First-passage-time transfer functions for groundwater tracer tests conducted in radially convergent flow

Forced-gradient groundwater tracer tests may be conducted using a variety of hydraulic schemes, so it is useful to have simple semi-analytic models available that can examine various injection/withdrawal scenarios. Models for radially convergent tracer tests are formulated here as transfer functions, which allow complex tracer test designs to be simulated by a series of simple mathematical expressions. These mathematical expressions are given in Laplace space, so that transfer functions may be placed in series by simple multiplication. Predicted breakthrough is found by numerically inverting the composite transfer function to the time-domain, using traditional computer programs or commercial mathematical software. Transport is assumed to be dictated by a radially convergent or uniform flow field, and is based upon an exact first-passage-time solution of the backward Fokker–Planck equation. These methods are demonstrated by simulating a weak-dipole tracer test conducted in a fractured granite formation, where mixing in the injection borehole is non-ideal.     

Effects of crowding and wave exposure on penis morphology of the acorn barnacle, Semibalanus balanoides

Wave action and low population density can strongly reduce the ability of sessile acorn barnacles to find mates and copulate. For Semibalanus balanoides, penis morphology varies with wave exposure and with characteristics of the mating neighborhood. Field experiments were conducted at five intertidal sites on Long Island, New York, USA from July to December 2005 to determine how wave exposure and aggregation structure influence the length, diameter, mass, and number of annulated folds of the penis. Sparsely crowded barnacles had more annulations in the penis and are inferred to have greater ability to stretch. At higher wave exposure, the diameter of the penis was greater, but the mass was not. This study identifies density of crowding as the most important cue that barnacles respond to when perceiving their mating group and details how penis morphology varies in response to wave exposure.     

Relationships between development and disease

Summary The close links which exist between poverty, disease and development are surveyed, particularly with reference to the situation in Africa. Poverty may impede the correct use of the land which can in turn lead to malnutrition and a higher incidence of disease. A population in poor health cannot effectively improve its own economic condition or make full use of aid. Poor health may be due to a colonial heritage of unsatisfactory land use, inappropriate transfer of technology, short-sighted administration, or other causes. Not all development brings improvement in health, for instance, inadequate urban planning can induce health problems.The wealthy and secure nations of the world will realise that they cannot possibly remain either wealthy or secure if they continue to close their eyes to the pestilence of poverty that covers the whole southern half of the globe. They will act, if only to preserve their own immunity from infection.(McNamara, 1968)Paul Milligan, is a Research Assistant in the Department of Biological Sciences at the University of Salford. He has an active interest in the computer analysis of environmental data and has worked on material relating to the control of river blindness in the Volta Basin of West Africa and in a wider African context on attempts to control sleeping sickness.Dr Michael Pugh Thomas, is Deputy Director of the Environmental Institute at the University of Salford. He is actively involved in environmental education and he is the current Chairman of the Institution of Environmental Sciences. His research has been concerned with the environmental impact of economic development and has related to estuarine ecology and the ecological effects of attempts to control insect vector bourne diseases.     

The relationship between blend miscibility and biodegradation of cellulose acetate and poly(ethylene Succmate) blends

The miscibility of cellulose acetate (CA; degree of substitution = 2.5) and poly(ethylene succinate) (PES) has been investigated using a variety of thermal techniques and by solid-state carbon13 NMR spectroscopy. The blends containing greater than ca. 70% CA were found to be miscible. In the case of blends containing less than ca. 70% CA, a combination of thermal and NMR analyses suggests that these blends are not fully miscible on a 2.5- to 5-nm scale. On the scale which can be probed by dynamic mechanical thermal analysis (15 nm), the low-percentage CA blends exhibit “significant local concentration fluctuations≓. Investigation of the biodegradation of the blend components and of the blends revealed that PES degraded relatively rapidly and that CA degraded slowly. The blends degraded at a rate essentially identical to that of CA. Miscibility (75% CA blend) or crystallization of PES (30% CA blend) had no significant effect. These data suggest that a significant mode of degradation ófPES during composting involves chemical hydrolysis of the polymer followed by biological assimilation of monomers. Degradation of the blends is initiated in the amorphous phase. Because CA is a significant component of the amorphous phase, a small amount of CA significantly impacts the biodegradation rates of the blends.     

Pollution and Genetic Structure of North American Populations of the Common Dandelion (Taraxacum Officinale)

Assessing the genetic structure of natural populations differentially impacted by anthropogenic contaminants can be a useful tool for evaluating the population genetic consequences of exposure to pollution. In this study, measures of genetic diversity at variable-number-tandem-repeat loci in six dandelion populations (3 urban and 3 rural) showed patterns that may have been influenced by exposure to environmental contaminants. Mean genetic similarity among individuals within a population was significantly and positively correlated with increasing levels of airborne particulate matter ( 10 m, PM₁₀) and soil concentrations of four metals (Cd, Fe, Ni and Pb). In addition, mean genetic similarity was always significantly higher at the urban sites compared to rural sites. There was a significant negative correlation between the number of genotypes at a site and increasing amounts of PM₁₀, concentrations of five soil metals (Cd, Cu, Fe, Ni and Pb), leaf tissue levels of Fe and a significant positive correlation between the extent of clonality at a site and levels of PM₁₀ and soil concentrations of five metals (Cd, Cu, Fe, Ni and Pb). Although, this study does not directly establish a causal link between the specific contaminants detected at the study sites and differences in genetic diversity, our data are consistent with the hypothesis that pollution-induced selection has contributed in some fashion to the lower genetic diversity found at the urban sites.     

The corporate impact of addressing social issues: a financial case study of a project in Peru

Large, multinational resource development projects can affectmany aspects, including social, economic and ecological realities, in the regions where they operate. Social and environmental issues that are usually ignored in such projectsare increasingly affecting the financial future of multinationalcorporations in negative ways. In this article, we advance the argument that corporations can successfully manage these issuesand that if they choose to view these management efforts as an investment rather than an expense, they may well acquire a competitive advantage over companies that do not. We describe asa case study the Camisea natural gas and condensates developmentproject in Peru, operated by Shell Prospecting and Development Peru (SPDP). Camisea is one of the first projects anywhere inthe world to conduct a detailed analysis of key industry-relatedsocial issues and the processes, required investment and financial impact of managing them. The Camisea example supportsthe argument that addressing social and environmental concerns makes financial sense. In present value terms, the benefit ofmanaging these concerns was expected to surpass the cost investment by approximately US$50 million.     

An analysis of the Canadian Research and Development System for Agriculture/Food

The report entitled An Analysis of the Canadian Research and Development System for Agriculture/Food which was presented to the Science Council of Canada in July, 1991 contains many far-reaching recommendations for revisions of the research and educational components of the Agriculture/Food System in Canada. The report calls for research of holistic and interdisciplinary nature. It calls for determination of research priorities by broadly constituted committees which would include reporesentaitves heretofore not included in the process of decisionmaking regarding scientific research. In addition, it calls for restructuring of the agricultural education system. The Co-editors of this Journal, believe that these recommendations should be wildely discussed and, therefore, requested publication of the Executive Summary of this Report.     

Mercury photoreduction and photooxidation in lakes: Effects of filtration and dissolved organic carbon concentration

Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic carbon(DOC) concentrations and particulates affect mercury photoreaction kinetics in freshwater lakes. To address this knowledge gap,samples were collected from ten lakes in Kejimkujik National Park, Nova Scotia(DOC: 2.6–15.4 mg/L). Filtered(0.2 μm) and unfiltered samples were analysed for gross photoreduction, gross photooxidation, and net reduction rates of mercury using pseudo first-order curves. Unfiltered samples had higher concentrations(p = 0.04) of photoreducible divalent mercury(Hg(II)RED)(mean of 754 ± 253 pg/L) than filtered samples(mean of 482 ± 206 pg/L);however, gross photoreduction and photooxidation rate constants were not significantly different in filtered or unfiltered samples in early summer. DOC was not significantly related to gross photoreduction rate constants in filtered(R~2= 0.43; p = 0.08) and unfiltered(R~2= 0.02; p = 0.71) samples; DOC was also not significantly related to gross photooxidation rate constants in filtered or unfiltered samples. However, DOC was significantly negatively related with Hg(Ⅱ)_(RED) in unfiltered(R2= 0.53; p = 0.04), but not in filtered samples(R~2= 0.04;p = 0.60). These trends indicate that DOC is a factor in determining dissolved mercury photoreduction rates and particles partially control available Hg(Ⅱ)_(RED) in lake water. This research also demonstrates that within these lakes gross photoreduction and photooxidation processes are close to being in balance. Changes to catchment inputs of particulate matter and DOC may alter mercury retention in these lakes and could partially explain observed increases of mercury accumulation in biota.     

Pasture diversification to combat climate change impacts on grazing dairy production

Among livestock systems, grazing is likely to be most impacted by climate change because of its dependency to feed quality and availability. In order to reduce the impact of climate change on grazing livestock systems, adaptation measures should be implemented. The goal of this study is to identify the best pasture composition for a representative grazing dairy farm in Michigan in order to reduce the impacts of climate change on production. In order to achieve the goal of this study, three objectives were sought: (1) identify the best pasture composition, (2) assess economic and resource use impacts of pasture compositions under future climate scenarios, and (3) evaluate the resiliency of pasture compositions. A representative farm was developed based on a livestock practices survey and incorporated into the Integrated Farm System Model (IFSM). For the pasture compositions, four cool-season grass species and two legumes were evaluated under both current and future climate scenarios. The effectiveness of adaptation measures based on economic and resource use criteria was evaluated. Overall, the pasture composition with 50% perennial ryegrass (Lolium multiflorum) and 50% red clover (Trifolium pratense) was identified as the best. In addition, the increase in precipitation and temperature of the most intensive climate scenario could significantly improve farm net return per cow (Bos taurus) and whole farm profit while no significant impact was observed on resource use criteria. Finally, the overall sensitivity assessment showed that the most resilient pasture composition under future climate scenarios was ryegrass with red clover and the least resilient was orchardgrass (Dactylis glomerata) with white clover (Trifolium repens).