内生菌协同宿主植物修复土壤复合污染的研究进展

土壤复合污染日益严重,危及植物生长及人类发展,寻找修复土壤复合污染的有效方法已经成为环境领域的优先事项。复合污染指同一环境中存在两种或两种以上的污染物,分为复合重金属污染、复合有机污染物污染及重金属-有机污染物复合污染。近些年发现内生菌能定殖在植物中,并且被感染的植物不会引起任何外在病症,其主要通过促进宿主植物生长,改变植物摄取污染物能力和酶促降解污染物等方法增强植物修复能力。本文综述了具有复合重金属和复合有机污染抗性的内生菌种类及其作用机制,并展望了内生菌协同宿主植物修复环境中复合污染物的研究方向。     

土壤中多环芳烃污染对植物生理生态的影响

多环芳烃(PAHs)是一类广泛存在于天然环境中的持久性有机污染物,对土壤的污染尤为突出,给生态环境、植物和人类健康造成严重的潜在威胁.当前,修复受PAHs污染的土壤是国际土壤和环境领域研究的热点,而植物修复是最具潜力的环境修复技术之一.本文对近年来土壤PAHs及其与其他污染物复合胁迫对植物生长及其形态结构、光合作用和抗氧化系统等影响研究的最新进展进行综述,并对今后的重要领域和研究热点进行了展望.     

根际圈在污染土壤修复中的作用与机理分析

根际圈以植物根系为中心聚集了大量的生命物质及其分泌物,构成了极为独特的“生态修复单元”。本文叙述了根在根际圈污染土壤修复中的生理生态作用,富集、固定重金属,吸收、降解有机污染物等功能;菌根真菌对根际圈内重金属的吸收、屏障及螯合作用,对有机污染物的降解作用;根际圈内细菌对重金属的吸附与固定,对有机污染物的降解作用以及根际圈真菌和细菌的联合修复作用等,同时对可能存在的机理进行了分析,认为根际圈对污染土壤的修复作用是植物修复的重要组成部分和主要理论基础之一,并指出利用重金属超富集植物修复重金属污染土壤具有广阔的应用前景;筛选对水溶性有机污染物高吸收富集及其根 发泌能力强的特异植物,同时接种利于有机污染物降解的专性或非专性真菌和细菌可能会成为有机污染土壤植物修复研究的重要方向之一。     

根系分泌物及其在植物修复中的作用

 近年来环境污染日益严重,污染物在土壤植物中的行为引起了人们的高度关注。利用植物去除土壤水体等介质中污染物的植物修复是近10年来兴起的一项安全、廉价的技术,已成为污染生态学和环境生态学的研究热点,它通过植物吸收、根滤、稳定、挥发等方式清除环境中的重金属和有机污染物。国内外有关植物修复的研究报道和概述很多, 但对植物根系分泌物在植物修复中所起的作用及其机理少有述评。 本文从根系分泌物对土壤重金属和土壤有机污染物的去除作用出发,对根系分泌物的种类、数量及其在去除环境污染物中的作用机理和功能地位进行了总结,并借助研究事例对影响植物根系分泌的内外因子,如植物种类、营养胁迫、重金属胁迫、根际环境的理化性质、土壤微生物及其它环境因子进行了讨论。概言之,根系分泌物在修复污染土壤中的重金属途径是多种多样的,主要是通过调节根际pH值、与重金属形成螯合物、络合反应、沉淀、提高土壤微生物数量和活性来改变重金属在根际中的存在形态以及提高重金属的生物有效性,从而减轻它对环境的危害。在清除有机污染物时,根系分泌物中的酶可以对有机污染物进行直接降解,根系分泌物影响下的微生物也可以对有机污染物进行间接降解,且被认为是主要的降解途径。根系分泌物在植物修复过程中确实起着某些重要作用,今后应将这方面的研究重点放在某些特异性根系分泌物植物,尤其是某些重金属超富集植物资源的寻找、筛选上,通过室内实验和野外研究确定其根系分泌物对清除重金属和有机污染物的效率,证实超富集植物根系分泌物的特异性与污染物超富集的内在联系,找到污染土壤生态恢复和治理的有效方法并加以推广应用,如针对性地在被污染地大面积种植此类具特异性根分泌物植物,并辅以营林措施如修剪等,加快生物修复进程,提高修复效率。植物根系分泌物在植物修复过程中所具有的重要生态意义和可能应用前景,为污染生态学和化学生态学之间的联合研究开拓了全新的领域,今后将取得新的突破和重要进展。     

有机污染物的土壤微界面过程及其影响因素

土壤是环境的重要组成部分,是连接大气圈、水圈、岩石圈和生物圈的纽带。随着工农业生产的迅速发展,越来越多的有机污染物通过各种途径进入土壤环境。本文主要对有机污染物在土壤中的吸附-解吸、降解-积累、溶解-沉淀等微界面过程进行了较为系统的阐述,探讨了土壤有机组分、无机组分、植物和微生物等生态因子对有机污染物相关土壤微界面过程的影响;同时,结合国内外的研究现状和趋势,对今后土壤微界面过程的研究方向以及采用的方法手段进行了建议和展望。     

持久性有机污染土壤的植物修复及其机理研究进展

随着人类对化学品的依赖程度越来越高,环境的有机污染状况也越来越严重.有机污染土壤的植物修复是指利用植物在生长过程中,吸收、降解、钝化有机污染物的一种原位处理污染土壤的方法,具有应用成本低、生态风险小、对环境副作用小等特点.本文综述了近年来国内外有机污染土壤的植物修复研究进展情况,重点介绍了多氯联苯、多环芳烃、农药和硝基芳香化合物等持久性有机污染物的植物修复,阐述了有机污染土壤植物修复的关键机制,并分析了该技术在实际工程应用中的局限性及应考虑的因素.最后,指出了今后该领域的重点研究方向.     

丛枝菌根对有机污染土壤的修复作用及机理

丛枝菌根(AM)是丛枝菌根真菌(AMF)与植物根系相互作用的互惠共生体,能改良土壤结构,增强植物抗性.自然界中已知的AMF有170多种,分布广泛,且可与大多数植物共生.利用AM修复有机污染土壤正成为一个崭新的研究方向.本文综述了AM对多环芳烃、酞酸脂、石油和农药等一些典型有机污染物污染土壤的修复作用.AM修复有机污染土壤的机理主要包括:AMF代谢有机污染物;AM分泌酶,降解污染物;AM影响根系分泌作用,并促进根际微生物对有机污染物的降解;AMF宿主植物吸收积累污染物.AM修复研究中,高效AMF的筛选、复合菌种效应、土壤老化、AM作用下植物对有机污染物的吸收积累等几方面仍有待于深入研究.     

生物基因技术修复石油污染土壤研究进展

植物修复油污土壤是控制环境污染的有效途径,但在实际应用中存在着植物生物量较小、生长缓慢等不足。将具有修复功能的外源基因引入植物中,使转基因植物的生物修复功能大大增强,为解决土壤石油污染问题提供了有效手段。文章系统论述了转基因植物对石油污染土壤中有机污染物,尤其是对持久性有机污染物（POPs）的吸收、转化和降解作用以及近年来所取得的突破性进展,并指出了利用生物基因修复技术进行土壤石油污染研究的发展趋势。     

生物炭对污染物的土壤环境行为影响研究进展

近年来,生物炭已成为农业、生态修复和环境保护领域的研究热点。一般认为,生物炭具有改善土壤质量、增加土壤碳汇、减少大气CO2浓度以及修复污染环境等功能。大量的生物炭施用到土壤后会改变土壤性质,影响重金属和有机污染物在土壤中的环境行为以及它们在环境中的归趋。本文就生物炭对土壤中重金属的吸附-解吸、在土壤中的形态转化、在土壤-植物系统中迁移行为、对有机污染物的吸附挥发及生物有效性进行了概述;在此基础上,扼要分析了当前生物炭应用存在的环境风险等问题,并从生物炭在土壤中的迁移转化及其归趋、生物炭的长期环境效应以及生物炭应用方向等方面进行了展望。     

植物根系分泌物生态效应及其影响因素研究综述

植物根系分泌物的形成是植物体代谢过程中重要的生理现象,为“植物-土壤”体系物质周转的重要环节.研究植物根系分泌物对于了解陆地生态系统质能过程、碳氮收支平衡及提高生态系统的初级生产具有重要意义.本文从植物根系分泌物对植物生理性状、土壤微生物、土壤物质周转及有机污染物降解影响等4个方面对植物根系分泌物的生态效应进行综述,并从重金属含量、营养元素水平、土壤水分和光热条件、物种基因型、土壤微生物状况和外源有机污染物添加的角度综述了影响植物根系分泌物的因素,旨在对植物根系分泌物的生态效应和影响因素进行总结,并根据目前的研究现状,从研究对象、研究方法和效应评估方面进行了展望.     

土壤有机污染植物修复的机理与影响因素

在综述大量国内外文献的基础上,分析了土壤有机污染植物修复的机理,重点介绍了国内外在植物吸收转运、植物根际降解和植物修复模型的研究进展。同时,从污染物的物理化学性质、植物种类、土壤性质、共存有机物和气象条件5个方面分析了影响土壤有机污染植物修复的主要因素,并展望了该领域的研究方向：深化植物修复机理,完善植物修复模型。加强植物-微生物协同修复的机理研究和技术应用,利用表面活性剂提高植物修复效率,加强复合有机污染植物修复研究。     

Understanding plant-microbe interactions for phytoremediation of petroleum-polluted soil

Plant-microbe interactions are considered to be important processes determining the efficiency of phytoremediation of petroleum pollution, however relatively little is known about how these interactions are influenced by petroleum pollution. In this experimental study using a microcosm approach, we examined how plant ecophysiological traits, soil nutrients and microbial activities were influenced by petroleum pollution in Phragmites australis, a phytoremediating species. Generally, petroleum pollution reduced plant performance, especially at early stages of plant growth. Petroleum had negative effects on the net accumulation of inorganic nitrogen from its organic forms (net nitrogen mineralization (NNM)) most likely by decreasing the inorganic nitrogen available to the plants in petroleum-polluted soils. However, abundant dissolved organic nitrogen (DON) was found in petroleum-polluted soil. In order to overcome initial deficiency of inorganic nitrogen, plants by dint of high colonization of arbuscular mycorrhizal fungi might absorb some DON for their growth in petroleum-polluted soils. In addition, through using a real-time polymerase chain reaction method, we quantified hydrocarbon-degrading bacterial traits based on their catabolic genes (i.e. alkB (alkane monooxygenase), nah (naphthalene dioxygenase) and tol (xylene monooxygenase) genes). This enumeration of target genes suggests that different hydrocarbon-degrading bacteria experienced different dynamic changes during phytoremediation and a greater abundance of alkB was detected during vegetative growth stages. Because phytoremediation of different components of petroleum is performed by different hydrocarbon-degrading bacteria, plants' ability of phytoremediating different components might therefore vary during the plant life cycle. Phytoremediation might be most effective during the vegetative growth stages as greater abundances of hydrocarbon-degrading bacteria containing alkB and tol genes were observed at these stages. The information provided by this study enhances our understanding of the effects of petroleum pollution on plant-microbe interactions and the roles of these interactions in the phytoremediation of petroleum-polluted soil.     

Methyl-branched poly(hydroxyalkanoate) biosynthesis from 13-methyltetradecanoic acid and mixed isostearic acid isomer substrates

Nonylphenol, the most abundant environmental pollutant with endocrine disrupting activity, is also toxic to plants and microorganisms, but its actual impact in the field is unknown. In this study, diversity of culturable soil microfungal and plant communities was assessed in a disused industrial estate, at three sites featuring different nonylphenol pollution. Although soil microfungal assemblages varied widely among the sites, no significant correlation was found with point pollutant concentrations, thus suggesting indirect effects of soil contamination on microfungal assemblages. The potential of indigenous fungi and plants to remove nonylphenol was assessed in mesocosm experiments. Poplar plants and a fungal consortium consisting of the most abundant strains in the nonylphenol-polluted soil samples were tested alone or in combination for their ability to reduce, under greenhouse conditions, nonylphenol levels either in a sterile, artificially contaminated sand substrate, or in two non-sterile soils from the original industrial area. Introduction of indigenous fungi consistently reduced nonylphenol levels in all substrates, up to ca. 70% depletion, whereas introduction of the plant proved to be effective only with high initial pollutant levels. In native non-sterile soil, nonylphenol depletion following fungal inoculation correlated with biostimulation of indigenous fungi, suggesting positive interactions between introduced and resident fungi. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Behavior of Cu and Zn under combined pollution of 2,4-dichlorophenol in the planted soil

Behavior of heavy metals under combined pollution of 2,4-dichlorophenol (2,4-DCP) was investigated using metal contaminated soil which was sampled from the heavily industrialized areas, Fuyang county, Zhejiang Province, P.R. China and pretreated with 100 μg g^?1 2,4-DCP for 1 month. Metal complexes were the predominant species for Cu and Zn in the soil solution. The treatment of 2,4-DCP had limited effect on the dissolution of Cu and Zn in the soil without plant root growth. But the metal species might be changed due to the addition of organic pollutant. Planting with rye grass for 1 month, greatly increased both water soluble Cu and Zn. The increase of water soluble Cu and Zn in the presence of 2,4-DCP was much more than that in the absence of 2,4-DCP, which suggested more attention should be paid to the behavior of heavy metals under combined pollution of organic pollutants in the planted soil. The results also indicated that in comparison to Cu, soil planted with ryegrass was more effective in activating Zn from soils, which was consistent with its relative weak chemisorptions on clays, oxides and humus of soils.     

Water Organic Pollution and Eutrophication Influence Soil Microbial Processes,Increasing Soil Respiration of Estuarine Wetlands: Site Study in Jiuduansha Wetland

Undisturbed natural wetlands are important carbon sinks due to their low soil respiration. When compared with inland alpine wetlands, estuarine wetlands in densely populated areas are subjected to great pressure associated with environmental pollution. However, the effects of water pollution and eutrophication on soil respiration of estuarine and their mechanism have still not been thoroughly investigated. In this study, two representative zones of a tidal wetland located in the upstream and downstream were investigated to determine the effects of water organic pollution and eutrophication on soil respiration of estuarine wetlands and its mechanism. The results showed that eutrophication, which is a result of there being an excess of nutrients including nitrogen and phosphorus, and organic pollutants in the water near Shang shoal located upstream were higher than in downstream Xia shoal. Due to the absorption and interception function of shoals, there to be more nitrogen, phosphorus and organic matter in Shang shoal soil than in Xia shoal. Abundant nitrogen, phosphorus and organic carbon input to soil of Shang shoal promoted reproduction and growth of some highly heterotrophic metabolic microorganisms such as β-Proteobacteria, γ-Proteobacteria and Acidobacteria which is not conducive to carbon sequestration. These results imply that the performance of pollutant interception and purification function of estuarine wetlands may weaken their carbon sequestration function to some extent.     

Linking soil biodiversity and vegetation: implications for a changing planet

Soil biota are intimately tied to plant communities through herbivory and symbiosis and indirectly by the decomposition of dead organic plant material. Through both roots and aboveground organic material (e.g., leaves and wood), plants provide substantial inputs of organic matter to soil systems. Plants are the basis for most biotic soil food webs that comprise an enormous diversity of species whose multiple interactions function to help regulate nutrient cycling, which in turn influences plant growth. Many factors govern the biogeography of soil biota, including the physical and chemical properties of soil, climate, the composition and type of vegetation, and interactions with other soil biota. Despite awareness of factors influencing soil communities, no single factor allows predictions of soil animal diversity or distribution. However, research is showing that plants can have unique soil biotic communities. Degradation of soil, which removes predators and biotic regulation that occurs in less managed ecosystems, can result in increased pathogens and pests that affect humans, other animals and plants. Global changes such as land use, desertification, and soil pollution all have been shown to alter soil animal diversity and abundance. Because of our dependence on soils and plant production, studies linking soil biotic communities to primary productivity are needed to assure long-term soil sustainability.     

Microbiological aspects of surfactant use for biological soil remediation

Biodegradation of hydrophobic organic compounds in polluted soil is a process involving interactions among soil particles, pollutants, water, and micro-organisms. Surface-active agents or surfactants are compounds that may affect these interactions, and the use of these compounds may be a means of overcoming the problem of limited bioavailability of hydrophobic organic pollutants in biological soil remediation. The effects of surfactants on the physiology of micro-organisms range from inhibition of growth due to surfactant toxicity to stimulation of growth caused by the use of surfactants as a co-substrate. The most important effect of surfactants on the interactions among soil and pollutant is stimulation of mass transport of the pollutant from the soil to the aqueous phase. This can be caused by three different mechanisms: emulsification of liquid pollutant, micellar solubilisation, and facilitated transport. The importance of these mechanisms with respect to the effect of surfactants on bioavailability is reviewed for hydrophobic organic pollutants present in different physical states. The complexity of the effect of surfactants on pollutant bioavailability is reflected by the results in the literature, which range from stimulation to inhibition of desorption and biodegradation of polluting compounds. No general trends can be found in these results. Therefore, more research is necessary to make the application of surfactants a standard tool in biological soil remediation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Use of olive mill wastewater compost for crop production

Vast amounts of olive mill wastewaters (OMW) are produced in Mediterranean countries, where their treatment and disposal are becoming a serious environmental problem. Increasing attention has been paid to discovering a use for OMW and a wide range of technological treatments are available nowadays for reducing their pollutant effects and for their transformation into valuable products, the most suitable procedures being found to involve recycling rather than the detoxication of these wastes. Direct application of OMW to soil has been considered as an inexpensive method of disposal and recovery of their mineral and organic components but, because of their organic acid and phenol contents, OMW are also a source of pollution. By using composting technologies, it is possible to transform either fresh OMW or sludge from pond-stored OMW mixed with appropriate plant waste waterials (carriers) into organic fertilizers (composts) with no phytotoxicity to improve soil fertility and plant production, the process involving the microbial degradation of the polluting load of the wastes. Results of field and pot experiments using OMW-composts to cultivate horticultural and other crops have shown that yields obtained with organic fertilization are similar, and sometimes higher, to those obtained with a balanced mineral fertilizer. A comparison between the macro and micronutrient contents of plants cultivated with organic or mineral fertilizers did not generally reveal important differences. However, the cases of iron and manganese are worth mentioning as their bio-availability may be linked to the soil humic complexes originated by the OMW organic fertilizers.     

复合污染研究的新进展

对多种污染物相互作用形成的复合污染效应的研究已成为环境科学发展的重要方向之一。本文从元机复合污染、无机－有机复合污染以及有机复合污染3个方面对复合污染效应的最新进展进行了综述,并从化学、生理学、酶学、细胞学等角度出发探计了复合污染机理,指出了复合污染研究中存在的若干问题和发展方向。