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Greenhouse vegetable production is currently one of the main agricultural planting methods. The heavy metal pollution is the relatively prominent problem in the greenhouse vegetable field which is under a semi-closed state with high temperature, high humidity and high fertilizer input. Due to the complexity of soil environment, and the diversity of sources and the specificity of distribution of heavy metal pollution, a comprehensive and detailed system for the source apportionment of heavy metals in soils has not been established. Little is reported in literature on the source apportionment of heavy metal pollution in greenhouse vegetable fields. In this paper, the application of source apportionment of heavy metals in greenhouse vegetable fields was reviewed based on the related literature. In view of the limited application of quantitative source apportionment of heavy metals in greenhouse vegetable fields, several suitable methods were recommended and their advantages and disadvantages were summarized. Meantime, the prospect of the research on the source apportionment methods of heavy metals in greenhouse vegetable fields was put forward, so as to provide the technical support to solve the problem of heavy metal pollution in greenhouse vegetable fields from the source. [ABSTRACT FROM AUTHOR]

Based on the bibliometrics analysis, this paper firstly identifies that the research focus of humic acid-based material immobilization field is on immobilization remediation effect and remediation mechanism.Based on the two research focuses identified, the heavy metals in soil were classified into those in the form of cations（e.g.Cd, Pb, Hg, etc.) and those in the form of oxygen anions（e.g.As and Cr),and the immobilization effects and immobilization mechanisms of humic acid and humic acid-based materials on soil heavy metals were systematically reviewed.Humic acid and humic acid-based materials have highly effective to immobilize soil heavy metals, and their immobilization mechanisms mainly include complexation, ion exchange, electrostatic interaction, redox and co-precipitation with introduced modified materials.This review further points out the shortcomings of humic acid-based materials in immobilization remediation technology in terms of practical applications and provides an outlook on future research directions, in order to provide scientific references for in situ immobilization remediation of heavy metal contaminated soils. [ABSTRACT FROM AUTHOR]

Isitu passivation repair technology for heavy metals is a promising processing technology. This technology mainly adds exogenous remediation agents to the contaminated soil, and undergoes a series of reactions such as adsorption, ion exchange, precipitation, oxidation-reduction and other heavy metal ions to convert heavy metals into a more stable form and fix them in the soil, thereby preventing heavy metals from passing through plant roots migrate to the upper part of the ground to achieve the purpose of repairing the soil. This paper systematically expounds the effect and repair mechanism of passivation technology, deeply analyzes the types of passivation materials, and further puts forward the problems to be solved in passivation repair technology from the practical application, and prospects for future research directions. [ABSTRACT FROM AUTHOR]

Combined with the existing research, the research progress of biochar remediation of heavy metal pollution is reviewed. This paper focuses on the mechanism of biochar immobilization of heavy metals in soil, the effect of biochar on the absorption of heavy metals by plants, the research results of the application of biochar in field engineering, and the risks and shortcomings o£ biochar as a soil improver. Finally, it is hoped that on the premise of meeting safe production, the popularization of biochar should be promoted in agricultural production, rather than limited to scientific research. Start the life cycle assessment of biochar and establish a biochar life cycle database to provide a comprehensive and effective scientific basis for the future use of biochar. [ABSTRACT FROM AUTHOR]

Solidification and stabilization (S/S) is one of the primary technologies for the treatment of heavy metals in soil. It is particularly important to strengthen the concept of solidification and stabilization materials in the research and development of materials. The mechanisms of solidification and stabilization materials on soil heavy metals include precipitation, adsorption, coordination, organic complexation, and redox reactions. This paper mainly focuses on the systematic study of materials in soil heavy metal solidification and stabilization, proposes research & development methods for soil heavy metal solidification and stabilization, including screening and comparison, optimization and combination, surface modification, surface loading, and bridging composite methods. The basic research on the application of solidification materials includes five aspects of the framework, solidification and stabilization materials-heavy metals-water bodies, solidification and stabilization materials-soil-heavy metals, solidification and stabilization materials-soil-plant-heavy metals, solidification and stabilization materials-field-crop-heavy metals, and the evaluation of environmental safety and application effect on heavy metal treatment. For each aspect, the main content and key linked points of the research are explained. This holds importance for promoting the study of materials in soil heavy metal solidification and stabilization, and strengthening the application based on this process. [ABSTRACT FROM AUTHOR]

Taking an industrial waste dump plate as the example，the pollution characteristics of heavy metals in the waste residue，soil and groundwater were discussed, and the carcinogenic risk and harm quotient of heavy metal pollution to human body were evaluated emphatically in this paper. Results show that： 1)8 kinds of heavy metals (As，Cu，Ni，Zn，Cd，Pb，Cr and Hg) in the slag exceed certain limits to some extent, with the maximum value of As (up to 91 % in the rate of exceeding standard) and a highly concentrated contaminated area for Cr. Contents of Cu，Ni，Zn and Cd in the soil are greater than local background values. As and Ni in the groundwater also exceed standards. 2)The carcinogenic risk levels of As，Ni and Cr in waste residues and soils all exceed the acceptable level of carcinogenic risk(l. 0 X 10-6)，with the highest carcinogenic risk of Cr，up to 5, 3 X 10-5. For the same heavy metal the carcinogenic risk values in waste residues are greater than in soils. 3)The hazard quotients of As，Cr and Cd in the waste residues are greater than the acceptable level(1), with the highest hazard quotients of Cr(up to 7, 5)， while the hazard quotients of all heavy metals (except As) in the soils are basically lower than the acceptable level. 4) The three exposure pathways are listed in descending order according to their contribution rates as follows: oral intake > inhaled soil particles > through skin contact. [ABSTRACT FROM AUTHOR]

Ningxia Helan County was taken as the research area in this paper to study the distribution characteristics and ecological risk of heavy metals in farmland soil in northwest China. 140 topsoil samples were collected aiming to analyze and measure the concentration of Cr, Ni, Cu, Zn, As, Cd and Pb belonging to heavy metal elements. The distributions, soil environment status and ecological risk of the seven heavy metals were studied by Nemerow pollution index and Håkanson potential ecological risk index methods. The results showed that concentrations of Cr, Ni, Cu, Zn, As and Pb were all lower than the second-level of Environmental Quality Standard for Soils of China except that concentrations of Cd of 1.42% samples were appeared to exceed the standard. Compared with the background values, seven heavy metals of all samples showed different degree accumulation, in which Cd, Ni elements beyond the background value ratio reached 100% and 85%. Spatial distribution of the concentrations of the seven heavy metals had obvious accordance. The content of each element was evenly distributed. The high content of each element was concentrated in the central and eastern part of Helan County, which was related to human activities. The calculation results of single-factor pollution index showed that among the 140 soil samples, 0.71% of Cd were moderate contamination, 7.14% of Ni and 5% of As were slight clean, Cr, Cu, Zn, Pb of all samples were all clean. According to the individual potential ecological risk index（Ei r）of heavy metals, the average potential ecological risk index of Cd element was 97.68, which indicated that Cd had reached the serious risk level, becoming the main element of potential ecological risk. All in all, the quality of farmland soil in Helan County of Ningxia is good, but it is noteworthy that the concentration of Cd, Ni has a serious accumulation. [ABSTRACT FROM AUTHOR]

[Objective]The aim of this paper is to provide the basic information and decision basis for rare plant conservation and tourism sustainable development in Fanjing Mountain Nature Reserve. [Method]The heavy metals in woodland soil with different profile, elevation and vegetation type in Fanjing Mountain Nature Reserve are investigated and evaluated and the enrichment characteristics is discussed by enrichment factor method. [Result] Cd and Pb content in soil decreases with increase of soil depth but Cu content in soil increases with increase of soil depth. Cr content in soil presents a decrease-increase-decrease trend with increase of elevation. Cd content in soil presents a first increase and then decrease trend with increase of elevation. Pb, Cu, H and As content in soil presents an increase-decrease-increase trend with increase of elevation. The content of heavy metals in soil with Taxus chine ns is , Euonynus hamiltonianus, Rhododendron and Davidia in-volucrata vegetation is Cr > Pb > Cu > As > Cd > Hg. The content of heavy metals in soil with Abies fanjingshanensis vegetation is Pb > Cr > Cu > As > Cd > Hg. The enrichment factor of Cu, Cd, Hg and Pb in soil with 0 - 20 , 20 - 40 and 40 - 60 cm depth is > 1. The enrichment factor of Cd, Pb and Hg in soil with an elevation of 500 - 1000. 1001 - 1500, 1501-2000 and >2000 m is > 1. The enrichment factor of Cu and As with an elevation of > 2000m is > 1. The enrichment factor of Cr with an elevation of 500 - 1000 m is > 1. The enrichment factor of Cr, Cd, Pb and Hg in soil with T. chinensis, E. hamiltonianus and I), involucrata vegetation is > 1. The enrichment factor of Cr,Cu, Cd, Hg and As in soil with Rhododendron vegetation is > 1. The enrichment factor of Cu, Cd, Hg and As in soil with A. fanjingshanensis vegetation is > 1. The soil of woodland in Fanjing Mountain Nature Reserve is mainly affected by Cd, Pb and Hg. [ABSTRACT FROM AUTHOR]

Economic development requires exploration and exploitation of mineral resources. It is difficult to find surface outcrop deposits，which will cause soil pollution by heavy metals that is a severe hazard to the environment and human health. Microorganisms in nature interact with heavy metals in air. Microorganisms with this specificity can be applied to metal prospect exploration and environmental bioremediation of heavy metal pollution and its application to exploration and environmental bioremediation of heavy metal pollution have been reviewed. The focus of this paper is on the adsorption， accumulation and transformation process between specific microorganisms and heavy metal ions， as well as the of microbial organisms changing heavy metal distribution， occurrence and toxicity. The interaction mechanism between Bacillus cereus and gold and its application potential to find concealed gold deposits were reviewed. Removal of heavy metals in the soil by the specific microorganism through the adsorption of metabolites and assisting plants to repair heavy metal pollution were introduced and elaborated upon. [ABSTRACT FROM AUTHOR]