稀水溶液中Cr(Ⅵ)的光催化还原研究

以甲醇、正丙醇、丙三醇和苯酚作为俘获剂,研究稀水溶液中Cr(VI)的光催化还原过程,考察Cr(VI)在催化剂表面上的界面吸附行为及溶液pH值、俘获剂类型等对其光催化还原过程的影响.结果表明,溶液pH值对Cr(VI)吸附的影响为:(1)溶液pH<2.4时,随pH值升高,吸附量减少;(2)pH值在2.4-5.0时,随pH值的升高,吸附量上升,在pH＝5.0时吸附量达到最大;(3)pH>5.0时,吸附量迅速下降.但溶液pH值对Cr(VI)光催化还原的影响与其对Cr(VI)吸附的影响存在显著差异,随pH值的升高,Cr(VI)的还原率下降,在溶液pH＝1.0时60min内可还原完全,而在pH＝9.0时经相同时间后Cr(VI)仍残余65.18%.俘获剂类型对Cr(VI)的还原也有一定影响.     

纳米Fe0对Cr(Ⅵ)的还原及其影响因素

采用纳米Fe0还原水溶液中的Cr(Ⅵ),考察纳米Fe0投加量、Cr(Ⅵ)初始浓度、溶液pH值和有机酸等因素对Cr(Ⅵ)还原的影响.结果表明,纳米Fe0对Cr(Ⅵ)的还原效果明显,其对Cr(Ⅵ)的还原率分别是铁粉和铁屑的7和13倍.Cr(Ⅵ)溶液初始质量浓度为20 mg·L-1、Fe0投加量为5g·L-1条件下,反应24 h时纳米Fe0对Cr(Ⅵ)的还原率达82.7％.溶液低pH值可以促进Fe0的腐蚀速度,提高反应速率,当pH值为3.0时还原效果最好.草酸、丙二酸和丁二酸对纳米Fe0还原Cr(Ⅵ)均有明显的促进作用,3种有机酸对Cr(Ⅵ)还原率的提高幅度由高到低依次为草酸、丙二酸和丁二酸.     

模拟日光照射下草酸协同黄铁矿对Cr(Ⅵ)的还原作用

研究了模拟日光照射下草酸协同黄铁矿对Cr(Ⅵ)的还原作用机理及其影响因素.结果表明,加入草酸后,反应体系中生成了光化学活性高的草酸铁(Ⅲ)配合物,同时还可能阻止了黄铁矿表面Fe(Ⅲ)水解产物Fe(OH)3和CrxFe1-x(OH)3的生成,从而使黄铁矿还原Cr(Ⅵ)的速率明显得到提高.增加溶液酸度、草酸浓度和黄铁矿质量浓度,有利于Cr(Ⅵ)的还原.     

纳米Fe0对Cr（VI）的还原及其影响因素

采用纳米Fe0还原水溶液中的Cr（Ⅵ）,考察纳米Fe0投加量、Cr（Ⅵ）初始浓度、溶液pH值和有机酸等因素对cr（Ⅵ）还原的影响。结果表明,纳米Fe。对Cr（Ⅵ）的还原效果明显,其对Cr（Ⅵ）的还原率分别是铁粉和铁屑的7和13倍。Cr（Ⅵ）溶液初始质量浓度为20mg·L-1、Fe。投加量为5g·L“条件下,反应24h时纳米Fe0对Cr（Ⅵ）的还原率达82．7％。溶液低pH值可以促进Fe。的腐蚀速度,提高反应速率,当pH值为3．0时还原效果最好。草酸、丙二酸和丁二酸对纳米Fe。还原Cr（Ⅵ）均有明显的促进作用,3种有机酸对Cr（Ⅵ）还原率的提高幅度由高到低依次为草酸、丙二酸和丁二酸。     

木本泥炭对Cr(Ⅵ)的吸附性能

以木本泥炭为吸附材料,用于去除水中的Cr(Ⅵ).研究了溶液pH值、吸附时间、木本泥炭用量、缓冲液浓度和初始浓度对Cr(Ⅵ)吸附的影响,以及溶液pH值对Cr(Ⅵ)解吸附的影响.结果表明,木本泥炭对Cr(Ⅵ)的去除率随溶液pH值的增大而减小,当溶液pH值为4时,木本泥炭对Cr(Ⅵ)的吸附能力最强,3.33 g·L~(-1)木本泥炭对100 mg·L~(-1)Cr(Ⅵ)的吸附量为29. 98 mg·g~(-1);当磷酸盐缓冲液浓度在0. 10—0.20 mol·L~(-1)范围内时,随着缓冲液浓度的增大Cr(Ⅵ)的吸附量逐渐减小;木本泥炭对Cr(Ⅵ)的吸附符合准一级反应动力学,其吸附等温线符合Langmuir吸附模型;当溶液pH值小于6时,Cr(Ⅵ)的解吸率低于0.32%.     

含氧水溶液中δ-MnO2对非晶态Cr（OH）3的化学氧化：影响因素和作用机理

对六价铬污染水体和土壤修复常采用化学还原方法,但是当前研究对还原产物非晶态Cr（OH）₃的再氧化过程以及环境酸碱性、有机质等因素对该过程的影响仍有较多分歧.本研究通过批试验,观测了含氧水溶液体系中非晶态Cr（OH）₃的长期稳定性及pH和溶解性有机质（Dissolved organic matter,DOM）对δ-MnO₂氧化非晶态Cr（OH）₃的影响.研究结果表明,在含氧水溶液中,Cr（OH）₃具有较好的长期稳定性;δ-MnO₂会显著增大Cr（OH）₃的氧化量,Cr（Ⅵ）生成量从0.03mg·L^-1增大为0.83 mg·L^-1.环境酸碱性可显著影响δ-MnO₂对Cr（OH）₃的氧化行为,碱性条件下Cr（Ⅵ）生成量更大.当pH=8,反应365 d时,总Cr（Ⅵ）浓度可达0.83 mg·L^-1; pH=6时,反应365 d时,总C...     

水相中羟基自由基诱导二甲基硫氧化的研究

用激光闪光光解技术研究了水相中二甲基硫(DMS)与羟基自由基(·OH)的反应机理,并讨论了溶液pH值和O2对该反应的影响,进而比较了气液相DMS与·OH反应的不同,初步评估了由·OH氧化引起的海洋和大气液相中DMS的寿命.结果表明:在pH 6-9时, ·OH会与DMS反应生成·DMSOH, ·DMSOH在水相中继续与DMS反应生成(DMS) 2, (DMS) 2与氧气的反应速度很慢,其衰减受pH影响较大.     

黑炭/零价铁复合材料耦合金属还原菌对溶液中Cr(Ⅵ)的去除

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。     

纳米零价铁去除垃圾渗滤液中铬(Ⅵ)的性能及机理研究

利用柠檬酸处理后的纳米零价铁(NZVI)对铬(Cr(Ⅵ))的去除进行了研究.NZVI对Cr(Ⅵ)的去除率受Cr(Ⅵ)初始浓度、pH值、反应温度和NZVI的浓度等因素影响,在Cr(Ⅵ)初始浓度为20mg·1-1、pH=5.0、NZVI投加量为1.0g·1-1和20℃条件下,Cr(Ⅵ)去处率达到了100%.腐殖酸(HA)与Cr(Ⅵ)可以形成稳定的HA-Cr螯合物,这种螯合物减少了溶液中有效的Cr(Ⅵ)浓度;同时,HA与NZVI的反应减少了NZVI的有效活性位点,HA的存在对NZVI去除Cr(Ⅵ)有竞争抑制的作用.     

锰铁氧体吸附及催化柠檬酸还原六价铬的过程及机理

本文探究了磁性纳米铁锰氧体(MnFe_2O_4)及其黏土矿物负载材料对六价铬(Cr(Ⅵ))的吸附作用,同时研究了锰铁氧体-柠檬酸溶液体系中,铁锰氧体催化柠檬酸还原Cr(Ⅵ)的机理.结果表明,MnFe_2O_4材料对Cr(Ⅵ)的吸附量随着吸附时间的增加而增加,在0—5 min内快速吸附并达到平衡,符合准二级动力学模型.伴随MnFe_2O_4负载量的增加,凹凸棒土负载铁锰氧体(ATP-Fe Mn)的吸附量大幅增加,ATP-FeMn14吸附量最大达到了29.2 mg·g~(-1),且吸附等温线均可用Langmuir方程或Freundlich方程拟合,属于单分子层吸附.MnFe_2O_4和负载ATP材料吸附Cr(Ⅵ)的最佳pH值为3—4,ATP-FeMn14对六价铬的去除率最高,最佳投加量为5 g·L~(-1).在铁锰氧体-柠檬酸体系中,溶液pH值是影响Cr(Ⅵ)的去除效率的重要因素,当溶液pH值在4和5时,Cr(Ⅵ)的去除率(76.5%、66.2%)显著高于其他处理;4 mmol·L~(-1)柠檬酸的处理去除率(89.8%)显著高于其他浓度柠檬酸的处理去除率;而在相同体系中,MnFe_2O_4的处理去除率(89.8%)显著高于其他研究材料.本研究表明铁锰氧体不仅对Cr(Ⅵ)具有良好的吸附性能,在与有机酸共存时,还可以催化有机酸还原Cr(Ⅵ),降低Cr(Ⅵ)的环境风险.     

Achieving Open Access to Conservation Science

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     

Rapid,recurring, structured survey versus bioblitz for generating biodiversity data and analysis with a multispecies abundance model

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.     

Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters

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.     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

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.     

A palaeo-hydrogeological model for arsenic contamination in southern and south-east Asia

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.     

Sequestration of cucurbitacin analogs by New and Old World chrysomelid leaf beetles in the tribe Luperini

Summary Two South American polyphagous leaf beetles,Diabrotica speciosa andCerotoma arcuata, selectively accumulated the bitter tasting compound 23,24-dihydrocucurbitacin D in their body after ingesting root tissues of cucurbit plants. Similarly, three Asian Cucurbitaceae-feeding specialists in the genusAulacophora were found to sequester the same compound. Cucurbitacin analogs were shown to deter feeding by a bird predator, indicating an allomonal role for these compounds in cucurbitacin-associated chrysomelid leaf beetles both of New and Old Worlds. The strong affinity to cucurbitacins, selective sequestration of the analogs and consequent protection from predators suggested an ecological adaptation mechanism developed in common among these two geographically isolated subtribes in the Luperini.     

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

Abstract: In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9‐ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3‐year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more‐lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already‐declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.     

Cost‐effective conservation of an endangered frog under uncertainty

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.     

Parasitic wasps orient to green leaf volatiles

Summary Undamaged plants emit low levels of green leaf volatiles (GLVs), while caterpillar-damaged and artificially damaged plants emit relatively higher levels of certain GLVs. Female braconid parasitoids,Microplitis croceipes, oriented to both damaged plants and to individual GLVs in no-choice tests in a wind tunnel, but seldom oriented to undamaged plants. Female ichneumonid parasitoids,Netelia heroica, also oriented to individual GLVs in a wind tunnel. Males of both wasp species failed to orient to the GLVs. These data show that leaf-feeding caterpillars can cause the release of GLVs, and that parasitic wasps can respond to these odors by flying upwind (chemoanemotactic response), which brings the wasps to their caterpillar hosts. This supports the hypothesis that plants communicate with members of the third trophic level,i.e., plants under herbivore attack emit chemical signals that guide natural enemies of herbivores to sites of plant damage. In this interaction, the GLVs serve as tritrophic plant-to-parasitoid synomones. That parasitoids from two different wasp families oriented to GLVs suggests that the response may be widespread among the Hymenoptera.Mention of a commercial or proprietary product does not constitute an endorsement by the U.S. Department of Agriculture     

What Every Conservation Biologist Should Know about Economic Theory

Abstract: The last century has seen the ascendance of a core economic model, which we will refer to as Walrasian economics. This model is driven by the psychological assumptions that humans act only in a self‐referential and narrowly rational way and that production can be described as a self‐contained circular flow between firms and households. These assumptions have critical implications for the way economics is used to inform conservation biology. Yet the Walrasian model is inconsistent with a large body of empirical evidence about actual human behavior, and it violates a number of basic physical laws. Research in behavioral science and neuroscience shows that humans are uniquely social animals and not self‐centered rational economic beings. Economic production is subject to physical laws including the laws of thermodynamics and mass balance. In addition, some contemporary economic theory, spurred by exciting new research in human behavior and a wealth of data about the negative global impact of the human economy on natural systems, is moving toward a world view that places consumption and production squarely in its behavioral and biophysical context. We argue that abandoning the straightjacket of the Walrasian core is essential to further progress in understanding the complex, coupled interactions between the human economy and the natural world. We call for a new framework for economic theory and policy that is consistent with observed human behavior, recognizes the complex and frequently irreversible interaction between human and natural systems, and directly confronts the cumulative negative effects of the human economy on the Earth's life support systems. Biophysical economics and ecological economics are two emerging economic frameworks in this movement.