微生物矿化固结土壤中重金属研究

选取到一种土壤菌--菌株A,利用其在底物诱导下产生的酶化作用,分解产生CO2-3,矿化固结土壤中的有效态重金属(以Cd2 的处理为代表),使其沉积为稳定态的碳酸盐;对被复合重金属(Cd、Cu、Pb、Zn等)污染的土壤样进行微生物修复的实验中,有效态重金属去除率达50%～70%,环境友好,工艺简单,实用价值高,以期应用于重金属污染土壤中的活性态重金属的处理,防止重金属污染物进入生物链下游,保障人类生存安全.     

环境友好型土壤重金属修复技术及其应用

针对全球土壤重金属污染不容忽视的现状,国内外学者在土壤修复方面进行了大量研究。当前的土壤修复政策和评价标准主要指向土壤中重金属总量的减少,忽略了重金属的形态变化。然而重金属形态才是影响其生物有效性和毒性的关键因素。2019年我国农业农村部规定在土壤污染的治理中,在达成基本目标的同时应优先考虑修复方法对土壤性质的损伤风险以及环境污染风险,防止二次污染,保证耕地可持续利用。因此,如何在对土壤环境产生最低甚至无损害的前提下减少重金属总量或改变重金属形态从而降低其风险是土壤污染修复的热点。虽然土壤重金属污染修复技术众多,但目前对土壤无损伤且有效的土壤修复技术有固定/稳定化、植物和微生物修复这三种。固定/稳定化技术可以短期内降低土壤重金属有效性,但易失去钝化效果,导致被固定重金属的重新活化;植物、微生物修复可稳定改变重金属有效性和总量,但其修复周期长,环境限制大。本文主要就上述三种环境友好型修复技术进行了总结分析,阐述了各修复技术的作用机制、优缺点、环境风险和应用前景,并从提高重金属生物有效性、调节生物代谢活动、吸附钝化重金属、改善土壤修复环境四个方面阐述了不同强化方式的原理、修复效果、优势以及...     

土壤重金属污染用微生物修复的研究

土壤重金属污染物在土壤中的存在用微生物修复方法。重金属土壤污染问题迫切需要解决,治理重金属污染,从生物修复方面阐述了重金属的治理方法、手段,微生物修复的可行性和环保等优点。     

耐低温真菌对土壤中吸附态PAHs的降解特性

为寻找适用于北方寒冷地区有机污染土壤的生物修复材料,从某炼油厂冻融土壤中筛选出一株以腐殖酸（HA）吸附态PAHs为碳源和能源且生长良好的耐低温真菌（命名为JDR7）,经鉴定为高山被孢霉（Mortierella alpina）,并研究了其对冻融土壤中HA吸附态PAHs的降解动态,用Michaelis-Menton和Monod动力学模型对结果进行拟合。结果表明：经42d,JDR7对冻融土壤中Pyr和Ba P的降解率分别为68.13%和59.51%。加入HA后,42d的降解率分别提高13.8%和12.3%;降解初期加入HA可显著提高Pyr和Ba P的降解速率,第一周降解速率分别提高29.69%和32.93%,后期促进降解效果减弱。该研究为北方寒冷地区土壤PAHs污染微生物修复提供新的修复材料。     

污染土壤修复标准及修复效果评定方法探讨

制定污染土壤修复标准的目的是将污染严重的土壤环境中的污染物水平降低到造成更大的生态破坏和健康危害水平以下,同时确保被污染场地满足再利用要求。本文将结合部分发达国家的土壤修复标准,以及中国土壤污染的实际情况,综合考虑污染控制因素和生态毒理学评价,以清洁技术为基础,对我国的土壤生物修复标准进行回顾,建立土壤背景值及适用标准。针对污染土壤修复效果评价的研究,本文简要介绍了评价修复效果的常用方法:植物毒性评价方法、陆地无脊椎动物评价方法、土壤微生物评价方法和生物标志物评价方法,对污染土壤的修复效果进行评估,并对评估技术的发展前景以及评价方法进行了展望。     

微生物治理土壤重金属污染的研究进展

近年来,土壤重金属污染问题日益严重,对其的治理已成为当今的热点话题。本文根据国内外的研究成果对微生物用于土壤重金属污染治理进行了综述,介绍了微生物修复技术、微生物展示技术、微生物和植物联合修复,以及它们的概念、基本原理和研究进展等,并展望了其发展前景。     

某电镀厂旧址土壤污染治理与修复效果评估分析

某电镀厂停产搬迁后,旧址土壤受到六价铬和氰化物污染,根据场地污染土壤的理化特征及污染情况,对六价铬、氰化物分别采用还原、氧化技术修复污染土壤及修复效果评估等方面进行分析,结果表明：六价铬采用还原作业、氰化物采用氧化作用后,采集的所有土壤样品中六价铬、氰化物浓度均低于修复目标限值,修复效果达到设计目标值,修复取得良好的效果,确保了土地达到后续开发利用的要求。     

土壤重金属污染特点及修复技术研究

本文综述了生物修复、物理修复和化学修复等不同修复技术在重金属污染土壤修复方面的研究进展,分析了重金属污染土壤各修复技术在实际应用中存在的问题。     

污染土壤修复技术研究现状与趋势分析

污染土壤中存在农药残留与重金属等有害物质,会对周边的农业、养殖业发展造成影响,出现食品安全问题,阻碍当地的经济发展。基于此,污染土壤修复技术成为学术界研究的热点,该文从生物、化学与物理3个角度入手,分析污染土壤修复技术的研究现状,明确污染土壤修复中各项技术的应用效果、适用范围与优缺点等,并阐述了污染土壤修复技术的研究趋势,为专家学者研发新型污染土壤修复技术提供参考,切实解决土壤污染问题,保护生态环境。     

不同改良剂对镉污染土壤的化学固定修复的比较研究

本文研究纳米沸石、沸石、电气石、粉煤灰4种修复剂对重金属Cd污染土壤的化学固定修复效果。在土壤中添加改良剂均为50g／kg土。采用BCR分级提取实验和土柱淋滤实验两种化学提取方法评价实验结果。结果表明：纳米沸石、沸石、电气石、粉煤灰4种修复剂都可以一定程度的降低污染土壤中可交换态Cd含量,其中以纳米沸石降低土壤有效态Cd的效果最好。     

Bioremediation of Pb-contaminated soil by incubating with Phanerochaete chrysosporium and straw

The bioremediation of the simulated lead (Pb)-contaminated soils by incubating with Phanerochaete chrysosporium and straw was studied at laboratory-scale. The soil pH, Pb concentration, soil microbial biomass, microbial metabolic quotient, microbial quotient and microbial biomass C-to-N ratios were monitored. The above indicators were to study the stress of Pb on soil and the microbial effects during the bioremediation process. It was found that the soils treated with P. chrysosporium and straw showed a much lower concentration of soluble-exchangeable Pb, lower metabolic quotient and biomass C-to-N ratios (0mgkg(-1) dry weight soil, 1.9mg CO(2)-Cmg(-1) biomass carbon and 4.9 on day 60, respectively) and higher microbial biomass and microbial quotient (2258mgkg(-1) dry weight soil and 7.86% on day 60, respectively) compared with the controls. In addition, the kinetic parameters in the model based on logistic equation were calculated by the BIOLOG data. By analyzing those kinetic parameters some information on the metabolic capacity of the microbial community could be obtained. All the results indicated that the bioavailability of Pb in contaminated soil was reduced so that the potential stress of Pb was alleviated, and also showed that the soil microbial effects and the metabolic capacity of microbial community were improved.     

A new direct microscopy based method for evaluating in-situ bioremediation.

A new epifluorescent microscopy based method using 5-cyano-2, 3-ditolyl tetrazolium chloride (CTC) and 5-(4,6-dichlorotriazinyl) aminofluoroscein (DTAF) was developed for quantifying total microbial biomass and evaluating levels of microbial activity. CTC is a tetrazolium dye that forms fluorescent intracellular formazan when biologically reduced by components of the electron transport system and/or dehydrogenases of metabolically active bacteria. DTAF is a fluorescein-based fluorochrome that selectively stains bacterial cell walls thereby enabling quantification of total bacterial biomass. CTC can be used in conjunction with DTAF to provide the optical resolution necessary to differentiate metabolically active cells from inactive cells in microbial populations associated with subsurface soils. The CTC/DTAF staining method has been shown to be effective for quantifying the metabolic activity of not only aerobic bacteria, but also diverse groups of anaerobic bacteria. This method allows for the rapid quantification of total and active bacterial numbers in complex soil samples without enrichment or cell elution. In this study, CTC/DTAF staining was applied to evaluate in-situ microbial activity in petroleum hydrocarbon contaminated subsurface soils from Sites 3 and 13 at Alameda Point, CA. At each site, subsurface microbial activity at two locations within contaminated plumes were examined and compared to activity at two geologically similar but uncontaminated background locations. Significant bacterial populations were detected in all soils examined, and the biomass estimates were several orders of magnitude higher than those obtained by conventional culture-based techniques. Both the total bacterial concentrations and the numbers of active bacteria in soils from contaminated areas were substantially higher than those observed in soils from background locations. Additionally, the percentages of metabolically active bacteria in the contaminated areas were consistently higher than those detected in background areas, suggesting that the enhanced microbial activity was due to microbial contaminant degradation. Although conventional heterotrophic plate counts failed to show significant microbial activity at either of the sites, soil gas carbon dioxide and methane measurements confirmed that hydrocarbon contaminant degradation was occurring in both areas. The CTC/DTAF staining protocol proved to be a rapid, reliable, and inexpensive method to evaluate the progress of in-situ bioremediation.     

Assessment of lead bioaccessibility in peri-urban contaminated soils

Lead (Pb) bioaccessibility was assessed in a range of peri-urban soils (n=31) with differing sources of Pb contamination, including shooting range soils, and soils affected by incinerator, historical fill, mining/smelting, and gasworks activities. A gossan soil sample was also included. Lead bioaccessibility was determined using both gastric and intestinal phases of the SBRC in vitro assay and in vitro data was then incorporated into in vivo-in vitro regression equations to calculate Pb relative bioavailability. Lead bioaccessibility ranged from 26.8-105.2% to 5.5-102.6% for gastric and intestinal phase extractions respectively. Generally, Pb bioaccessibility was highest in the shooting range soils and lowest in the gossan soil. Predictions of relative Pb bioavailability derived from in vitro data were comparable for shooting ranges soils, but highly variable for the other soils examined. For incinerator, historical fill, gasworks and gossan soils, incorporating in vitro gastric data into the in vivo-in vitro regression equation resulting in more conservative Pb relative bioavailability values than those derived using the intestinal in vitro data.     

Influence of Rhizobium meliloti on phytoremediation of polycyclic aromatic hydrocarbons by alfalfa in an aged contaminated soil

Microbe-assisted phytoremediation is emerging as one of the most effective means by which plants and their associated rhizosphere microbes degrade organic contaminants in soils. A pot study was conducted to examine the effects of inoculation with Rhizobium meliloti on phytoremediation by alfalfa grown for 90 days in an agricultural soil contaminated with weathered polycyclic aromatic hydrocarbons (PAHs). Planting with uninoculated alfalfa (P) and alfalfa inoculated with R. meliloti (PR) significantly lowered the initial soil PAH concentrations by 37.2 and 51.4% respectively compared with unplanted control soil. Inoculation with R. meliloti significantly increased the counts of culturable PAH-degrading bacteria, soil microbial activity and the carbon utilization ability of the soil microbial community. The results suggest that the symbiotic association between alfalfa and Rhizobium can stimulate the rhizosphere microflora to degrade PAHs and its application may be a promising bioremediation strategy for aged PAH-contaminated soils.     

Combined effects of bacterial-feeding nematodes and prometryne on the soil microbial activity

Microcosm experiments were carried out to study the effects of bacterial-feeding nematodes and indigenous microbes and their interactions on the degradation of prometryne and soil microbial activity in contaminated soil. The results showed that soil indigenous microbes could degrade prometryne up to 59.6-67.9%; bacterial-feeding nematodes accelerated the degradation of prometryne in contaminated soil, and prometryne degradation was raised by 8.36-10.69%. Soil microbial biomass C (C_mic), basal soil respiration (BSR), and respiratory quotient (qCO₂) increased in the beginning of the experiment and decreased in the later stage of the experiment. Nematodes grew and reproduced quite fast, and did increase the growth of soil microbes and enhance soil microbial activity in prometryne contaminated soil during the incubation period.     

Role of organic amendments on enhanced bioremediation of heavy metal(loid) contaminated soils

As land application becomes one of the important waste utilization and disposal practices, soil is increasingly being seen as a major source of metal(loid)s reaching food chain, mainly through plant uptake and animal transfer. With greater public awareness of the implications of contaminated soils on human and animal health there has been increasing interest in developing technologies to remediate contaminated sites. Bioremediation is a natural process which relies on soil microorganisms and higher plants to alter metal(loid) bioavailability and can be enhanced by addition of organic amendments to soils. Large quantities of organic amendments, such as manure compost, biosolid and municipal solid wastes are used as a source of nutrients and also as a conditioner to improve the physical properties and fertility of soils. These organic amendments that are low in metal(loid)s can be used as a sink for reducing the bioavailability of metal(loid)s in contaminated soils and sediments through their effect on the adsorption, complexation, reduction and volatilization of metal(loid)s. This review examines the mechanisms for the enhanced bioremediation of metal(loid)s by organic amendments and discusses the practical implications in relation to sequestration and bioavailability of metal(loid)s in soils.     

Use of chemical methods to assess Cd and Pb bioavailability to the snail Cantareus aspersus: a first attempt taking into account soil characteristics

Bioavailability is a key parameter in conditioning contaminant transfer to biota. However, in risk assessment of terrestrial contamination, insufficient attention is being paid to the influence of soil type on trace metal bioavailability. This paper addresses the influence of soil properties on the chemical availability of cadmium (Cd) and lead (Pb) (CaCl(2) extraction and ionic activity) and bioavailability (accumulation kinetics) to the land snail Cantareus aspersus. Snails were exposed to nine contaminated soils differing by a single characteristic (pH or organic matter content or clay content) for 28 days. Toxicokinetic models were applied to determine metal uptake and excretion rates in snails and multivariate regression was used to relate uptake parameters to soil properties. The results showed that alkalinisation of soil and an increase of the organic matter content decreased Pb and Cd bioavailability to snails whereas kaolin clay had no significant influence. The CaCl(2)-extractable concentrations tended to overestimate the effects of pH when used to explain metal uptake rate. We conclude that factors other than those controlling the extractable fraction affect metal bioavailability to snails, confirming the requirement of biota measurements in risk assessment procedures.     

Enhanced TCDD degradation by Fenton's reagent preoxidation

The dioxin isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been called the most toxic compound known to man. Because of its poor bioavailability and low biodegradibility, bioremediation technology cannot effectively degrade TCDD when used alone. In this study, chemical pretreatment (partial oxidation) in combination with biodegradation technique was developed to efficiently remediate TCDD-contaminated soils. An oxidizing reagent [Fenton's Reagent (FR)] was applied in a slurry reactor to transform TCDD with a concentration of 96 microg per kg of soil to compounds more amenable to biodegradation. Up to 99% TCDD was transformed after the chemical pretreatment process. The slurry reactor was then converted to a bioreactor for the following biodegradation experiment. The detected TCDD oxidation byproducts including chlorophenols (CPs) and chlorobenzenes (CBs) were transformed in this bioreactor under aerobic conditions. Two other biodegradation experiments were performed in parallel to investigate the biodegradabiliy of TCDD under aerobic and anaerobic conditions without chemical pretreatment. Approximately 53% TCDD was transformed under anaerobic conditions possibly due to the reductive dechlorination process using organic materials contained in the activated sludge as the primary substrates. No TCDD degradation was observed under aerobic conditions. Results show that FR can oxidize TCDD to less-chlorinated and less-toxic byproducts, promoting their bioavailability to microbial communities. The bench-scale results indicate that the two-stage (partial oxidation followed by biodegradation) system has the potential to be developed to remediate TCDD-contaminated soils on-site.     

Effect of toluene as gaseous cosubstrate in bioremediation of hydrocarbon-polluted soil

The stimulation of the microbial population by a more bioavailable supplementary carbon source and by a surfactant pretreatment was studied in petroleum hydrocarbon-polluted soils bioremediation. Two types of soils were used, Soil A which had been recently polluted and the aged Soil B. They contained 52.4 and 50.4 g of total petroleum hydrocarbons per kg of dry soil, respectively. The effect of passing a continuous small stream of air containing a low concentration of gaseous toluene through packed 0.5 l (?=5.5 cm) columns was studied. For Soil A, after 62 days the THPs degradation was 28% higher in the toluene treated columns than in controls. In aged Soil B the effect of toluene was not significant, probably due to bioavailability limitations. With Soil B, the combined effect of toluene as cosubstrate and a surfactant pretreatment was studied and the hydrocarbons degradation was 29% higher in the toluene-amended columns than in the controls. Toluene removal was higher than 99% in all cases. Surfactant addition increased hydrocarbon degradation when toluene was also added suggesting that the biological reaction was the limiting process. The study shows the possibilities of using gaseous substrates, such as toluene, for the in situ or ex situ treatment of petroleum hydrocarbon-polluted soil in processes limited by the biological reaction. The main advantage of the treatment is that the compound can be easily and directly delivered to the polluted soil through the venting system.     

Pb speciation versus TCLP release in army firing range soils

A series of soil parameter and mineralogical investigative techniques were applied to assess the Pb speciation in four US Army firing range soils that presented significantly different Pb leaching regimes and soil characteristics. Soil gradation tests were complemented by total chemical analyses, X-ray powder diffraction (XRPD), Rietveld quantification, optical microscopy and scanning electron microscopy (SEM) analyses. The bulk geotechnical, mineralogical and chemical analyses pointed to two possible Pb retention mechanisms: precipitation as lead carbonate and sorption in the case of fine-grained soils. Lead speciation and mobility was further investigated by the toxicity characteristic leaching procedure (TCLP) and sequential extraction test (SET). As the TCLP Pb concentrations did not necessarily reflect the total Pb analysis of the soils, the Pb leachability ratio (TCLP/total) was found to be controlled by soil mineralogy and its response to changes in system pH. Geochemical modeling, using Visual MINTEQ, was employed to evaluate the mechanisms that controlled the observed TCLP Pb leaching behavior. It was found that lead carbonate precipitation/dissolution reactions controlled Pb TCLP leachability in all soils, while sorptive phenomena did not seem to play a role even in the case of fine-grained soils. More specifically, TCLP Pb leachability was controlled by the pH, the available Pb and the available carbonate in solution. This indicates that geochemical modeling strongly complimented TCLP Pb analyses. Thus, geochemical modeling is an important assessment tool to evaluate the magnitude of site-specific Pb-related environmental problems in firing range soils. Carbonation reactions, involving metallic Pb, that occur during the SET obscure its ability to reliably ascertain Pb speciation. More specifically, SET lumps the extractable Pb into predetermined phase categories that may not be truly representative of the actual soil mineralogy or dominant forms of Pb in the soil. A thorough geotechnical, mineralogical and chemical investigation of firing range soils, complemented by geochemical modeling, was therefore found to be a more reliable approach to evaluate Pb speciation and TCLP release in firing range soils.