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A comparative study was performed in order to determine the relative accuracy of a gaussian dispersion model. The U.S. EPA’s RAM (Urban) model was chosen to estimate 24-hour average sulfur dioxide concentrations in the Cleveland, Ohio area. Point and area source emissions, along with a background concentration were included in the modeling effort. Projections from the model made at the ambient air stations were compared to measured sulfur dioxide concentrations. A total of 3020 comparisons were performed at 33 monitoring sites. An analysis of the results illustrates that, on a daily basis, the predictions of the model did not reflect actual air quality. The correlation coefficients of the 24-hour comparisons at the monitoring sites varied from a low of —0.121 to a high of 0.541. When the highest and second highest modeled concentrations were evaluated with respect to the highest and second highest measured concentrations, over a period of a year, a more favorable comparison was observed.  相似文献   
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Objectives: Though there is a growing body of literature on crash risks in the developed world, little is known about how well these models apply to motoring in developing countries, the context in which the majority of road traffic fatalities occur. This qualitative study explores factors perceived to influence crash risks for commercial drivers in Ghana.

Method: Twenty commercial drivers of varied ages and experience were sampled from 7 major lorry terminals in 3 regions (Greater Accra, Ashanti, and Volta) of Ghana. Data were collected through semistructured interviews.

Results: The participants identified some issues that are shared with drivers in the developed world, though moderated by the Ghanaian context. These included work pressures (e.g., fatigued driving), speeding, distracted driving, and inadequate vehicle maintenance. Other factors identified by participants are less frequently considered in research addressing driving behavior in developed countries. These included aggressive competition over passengers and corruption (e.g., improper licensing practices), among others.

Conclusion: The findings have implications for building a research base to support the development of road safety policy and interventions in developing countries.  相似文献   

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Decapod crustaceans are faceless animals with five pairs of legs, an external skeleton and multiple nerve centres (ganglia) rather than a single brain (as in vertebrates). They include common seafood species such as crayfish, crabs, lobsters, prawns and shrimp. These characteristics make them difficult to empathise with and consequently legal protection of decapods ranges from strong (Norway and New Zealand), through circumstantial (Australia and Italy) to non-existent (in many other countries). Whether they are capable of experiencing pain depends on definitions and the requirement for absolute proof of an inherently subjective psychological experience. Yet like other animals, decapods fulfil neuroanatomical, pharmacological and behavioural criteria that are consistent with a pain response. Whether they experience stress, harm and distress is less controversial because these conditions are more measurable than the pain response. To balance animal welfare concerns with scientific merit whilst providing confidence for the growing public awareness of crustacean welfare, use of decapod crustaceans in research should require ethical review.  相似文献   
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A numerical model ‘BioClog’ is used to examine clogging of granular drainage material within finger drains at the base of landfills. The reduction in porosity of drainage material is evaluated as the accumulation of clog mass reduces the pore spaces of granular media. The leachate mounding within the landfills caused by the reduction in hydraulic conductivity of finger drain is modeled. The effect of overburden pressure on the engineering properties of waste material and consequent leachate mounding is considered. The calculated rates of leachate mound development for two landfills with finger drain leachate collection are shown to be in encouraging agreement with the observed data at the times when data were available. It is demonstrated that a significant leachate mound can be expected to develop over time when the leachate collection system is comprised of finger drains; however the rate of increase and the magnitude at a given time will depend on a number of factors including the grainsize, thickness and spacing of the finger drains, and the thickness of waste as well as the leachate generation rate.  相似文献   
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ABSTRACT: The U.S. Geological Survey (USGS) collected or compiled data on volatile organic compounds (VOCs) in samples of untreated ground water from 1,926 rural private wells during 1986 to 1999. At least one VOC was detected in 12 percent of samples from rural private wells. Individual VOCs were not commonly detected with the seven most frequently detected compounds found in only 1 to 5 percent of samples at or above a concentration of 0.2 microgram per liter (μg/l). An assessment level of 0.2 μg/l was selected so that comparisons of detection frequencies between VOCs could be made. The seven most frequently detected VOCs were: trichloromethane, methyl tert‐butyl ether, tetrachloroethene, dichlorodifluoromethane, methylbenzene, 1,1,1‐trichloroethane, and 1,2‐dibromo‐3‐chloropropane. Solvents and trihalomethanes were the most frequently detected VOC groups in private wells. The distributions of detections of gasoline oxygenates and fumigants seemed to be related to the use patterns of compounds in these groups. Mixtures were a common mode of occurrence of VOCs with one‐quarter of all samples with detections including two or more VOCs. The concentrations of most detected VOCs were relatively small and only 1.4 percent of samples had one or more VOC concentrations that exceeded a federally established drinking water standard or health criterion.  相似文献   
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We provide an overview of research related to environmental effects of disposal of coal combustion residues (CCR) in sites in the United States. Our focus is on aspects of CCR that have the potential to negatively influence aquatic organisms and thehealth of aquatic ecosystems. We identify major issues of concern, as well as areas in need of further investigation.Intentional or accidental release of CCR into aquatic systemshas generally been associated with deleterious environmental effects. A large number of metals and trace elements are presentin CCR, some of which are rapidly accumulated to high concentrations by aquatic organisms. Moreover, a variety of biological responses have been observed in organisms following exposure to and accumulation of CCR-related contaminants. In some vertebrates and invertebrates, CCR exposure has led to numerous histopathological, behavioral, and physiological (reproductive, energetic, and endocrinological) effects. Fish kills and extirpation of some fish species have been associatedwith CCR release, as have indirect effects on survival and growth of aquatic animals mediated by changes in resource abundance or quality. Recovery of CCR-impacted sites can be extremely slow due to continued cycling of contaminants withinthe system, even in sites that only received CCR effluents forshort periods of time. The literature synthesis reveals important considerations for future investigations of CCR-impacted sites. Many studies have examined biological responses to CCR with respect to Se concentrations and accumulation because of teratogenic andreproductively toxic effects known to be associated with thiselement. However, the complex mixture of metals and traceelements characteristic of CCR suggests that biologicalassessments of many CCR-contaminated habitats should examine avariety of inorganic compounds in sediments, water, and tissuesbefore causation can be linked to individual CCR components. Most evaluations of effects of CCR in aquatic environments havefocused on lentic systems and the populations of animalsoccupying them. Much less is known about CCR effects in loticsystems, in which the contaminants may be transported downstream,diluted or concentrated in downstream areas, and accumulated bymore transient species. Although some research has examinedaccumulation and effects of contaminants on terrestrial and avianspecies that visit CCR-impacted aquatic sites, more extensiveresearch is also needed in this area. Effects in terrestrial orsemiaquatic species range from accumulation and maternal transferof elements to complete recruitment failure, suggesting that CCReffects need to be examined both within and outside of theaquatic habitats into which CCR is released. Requiring specialattention are waterfowl and amphibians that use CCR-contaminatedsites during specific seasons or life stages and are highlydependent on aquatic habitat quality during those periods.Whether accidentally discharged into natural aquatic systems or present in impoundments that attract wildlife, CCR appears topresent significant risks to aquatic and semiaquatic organisms. Effects may be as subtle as changes in physiology or as drasticas extirpation of entire populations. When examined as a whole,research on responses of aquatic organisms to CCR suggests thatreducing the use of disposal methods that include an aquaticslurry phase may alleviate some environmental risks associatedwith the waste products.  相似文献   
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Sweden has led the way in Europe in environmental protection, ecologically based technological innovation and social democracy. As new economic and ethnographic realities impact upon it, it faces challenges to its policies and practices long familiar elsewhere in Europe. We report on a study for the Swedish Research Councils in which we examined the national framework and political strategy for sustainable development, and how the strategy is being implemented in Sweden's three major cities and two case-study municipalities. History and tradition, cultural homogeneity and a strong and shared sense between sectors of 'the public good', emerged as very important. Until recently, these have obviated the need for formal links between the environmental, social and economic agendas. They now appear inadequately developed at all levels of governance. Tensions in policy are being played out at the level of the municipality, to which power is highly devolved, and Local Agenda 21, interpreted as project rather than process, seems unequal to the task of integration. We suggest what lessons may be drawn from the Swedish experience if issues of power and trust, leadership and participatory vs representative democracy are to be resolved.  相似文献   
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The observed temperatures in different landfills are used to establish a number of idealized time–temperature histories for geomembrane liners in municipal solid waste (MSW) landfills. These are then used for estimating the service life of different HDPE geomembranes. The predicted antioxidant depletion times (Stage I) are between 7 and 750 years with the large variation depending on the specific HDPE geomembrane product, exposure conditions, and most importantly, the magnitude and duration of the peak liner temperature. The higher end of the range corresponds to data from geomembranes aged in simulated landfill liner tests and a maximum liner temperature of 37 °C. The lower end of the range corresponds to a testing condition where geomembranes were immersed in a synthetic leachate and a maximum liner temperature of 60 °C. The total service life of the geomembranes was estimated to be between 20 and 3300 years depending on the time–temperature history examined. The range illustrates the important role that time–temperature history could play in terms of geomembrane service life. The need for long-term monitoring of landfill liner temperature and for geomembrane ageing studies that will provide improved data for assessing the likely long-term performance of geomembranes in MSW landfills are highlighted.  相似文献   
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