生物修复技术在土壤污染治理中的应用研究

现阶段,我国面临严峻的土壤污染形势,诸多耕地都受到污染,致使我国的耕地面积逐渐减少,进而影响农产品产量和居民日常生活。土壤生物修复技术操作简单,成本低,对环境扰动少,不易造成二次污染。国家相关部门高度重视土壤污染问题,因此逐渐把生物修复技术应用到土壤污染治理中。鉴于此,本文探究了生物修复技术在土壤治理污染中的应用。

Bioremediation of Oil Spills in Cold Environments: A Review

Oil spills have become a serious problem in cold environments with the ever-increasing resource exploitation, transportation, storage, and accidental leakage of oil. Several techniques, including physical, chemical, and biological methods, are used to recover spilled oil from the environment. Bioremediation is a promising option for remediation since it is effective and economic in removing oil with less undue environmental damages. However, it is a relatively slow process in cold regions and the degree of success depends on a number of factors, including the properties and fate of oil spilled in cold environments, and the major microbial and environmental limitations of bioremediation. The microbial factors include bioavailability of hydrocarbons, mass transfer through the cell membrane, and metabolic limitations. As for the environmental limitations in the cold regions, the emphasis is on soil temperatures, freeze-thaw processes, oxygen and nutrients availability, toxicity, and electron acceptors. There have been several cases of success in the polar regions, particularly in the Arctic and sub-Arctic regions. However, the challenges and constraints for bioremediation in cold environments remain large.

Optimization of Cr(VI) bioremediation in contaminated soil using indigenous bacteria

Bench-scale soil column experiments were carried out to evaluate the effectiveness of Cr（VI） bioremediation process in soils by using indigenous bacteria with the addition of bacteria nutrient media. Effects of particle size, spray intensity, initial Cr（VI） concentration, circulation mode and soil depth on Cr（VI） remediation were studied. Results show that soils after 6 d remediation with spray intensity controlled in the range of 29.6-59.2 mL/min could well fulfill the requirement of concrete aggregate and roadbed material usage, for the leaching toxicity concentration of the Cr（VI） in treated soils under the chosen condition is far less than 5 mg/L The leaching toxicity and fractions of both hexavalent chromium and trivalent chromium from remediated soils were determined and compared with that of untreated soil. The results show that water soluble Cr（VI） declines from 1520.54 mg/kg to 0.68 mg/kg, exchangeable Cr（VI） decreases from 34.83 mg/kg to 0.01 mg/kg and carbonates-bonded Cr（V1） falls from 13.55 mg/kg to 0.68 mg/kg. Meanwhile, a corresponding increase in carbonate-bonded Cr（III）, Fe and Mn oxides-bonded Cr（III） and organic matter-bonded Cr（III） are found. It reveals that indigenous bacteria can leach out water soluble Cr（VI）, exchangeable Cr（VI） and carbonates-bonded Cr（VI） from contaminated soil followed by converting into carbonate-bonded Cr（III）, Fe and Mn oxides-bonded Cr（IlI）, organic matter-bonded Cr（III） and residual Cr（III）.

Application of Biotechnology in Environmental Remediation of Mining Area

Based on the characteristics of the ecological environmental remediation of mining area, the application of biotechnology was proposed to do the remediation of the polluted environment in the mining area, mainly including the treatment of gangue dump and tailing heap, improvement of reclamation soil as well as the re- mediation of contaminated soil. Finally, the application and deveiopment trend of biotechnology in environmental remediation and soil remediation of mining area were pointed out.

Bioremediation of Oil-Polluted Cultivated Soils in the Euro-Arctic Region

It has been studied restoration processes in oil products-polluted soils at high northern latitudes （the Murmansk region, Russia）. Mineral and organic fertilizers and a bacterial preparation （based on the local strains of hydrocarbon-oxidizing bacteria） were applied for restore polluted soils. Periods of removing OP （oil products） from soil were determined by the reduction of the pollutant concentration and by soil biological activities--the dynamics of bacteria number and CO2 emission from soil. The soil OP even at such a high concentration （as 10 L/m^2） had stimulated bacterial reproduction. In three summer month levels in the control variant without ameliorators of OP content decreased by 59% from the initial level, in the variant with mineral and organic fertilizers by 86%, in the variant with the bacterial preparation by 84%. Stimulating of indigenous microorganisms activity with additional nutrients was no less effective technique of OP-polluted soil bioremediation, than applying the bacterial preparation, which requires considerable financial investment. Moderately contaminated of OP soil is a source of additional carbon dioxide emission in the atmosphere. Pollution soil with OP caused for increasing of share of potentially pathogenic fungi in the fungal community.

Biotechnological Strategies for Phytoremediating Triazinic Herbicides in the Humid Pampa （Argentine）

In agricultural producer countries, the use of chlorinated herbicides （atrazine）, associated to intensive farming practices, overflows the ecosystems natural attenuation capacity. Thus, herbicide residues contaminate the soils and water sources, increasing the risk for human health and wildlife. Humid Pampa is the main agricultural region in one of the world＇s largest herbicide consumer countries; hence, technologies to remediate its residues are needed. In this context, phytoremediation is an effective, environmental friendly and publicly accepted option. Accordingly, the objective of designing biotechnological strategies for phytoremediating triazinic herbicide residues in an integrated approach to the ongoing Humid Pampa agricultural trend is raised. In this way, strategies according to the edaphic, topogeographic and fanning practices characteristics of this region where established. In those strategies, the adequate selection of plant species is essential. For that purpose, atrazine tolerance assays were performed in simple （semisolid agar medium） and complex （microcosms） experimental systems implanted with Lolium multiflorum, Lotus sp. and Quenopodium quinoa. L. multiflorum was selected and evaluated via atrazine dissipation assays with soil. Atrazine soil content was determined by solvent extraction and subsequent HPLC-UV analysis, observing statistically significant attenuation levels at 21 days. According to the observed results, a strategy for scaling up the application to field conditions is proposed.

Isolation and Screening of Rhizobacteria from Scirpus Grossus Plant after Lead （Pb） Exposure

Phytoremediation is one of method which can be applied to remediate the contaminated environment. In most cases, microorganisms bacteria and fungi, living in the rhizosphere closely associated with plants, may contribute to mobilize metal ions by increasing the bioavailable fraction. Some studies have evidenced that heavy metal-resistant bacteria can enhance metal uptake by hyperaccumulator plants. Lead-resistant bacteria which could help to increase the lead uptake by Scirpus grossus was isolated and screened. The samples were taken from plant roots after being exposed in a range finding test by spiking analytical grade of Pb（NO3）2 solution in variation of Pb concentrations. The results of rhizobacteria isolation showed that there were several colonies having resistance to grow and survive in contaminated environment even the host plant had withered. Only a few of rhizobacteria colonies were affected by high concentrations of lead exposure during screening test. The screening test was conducted by growing the isolated colonies on plates containing tryptic soy agar （TSA） medium containing of 200, 400 and 600 mg/L Pb solution including the plate with only TSA media without any lead exposure acting as a control medium, and incubating them at 30℃ for 72 hours. Isolation of bacteria from rhizosphere had found 47 colonies including several colonies from the withered plants. These all 47 colonies then become 28 after characterization by using color and colony morphology, followed by Gram stain, catalase, oxidase and motility test. The screening test of lead resistant bacteria colonies resulted 3 groups which is scored high, medium and low. The screened colonies will then be used for further study.

Morphological and Physiological Responses of Plants to Cadmium Toxicity: A Review

Cadmium(Cd) contamination has posed an increasing challenge to environmental quality and food security. In recent years,phytoremediation has been particularly scrutinized because it is cost-effective and environmentally friendly, especially the use of metal-hyperaccumulating plants to extract or mine heavy metals from polluted soils. Under Cd stress, responses of hyperaccumulator and non-hyperaccumulator plants differ in morphological responses and physiological processes such as photosynthesis and respiration,uptake, transport, and assimilation of minerals and nitrogen, and water uptake and transport, which contribute to their ability to accumulate and detoxify Cd. This review aims to provide a brief overview of the recent progresses in the differential responses of hyperaccumulator and non-accumulator plants to Cd toxicity in terms of growth and physiological processes. Such information might be useful in developing phytoremediation technology for contaminated soils.

Natural Organic Amendments for Improved Phytoremediation of Polluted Soils:A Review of Recent Progress

Environmental pollution caused by metals, radionuclides and organic pollutants affects quality of the biosphere: soil, water and air.Currently, great efforts have been made to reduce, remove or stabilize contaminants in polluted sites. There has been increasing interest in phytoremediation—the use of plants to reduce concentration of pollutants or to render them harmless. This paper provides a brief review of recent progress in the research and practical application of phytoremediation techniques. Improvements in phytoremediation due to utilization of organic amendments, namely, agro- and industrial wastes(such as sugar beet residue, composted sewage sludge or molasses), biochar, humic substances, plant extracts and exudates are discussed, as well as their influences on soil structure and characteristics, plants growth and bioavailability of pollutants. Both plant-assisted phytoremediation and the use of natural materials in the absence of remediating plant are believed to be cost-effective and environmentally friendly approaches for soil cleanup. However,the characterization and quantification of a range of natural materials used in phytoremediation are essential in order to implement these approaches to practice.

Interactions Between Arbuscular Mycorrhizae and Plants in Phytoremediation of Metal-Contaminated Soils: A Review

Metal contamination in the environment is a global concern due to its high toxicity to living organisms and its worldwide distribution. The principal goal of this review is to examine the current strategies and technologies for the remediation of metal- contaminated soils by metal-accumulating plants and assess the roles of arbnscular mycorrhizal （AM） fungi in remediation of soils under hyperaccumulator or non-accumulator plants. The use of plants to remove metals from the environment or reduce the toxicity, known as phytoremediation, is an environmentally sustainable and low cost remediation technology. The mechanisms of the use of hyperaccumulator plants for phytoremediation included solubilization of the metal in the soil matrix, the plant uptake of the metal, detoxification/chelation and sequestration, and volatilization. Recently, some ecologists have found that phytoremediation with the aids of mycorrhizae can enhance efficiency in the removal of toxic metals. AM fungi can facilitate the survival of their host plants growing on metal-contaminated land by enhancing their nutrient acquisition, protecting them from the metal toxicity, absorbing metals, and also enhancing phytostabilization and phytoextraction. Such information may be useful for developing phytoremediation program at metal-contaminated sites.

Plant Growth-Promoting Traits in Rhizobacteria of Heavy Metal-Resistant Plants and Their Effects on Brassica nigra Seed Germination

Phytoremediation is an emerging technology that uses plants and their associated microbes to clean up pollutants from the soil, water, and air. In order to select the plant growth-promoting rhizobacteria （PGPR） for phytoremediation of heavy metal contamination, 60 bacterial strains were isolated from the rhizosphere of two endemic plants, Prosopis laevigata and Spharealcea angustifolia, in a heavy metal-contaminated zone in Mexico. These rhizobacterial strains were characterized for the growth at different pH and salinity, extracellular enzyme production, solubilization of phosphate, heavy metal resistance, and plant growth-promoting （PGP） traits, including production of siderophores and indol-3-acetic acid （IAA）. Overall, the obtained rhizobacteria presented multiple PGP traits. These rhizoba^teria were also resistant to high levels of heavy metals （including As as a metalloid） （up to 480 mmol L-1 As（V）, 24 mmol L-1 Pb（II）, 21 mmol L-1 Cu（II）, and 4.5 mmol L-1 Zn（II））. Seven rhizobacterial strains with the best PGP traits were identified as members of Alcaligenes, Bacillus, Curtobacterium, and Microbacterium, and were selected for further bioassay. The inoculation of Brassica nigra seeds with Microbacteriurn sp. CE3R2, Microbacterium sp. NE1R5, Curtobacterium sp. NM1R1, and Microbacterium sp. NM3E9 facilitated the root development; they significantly improved the B. nigra seed germination and root growth in the presence of heavy metals such as 2.2 mmol L-1 Zn（II）. The rhizobacterial strains isolated in the present study had the potential to be used as efficient bioinoculants in phytorremediation of soils contaminated with multiple heavy metals.

Soil Contamination due to Activities： A Review with E-Waste Disposal and Recycling Special Focus on China

This paper presents a review of soil contamination resulting from e-waste recycling activities, with a special focus on China, where many data have been collected for a decade. Soils in the e-waste areas are often contaminated by heavy metals and organic compounds, mainly polycyclic aromatic hydrocarbons （PAHs）, polybrominated diphenyl ethers （PBDEs）, polychlorinated and polybrominated biphenyls （PCBs and PBBs）, dechlorane plus （DP）, hexabromocyclododecanes （HBCDs）, polychlorinated and polybrominated dibenzo- p-dioxins （PCDDs and PBDDs）, and polychlorinated and polybrominated dibenzofurans （PCDFs and PBDFs）, while other compounds, not systematically monitored, can be found as well. Pollutants are generally present in mixtures, so pollution situations are complex and diversified with a gradient of contamination from agricultural soils to hot spots at e-waste sites and mainly in open burning areas. It has been proved that pollutants were transferred to the food chain via rice in China, and that the population was threatened since high levels of various pollutants were detected in blood, placentas, hair, etc., of residents of e-waste sites. Eventually, soil remediation techniques are reviewed. Although there are many available techniques devoted to heavy metals and persistent organic pollutants, the current techniques for the e-waste sites, where these contaminants coexist, are very sparse. Phytoremediation has been investigated and co-cropping appears as a promising approach for the slightly contaminated agricultural soils. In some cases, different remediation techniques should be combined or trained, while the influence of coexisting contaminants and the removal sequence of contaminants should be considered. In hot spots, physical and chemical techniques should be used to reduce high pollution levels to prevent further pollutant dissemination. This review highlights the urgent needs for 1） characterization of pollution status in all the countries where e-wastes are recycled, 2） research on fate and toxicity of pollutant mixtures, and 3） development of combined techniques and strategies to remediate agricultural fields and hot spots of pollution.

Improving arsenic mobility concentration from As-polluted soils by the functional strains

Arsenic （As） contamination has become the environment issue of global concern. In China, large area of farmland and the site soil were contaminated by As, which means that suitable remedying methods were urgently needed. Phytoremediation, as one of environment-friendly soil remediation techniques developed in recent years, shows a bright future for the remediation of As contaminated soils. However, phytoremediation efficiency needs to be enhanced further because of low concentration of bio- available As in the soils. A triangle flask culture experiment was carried out to study the effects of functional species, isolated from As-polluted soils, that could improve As mobility from the soil. These species included two bacilli, B 1 and B2 （Breviba- cillus） and two fungi, F1 （Trichoderma）, F2 （Fusarium）. They could transform the concentration of As fractionation in the soil sterilized by the method of 6~Co-T ray. Through the experiment, the concentrations of non-specifically-sorbed and specifical- ly-sorbed As fractionation, and pH value of culture solution with inoculated treatment were higher than that with the control. Especially, the concentration of non-specifically-sorbed As fractionation in the treatment-inoculated species was 2 to 6 times higher than that of non-inoculation treatment. Moreover, two bacilli and two fungi could produce IAA, which was conducive to the plant survival when they were jointly used in remedying the As-contaminated soil.

Biochar and alternate partial root-zone irrigation greatly enhance the effectiveness of mulberry in remediating lead-contaminated soils

Aims Soil lead contamination has become increasingly serious and phytoremediation can provide an effective way to reclaim the contaminated soils.This study aims to examine the growth,lead resistance and lead accumulation of mulberry(Morus alba L.)seedlings at four levels of soil lead contamination with or without biochar addition under normal or alternative partial root-zone irrigation(APRI).Methods We conducted a three-factor greenhouse experiment with biochar(with vs.without biochar addition),irrigation method(APRI vs.normal irrigation)and four levels of soil lead(0,50,200 and 800 mg·kg^(-1)).The performance of the seedlings under different treatments was evaluated by measuring growth traits,osmotic substances,antioxidant enzymes and lead accumulation and translocation.Important Findings The results reveal that mulberry had a strong ability to acclimate to soil lead contamination,and that biochar and APRI synergistically increased the biomass and surface area of absorption root across all levels of soil lead.The seedlings were able to resist the severe soil lead contamination(800 mg·kg^(-1) Pb)by adjusting glutathione metabolism,and enhancing the osmotic and oxidative regulating capacity via increasing proline content and the peroxidase activity.Lead ions in the seedlings were primarily concentrated in roots and exhibited a dose–effect associated with the lead concentration in the soil.Pb,biochar and ARPI interactively affected Pb concentrations in leaves and roots,translocation factor and bioconcentration.Our results suggest that planting mulberry trees in combination with biochar addition and APRI can be used to effectively remediate lead-contaminated soils.