柠檬酸-Fe(Ⅱ)/K2S2O8对敌草隆降解的研究

研究了初始pH值为3.0时敌草隆在柠檬酸-Fe(Ⅱ)/K2S2O8体系中的降解行为.结果显示,0.1mmol·l-1敌草隆的最佳降解条件为:[K2S2O8]=2.0mmol·l-1,[Fe(Ⅱ)]=1.0mmol·l-1,[CA]=0.5mmol·l-1.在该条件下,敌草隆的降解符合一级反应动力学,半衰期为30.5min.此外,采用分子探针法鉴定了体系中产生的硫酸根自由基和羟基自由基.并采用液-质联用技术鉴定了敌草隆在柠檬酸-Fe(Ⅱ)/K2S2O8体系中的降解产物,探讨敌草隆在柠檬酸-Fe(Ⅱ)/K2S2O8体系中可能的降解机理.     

水体系中Fe(Ⅱ)/K2S2O8降解敌草隆的研究

在初始pH 7.0的Fe(Ⅱ)/K2S2O8体系中,分别研究了K2S2O8和Fe(Ⅱ)初始浓度以及Fe(Ⅱ)分批加入对敌草隆降解的影响,结果表明,在pH 7.0,K2S2O8和Fe(Ⅱ)初始浓度分别为2.0mmol·l-1和1.0mmol·l-1时,反应300min后,0.1mmol·l-1敌草隆的降解率达到40.0%,Fe(Ⅱ)分批加入能够促进敌草隆的降解.另外,通过对Fe(Ⅱ)/K2S2O8,EDTA-Fe(Ⅱ)/K2S2O8,柠檬酸-Fe(Ⅱ)/K2S2O8以及K2S2O3-Fe(Ⅱ)/K2S2O8四种Fe(Ⅱ)/K2S2O8体系的对比研究,发现在Fe(Ⅱ)/K2S2O8体系中,加入Fe(Ⅱ)的螯合剂EDTA和柠檬酸以及还原剂K2S2O3能够明显促进敌草隆降解.采用分子探针法的竞争实验鉴定了体系中产生的硫酸根自由基.     

光电Fenton耦合转盘技术处理四环素废水

本实验中,我们开发了一种耦合紫外光催化和转盘技术的电Fenton反应器用于降解含有四环素的有机废水.在该反应器中,O_2首先在旋转的石墨阴极表面发生还原反应生成H_2O_2,随后H_2O_2被催化分解成活性自由基来降解矿化有机物.实验中了考察了pH,阴极电压,转速等实验条件对系统生成H_2O_2能力的影响.结果表明,在pH=3,阴极电压-0.8 V vs.SCE,转速为400 r·min~(-1)条件下,经过75 min反应H_2O_2的积累浓度有最大值(51.5 mg·L~(-1)).实验证明该系统对四环素有较好的降解和矿化效果.以1.0 mmol·L~(-1)的Fe~(2+)作为催化剂,紫外/电Fenton耦合转盘系统可以在45 min内将初始浓度50 mg·L~(-1)四环素降解94.2%且90 min时TOC的去除率为68.2%.紫外/电Fenton处理效果明显优于电Fenton系统.进一步实验分析发现,紫外线的引入可以通过两种途径来提升电Fenton的处理效果.一方面紫外光可以促进Fe~(3+)还原成Fe~(2+),加速体系铁离子循环,从而提升电Fenton的处理效果;另一方面还可以通过直接激发H_2O_2分解成活性自由基加速降解四环素.     

碱性条件下日光/FeEDTA/H2O2降解2,4-二氯苯酚的研究

采用日光/FeEDTA/H2O2体系降解2,4-二氯苯酚废水,探讨了pH值,H2O2,FeEDTA以及2,4-二氯苯酚初始浓度对2,4-二氯苯酚去除率以及CODCr去除率的影响,发现该体系可在较宽的pH范围(pH=2-11)降解2,4-二氯苯酚.碱性条件下(pH=9)对250mg·l-1的2,4-二氯苯酚废水,最佳处理条件为:[H2O2]=30mmol·l-1,[FeEDTA]=0.5mmol·l-1,此条件下,反应2h后,2,4-二氯苯酚的去除率高达99%,CODCr去除率达91%.另外,通过对传统Fenton,FeEDTA,草酸铁以及柠檬酸铁四种Fenton体系的对比研究,发现FeEDTA体系在碱性条件下处理2,4-二氯苯酚废水具有明显的优势.     

Fe_3O_4@Graphite电极中性条件下电Fenton降解有机污染物

制备了Fe3O4复合石墨电极(Fe3O4@graphite),通过循环伏安测定,对自制电极的电化学特性进行了表征.在外加电压无隔膜反应池中,基于Fe3O4@graphite为阴极,铂网为阳极,在pH7.0中性条件下,探讨了降解有机染料罗丹明B(Rhodamine B,RhB)及无色小分子2,4-二氯苯酚(2,4-dichlorophenol,DCP)的电Fenton反应特性,结果表明,对1.0×10-5mol.l-1RhB在外加电压6 V和支持电解质Na2SO410 g.l-1条件下,电Fenton反应120 min,RhB降解率达100%.采用过氧化物酶催化反应吸光光度法和苯甲酸荧光分析法跟踪测定RhB降解反应过程中H2O2和羟基自由基(.OH)的变化,表明RhB降解过程涉及.OH历程.采用红外光谱分析和TOC测定RhB降解过程中深度氧化变化,表明电Fenton反应条件下,RhB反应过程中其分子结构被破坏,生成羧酸或者胺类小分子化合物,同时180 min矿化率达59.2%,对2,4-DCP而言,240 min降解率为98.6%,14h矿化率为86.8%.     

电-Fenton法降解青霉素的动力学研究

采用电-Fenton法处理青霉素钠(Penicillin G sodium, PGN)模拟废水,当T=20℃,pH=3时,投加0.5g·l-1 FeSO4和0.2ml·l-1 H2O2,在0.6A电流下降解青霉素钠废水(100 mg·l-1), 20min后青霉素钠去除率为79%,40min后去除率为95%.拟合实验数据得到青霉素钠降解反应的速率方程式为:-d[PGN]/dt=2.35×106 exp(-32869.4/RT )[Fe2 ]0.53[H2O2]0.8[PGN]1.14反应速率常数和反应级数表明,初始阶段降解反应进行非常迅速,且H2O2浓度比Fe2 浓度对电-Fenton降解反应的影响重要.     

二甲亚砜作探针试剂研究Fenton反应条件

随着高级氧化技术成为废水处理的研究热点,羟基自由基的产生、测定及测定条件等相关问题的探索,成为发展高级氧化技术的重要条件及其重要组成部分。以分光光度法为主要分析方法,以二甲亚砜作为·OH的探针试剂,对Fenton反应及其反应的最佳条件进行研究。结果表明,在实验条件下,H2O2初始浓度为11.5mmol/L,Fe2+/H2O2的浓度比值在1:23左右,pH范围为3～4时,·OH产率最高。     

Fenton法和类Fenton法降解土壤中的二苯砷酸

本文对Fenton法与类Fenton法降解土壤中的二苯砷酸(diphenylarsinic acid,DPAA)进行了研究.考察了H2O2投加量和催化剂种类(Fe2+/Fe3+)对红壤及黑土中DPAA降解效果的影响,并采用高效液相色谱-质谱联用法(HPLC-MS/MS)对降解中间产物进行了初步鉴定.结果显示,针对红壤与黑土分别采用类Fenton法与Fenton法,在H2O2投加浓度为1 mol·L-1,含铁催化剂浓度为0.25 mol·L-1,土水比为1∶3,反应时间为1h的条件下,红壤及黑土中DPAA的降解率均可达到65%以上.HPLC-MS/MS的分析结果表明,DPAA可脱苯环形成降解产物苯砷酸(phenylarsinic acid,PAA),而PAA进一步氧化生成无机砷,这可能是Fenton/类Fenton法降解DPAA的途径之一.     

光电协同催化降解2-氯-4-甲氧基苯酚

以2-氯-4-甲氧基苯酚作为模型物,以TiO2为催化剂,低压汞灯作为光源,采用外循环悬浮态多相光催化反应体系,考察紫外光与电场协同催化降解的影响因素,实验结果表明,2-氯-4-甲氧基苯酚初始浓度为0.0125mmol·l-1,TiO2用量250mg·l-1,循环流量20L·h-1,pH值为10,外加偏压3V,曝气,反应时间270min时,2-氯-4-甲氧基苯酚降解率可达到98.7%.     

铁锰矿类Fenton异相光催化降解有毒有机染料

选取6种天然铁锰矿石为光催化剂,以可见光(λ420nm)照射下活化H2O2降解有机染料罗丹明B(RhodamineB,RhB)为探针反应,筛选出活性较高的天然矿石(磁赤铁矿)催化降解RhB及2,4-二氯苯酚(2,4-Dichlorophenol,DCP).实验表明,可见光下磁赤铁矿在pH=7.0的介质体系,H2O2浓度为3×10-3mol·l-1条件下可有效降解RhB.通过反射紫外光谱、原子吸收分光光度法、XRD初步表征了磁赤铁矿组成结构;采用紫外-可见吸收光谱(UV-vis)、红外光谱(IR)、总有机碳(TOC)测定等方法,研究了其可见光照射下对RhB光催化降解特性.结果表明,在实验条件下RhB矿化率达60%,DCP矿化率达到63.93%.利用电子自旋捕捉技术(ESR)跟踪测定RhB降解过程中氧化物种,表明催化降解过程涉及羟基自由基(·OH)氧化过程.拟定异相矿石类Fenton体系与传统均相Fenton体系相比,具有反应介质pH范围宽(3.0—7.0)、可见光激发及催化剂易得廉价等优势。     

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.     

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.     

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     

Potential for Electropositive Metal to Reduce the Interactions of Atlantic Sturgeon with Fishing Gear

Atlantic sturgeon (Acipenser oxyrhynchus) populations have been declared either endangered or threatened under the U.S. Endangered Species Act. Effective measures to repel sturgeon from fishing gear would be beneficial to both fish and fishers because they could reduce both fishery‐associated mortality and the need for seasonal and area closures of specific fisheries. Some chondrostean fishes (e.g., sturgeons and paddlefishes) can detect weak electric field gradients (possibly as low as 5 Μv/cm) due to arrays of electroreceptors (ampullae of Lorenzini) on their snout and gill covers. Weak electric fields, such as those produced by electropositive metals (typically mixtures of the lanthanide elements), could therefore potentially be used as a deterrent. To test this idea, we recorded the behavioral responses of juvenile Atlantic sturgeon (31–43 cm fork length) to electropositive metal (primarily a mixture of the lanthanide elements neodymium and praseodymium) both in the presence and absence of food stimuli. Trials were conducted in an approximately 2.5 m diameter × 0.3 m deep tank, and fish behaviors were recorded with an overhead digital video camera. Video records were subsequently digitized (x, y coordinate system), the distance between the fish and the electropositive metal calculated, and data summarized by compiling frequency distributions with 5‐cm bins. Juvenile sturgeon showed clear avoidance of electropositive metal but only when food was present. On the basis of our results, we conclude that the electropositive metals, or other sources of weak electric fields, may eventually be used to reduce the interactions of Atlantic sturgeon with fishing gear, but further investigation is needed. El Potencial del Metal Electropositivo para Reducir las Interacciones del Esturión Atlántico con Instrumentos de Pesca Bouyoucos, Bushnell & Brill 13–003     

The role of time and species identities in spatial patterns of species richness and conservation

Many conservation actions are justified on the basis of managing biodiversity. Biodiversity, in terms of species richness, is largely the product of rare species. This is problematic because the intensity of sampling needed to characterize communities and patterns of rarity or to justify the use of surrogates has biased sampling in favor of space over time. However, environmental fluctuations interacting with community dynamics lead to temporal variations in where and when species occur, potentially affecting conservation planning by generating uncertainty about results of species distribution modeling (including range determinations), selection of surrogates for biodiversity, and the proportion of biodiversity composed of rare species. To have confidence in the evidence base for conservation actions, one must consider whether temporal replication is necessary to produce broad inferences. Using approximately 20 years of macrofaunal data from tidal flats in 2 harbors, we explored variation in the identity of rare, common, restricted range, and widespread species over time and space. Over time, rare taxa were more likely to increase in abundance or occurrence than to remain rare or disappear and to exhibit temporal patterns in their occurrence. Space–time congruency in ranges (i.e., spatially widespread taxa were also temporally widespread) was observed only where samples were collected across an environmental gradient. Fifteen percent of the taxa in both harbors changed over time from having spatially restricted ranges to having widespread ranges. Our findings suggest that rare species can provide stability against environmental change, because the majority of species were not random transients, but that selection of biodiversity surrogates requires temporal validation. Rarity needs to be considered both spatially and temporally, as species that occur randomly over time are likely to play a different role in ecosystem functioning than those exhibiting temporal structure (e.g., seasonality). Moreover, temporal structure offers the opportunity to place management and conservation activities within windows of maximum opportunity.     

Main nutrient compounds in food bodies of Mexican <Emphasis Type="Italic">Acacia</Emphasis> ant-plants

Summary. Myrmecophytic plants use obligate ant mutualists as a constitutive indirect defence mechanism. These plants often produce cellular food bodies (FBs) to nourish their resident ants. Lipids, proteins, and even highly specialised compounds such as glycogen have been reported from FBs, but detailed chemical analyses of FB composition have so far been presented only for Southeast Asian Macaranga and Central American Piper myrmecophytes. Here we report the chemical composition of FBs of five myrmecophytic Acacia (Fabaceae) species from Mexico using HPLC (carbohydrates and proteins) and GC-MS (lipids). Feeding experiments revealed no hints on any use of external food sources by the inhabiting Pseudomyrmex ants. These ants obviously rely completely on FBs and extrafloral nectar provided by their hosts. The total content of nutrients in Acacia FBs was 15-25% of FB dry mass, being much lower than in Macaranga or Piper FBs. Proteins were dominating (8-14 % dm) in Acacia FBs and thus were present in higher amounts than in Macaranga FBs, yet in lower amounts than in Piper. Lipids contributed 1-9 % of dry mass, showing a lower proportion than in FBs of Macaranga or Piper. Carbohydrates made up 3-11 % dm, reaching in most Acacia species the same range as observed in Macaranga and in Piper FBs. Water content was 18-24 % of FB fresh mass, and structural tissue obviously made up a much higher proportion in Acacia FBs than in Macaranga or Piper FBs. Both characters might represent an adaptation to producing FBs unprotected at the leaf tips under dry conditions. Acacia FBs contain all amino acids and all fatty acids that are considered essential for insects, and their contents of lipids and proteins are higher than in the leaves from which they are ontogenetically derived. This indicates a putatively adaptive enrichment of nutritionally valuable compounds in structures functioning as ant-food.     

Examining the uncertain origin and management role of martens on Prince of Wales Island,Alaska

Conservation biologists are generally united in efforts to curtail the spread of non‐native species globally. However, the colonization history of a species is not always certain, and whether a species is considered non‐native or native depends on the conservation benchmark. Such ambiguities have led to inconsistent management. Within the Tongass National Forest of Alaska, the status of American marten (Martes americana) on the largest, most biologically diverse and deforested island, Prince of Wales (POW), is unclear. Ten martens were released to POW in the early 1930s, and it was generally believed to be the founding event, although this has been questioned. The uncertainty surrounding when and how martens colonized POW complicates management, especially because martens were selected as a design species for the Tongass. To explore the history of martens of POW we reviewed other plausible routes of colonization; genetically and isotopically analyzed putative marten fossils deposited in the late Pleistocene and early Holocene to verify marten occupancy of POW; and used contemporary genetic data from martens on POW and the mainland in coalescent simulations to identify the probable source of the present‐day marten population on POW. We found evidence for multiple routes of colonization by forest‐associated mammals beginning in the Holocene, which were likely used by American martens to naturally colonize POW. Although we cannot rule out human‐assisted movement of martens by Alaskan Natives or fur trappers, we suggest that martens be managed for persistence on POW. More generally, our findings illustrate the difficulty of labeling species as non‐native or native, even when genetic and paleo‐ecological data are available, and support the notion that community resilience or species invasiveness should be prioritized when making management decisions rather than more subjective and less certain conservation benchmarks.