Colloid transport in unsaturated porous media: the role of water content and ionic strength on particle straining

Packed column and mathematical modeling studies were conducted to explore the influence of water saturation, pore-water ionic strength, and grain size on the transport of latex microspheres (1.1 microm) in porous media. Experiments were carried out under chemically unfavorable conditions for colloid attachment to both solid-water interfaces (SWI) and air-water interfaces (AWI) using negatively charged and hydrophilic colloids and modifying the solution chemistry with a bicarbonate buffer to pH 10. Interaction energy calculations and complementary batch experiments were conducted and demonstrated that partitioning of colloids to the SWI and AWI was insignificant across the range of the ionic strengths considered. The breakthrough curve and final deposition profile were measured in each experiment indicating colloid retention was highly dependent on the suspension ionic strength, water content, and sand grain size. In contrast to conventional filtration theory, most colloids were found deposited close to the column inlet, and hyper-exponential deposition profiles were observed. A mathematical model, accounting for time- and depth-dependent straining, produced a reasonably good fit for both the breakthrough curves and final deposition profiles. Experimental and modeling results suggest that straining--the retention of colloids in low velocity regions of porous media such as grain junctions--was the primary mechanism of colloid retention under both saturated and unsaturated conditions. The extent of stagnant regions of flow within the pore structure is enhanced with decreasing water content, leading to a greater amount of retention. Ionic strength also contributes to straining, because the number of colloids that are held in the secondary energy minimum increases with ionic strength. These weakly associated colloids are prone to be translated to stagnation regions formed at grain-grain junctions, the solid-water-air triple point, and dead-end pores and then becoming trapped.     

Use of a biologically active cover to reduce landfill methane emissions and enhance methane oxidation

Biologically-active landfill cover soils (biocovers) that serve to minimize CH4 emissions by optimizing CH4 oxidation were investigated at a landfill in Florida, USA. The biocover consisted of 50 cm pre-composted yard or garden waste placed over a 10-15 cm gas distribution layer (crushed glass) over a 40-100 cm interim cover. The biocover cells reduced CH4 emissions by a factor of 10 and doubled the percentage of CH4 oxidation relative to control cells. The thickness and moisture-holding capacity of the biocover resulted in increased retention times for transported CH4. This increased retention of CH4 in the biocover resulted in a higher fraction oxidized. Overall rates between the two covers were similar, about 2g CH4 m(-2)d(-1), but because CH4 entered the biocover from below at a slower rate relative to the soil cover, a higher percentage was oxidized. In part, methane oxidation controlled the net flux of CH4 to the atmosphere. The biocover cells became more effective than the control sites in oxidizing CH4 3 months after their initial placement: the mean percent oxidation for the biocover cells was 41% compared to 14% for the control cells (p<0.001). Following the initial 3 months, we also observed 29 (27%) negative CH4 fluxes and 27 (25%) zero fluxes in the biocover cells but only 6 (6%) negative fluxes and 22 (21%) zero fluxes for the control cells. Negative fluxes indicate uptake of atmospheric CH4. If the zero and negative fluxes are assumed to represent 100% oxidation, then the mean percent oxidation for the biocover and control cells, respectively, for the same period would increase to 64% and 30%.     

A novel application of cultural consensus models to evaluate conservation education programs

Conservation professionals recognize the need to evaluate education initiatives with a flexible approach that is culturally appropriate. Cultural‐consensus theory (CCT) provides a framework for measuring the extent to which beliefs are communally held and has long been applied by social scientists. In a conservation‐education context, we applied CCT and used free lists (i.e., a list of items on a topic stated in order of cultural importance) and domain analysis (analysis of how free lists go together within a cultural group) to evaluate a conservation education program in which we used a children's picture book to increase knowledge about and empathy for a critically endangered mammal, the Javan slow loris (Nycticebus javanicus). We extracted free lists of keywords generated by students (n = 580 in 18 schools) from essays they wrote before and after the education program. In 2 classroom sessions conducted approximately 18 weeks apart, we asked students to write an essay about their knowledge of the target species and then presented a book and several activities about slow loris ecology. Prior to the second session, we asked students to write a second essay. We generated free lists from both essays, quantified salience of terms used, and conducted minimal residuals factor analysis to determine presence of cultural domains surrounding slow lorises in each session. Students increased their use of words accurately associated with slow loris ecology and conservation from 43% in initial essays to 76% in final essays. Domain coherence increased from 22% to 47% across schools. Fifteen factors contributed to the domain slow loris. Between the first and second essays, factors that showed the greatest change were feeding ecology and slow loris as a forest protector, which increased 7‐fold, and the humancentric factor, which decreased 5‐fold. As demonstrated by knowledge retention and creation of unique stories and conservation opinions, children achieved all six levels of Bloom's taxonomy of learning domains. Free from the constraints of questionnaires and surveys, CCT methods provide a promising avenue to evaluate conservation education programs.     

Differences in volatile methyl siloxane (VMS) profiles in biogas from landfills and anaerobic digesters and energetics of VMS transformations

The objectives of this study were to compare the types and levels of volatile methyl siloxanes (VMS) present in biogas generated in the anaerobic digesters and landfills, evaluate the energetics of siloxane transformations under anaerobic conditions, compare the conditions in anaerobic digesters and municipal solid waste (MSW) landfills which result in differences in siloxane compositions. Biogas samples were collected at the South District Wastewater Treatment Plant and South Dade Landfill in Miami, Florida. In the digester gas, D4 and D5 comprised the bulk of total siloxanes (62% and 27%, respectively) whereas in the landfill gas, the bulk of siloxanes were trimethylsilanol (TMSOH) (58%) followed by D4 (17%). Presence of high levels of TMSOH in the landfill gas indicates that methane utilization may be a possible reaction mechanism for TMSOH formation. The free energy change for transformation of D5 and D4 to TMSOH either by hydrogen or methane utilization are thermodynamically favorable. Either hydrogen or methane should be present at relatively high concentrations for TMSOH formation which explains the high levels present in the landfill gas. The high bond energy and bond distance of the Si–O bond, in view of the atomic sizes of Si and O atoms, indicate that Si atoms can provide a barrier, making it difficult to break the Si–O bonds especially for molecules with specific geometric configurations such as D4 and D5 where oxygen atoms are positioned inside the frame formed by the large Si atoms which are surrounded by the methyl groups.     

绿色团队

当主流商学院开始将更多的企业社会责任（CSR）话题带入教室时，一些教育家仍认为这些机构的努力不够。他们相信，现在所需要的，是围绕可持续发展概念来确定MBA教学大纲，大纲仍然讲授基础科目，但要染上绿色。     

Functional reference in an alarm signal given during nest defence: seet calls of yellow warblers denote brood-parasitic brown-headed cowbirds

Field observations and model-presentation experiments have shown that yellow warblers (Dendroica petechia) produce seet calls preferentially in response to brood-parasitic brown-headed cowbirds (Molothrus ater). In this study, we investigated whether seet calls are functionally referential alarm calls denoting cowbirds by determining whether female warblers responded appropriately to seet calls in the absence of a cowbird, whether alarm calling by warblers varied with response urgency, and how warblers in a population allopatric with cowbirds responded to cowbird and avian predator models and seet playbacks. As a control, we presented chip calls, which are elicited by nest predators as well as by non-threatening intruders, but are not strongly associated with cowbirds. Yellow warblers responded differently to playbacks of seet than chip calls. To seet playbacks, almost 60% of females gave seet calls and rushed to sit in their nests, responses typically elicited by cowbirds, whereas these responses were given infrequently in response to chip calls. Yellow warblers seet called equally in situations that simulated low, medium and high risk of parasitism, which suggests that these calls did not vary with response urgency. In a population allopatric with cowbirds, seet calls were rarely produced in response to cowbird or avian nest predator models and never to seet playbacks. These results suggest that seet calls are functionally referential signals denoting cowbirds and that cowbird parasitism was a strong selective pressure in the evolution of functional referentiality in the seet call of yellow warblers.Communicated by W.A. Searcy     

Testis size variation in frogs: testing the alternatives

While sperm competition may be a major factor affecting relative testis size in vertebrates as a whole, additional hypotheses have not been given much attention in frogs. This is important because sperm competition is relatively uncommon in frogs and relative testis size varies in frogs that do not have multiple-male breeding systems. This paper tests two additional hypotheses for differences in relative testis size among frogs: relative clutch size (number of eggs/snout vent length) and androgen level. Testis size was measured in 90 species of frogs belonging to five families. Relative testis size was found to be positively correlated with relative clutch size in species that lack sperm competition. Mean androgen levels of species also positively covaried with relative testis size. However, there was no correlation between relative testis size and level of male agonistic behavior among species, despite other work indicating that testosterone levels are positively correlated with agonistic behavior in at least some species. These findings suggest that a number of factors in addition to sperm competition are important in the evolution of testis size in male frogs. Received: 17 January 1997 / Accepted after revision: 23 June 1997     

氮沉降的全球化:对于陆地生态系统的意义

人类活动产生的氮(N),包括农田氮肥施肥和矿物燃料燃烧过程中所固定的氮,其来源和分布正在迅速地扩展到全球范围.这部分氮进入到陆地生态系统中,将会促进植物的生长,并产生过量的氮,最终通过淋溶和痕量气体排放的形式,增加了氮的损失.在某种情况下,还会导致物种组成的变化和生态系统功能的衰减.但并非所有的生态系统都对氯沉降具有类似的响应.它们的响应情况,取决于氮沉降的连续性、生态系统的类型,生态系统对氮的需求或保持能力、土地利用的历史、土壤状况、地形条件、气候背景以及氮沉降的速度、时间和类型等因素.我们认为,起重要作用的是:一些对人类影响具有显著意义的条件、一些控制生态系统响应变化的因素以及一些由于资料缺乏而使不确定性增大的地方.     

An integrated approach to the toxicity assessment of Irish marine sediments: application of porewater Toxicity Identification Evaluation (TIE) to Irish marine sediments

An integrated approach to the ecotoxicological assessment of Irish marine sediments was carried out between 2004 and 2007. Phase I Toxicity Identification Evaluation (TIE) of sediment porewaters from two sites on the east coast of Ireland were conducted. Initial Tier I screening of three Irish sites identified the need for TIE after significant toxicity was observed with Tisbe battagliai and the Microtox assay at two of the assayed sites (Alexandra Basin and Dunmore East). Porewaters classified as toxic were characterised using four manipulations, ethylenediaminetetraacetic acid (EDTA) chelation, sodium thiosulphate addition, C(18) Solid Phase Extraction (SPE) and Cation Exchange (CE) SPE. Prior to initial testing, and TIE manipulations, all porewater samples were frozen at -20 degrees C for several months until required. After initial Tier I testing Alexandra Basin porewater was classified as highly toxic by both assays while Dunmore East porewater only warranted a TIE with T. battagliai. Results of TIE manipulations for Alexandra Basin porewater and the Microtox Basic test were inconclusive. The toxicity of the porewater in this assay was significantly reduced after freezing. Three experimental episodes were conducted with one month between each for the Alexandra Basin porewater. After each month of freezing the baseline toxicity was further reduced in the Microtox assay, therefore it was not possible to draw accurate conclusions on the nature of the active contaminants in the sample. However, toxicity to T. battalgiai did not change after storage of the porewater. The C(18) and CE SPE decreased the toxicity of Alexandra Basin porewater to the copepod indicating that both organic and cationic compounds (e.g. metals) were active in the sample. Dunmore East porewater was assayed with T. battalgiai and again a combination of organic and inorganic compounds were found to be partly responsible for the observed toxicity (C(18), CE SPE and EDTA reduced toxicity). Results from these TIEs provide insight into the complexity of interpreting marine TIE data from porewater studies where mixtures of unknown substances are present.     

Is legislation a barrier to the sustainable management of game species? A case study of wild deer in Britain

Wild game management for hunting in Western society has become increasingly complex as stakeholders have multiplied and as ‘sustainability’ influences the contemporary debate. This paper questions whether the current legal framework for game management, which has evolved from early European civilisations to focus on ‘hunting rights’, is relevant to regulate the contemporary environmental, social and economic dimensions of wild game and their management. Employing a narrative analysis to focus on deer, the study identifies key legislative tenets and highlights the pertinence of historical laws to contemporary conflicts. The analysis suggests that current legislation is increasingly divergent from contemporary trends and has created inertia with respect to sustainable deer management. The paper offers four options to redress this: state intervention; voluntary collaboration; financial incentives; and establishing a legal responsibility for management. It is concluded that significant innovation is required in one or more of these four areas to facilitate the contemporary sustainable management of wild deer in Britain.