电动微生物法修复石油和镍污染土壤的研究

针对石油-重金属污染的土壤日益严峻的现象及各种土壤修复技术存在的不足,采用快速、高效、对环境干扰较小的电动微生物法,对石油烃含量为16 000 mg/kg,镍含量为400 mg/kg的共污染土壤进行修复。在不同电压梯度下对土壤pH值、电导率和石油烃的降解和镍的去除效果进行研究,同时采用石油烃组分分析法和BCR法分步提取不同形态的镍,对不同组分的石油烃组分的降解和不同形态镍的迁移转化情况进行分析。实验结果表明,随着电压的增加,土壤中不同形态的镍去除效果明显,不同组分的石油烃的去除最佳电压值为1 V/cm。阴阳离子交换膜的使用和电解质的定期更换表明,阴阳离子交换膜的作用可以维持土壤pH值的稳定,从而增强微生物对石油烃的降解和电场对重金属Ni不同形态的迁移转化。在最佳修复电压值1 V/cm下,15 d后,石油烃的降解率达到了46.85%,镍的去除率达到了38.52%。因此,采用阴阳离子交换膜的电动微生物法,是修复混合污染土壤的理想的修复方法之一。     

强化电动修复重金属污染土壤的研究

采用逼近电极法强化电动修复废弃电镀厂周边重金属镍污染的土壤,电场强度1 V/cm修复48 h得到67.2%土壤镍去除率,相对于传统的固定电极电动修复法镍31.5%去除效率,逼近电极法强化电动修复去除效率的提高,归因于靠近阳极产生了更多的H+和镍离子从土壤中解析出来,因此,强化了土壤重金属污染修复。     

酸化-电动强化修复铬渣场地污染土壤

为解决常规电动修复方法对Cr污染土壤Cr(T)(总Cr)去除效率低的问题,提出了酸化预处理-电动强化修复技术. 以国内某化工厂铬渣堆放场地Cr污染土壤为研究对象,通过改变土壤酸化条件,分析乙酸和柠檬酸的酸化时间、酸浓度(以c计)对电动修复Cr污染土壤中Cr去除率的影响,并对土壤中Cr的形态进行分析. 结果表明:①酸化预处理-电动强化修复技术可以显著提高Cr污染土壤中Cr的去除率,其中0.9 mol/L柠檬酸酸化5 d组Cr(T)和Cr(Ⅵ)的去除率由对照组的6.23%、19.01%分别升至26.97%、77.66%. ②土壤酸化可以将部分Cr由碳酸盐结合态向水溶态转化,进而提高Cr去除率;在适宜的酸浓度范围内,酸浓度越高,土壤释放的Cr越多,Cr去除效果就越好. ③与乙酸组相比,柠檬酸组Cr的去除率较高,因为柠檬酸本身也是一种络合剂,在酸化作用释放碳酸盐结合态Cr的基础上,柠檬酸能与Cr发生络合作用,进一步提升了Cr的去除率. 电动修复过程中迁移出土壤的Cr主要以醋酸可提取态、可还原提取态和可氧化提取态为主,残留Cr的生物可利用性降低.      

电动修复技术去除土壤重金属污染研究进展

电动修复技术可能是唯一可行的低渗透性污染土壤原位修复方法,受到广泛关注。本文尝试总结论述了电动修复技术去除土壤重金属污染的相关研究进展,介绍了电动修复技术的基本原理及局限性,探讨比较各种强化电动修复技术的方法,包括电极接近法、交换电极法、离子交换膜、电场强化法(垂直电场、交流电场、脉冲电场)、试剂强化法(pH调节、螯合剂、表面活性剂),重点阐述目前新的螯合剂和表面活性剂的开发研究状况,以及电动修复目前主要的联用技术类型(电动-淋洗、电动-植物、电动-微生物、电动-可渗透反应墙)。此外,简要论述了电动修复对变价金属(Hg、Cr、As)的修复效果。最后在回顾总结该技术研究的基础上,对电动修复技术在去除土壤重金属污染的发展方向进行展望。     

阳极电解液pH值对Cr(Ⅵ)污染土壤电动修复效率的影响研究

为研究不同阳极电解液初始pH值条件对铬污染土壤电动修复效率的影响,试验以氯化铜溶液为阴极电解液,不同初始pH值(pH=3、4、5)的柠檬酸-柠檬酸钠缓冲溶液为阳极电解液,并在阴极室靠近土壤处放置阳离子交换膜,以此阻隔阴极的OH-进入土壤,采用电动力学方法修复Cr(Ⅵ)污染土壤。结果表明:经过400h电动修复后,当阳极电解液初始pH=3时土壤中铬的去除效果最佳,此时靠近阴极部分S7区域土壤为最大截面去除率,达到84.5%。采用BCR四步连续提取法对电动修复前后铬污染土壤中铬的形态变化进行分析,结果表明电动修复过程中主要是对土壤中可氧化态和弱酸可提取态的铬进行了去除,而残渣态铬含量几乎不变。选用铜盐作为阴极电解液可以有效促进铬的迁移与去除。     

尾矿库重金属污染土壤电动-植物模拟修复方法研究

尾矿库重金属污染土壤的修复过程复杂且缓慢。为缩短修复周期,促进土壤修复技术的智能化和精细化发展,灵活运用电动修复+植物萃取法的机理与规律,建立修复变量评价指标体系,融合随机森林分类器和GRA模拟算法,建立土壤模拟修复GRA-RF模型,并进行了模拟修复与实验修复对比。结果表明:1）修复变量中电压梯度（0.092）重要度等级值最高,其后是电流大小（0.078）、土壤湿度（0.074）、通电时间（0.069）、土壤动态pH值（0.066）、电极间距（0.063）、电极布置方式（0.06）、添加剂种类（0.057）和电极材料（0.053）,其余变量等级值小于平均值。按照变量重要度次序改变修复变量大小,直到获得最优修复效果;2）8个修复样本的模拟修复效率高于实验修复效率,修复环境A1~A4的相对误差分别为2.22%、4.72%、8.75%和3.89%,B1~B4分别为9.91%、8.28%、6.74%和5.63%,环境A下Cd、Cu和Pb的修复效果优于环境B,而Zn的修复效果则相反;3）通过对比算法错误率,GRA-RF模型的修复效果优于Random-RF。该方法真实模拟了污染土壤强化修复过程,通过优化修复变量指标提高土壤修复效率,为制定和改进土壤修复方案提供了参考。     

过硫酸盐对电动-铁/碳复合材料联合修复多氯联苯污染土壤的强化作用

研究了3种浓度过硫酸盐溶液(2、20和200 g·L^-1,以下分别表示为0.2%、2%、20%)作为电解液对电动-铁/碳复合材料（EK-Fe/C）联合修复多氯联苯（PCBs）污染土壤的强化作用,并探究了EK-Fe/C-PS修复技术对土壤理化性质的影响.结果表明,EK-Fe/C-PS修复7 d后,土壤温度和可溶性有机质含量增加,p H显著降低,电导率下降.PS对EK-Fe/C联合修复PCB28污染土壤具有显著的强化作用,修复效果整体随PS浓度增加而增加.在PS浓度为20%时,PCB28的7 d平均去除效率最高（60.9%）,是EK-Fe/C处理组（20.5%）的3倍,EK-20%PS处理组（32.0%）的近2倍.阳极侧土壤PCB28去除效率显著高于阴极侧,达到92.7%±7.7%.在两个电极中间区域,PS浓度增加对修复效果的影响不显著.为降低修复成本和对土壤的影响,污染土壤修复实践中可先使用高浓度PS快速修复阳极和阴极侧土壤,再使用低浓度PS强化修复中间区域土壤.     

电动-微生物修复对胶质结构的改变及毒性的削减

我国开采原油的稠油比重大、胶质含量高、环境风险突出,亟需解决石油污染土壤中胶质组分的解毒问题.由于胶质结构复杂、难以降解,所以对胶质结构变化的研究较少,其降解率也并不足以说明胶质污染土壤的修复效果,因此本文着重分析了修复过程中胶质结构与毒性的变化,为污染土壤修复体系提供重要指标.本文从辽河油田原油中提取胶质配制污染土,并加入构建的混合菌群.设计微生物修复(Bio)、电动-微生物修复(EK+Bio1)、电动-微生物补充营养修复(EK+Bio2)及间断电动-微生物修复(EK+Bio3)共4种处理.结果表明,胶质平均降解率EK+Bio2EK+Bio3EK+Bio1Bio,降解率最高为9.67%,为Bio处理的3.05倍(3.15%).元素分析结果表明,修复前后胶质平均化学式为C_(106)H_(157)N、C_(96)H_(174)N,碳氢比降低,不饱和度降低.光谱分析与~1H-核磁共振结果表明,修复后胶质碳链变短,芳香环、羧基与酚类结构数量减少.根据B-L法计算胶质芳碳率(f_A)由0.28减少到0.11,可推测胶质的结构模型.MicroResp~(TM)与小麦种子发芽实验结果表明,修复后土壤中微生物活性增强,小麦种子发芽率大大提高,说明结构的变化使胶质毒性降低.因此,电动-微生物修复使胶质结构发生变化,并在一定程度上有效削减了胶质毒性,较好的对胶质污染土壤进行了修复.     

抗坏血酸与柠檬酸对尾矿Pb污染土壤电动修复的强化效果

为研究抗坏血酸与柠檬酸作为增强试剂对高酸性缓冲能力的尾矿Pb污染土壤[w（Pb）为（5491.9±24）mg/kg]电动修复的强化效果,利用0.1 mol/L柠檬酸作为阴极电解液并控制阴极pH在2~3之间,系统分析土壤饱和液中c（抗坏血酸）（0~0.4 mol/L）、修复电压梯度（1~3 V/cm）对电动修复Pb污染土壤的影响,并对土壤中Pb的存在形态进行分析.结果表明:当电动修复过程中施加电压梯度为1 V/cm、c（抗坏血酸）（0~0.4 mol/L）作为饱和液时,随着c（抗坏血酸）的增加,土壤中Pb的迁移能力随之增加,Pb的去除率得到提高.当c（抗坏血酸）达到0.4 mol/L时,土壤中Pb的去除率为36.86%;保持c（抗坏血酸）为0.4 mol/L,当施加电压梯度由1 V/cm增至2 V/cm时,土壤中Pb的去除率得到增加（最高可达87.09%）,通过Pb的形态变化可知,w（弱酸提取态Pb）由初始的2.99%（1 V/cm）最大可降至0.34%（2 V/cm）,w（可还原态Pb）由初始的83.86%（1 V/cm）最大降至2.94%（2 V/cm）.研究显示,当c（抗坏血酸）为0.4 mol/L、柠檬酸（作为阴极电解液）控制阴极电解室pH在2~3之间、施加电压梯度为2 V/cm时,土壤中Pb的迁移能力显著提高并达到较好的修复效果.      

柱淋洗法修复铬污染土壤的效果研究

以铬渣污染土壤为供试土壤,采用土柱淋洗法研究柠檬酸、草酸和盐酸单一淋洗以及复合淋洗对铬去除动态和修复效果的影响,并对淋洗前后土壤中铬形态进行分析,探讨修复机理。结果表明,各淋洗方案中,以10体积0.5 mol/L草酸溶液为淋洗剂时的修复效果最好,总Cr累计淋出量为2 304 mg/kg,上层、中层和下层土壤总Cr去除率分别为79.6%、78.1%和69.6%,Cr(VI)去除率为87.8%、86.2%和75%,且土壤Cr(VI)和总Cr随着土壤深度的增加而升高,有在底部积累的可能;淋洗后土壤明显酸化,p H值从10.5降至3左右;以酸作为淋洗剂能有效降低土壤可氧化态铬含量,将其转化为移动性较强的酸可提取态,这有助于达到预期修复效果。     

Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

Intraspecific differences in effects of co-contamination of cadmium and

A hydroponic experiment was carried out to study intraspecific differences in the effects of different concentrations of cadmium (Cd)(0-10 mg/L) and arsenate (As(V)) (0-8 mg/L) on the growth parameters and accumulation of Cd and As in six wheat varieties Jing-9428, Duokang-1, Jingdong-11, Jing-411, Jingdong-8 and Zhongmai-8. The endpoints of wheat seedlings, including seed germination,biomass, root length and shoot height, decreased with increasing the Cd and As concentrations. Significant differences in seed germination, biomass, root length, shoot height and the accumulation of Cd and As were observed between the treatments and among the varieties (p ＜ 0.05). The lethal dosage 50% were about 20, 80, 60, 60, 80 and 20 mg As/L for Jing-9428, Duokang-1, Jingdong-11,Jing-411, Jingdong-8 and Zhongmai-8, respectively, and the corresponding values for Cd were about 30, 80, 20, 40, 60 and 10 mg Cd/L, respectively. Among the six varieties, Duokang-1 was found to be the most resistant to Cd and As toxicity, and Zhongmai-8 was the most sensitive to Cd and As co-contamination. The resistance of the six varieties was found dependant on the seedling uptake of Cd and As. Duokang-1 was the most suitable for cultivation in Cd and As co-contaminated soils.     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.