Pollution source identification methods and remediation technologies of groundwater: A review

Groundwater is an important source of drinking water.Groundwater pollution severely endangers drinking water safety and sustainable social development.In the case of groundwater pollution,the top priority is to identify pollution sources,and accurate information on pollution sources is the premise of efficient remediation.Then,an appropriate pollution remediation scheme should be developed according to information on pollution sources,site conditions,and economic costs.The methods for identifying pollution sources mainly include geophysical exploration,geochemistry,isotopic tracing,and numerical modeling.Among these identification methods,only the numerical modeling can recognize various information on pollution sources,while other methods can only identify a certain aspect of pollution sources.The remediation technologies of groundwater can be divided into in-situ and ex-situ remediation technologies according to the remediation location.The in-situ remediation technologies enjoy low costs and a wide remediation range,but their remediation performance is prone to be affected by environmental conditions and cause secondary pollution.The ex-situ remediation technologies boast high remediation efficiency,high processing capacity,and high treatment concentration but suffer high costs.Different methods for pollution source identification and remediation technologies are applicable to different conditions.To achieve the expected identification and remediation results,it is feasible to combine several methods and technologies according to the actual hydrogeological conditions of contaminated sites and the nature of pollutants.Additionally,detailed knowledge about the hydrogeological conditions and stratigraphic structure of the contaminated site is the basis of all work regardless of the adopted identification methods or remediation technologies.

Study on Obstacles to Continuous Cropping of Vegetables and Soil Remediation Technology

Firstly,this paper analyzes the cause of obstacles to continuous cropping of vegetables,and then introduces the soil ecological remediation technology used for overcoming obstacles to continuous cropping of vegetables. Finally,this paper analyzes the effect of applying soil ecological remediation technology in overcoming obstacles to continuous cropping of vegetables.

Remediation Technology for Combined Pollution of Lead and Cadmium in Farmland Soil

At present,the problem of heavy metal pollution in farmland in southern China is serious. Especially,the cadmium and lead are two heavy metal elements with serious pollution and great harm to human body. This paper reviewed some common methods and materials used in the control of cadmium and lead pollution in farmland soil. Then,it discussed the problems in the repair of cadmium and lead pollution in farmland soil. It came up with the future research direction,to provide references for remediation of lead and cadmium pollution in farmland soil.

The Research Progress and Status of In-Situ Remediation Technology of Groundwater

The characteristics and application of the in-situ remediation technology of groundwater,including air sparing,electro kinetic remediation,in-situ chemical oxidation,in-situ groundwater bioremediation and permeable reactive barriers,were compared and evaluated.The results show that over 90%of

The Analysis and Remediation Technology of the Pollution of the Groundwater Environment in Longkou Plain, China

In order to study the groundwater environment in the Longkou plain,48 groups of water samples are collected,consisting of 7 groups of surface water samples and 41 groups of groundwater samples.The quality of groundwater in the Longkou Plain is poor,with class V water quality accounting for more than 90%,and no class I,II water quality,sporadic distribution of Class III and IV water quality.The influencing factors of water quality are mainly inorganic indicators such as nitrate,total hardness,chloride,salinity and sulfate,the detection rate of heavy metals is low.Nitrate is the main pollution index in this area,and the increase of nitrate content is closely related to the construction of underground reservoir.Based on the characteristics of groundwater pollution in the Longkou Plain,the in-situ chemical remediation of groundwater pollution is proposed.

Analysis of Soil Remediation Technology for Heavy Metalcontaminated Sites in Electroplating Enterprises

The advantages and disadvantages of chemical leaching,phytoremediation,in-situ/ex-situ solidification and stabilization,cement kiln co-disposal and safe landfill remediation are analyzed.In addition,the application of chemical leaching and in-situ/ex-situ solidification and stabilization technology in the treatment of heavy metal-contaminated soil in electroplating enterprises in China is introduced in detail to provide reference for the remediation of heavy metal-contaminated soil around electroplating enterprises in China.

Site Pollution Remediation and Its Technology

This paper summarized the connotation of contaminated site remediation,the differences between contaminated site and brownfield,the differences between contaminated site and soil pollution and land pollution,clarified the relationship between the concepts,and introduced the remediation technology of contaminated site.

Overview of Patented Technologies for Remediation of Soil Pollution

Soil, an important material basis for human activities, is an indispensable natural rasource that is difficult to regenerate. It is also an important part of human ecological environment. Currently, soil pollution has affected China＇s agricultural production and threatened human health and ecological safety, so it has been paid more attention to by the people and has become a hot spot in environmental field. Through continuous research, a variety of soil remediation patents and technologies also emerge. Here, by retrieving the main words through the website （www. soopat. corn） and Chinese patent net, types of soil pollution and remediation technologies under the authorization status of the patents were analyzed, and the major species of soil pollutants and soil remediation technologies were reviewed.

Source,migration,distribution,toxicological effects and remediation technologies of arsenic in groundwater in China

Groundwater with high arsenic(As) content seriously threatens human life and health. Drinking high-As groundwater for a long time will lead to various pathological changes such as skin cancer, liver cancer,and kidney cancer. High-As groundwater has become one of the most serious environmental geological problems in China and even internationally. This paper aims to systematically summarize the sources,migration, distribution, toxicological effects, and treatment techniques of As in natural groundwater in China based on a large number of literature surveys. High-As groundwater in China is mainly distributed in the inland basins in arid and semi-arid environments and the alluvial and lacustrine aquifers in river deltas in humid environments, which are in neutral to weakly alkaline and strongly reducing environments.The content of As in groundwater varies widely, and As(Ⅲ) is the main form. The main mechanism of the formation of high-As groundwater in China is the reduced dissolution of Fe and Mn oxides under the action of organic matter and primary microorganisms, alkaline environment, intense evaporation and concentration, long-term water-rock interaction, and slow groundwater velocity, which promote the continuous migration and enrichment of As in groundwater. There are obvious differences in the toxicity of different forms of As. The toxic of As(Ⅲ) is far more than As(V), which is considered to be more toxic than methyl arsenate(MMA) and dimethyl arsenate(DMA). Inorganic As entering the body is metabolized through a combination of methylation(detoxification) and reduction(activation) and catalyzed by a series of methyltransferases and reductases. At present, remediation methods for high-As groundwater mainly include ion exchange technology, membrane filtration technology, biological treatment technology, nanocomposite adsorption technology, electrochemical technology, and so on. All the above remediation methods still have certain limitations, and it is urgent to develop treatment materials and technical means with stronger As removal performance and sustainability. With the joint efforts of scientists and governments of various countries in the future, this worldwide problem of drinking-water As poisoning will be solved as soon as possible. This paper systematically summarizes and discusses the hot research results of natural high-As groundwater, which could provide a reference for the related research of high-As groundwater in China and even the world.

Remediation Technologies for Cadmium Contamination in Greenhouse Vegetable Fields

Based on the literature and experimental results, three kinds of soil amendments, namely rice biochar, hydroxyapatite and potassium dihydrogen phosphate(KH2PO4), and deeper ploughing were selected to evaluate the field application effect of soil amendments and agronomic measures on the remediation of Cd contamination in greenhouse vegetable fields. Cd-contaminated greenhouse screening was conducted from 2015 to 2017. In September 2017, comparative tests of eight treatments were performed, and a preferred test was performed in September 2018. The screening results of the contaminated areas indicated that the distribution of over-standard sites was uneven, and Cd content was significantly different. Over-standard rate of No.4 greenhouse was 83.33% and was the highest, and the average content of Cd in soil was 0.535 mg/kg. It was used as a comparative test greenhouse for eight treatments. No.1 greenhouse was selected as the preferred test greenhouse, with three over-standard plots having average Cd concentrations of 0.530, 0.568 and 0.792 mg/kg. The comparative test results showed that after 8 months of remediation, the content of available Cd in the treatment of hydroxyapatite+rice biochar+deeper ploughing(T6) was reduced by 32.55% compared with CK(the control) and 24.96% than 2 months of remediation. The content of available Cd using the treatment of potassium dihydrogen phosphate+rice biochar+deeper ploughing(T7) decreased by 47.88% compared with CK and 31.00% than 2 months of remediation. The preferred remediation test results showed that in the treatment of hydroxyapatite+rice biochar+deeper ploughing: the mean Cd content decreased from 0.489 to 0.372 mg/kg, reducing by 23.86%, and the mean did not exceed the standard. Compared with CK, the mean content of available Cd decreased by 10.71% after 8 months, and the lowest content of available Cd in three treatments was 0.133 mg/kg. In addition, the Cd content, bioconcentration factor(BCF) and translocation coefficient(TF) of bean aboveground plants were decreased by 15.86%, 23.68% and 25.77%, respectively when compared with CK. Rice biochar+hydroxyapatite +deeper ploughing is a favoured technology for the remediation of Cd-contaminated greenhouse vegetable fields.

Bio-ecological remediation of freshwater aquaculture environments:A systematic review and bibliometric analysis

Freshwater aquaculture plays an important role in the global aquaculture industry.The success of freshwater aquaculture relies on the integration of bio-ecological remediation technologies to ensure its sustainable development.This paper systematically reviews the global literatures on bio-ecological remediation of freshwater aquaculture environments from 1990 to 2021,and discusses in detail the research progress and status quo in this field using both bibliometric analysis and content analysis.Our results indicate that the number of publications per year has increased year by year,with a particularly rapid increase after 2015.Institutions and researchers from China and the USA publish the greatest number of papers and contribute the most to this field.By analyzing the research progress in this field,we also find that the protection and restoration of freshwater aquaculture environments has received attention since as early as 1990,such as the application of constructed wetlands and recirculating aquaculture systems.Recently,researchers have increasingly focused on the use of microbial communities in remediation.Furthermore,vanRijn,J's papers are of great value to the research in this field.In content analysis,the application of primary technologies,including plant selection,aquatic animals,microorganisms,and biological filtration and purification equipment,as well as ecological engineering technologies with combinations of various types of organisms,is described to improve the effectiveness and efficiency of remediation.The performance,advantages,disadvantages,or limitations and prospects of these technology applications are analyzed in detail.By comparison,ecological engineering is shown to be the best remediation technology,being most comprehensive,and well-established.Taken together,this paper composes and summarizes existing work in this field,and provides guidance for future research on the improvement of existing technologies and the development of new technologies,with the aim of enhancing remediation capability,improving ecological sustainability and ensuring economic viability.

Study of polluted soil remediation based on freezing and thawing cycles

It is generally known that soil pollution poses a terrible hazard to the environment, but the present techniques of contaminated soil remediation cannot control this growing threat. This paper compares the pollutant extraction efficiency of traditional pumping and treating, which is a typical washing technology for the remediation of contaminated soils, with methods that utilize freeze-thaw cycles. In the soil freezing process, water shifts from unfrozen soils to the freezing front, and the permeability of soil will be enhanced under certain temperature gradients and water conditions. Therefore, this paper discusses the purification of contaminated soil through freeze-thaw action. We conducted a cleansing experiment on clay and silica sand infused with NaCl（simulation of heavy metals） and found that the efficiency of purification was enhanced remarkably in the latter by the freeze-thaw action. To assess the effective extraction of DNAPLs in soil, we conducted an experiment on suction by freezing, predicated on the different freezing points of moisture and pollutants. We found that the permeability coefficient was significantly increased by the freezing-thawing action, enabling the DNAPL contaminants to be extracted selectively and effectively.

Current Research and Strategy on the Biosurfactants Used in the Remediation of Petrochemical Polluted Environment

Biosurfactants are biologically active metabolites, and the efficiency of direct screening of new biosurfactants from nature using traditional methods is low, which should be enhanced in the following studies by adopting advanced biotechnologies. Rapid development and wide application of microbial culture independent methods, such as metagenomics, metatranscriptomics, metaproteomics and metabonomics, etc., contributes to quickly and precisely screening of novel biological surfactants. We mainly represented the current status of research and applications of biosurfactants in the remediation of petrochemical polluted environment, and also prospected avenues for future research.

Research Progress on the Remediation Benefits of Mineral Passivators on Heavy Metal Contaminated Soil

With the continuous development of society,the development of agricultural economy is also accelerating.Meanwhile,a large amount of sludge and waste materials enter the farmland system,and the state of soil heavy metal pollution is becoming more and more serious.In order to ensure food security and the health of people’s lives,a large number of experts and scholars have begun to look for remediation methods for heavy metal contaminated soil.At present,the use of mineral passivators in the remediation technology of heavy metal contaminated soil is a new and healthy recovery method,and has received extensive attention.

土壤中铬价态转化的影响因素与作用机制研究进展

土壤中铬(Cr)污染是全球性环境问题,六价铬Cr(Ⅵ)因其高毒性及致癌性而成为关注焦点。土壤中的Cr主要以Cr(Ⅲ)和Cr(Ⅵ)的形式存在,两者之间的转化受到诸如土壤pH值、氧化还原电位(Eh)、天然氧化还原剂、有机质和微生物的影响。随着工农业活动的增多,土壤中的Cr浓度不断增加,并通过植物吸收进入食物链等多种途径,对生态系统和人体健康构成威胁。本文对Cr在全球范围内的污染现状及来源、土壤中Cr的不同价态及其毒性特征进行了评述,并分析了pH、Eh对土壤中Cr的具体存在形态与价态的影响,及天然氧化还原剂、有机质等因素利用自身化学性质充当电子供体或受体的角色对土壤中Cr价态进行转化的氧化还原机理,以及不同影响因素之间的相互作用关系,从而可以全面理解土壤中Cr价态转化的行为机制。此外,在对Cr价态影响因素深入了解的基础上,总结了以生物炭和纳米材料为代表的先进修复技术方法,这些材料和方法由于能够将Cr(Ⅵ)有效地还原为毒性较小的Cr(Ⅲ),从而降低生态环境风险,因而是一类具有巨大潜在应用价值的修复材料和修复方法,但大规模应用的可行性及其修复效果仍需要进一步验证。

Research Progress of Analysis and Control Technologies against Urban Landscape Water Pollution

The root causes of urban landscape water pollution were analyzed in this study, the bio-ecological restoration technologies combing both exogenous and endogenous pollution control were put forward.

Suitability evaluation of remediation technology for polluted farmland

The suitability evaluation model of the remediation technology of polluted farmland has been constructed by analytic hierarchy process.The evaluation index of remediation technology has been constructed based on the physical and chemical index of farmland,farming system and the characteristic of remediation technology.In addition,the potential risk factors such as the distance of the industrial and mining enterprises,and the economy factors such as repair cost and local economy level have all been considered to construct the suitability evaluation system of the remediation technology of polluted farmland.Shilou town in Beijing was selected for the testing site,with the pollution of cadmium,arsenic and organic matter pollution.Chemical passivation,phytoremediation and biological compost technology were used for restoring the polluted farmland.According to the suitability evaluation model,the phytoremediation technology is suitable for general pollution.And chemical passivation and biological compost technology are more suitable to restore the polluted farmland.The combined remediation technologies of chemical passivation and phytoremediation are more suitable.It can avoid the limit of the one technology,complement the defect for each other and receive more remediation effects.

Managing international collaboration for the development and application of environmental technologies: opportunities for China & other Asia Pacific countries

Increased international cooperation in the field of contaminated site management has resulted in the formation of numerous networks and fora. The key benefits of increased co\|operation are perceived to be in the reduction of duplication in efforts, particularly related to industry, in the co\|ordination of contaminated site research, policy development and information dissemination. The paper introduces and briefly discusses key networks and collaborative projects currently in operation throughout the world relating to contaminated site management. The experience shared within these groups should prove useful to the application of such environmental problems in China and the Asia\|Pacific region.

基于应对土壤污染的优化淋洗技术研究

随着土壤污染问题的愈发严峻,土壤淋洗技术作为应用最为广泛的土壤修复技术之一,正受到广泛聚焦。本文通过对ALLU斗与异位土壤淋洗技术结合处理污染土的研究,从技术路线、修复车间剖面布置、平面布置3个维度进行设计,以某氰化物污染地为实验对象进行两次现场试验。实验结果表明了研究提出的ALLU斗与异位土壤淋洗技术结合处理污染土可行。

电动力耦合循环井技术修复低渗透含水层污染

提出一种电动力耦合循环井修复技术,以铬酸盐为典型目标污染物,研究该技术对低渗透含水层中地下水污染的修复效果及去除规律.结果表明:电动力耦合循环井技术相比循环井技术,修复半径扩大为原来的1.25倍,修复盲区面积占比从35.56%降为0,污染物的去除率从76.01%提高到了90.56%,相较于电动力修复技术电动力能耗降低了3个数量级,污染物去除率更高,可提升2~3倍.该技术耦合电动力方法实现了低渗透含水层中带电离子组分的强化定向迁移,解决了循环井在低渗透含水层中传质效率低、修复范围小、存在水力循环盲区等问题,修复效果显著提升.