实验所得结果相吻合,证明该模型用于电动修复多环芳烃污染土壤的适用性。     

电动力学法修复土壤环境重金属污染的研究进展

介绍了电动力学法的基本原理和国外的一些电动力学修复重金属污染土壤的工艺,如Lasagna工艺、阴极区注导电性溶液工艺、阳离子选择性透过膜、CEHIXM工艺、Electro—Klean^TM电分离技术、电化学自然氧化技术、电化学离子交换技术、电吸附技术等,并指出了这些工艺的优缺点。评价了电动力学法处理地下土壤环境中重金属污染的优势及目前存在的问题。     

高岭土模拟铜污染土壤电动力学修复

采用电动力学方法修复重金属污染土壤。研究中采用高岭土模拟铜污染土壤,结合电动力学修复理论,考察了不同电压、添加络合剂条件下铜的修复效果。结果表明,当电压强度为0．5V／cm时,最靠近阴极部分的土壤中Cu^2＋的C／C。为1．596,当电压强度为1V／cm时,C／C0为2．245,说明适当提高电压强度能够有效的增加Cu^2＋的迁移效果;土壤中未加入络合剂时,Cu^2＋大部分集中在第5段土壤中,C／C0为1．339,在土壤中加入络合剂以后Cu^2＋大部分集中在靠近阴极部分的土壤中,C／C。为1．716,说明在污染土壤中加入一定量的络合剂可以与Cu^2＋结合生成螯合物,提高Cu^2＋的迁移效果。     

污染土壤电动修复增强方法研究进展

污染土壤电动修复是一项新兴绿色原位修复技术。其原理是在土壤上施加直流电场 ,利用电迁移和电渗去除污染物 ,土壤pH、Zeta电位以及土壤化学性质等因素影响电动修复效果。为了提高修复效率和扩大电动修复应用范围 ,现在已经发展了针对不同类型土壤和污染物的增强修复技术。本文归纳总结了 1995年以来土壤电动修复中常用增强处理效果的 8种方法 ,即酸碱中和法、阳离子选择膜法、电渗析法、络合剂法、表面活性剂法、氧化 还原法、EK 生物联用和LasagnaTM法 ,且对每种方法的典型实验装置、增强原理、方法特点和适用范围等进行了分析和讨论 ,为以后的实验设计提供了有益的参考     

Removal of fluorine from contaminated soil by electrokinetic treatment driven by solar energy

Instead of direct current power supply, a series of electrokinetic remediation experiments driven by solar energy on fluorine-contaminated soil were conducted in a self-made electrolyzer, in order to reduce energy expenditure of electrokinetic remediation. After the 12-day electrokinetic remediation driven by solar energy, the removal efficiency of fluorine was 22.3 %, and electrokinetic treatment had an impact on changes in partitioning of fluorine in soil. It proved that the combination of electrokinetics and solar energy was feasible and effective to some extent for the remediation of fluorine-contaminated soil. Meanwhile, the experimental results also indicated that the electromigration was a more dominant transport mechanism for the removal of fluorine from contaminated soil than electroosmosis, and the weather condition was the important factor in affecting the removal efficiency.     

Establishing and Evaluating the Risk Implications of Uniform Soil Remediation Goals

Abstract

There is growing interest in the establishment of uniform, concentration-based soil remediation goals to accelerate the cleanup of contaminated sites and to provide consistency in the extent of cleanup required for similar sites. If uniform goals are used in a region, post-remediation risk will vary across sites due to regional variability in site properties. Thus far, of the national and state agencies that have established or proposed uniform concentration guidelines, none have quantified the regional variability in risk that is likely to result with their use as remediation goals.

This paper describes a methodology for evaluating regional cancer risk variability resulting from use of uniform, concentration-based soil remediation goals, presents an example application of the methodology, and examines its utility for establishing uniform goals for organic contaminants in soil. The methodology is based on the integrated transport, fate, exposure, and risk model SoilRisk. Also addressed is the issue of contaminants for which regional risk variability is expected to be large with use of uniform soil remediation goals. An approach is described for reducing such variability by development of alternative uniform contaminant concentration levels for categories of sites differentiated by site geographic location or physical-chemical properties.     

植物修复重金属污染土壤的强化措施

植物修复技术作为一种新兴的绿色环保技术,有着高效、经济和生态协调等特点而成为当前研究的热点领域,而且由于其修复的彻底性和环境友好性而在治理污染土壤实地过程得到广泛应用.概述了当前植物修复研究的基本类型和修复机理,并着重从生物技术、农艺措施和物理化学等强化手段上阐述了利用超富集植物修复污染土壤,以进一步提高超富集植物的修复效率,为大规模治理重金属污染土壤和商业化应用提供技术途径和科学依据.     

Soil vapor extraction in sandy soils: influence of airflow rate

Airflow rate is one of the most important parameters for the soil vapor extraction of contaminated sites, due to its direct influence on the mass transfer occurring during the remediation process. This work reports the study of airflow rate influence on soil vapor extractions, performed in sandy soils contaminated with benzene, toluene, ethylbenzene, xylene, trichloroethylene and perchloroethylene. The objectives were: (i) to analyze the influence of airflow rate on the process; (ii) to develop a methodology to predict the remediation time and the remediation efficiency; and (iii) to select the most efficient airflow rate. For dry sandy soils with negligible contents of clay and natural organic matter, containing the contaminants previously cited, it was concluded that: (i) if equilibrium between the pollutants and the different phases present in the soil matrix was reached and if slow diffusion effects did not occur, higher airflow rates exhibited the fastest remediations, (ii) it was possible to predict the remediation time and the efficiency of remediation with errors below 14%; and (iii) the most efficient remediation were reached with airflow rates below 1.2 cm(3)s(-1) standard temperature and pressure conditions.     

Environmental features of two commercial surfactants widely used in soil remediation

One of the main limitations for a wider application of surfactants in soil remediation is the lack of knowledge about environmental fate and toxicity of surfactant itself especially for in situ application. Sorption behaviour, biodegradability, toxicity of parent compound and its metabolites are important processes that affect environmental fate of surfactants in site remediation applications. Tween 80 (poly(oxyethylene)(20)-sorbitane monooleate) and Aerosol MA+80 (dihexyl sodium sulfosuccinate) are surfactants that have been tested in laboratory and field scale remediation of soil and groundwater. In this work, the sorption and biodegradability of these surfactants were assessed to provide conditions and limitations for their use. The soil used in this experimentation was analysed for organic carbon content, soil bacteria, and size fraction and resulted to be a good model because is characterised by mean values for almost all considered parameters. Tween 80 showed high degree of biodegradability but a high affinity for soil matrix. Results suggest that Tween 80 could find its best application in ex situ solid phase remediation like ex situ bioremediation; its high affinity to soil could limit in situ applications. Biodegradation tests for Aerosol MA+80 show low degree of biodegradability and mineralisation. Biodegradation experiments, coupled with analysis of toxicity, could support the hypothesis that degradation of Aerosol MA+80 is not complete and leads to an accumulation of intermediates with at least the same toxicity of the parental compound. Therefore, aquifer remediation application with Aerosol MA+80 has to be conducted with necessary precautions to avoid product loss and excess surfactant should be flushed from the soil.     

Remediation of phenanthrene-contaminated soil by simultaneous persulfate chemical oxidation and biodegradation processes

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous compounds with carcinogenic and/or mutagenic potential. To address the limitations of individual remediation techniques and to achieve better PAH removal efficiencies, the combination of chemical and biological treatments can be used. The degradation of phenanthrene (chosen as a model of PAH) by persulfate in freshly contaminated soil microcosms was studied to assess its impact on the biodegradation process and on soil properties. Soil microcosms contaminated with 140 mg/kg_{DRY SOIL} of phenanthrene were treated with different persulfate (PS) concentrations 0.86–41.7 g/kg_{DRY SOIL} and incubated for 28 days. Analyses of phenanthrene and persulfate concentrations and soil pH were performed. Cultivable heterotrophic bacterial count was carried out after 28 days of treatment. Genetic diversity analysis of the soil microcosm bacterial community was performed by PCR amplification of bacterial 16S rDNA fragments followed by denaturing gradient gel electrophoresis (DGGE). The addition of PS in low concentrations could be an interesting biostimulatory strategy that managed to shorten the lag phase of the phenanthrene biological elimination, without negative effects on the physicochemical and biological soil properties, improving the remediation treatment.     

Removal of organic contaminants from soils by an electrokinetic process: the case of atrazine. Experimental and modeling

The atrazine behaviour in soils when submitted to an electric field was studied and the applicability of the electrokinetic process in atrazine soil remediation was evaluated. Two polluted soils were used, respectively with and without atrazine residues, being the last one spiked. Four electrokinetic experiments were carried out at a laboratory scale. Determination of atrazine residues were performed by enzyme-linked immunosorbent assay (ELISA). The results show that the electrokinetic process is able to remove efficiently atrazine in soil solution, mainly towards the anode compartment: Estimations show that 30-50% of its initial amount is removed from the soil within the first 24h. A one-dimensional model is developed for simulating the electrokinetic treatment of a saturated soil containing atrazine. The movement of atrazine is modelized taking into account the diffusion transport resulting from atrazine concentration gradients and the reversed electro-osmotic flow at acidic soil pH.     

From classic methodologies to application of nanomaterials for soil remediation: an integrated view of methods for decontamination of toxic metal(oid)s

Soil pollution with toxic elements is a recurrent issue due to environmental disasters, fossil fuel burning, urbanization, and industrialization, which have contributed to soil contamination over the years. Therefore, the remediation of toxic metals in soil is always an important topic since contaminated soil can affect the environment, agricultural safety, and human health. Many remediation methods have been developed; however, it is essential to ensure that they are safe, and also take into account the limitation of each methodology (including high energy input and generation of residues). This scenario has motivated this review, where we explore soil contamination with arsenic, lead, mercury, and chromium and summarize information about the methods employed to remediate each of these toxic elements such as phytoremediation, soil washing, electrokinetic remediation, and nanoparticles besides elucidating some mechanisms involved in the remediation. Considering all the discussed techniques, nowadays, different techniques can be combined together in order to improve the efficiency of remediation besides the new approach of the techniques and the use of one technique for remediating more than one contaminant.     

Physicochemical and biological quality of soil in hexavalent chromium-contaminated soils as affected by chemical and microbial remediation

Chemical and microbial methods are the main remediation technologies for chromium-contaminated soil. These technologies have progressed rapidly in recent years; however, there is still a lack of methods for evaluating the chemical and biological quality of soil after different remediation technologies have been applied. In this paper, microbial remediation with indigenous bacteria and chemical remediation with ferrous sulphate were used for the remediation of soils contaminated with Cr(VI) at two levels (80 and 1,276 mg kg^?1) through a column leaching experiment. After microbial remediation with indigenous bacteria, the average concentration of water-soluble Cr(VI) in the soils was reduced to less than 5.0 mg kg^?1. Soil quality was evaluated based on 11 soil properties and the fuzzy comprehensive assessment method, including fuzzy mathematics and correlative analysis. The chemical fertility quality index was improved by one grade using microbial remediation with indigenous bacteria, and the biological fertility quality index increased by at least a factor of 6. Chemical remediation with ferrous sulphate, however, resulted in lower levels of available phosphorus, dehydrogenase, catalase and polyphenol oxidase. The result showed that microbial remediation with indigenous bacteria was more effective for remedying Cr(VI)-contaminated soils with high pH value than chemical remediation with ferrous sulphate. In addition, the fuzzy comprehensive evaluation method was proven to be a useful tool for monitoring the quality change in chromium-contaminated soils.