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The objective of this paper is to elucidate the environmental capacity of heavy metal in soils of an urbanization gradient zone of Urumqi City, a total of 88 surface soil samples were thereby collected from the typical gradient zone including urban, suburban, rural and wasteland areas, and heavy metal contents of Cd, Hg, As, Pb, Cu, Ni, and Zn in soils were measured, and the characteristics and spatial distribution pattern of the environmental capacity of soils was analyzed based on the GIS and the method of comprehensive environmental index (PI). As a result, the investigation showed that heavy metal contents in topsoil of the urbanization gradient zone along the areas of urban, suburban, rural and wasteland differed in a certain degree, and Hg had been evidently enriched in soils of all the areas of the gradient zone; the mean PIs of heavy metals in soils of the urbanization gradient zone were arranged in order of decreasing magnitude: rural> suburban>wasteland> urban, the relevant environmental capacity of all the areas being mediocre. As to the spatial pattern, individual environmental capacity index of each single heavy metal in soils of those areas was different, and low PI mainly distributed in the urban area, which indicated a significant impact of urbanization on soil environmental capacity. The dynamic annual capacity and static annual capacity of each heavy metal were in order of decreasing magnitude: Zn> Ni> Pb> Cu> As> Hg> Cd. In addition, the dynamic annual capacity of heavy metals in soils of each arear of the gradient zone showed a trend 20 a > 40 a > 60 a > 80 a > 100 a. The aver-age dynamic annual capacity of every kind of heavy metal in soil of each gradient zone area was greater than the static annual capacity in fixed number of years, and as a whole, the environmental capacity of soils tended better. [ABSTRACT FROM AUTHOR]

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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]

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Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)