多孔钛板负载Pd-Cu催化还原水中硝酸盐氮的研究

研究了多孔钛板负载Pd-Cu(1:1)催化剂作为阴极,利用电化学反应器脱除水中的硝酸盐氮,在pH值为6.4,电极板的电流密度为2.3mA·cm-2的条件下,以0.1g·1-1无水硫酸钠作为支持电解质,反应4h后,硝酸盐氮的去除率可以达到36%,出水浓度已接近饮用水标准,然而在此催化剂负载比例下对副产物氨氮的选择率非常高.反应在300mA,pH值为6.4时脱硝效果最高.在合适的浓度下,NO3-占优势地位,受竞争吸附影响小,同时电极板吸附位未达到饱和时,电催化反硝化反应符合表观一级反应动力学.另外,溶液的传质对反硝化没有显著影响;进水口的外露形成的水流跌落有利于NH3的逸出,反应溶液中的NH4 -N副产物减少,但是硝酸盐氮的去除效果受到影响.     

无机膜复合催化反应器脱除水中硝酸盐氮

利用Pd-Cu/Al2O3陶瓷膜对催化还原硝酸盐氮废水进行试验,通过在陶瓷膜中添加离子吸附树脂负载的催化剂Pd-Cu/H103,形成复合催化膜,并调整pH值与氢气流量,硝酸盐脱除转化率达到98%以上.     

纳米铁的制备及其还原硝酸盐氮的产物与机理

采用微乳技术制备纳米铁粒子, 并在无氧环境、室温、中性条件下与NO-3反应, 研究纳米铁与硝酸盐反应的产物及反应机理.结果表明: 纳米铁在30min内能与99%硝酸盐反应, 反应的主要产物为氨氮, 且伴有亚硝酸盐产生, 亚硝酸盐氮的浓度在反应过程中出现极大值; 由质量平衡关系推出,纳米铁与硝酸盐反应是氧化还原与吸附作用同时存在的过程, 反应的主要路径为NO-3→NO-2→NH 4.     

电极生物膜自养脱氮系统中的电化学作用

设计构建三维电极生物膜反应器,成功启动后稳定运行,在全自养条件下能较好地处理低碳氮比含氮废水.结果表明,在进水不含有机碳源,电流强度为30 mA,电流密度为0.012 mA·cm-2,运行周期24 h的实验条件下,反应器处理进水氨氮浓度为30 mg·L-1的废水时,氨氮转化率达到了90.3%,总氮去除率为70.0%;处理进水硝态氮浓度为30 mg·L-1的废水时,硝态氮去除率达到了82.7%.在考察电极生物膜反应器脱氮性能的同时,探讨系统中纯电化学作用的脱氮能力.结果显示电极生物膜处理氨氮废水的系统中,纯电化学脱氮作用为系统总脱氮能力的10%左右;而处理硝态氮废水的电极生物膜系统中,无电化学还原去除NO-3-N作用.     

两种电化学-硫自养集成脱硝工艺的对比

研究了两种电化学 硫自养集成脱硝工艺去除饮用水中的硝酸盐 ,结果表明 ,在同样的条件下 ,当无石灰石反应器的最小电流高于石灰石反应器约 2mA时 ,两种反应器均能取得 90 %以上的NO-3 N去除率 ,并且反应器出水中不存在NO-2 N的积累 .同时 ,无石灰石反应器硫段出水中Ca2 的浓度没有增加 ,避免了出水中的硬度问题 ;而石灰石反应器硫段出水中Ca2 的浓度有所增加 ,造成电化学段的除垢负担 .在同样水力停留时间下 ,无石灰石反应器出水中SO2 -4 的浓度低于石灰石反应器约 1 5mg·l- 1 ;电流高于 3mA时 ,两种反应器出水的pH值均维持在 7左右 .另外 ,无石灰石反应器的出水指标优于石灰石反应器 ,表明在两种集成工艺中 ,硫自养段不填充石灰石的集成工艺优于硫段装填石灰石的集成工艺 .     

零价纳米铁炭微电解体系去除水中硝酸盐

用液相还原法制备以活性炭为载体的负载型纳米铁(NZVI/AC),采用不同分散剂合成NZVI/AC,对材料进行XRD、SEM等表征,用制备的材料进行硝酸盐批实验,考察不同分散剂条件下合成的材料对硝酸盐氮的还原情况,再进一步分析硝酸盐氮的还原过程以及动力学.结果显示用聚乙烯吡咯烷酮(PVP)作为分散剂得到性能较好的NZVI/AC,且该体系存在微电解作用,硝酸盐氮的还原过程首先是纳米铁对硝酸根的吸附,然后再发生还原反应,产物以氨氮为主,中间产物有亚硝酸盐的生成,符合准一级反应动力学方程.     

低温反硝化过程中pH对亚硝酸盐积累的影响

以乙酸钠为单一碳源,在C/N比为3、温度为12—14℃的低C/N比、低温条件下通过间歇试验研究p H对反硝化亚硝酸盐积累规律影响.试验结果发现,在C/N为3时,p H值在7—9的范围内都能形成亚硝酸盐积累.反应时间为60 min时,亚硝酸盐积累率最大可达50%左右.低温SBR反应器连续试验研究表明,p H值为7.4±0.1和p H值为8.4±0.1时,序批式活性污泥法(SBR)出水亚硝酸盐积累率分别为51%和48%,取p H值为7.4±0.1条件下SBR反应器活性污泥进行酶活力测定发现,硝酸盐还原酶活力是亚硝酸盐还原酶活力的1.2倍,硝酸盐还原酶活力与亚硝酸盐还原酶活力对外界条件变化敏感程度不同,亚硝酸盐还原酶对外界条件变化更为敏感,其受到的抑制作用要大于硝酸盐还原酶,进而造成NO-2-N的积累.     

太湖地区湖、河和井水中氮污染状况的研究

连续监测了 2 0 0 0年 9月至 2 0 0 1年 9月太湖、大运河和井水中的N污染状况。结果表明 ,太湖水体中无机氮年均浓度达 1.14mg·L-1,已超过水体富营养化的浓度下限 ;大运河和井水分别达 7.16mg·L-1和 15 .84mg·L-1;井水中NO-3 -N浓度高达 15 .4 7mg·L-1,超过WHO所规定的生活饮用水NO-3 -N浓度上限的 5 0 %。试验结果还表明 ,河水中氮污染源以NH 4 -N为主 ,浓度高达 5 .6 3mg·L-1,占无机氮(NO-2 -N含量很低 ,忽略不计 )的 79% ;而井水中无机氮以NO-3 -N为主 ,占 98%。湖、河及井水中不同深度水样的分析结果表明 ,NO-3 -N和NH 4 -N浓度差异不显著 ,但其随时间变化差异明显。     

北京密云水库小流域地下水硝酸盐污染来源示踪

为确定北京密云水库小流域地下水中氮污染特征及来源,分别在雨季和旱季采集34个地下水样进行分析.结果表明,该流域地下水中NO-3-N污染严重,雨季和旱季NO-3-N的平均含量分别为15.86 mg·L-1和14.67 mg·L-1,均超过世界卫生组织饮用水标准(10 mg·L-1),污染主要分布于人口密集、农业活动频繁的中部地区.研究区域NH+4-N和NO-2-N的含量较低,其中,NO-2-N分布极不均匀.雨季和旱季δ15N的变化范围分别为5.00‰—20.16‰和-5.90‰—12.28‰,表明地下水硝酸盐的主要来源为人畜粪便和污水的排放,也可能为土壤有机氮和农业施肥的混合,表明旱季发生反硝化作用造成同位素的分馏.雨季,硝态氮与村镇面积呈正相关;氨氮与村镇及地表水面积呈显著正相关关系.旱季,硝态氮与村镇面积呈正相关,氨氮与草地面积呈正相关,亚硝态氮与地表水面积呈显著的正相关关系.     

非贵金属催化电解无害化去除硝酸盐氮的反应机制

以Ti/Co-Fe-Cu为阴极,Ti/IrO2-RuO2为阳极组成无隔膜电解体系,对非贵金属催化电解无害化去除NO3--N的反应机制进行了实验研究和理论分析.结果表明,NO3--N阴极催化还原过程中,反应物、产物需要通过对流、扩散作用,克服电场力,迁移至目标位置;在非贵金属的催化作用下,NO3--N受还原剂攻击,逐步还原为NH4+-N;还原中间产物NO-N和NH-N直接生成N2-N的过程受抑制,产物NH4+-N难以被再度直接氧化.添加Cl-作为支持电解质,实验电解体系发生阳极析氯、Cl2水解、NH4+-N氯氧化等过程,可将NH4+-N氧化为N2-N,且出水中NO3--N、NO2--N、氯胺类浓度很低.NO3--N无害化去除的反应机制是NO3--N在催化作用下,经传质、吸脱附、电子交换过程,还原为NH4+-N,NH4+-N经由Cl-→Cl2→HOCl→Cl-电解氯氧化循环,最终生成N2-N.     

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     

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.     

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.     

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.     

Effects of Coffee Management on Deforestation Rates and Forest Integrity

Knowledge about how forest margins are utilized can be crucial for a general understanding of changes in forest cover, forest structure, and biodiversity across landscapes. We studied forest‐agriculture transitions in southwestern Ethiopia and hypothesized that the presence of coffee (Coffea arabica)decreases deforestation rates because of coffee's importance to local economies and its widespread occurrence in forests and forest margins. Using satellite images and elevation data, we compared changes in forest cover over 37 years (1973–2010) across elevations in 2 forest‐agriculture mosaic landscapes (1100 km² around Bonga and 3000 km² in Goma‐Gera). In the field in the Bonga area, we determined coffee cover and forest structure in 40 forest margins that differed in time since deforestation. Both the absolute and relative deforestation rates were lower at coffee‐growing elevations compared with at higher elevations (?10/20% vs. ?40/50% comparing relative rates at 1800 m asl and 2300–2500 m asl, respectively). Within the coffee‐growing elevation, the proportion of sites with high coffee cover (>20%) was significantly higher in stable margins (42% of sites that had been in the same location for the entire period) than in recently changed margins (0% of sites where expansion of annual crops had changed the margin). Disturbance level and forest structure did not differ between sites with 30% or 3% coffee. However, a growing body of literature on gradients of coffee management in Ethiopia reports coffee's negative effects on abundances of forest‐specialist species. Even if the presence of coffee slows down the conversion of forest to annual‐crop agriculture, there is a risk that an intensification of coffee management will still threaten forest biodiversity, including the genetic diversity of wild coffee. Conservation policy for Ethiopian forests thus needs to develop strategies that acknowledge that forests without coffee production may have higher deforestation risks than forests with coffee production and that forests with coffee production often have lower biodiversity value. Efectos de la Administración Cafetalera sobre las Tasas de Deforestación y la Integridad de los Bosques     

Globalization of the Cashmere Market and the Decline of Large Mammals in Central Asia

As drivers of terrestrial ecosystems, humans have replaced large carnivores in most areas, and human influence not only exerts striking ecological pressures on biodiversity at local scales but also has indirect effects in distant corners of the world. We suggest that the multibillion dollar cashmere industry creates economic motivations that link western fashion preferences for cashmere to land use in Central Asia. This penchant for stylish clothing, in turn, encourages herders to increase livestock production which affects persistence of over 6 endangered large mammals in these remote, arid ecosystems. We hypothesized that global trade in cashmere has strong negative effects on native large mammals of deserts and grassland where cashmere‐producing goats are raised. We used time series data, ecological snapshots of the biomass of native and domestic ungulates, and ecologically and behaviorally based fieldwork to test our hypothesis. In Mongolia increases in domestic goat production were associated with a 3‐fold increase in local profits for herders coexisting with endangered saiga (Saiga tatarica).That increasing domestic grazing pressure carries fitness consequences was inferred on the basis of an approximately 4‐fold difference in juvenile recruitment among blue sheep (Pseudois nayaur)in trans‐Himalayan India. Across 7 study areas in Mongolia, India, and China's Tibetan Plateau, native ungulate biomass is now <5% that of domestic species. Such trends suggest ecosystem degradation and decreased capacity for the persistence of native species, including at least 8 Asian endemic species: saiga, chiru (Pantholops hodgsoni), Bactrian camel (Camelus bactrianus), snow leopard(Panthera uncia), khulan(Equus hemionus), kiang (E. kiang), takhi (E. przewalski), and wild yak (Bos mutus). Our results suggest striking yet indirect and unintended actions that link trophic‐level effects to markets induced by the trade for cashmere. Globalización del Mercado de Cachemira y la Declinación de Mamíferos Mayores en Asia Central     

The lichen-rich coastal heath vegetation on the isle of Anholt, Denmark — conservation and management

The high conservational value of the lichen-rich vegetation and landscape of the marine foreland Ørkenen on the isle of Anholt is treated from a Danish as well as a European perspective. The sensitivity of the lichen-rich vegetation to physical disturbance is emphasized. The impact of invasive species such asPinus mugo as well as the effect of atmospheric deposition of nutrients on the heaths at Anholt is described. Considerations related to the development of a management plan for Ørkenen are presented.     

Behavior and ecology of Old World Luperini beetles of the genusAulacophora (Coleoptera: Chrysomelidae)

Summary The attraction of Old World leaf beetles in the genusAulacophora to kairomones and parakairomones which are effective lures for New WorldDiabrotica andAcalymma were investigated. Beetles captured on sticky traps baited with single and multicomponent lures were no different from the control traps for two species ofAulacophora. Yellow colored traps and squash blossoms are attractive toAulacophora beetles which detect sub-microgram quantities of cucurbitacins on silica gel. Leaf feeding behavior and flight activity data are correlated with varietal preference of threeAulacophora species. The common response byDiabrotica andAulacophora to cucurbitacins reinforces the two groups' coevolutionary association with the Cucurbitaceae. The apparent lack of a common response toCucurbita blossom volatiles suggests recent evolutionary pathways are substantially different for these two groups of beetles.     

Use of stochastic patch occupancy models in the California red-legged frog for Bayesian inference regarding past events and future persistence

Assessing causes of population decline is critically important to management of threatened species. Stochastic patch occupancy models (SPOMs) are popular tools for examining spatial and temporal dynamics of populations when presence–absence data in multiple habitat patches are available. We developed a Bayesian Markov chain method that extends existing SPOMs by focusing on past environmental changes that may have altered occupancy patterns prior to the beginning of data collection. Using occupancy data from 3 creeks, we applied the method to assess 2 hypothesized causes of population decline—in situ die-off and residual impact of past source population loss—in the California red-legged frog. Despite having no data for the 20–30 years between the hypothetical event leading to population decline and the first data collected, we were able to discriminate among hypotheses, finding evidence that in situ die-off increased in 2 of the creeks. Although the creeks had comparable numbers of occupied segments, owing to different extinction–colonization dynamics, our model predicted an 8-fold difference in persistence probabilities of their populations to 2030. Adding a source population led to a greater predicted persistence probability than did decreasing the in situ die-off, emphasizing that reversing the deleterious impacts of a disturbance may not be the most efficient management strategy. We expect our method will be useful for studying dynamics and evaluating management strategies of many species.