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1.
土壤铜镉污染的电动力学修复实验   总被引:2,自引:1,他引:1  
针对土壤典型重金属污染修复问题,通过实验方法研究了土壤铜镉污染的电动力学修复效果,并分析其迁移变化特征.实验结果表明,在电场作用下土壤中重金属的质量分数发生明显变化,使得大部分重金属能在电极附近富集而被去除,且土壤的pH值等是影响电动力学修复效果的重要因素.污染物Cd和Cu在电场作用下主要是在阴极附近产生富集,迁移方向由阳极向阴极,表明电场作用加强重金属Cd和Cu迁移效果.当实验电压为0.5 V/cm时,在阳极附近土壤中镉的去除效率为75.1%,铜的去除效率达到77.9%.另外,电动修复中由于阴阳两极的氧化还原反应造成电极附近pH值产生明显变化,其中阳极附近的pH值由开始时的7.5逐渐变小到4.7,而阴极附近则相反,由开始时的7.2逐渐增大到9.4,表明土壤的酸碱条件变化明显.  相似文献   

2.
在土壤修复技术中,电动力学修复技术具有处理效果好,没有二次污染,适用性广等特点。利用铁盐作为阴极电解液,柠檬酸-柠檬酸钠作为阳极电解液,结合阳离子膜研究不同电场强度(1.0 V·cm~(-1)、0.6 V·cm~(-1)、0.2 V·cm~(-1))对电动修复Zn污染土壤的影响,以期为电动修复技术的推广和应用提供理论基础。结果表明:在利用铁盐溶液作为阴极电解液时,Fe(Ш)可以消耗OH-,加快电解,有效维持土壤p H值,修复后土壤各截面的p H范围在3.1~9.8之间;随着电场强度的增大,电流逐渐增大,促进了土壤中Zn的解析,去除效率逐渐提高。随着电场强度的递减,相对应土壤截面Zn的最大去除率分别为86.47%、58.36%、41.72%;当电场强度为1 V·cm~(-1),修复400 h后土壤中Zn的总去除率达到54.1%。  相似文献   

3.
铬污染土壤的微生物修复   总被引:3,自引:0,他引:3  
采用淋溶实验研究微生物对铬污染土壤中Cr(Ⅵ)的修复,研究培养基成分、培养基添加量及淋溶液pH值对修复效果的影响.结果表明,培养基淋溶能完全修复铬污染土壤中水溶性Cr(Ⅵ),浸出液中Cr(Ⅵ)浓度由初始的700.3mg·L-1降低至检出限以下.单独加入碳源作为培养基时,土壤中Cr(Ⅵ)不能得到完全修复,碳源与氮源结合作...  相似文献   

4.
重金属污染土壤的电动原位修复技术研究   总被引:4,自引:0,他引:4  
电动力学修复技术作为一种新型的修复技术,由于其处理土壤污染的高效性,近几年来受到了越来越多的关注。综述了电动力学修复技术原理及近几年来其在重金属修复中的最新研究进展,阐述了电动力学修复技术相对于其它修复技术的优势,并指出了电动修复技术中需要克服的技术障碍,探讨了其大规模商业应用的可行性。电动技术能够强化土壤物质的传质过程,能够高效、快速定向迁移土壤中重金属离子达到去除的目的;同时电动技术可以与其它修复技术结合发展出系列组合修复技术,具有广泛的应用前景。从单一电动到复合电动是今后电动力学技术发展的重要方向。目前对污染物质复合电动力学效应下的迁移机理及模型、不同土壤性质(组分、酸碱性等)对于污染物质去除效率及其调控措施的研究仍需进一步深入。  相似文献   

5.
通过模拟降雨进行土柱淋溶实验来研究降雨条件下纳米零价铁镍(nZVI/Ni)对污染土壤六价铬迁移的影响,并测定淋溶液的Cr(Ⅵ)浓度、pH、电导率和累积释放量.使用改进BCR连续提取法测定淋溶后各层土壤的铬形态分布,分析施加nZVI/Ni对土壤中铬形态的影响.结果表明,降雨条件下六价铬的释放过程主要分为快速和慢速释放两个阶段.随着淋溶体积的增加,土壤淋溶液的pH逐渐升高后最后趋于平稳,电导率和Cr(Ⅵ)浓度迅速下降后趋于平稳.模拟降雨条件下,土壤中投加nZVI/Ni显著降低了淋溶液中Cr(Ⅵ)的累积释放量.投加0.10%nZVI/Ni土壤淋溶液的Cr(VI)累积释放量低于空白对照57.53%.在nZVI/Ni投加量相同时,模拟降雨的pH值越低nZVI/Ni的修复效果越好;降雨的淋溶次数对修复效果基本无影响;采用均匀混合的方式投加nZVI/Ni有着更好的修复效果.在土壤中nZVI/Ni对Cr(Ⅵ)修复过程中,纳米铁材料起主要作用,Fe(Ⅱ)的贡献很小.土壤经nZVI/Ni修复后,可还原态铬含量减少,可氧化态铬含量增加,表明纳米零价铁镍可以降低土壤中铬的迁移性,降雨条件下对六价铬污染土壤具有一定的修复效果.  相似文献   

6.
铬含量超标威胁生态环境安全,探究多种粘土矿物作用下铬的迁移转化机理,可以为铬污染土壤修复提供理论依据。主要从粘土矿物对铬的氧化-还原、吸附-解吸、催化作用等几个方面归纳分析了粘土矿物作用下铬迁移转化机理的研究现状,探讨了氧化物及微生物作用、pH、温度、有机质、矿物类型等因素对铬迁移转化的影响。首先,锰氧化物是氧化Cr(Ⅲ)的唯一天然矿物,其结构中Mn(Ⅱ)或Mn(Ⅲ)含量越高,氧化能力越强;低温、碱性条件下,Cr(Ⅲ)稳定性较高。锰氧化细菌会加速Cr(Ⅲ)的氧化,矿物表面吸附的Mn(Ⅱ)会抑制Cr(Ⅲ)的氧化。其次,黄铁矿、黑云母、绿泥石、柯绿泥石、磁铁矿等矿物常用于Cr(Ⅵ)还原,黄铁矿组成中的Fe(Ⅱ)和S2~(2-)能有效地还原Cr(Ⅵ),而黑云母、绿泥石只有经生物作用产生Fe(Ⅱ)才能还原Cr(Ⅵ),蒙脱石、伊利石、高岭石、黄铁矿对Cr(Ⅵ)的还原速率在pH4.5时较大。最后,高岭石、伊利石、蛭石、蒙脱石可吸附固持Cr(Ⅵ),且酸性、有机质含量低的条件下吸附效果明显,吸附顺序为:高岭石伊利石蛭石=蒙脱石;粘土矿物层间结合比表面结合更强,可对粘粒矿物进行改性以提高吸附效果。在吸附机理方面,研究者广泛采用Langumiur、Freundlich等方程来描述矿物对铬的吸附。粘土矿物作用下铬的迁移转化机理探究,可以使我们更加深入的了解沉积物、土壤对铬的解毒原理以及矿物在其中所起的作用,这对于矿物材料吸附性能的提高、铬污染土壤的治理具有深远的意义。  相似文献   

7.
针对黑炭/零价铁复合材料(BF)、金属还原菌(GY~(-1))单独使用修复Cr(Ⅵ)污染环境存在的问题,构建了黑炭零价铁与金属还原菌的耦合体系,考察了耦合体系中溶液pH值、Cr(Ⅵ)浓度、反应时间、温度对微生物生长和溶液中Cr(Ⅵ)去除的影响,并且研究了耦合体系中铁的动态变化。实验结果表明:黑炭/零价铁复合材料可作为金属还原菌的固定化载体,为金属还原菌提供繁殖场所的同时,提高其对Cr(Ⅵ)的抗性。耦合体系中Cr(Ⅵ)的去除效果明显优于单独使用零价铁/黑炭和单独铬还原菌的效果。在耦合体系中,3 mL细胞培养液(OD_(600)为1.2—1.6)和0.1 g黑炭负载零价铁材料,Cr(Ⅵ)初始质量浓度为100mg·L~(-1)条件下,反应24h后可将溶液中Cr(Ⅵ)完全去除。XPS结果显示,反应阶段Cr(Ⅵ)和Cr(Ⅲ)共同存在于耦合体系中,但大部分的Cr(VI)会被零价铁和铬还原菌还原为Cr(Ⅲ),此外,存在黑炭和菌体对Cr(Ⅵ)的吸附作用。耦合体系中Fe(Ⅱ)含量高于单独黑炭负载零价铁材料,说明微生物能还原零价铁钝化层的Fe(Ⅲ)为Fe(Ⅱ),使Fe(II)继续参与还原反应,产生循环效果,增强耦合体系对Cr(Ⅵ)的去除效果。同时,铁离子作为一种电子传递介质增强微生物对Cr(Ⅵ)还原过程中的电子传递,加速反应进行的同时,解决零价铁表面易钝化问题。  相似文献   

8.
本研究利用土柱试验研究了铬污染土壤微生物修复的各工艺参数,结果表明:土壤粒径、喷淋强度、以及修复工艺对铬污染土壤的修复效果有很大的影响.最佳的工艺参数为:土壤粒径1~2 cm、喷淋强度在29.6~59.2 mL·min-1、工艺制度Ⅱ(先用自来水淋洗1 d,接着用菌液循环喷淋).在土柱试验的基础上开展了25吨/批的中试试验,铬污染土壤经过7~10 d的处理,土壤中Cr(Ⅵ)浸出毒性浓度由53.8 mg·L-1降低至0.4 mg·L-1,达到《铬渣污染治理环境技术规范》(HJ/T301~2007)中铬渣用作路基材料和混凝土骨料的标准限值,证明铬污染土壤微生物修复工业化具有可行性,为铬污染土壤工程化修复提供了技术支撑.  相似文献   

9.
以铁屑和活性炭构建的原电池研究不同电极间距下高岭土中的镉在原电池电场下的电动力学迁移.随着反应时间的延长,电压和电流均逐渐减小.反应后,高岭土的pH值从阳极到阴极逐渐增加.高岭土中镉含量从阳极向阴极逐渐增加,镉的去除率随电极间距的增加而降低,高岭土的pH值愈低镉的迁移效果愈明显.10cm的电极间距高岭土中镉的去除率达77.9%,在50cm的电极间距下镉的迁移作用很小.表明利用铁炭原电池产生的电场可以驱动污染高岭土中镉的电动力学迁移.  相似文献   

10.
生物修复技术因其费用低、对环境不产生二次污染而被视为是一项具有广阔发展前景的技术。然而,一些强疏水性的有机污染物,生物可利用性很差,严重阻碍了其生物降解效率。电动与微生物联合修复技术(电动-微生物修复),在顽固性有机污染物的去除方面表现出巨大潜力。电场的施加可向土壤中分散外源物质、营养物质和微生物;或通过增强土壤中有机污染物与降解菌的传质过程,提高难降解有机物的生物可利用性;还可诱使土壤中的污染物产生电化学反应,增强污染物的去除效果。文章对有机污染土壤的电动-微生物修复过程的影响因素及优化措施进行了综述。文章认为,影响电动-微生物修复效率的因素主要有电场强度、污染物的生物可利用性、污染物结构和性质、微生物种群以及环境因素(如土壤pH值、土壤类型、营养物质、含水量等)。因此,在实施修复的过程中应根据污染场址的电化学特性选择合适的电流或电压梯度;另外,可通过施加表面活性剂、助溶剂或螯合剂,构建微生物群落,以及优化土壤环境条件,如调整土壤pH、提供营养物质、电子受体、共代谢基质等方式优化有机污染土壤电动-微生物修复的过程。深入研究有机污染土壤电动-微生物修复过程中的影响因素和优化措施,有望为电动-微生物修复技术在有机污染土壤的场地修复及过程调控中的应用提供一定的理论依据。  相似文献   

11.
A bioblitz inexpensively and quickly generates biodiversity data, but bioblitzes are often conducted with haphazard, unreplicated sampling. Results tend to be taxonomically, geographically, or temporally biased, lack metadata, and consist of lists of observed taxa that do not enable further analyses or correction for imperfect detection. A rapid, recurring, structured survey (RRSS) uses a structured sampling design and temporal and spatial replication to survey randomly selected sites on a conservation property. We participated in a loosely structured bioblitz and a subsequent RRSS at Big Canoe Creek Nature Preserve in Springville (St. Clair County), Alabama (USA) to compare observed richness derived from the 2 survey approaches. The RRSS data structure enabled us to fit models that accounted for imperfect detection to estimate abundances, occupancy probabilities, and habitat associations. The loosely structured bioblitz data could not be used in such models. We present a new integrated multispecies abundance model that we applied to avian RRSS data. Our model extension enables estimation for the community, employs data augmentation to estimate the number of undetected species, and incorporates covariates. The RRSS generated a more comprehensive and less biased list of observed taxonomic richness than the loosely structured bioblitz (e.g., 73 vs. 45 bird species and 104 vs. 63 insect families from the RRSS vs. loosely structured bioblitz, respectively). Models fit to the RRSS data identified seasonal patterns in avian community composition and allowed for estimation of habitat–occupancy relationships for insect taxa. The RRSS protocol has potential for broad transferability as a standardized, quick, and inexpensive way to inventory biodiversity and estimate ecological parameters while providing an outreach opportunity.  相似文献   

12.
Conservation science is a crisis discipline in which the results of scientific enquiry must be made available quickly to those implementing management. We assessed the extent to which scientific research published since the year 2000 in 20 conservation science journals is publicly available. Of the 19,207 papers published, 1,667 (8.68%) are freely downloadable from an official repository. Moreover, only 938 papers (4.88%) meet the standard definition of open access in which material can be freely reused providing attribution to the authors is given. This compares poorly with a comparable set of 20 evolutionary biology journals, where 31.93% of papers are freely downloadable and 7.49% are open access. Seventeen of the 20 conservation journals offer an open access option, but fewer than 5% of the papers are available through open access. The cost of accessing the full body of conservation science runs into tens of thousands of dollars per year for institutional subscribers, and many conservation practitioners cannot access pay‐per‐view science through their workplace. However, important initiatives such as Research4Life are making science available to organizations in developing countries. We urge authors of conservation science to pay for open access on a per‐article basis or to choose publication in open access journals, taking care to ensure the license allows reuse for any purpose providing attribution is given. Currently, it would cost $51 million to make all conservation science published since 2000 freely available by paying the open access fees currently levied to authors. Publishers of conservation journals might consider more cost effective models for open access and conservation‐oriented organizations running journals could consider a broader range of options for open access to nonmembers such as sponsorship of open access via membership fees. Obtención de Acceso Abierto a la Ciencia de la Conservación  相似文献   

13.
Land-use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland and creek), offsetting measure (e.g., enhancement, restoration, and creation), and an assessment of the projects’ compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.  相似文献   

14.
15.
Large, intact areas of tropical peatland are highly threatened at a global scale by the expansion of commercial agriculture and other forms of economic development. Conserving peatlands on a landscape scale, with their hydrology intact, is of international conservation importance to preserve their distinctive biodiversity and ecosystem services and maintain their resilience to future environmental change. We explored threats to and opportunities for conserving remaining intact tropical peatlands; thus, we excluded peatlands of Indonesia and Malaysia, where extensive deforestation, drainage, and conversion to plantations means conservation in this region can protect only small fragments of the original ecosystem. We focused on a case study, the Pastaza‐Marañón Foreland Basin (PMFB) in Peru, which is among the largest known intact tropical peatland landscapes in the world and is representative of peatland vulnerability. Maintenance of the hydrological conditions critical for carbon storage and ecosystem function of peatlands is, in the PMFB, primarily threatened by expansion of commercial agriculture linked to new transport infrastructure that is facilitating access to remote areas. There remain opportunities in the PMFB and elsewhere to develop alternative, more sustainable land‐use practices. Although some of the peatlands in the PMFB fall within existing legally protected areas, this protection does not include the most carbon‐dense (domed pole forest) areas. New carbon‐based conservation instruments (e.g., REDD+, Green Climate Fund), developing markets for sustainable peatland products, transferring land title to local communities, and expanding protected areas offer pathways to increased protection for intact tropical peatlands in Amazonia and elsewhere, such as those in New Guinea and Central Africa which remain, for the moment, broadly beyond the frontier of commercial development.  相似文献   

16.
An argument is presented in which areas of natural arsenic contamination of modern groundwaters throughout Asia have a common origin. Arsenic originally accumulated in oceanic ferro-manganoan sediments of the eastern Palaeo-Tethys. This was further concentrated through oceanic crustal extinction in what later became the south-east Chinese accreted mineralised terrain. Proto-Himalayan uplift of this area created the palaeo-drainage systems of the Ganges – Brahmaputra, Irrawaddy, Mekong, and Red Rivers, with consequent headwater erosion of arsenic-rich sediments. Their downstream deposition as immature and easily redistributed Neogene sandstones, silts, and iron-rich clays has created secondary and tertiary reservoirs of adsorbed and authigenic arsenic, from which the current arsenic-rich groundwaters have evolved. Considering river basins within the above palaeo-hydrogeological framework provides a basis for assessing the risk of arsenic in groundwater basins of south and south-eastern Asia.  相似文献   

17.
Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.  相似文献   

18.
Biogeographic theory predicts that rare species occur more often in larger, less‐isolated habitat patches and suggests that patch size and connectivity are positive predictors of patch quality for conservation. However, in areas substantially modified by humans, rare species may be relegated to the most isolated patches. We used data from plant surveys of 81 meadow patches in the Georgia Basin of Canada and the United States to show that presence of threatened and endangered plants was positively predicted for patches that were isolated on small islands surrounded by ocean and for patches that were isolated by surrounding forest. Neither patch size nor connectivity were positive predictors of rare species occurrence. Thus, in our study area, human influence, presumably due to disturbance or introduction of competitive non‐native species, appears to have overwhelmed classical predictors of rare species distribution, such that greater patch isolation appeared to favor presence of rare species. We suggest conservation planners consider the potential advantages of protecting geographically isolated patches in human‐modified landscapes because such patches may represent the only habitats in which rare species are likely to persist. Influencia Humana y Predictores Biogeográficos Clásicos de la Ocurrencia de Especies Raras  相似文献   

19.
The macro-algae communities observed in the south lake of Tunis are characterized by the predominance of nitrophilous algae which are in the order of biomass importance:Ulva, Cladophora andEnteromorpha. We have noted seasonal changes of alga distribution. The wind appears to be one of the most important factors influencing this distribution. The total biomass reaches a maximum in the spring. Rapid decomposition of the biomass leads to a severe ecological imbalance, resulting in crises of anoxia and fish death. A restoration project has already started. It aims at removal of contaminated muds and the introduction of a new circulation system. The main objectives of this work were to collect information on the distribution and biomass of the phytobenthic communities as a first step in the constitution of a database for further comparison.  相似文献   

20.
How should managers choose among conservation options when resources are scarce and there is uncertainty regarding the effectiveness of actions? Well‐developed tools exist for prioritizing areas for one‐time and binary actions (e.g., protect vs. not protect), but methods for prioritizing incremental or ongoing actions (such as habitat creation and maintenance) remain uncommon. We devised an approach that combines metapopulation viability and cost‐effectiveness analyses to select among alternative conservation actions while accounting for uncertainty. In our study, cost‐effectiveness is the ratio between the benefit of an action and its economic cost, where benefit is the change in metapopulation viability. We applied the approach to the case of the endangered growling grass frog (Litoria raniformis), which is threatened by urban development. We extended a Bayesian model to predict metapopulation viability under 9 urbanization and management scenarios and incorporated the full probability distribution of possible outcomes for each scenario into the cost‐effectiveness analysis. This allowed us to discern between cost‐effective alternatives that were robust to uncertainty and those with a relatively high risk of failure. We found a relatively high risk of extinction following urbanization if the only action was reservation of core habitat; habitat creation actions performed better than enhancement actions; and cost‐effectiveness ranking changed depending on the consideration of uncertainty. Our results suggest that creation and maintenance of wetlands dedicated to L. raniformis is the only cost‐effective action likely to result in a sufficiently low risk of extinction. To our knowledge we are the first study to use Bayesian metapopulation viability analysis to explicitly incorporate parametric and demographic uncertainty into a cost‐effective evaluation of conservation actions. The approach offers guidance to decision makers aiming to achieve cost‐effective conservation under uncertainty.  相似文献   

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