In this study, a correction was developed for the aethalometer to measure real-time black carbon (BC) concentrations in an environment dominated by fresh diesel soot. The relationship between the actual mass-specific absorption coefficient for BC and the BC-dependent attenuation coefficients was determined from experiments conducted in a diesel exposure chamber that provided constant concentrations of fine particulate matter (PM; PM(2.5); PM < 2.5 microm in aerodynamic diameter) from diesel exhaust. The aethalometer reported BC concentrations decreasing with time from 48.1 to 31.5 microg m(-3) when exposed to constant PM(2.5) concentrations of 55 +/- 1 microg m(-3) and b(scat) = 95 +/- 3 Mm(-1) from diesel exhaust. This apparent decrease in reported light-absorbing PM concentration was used to derive a correction K(ATN) for loading of strong light-absorbing particles onto or into the aethalometer filter tape, which was a function of attenuation of light at 880 nm by the embedded particles. 相似文献
Understanding contaminant distribution is critical to selection and implementation of effective and affordable containment and remediation efforts. This article describes the characterization of soil containing thorium at a training site on Kirtland Air Force Base, Albuquerque, NM. The site has been used by the Defense Nuclear Weapons School since the early 1960's to train personnel in emergency response to nuclear weapons accidents and for characterization and containment of radioactive contamination. The purpose of work reported herein is to describe the primary location and migration pattern of 232Thorium (232Th) and 232Th progeny (decay products) at the site. Soil containing thorium oxide (ThO2) was applied to the site for approximately 30 years (early 1960-1990) and was used to simulate a plutonium release from a nuclear weapons accident. Data presented indicate that surface 232Th and 232Th progeny at approximately 5 times background levels are approaching test site boundaries. However, the data also indicate that vertical migration has not exceeded 0.9 m because of the insoluble nature of ThO2. The major mechanisms of 232Th mobility appear to be surface migration mediated by precipitation runoff and wind-blown soil. 相似文献
The need to safely field test genetically modified organisms is a critical step in the sequence of research leading to the commercialization of biotechnology in agriculture. To address this need the United States Department of Agriculture has established the National Biological Impact Assessment Program (NBIAP) to facilitate the safe field testing of genetically modified organisms. NBIAP fosters safe field testing of genetically modified organisms through a computerized network for information exchange, facilitation of biological monitoring techniques and by providing support for research in biosafety to develop new field testing methods and better predictive models. 相似文献
Increasing volumes of municipal solid waste (MSW) pose disposal problems for many cities. Costs are rising as landfilling becomes more difficult. The production of clean transportation fuels (methanol or hydrogen) from MSW is one economically and environmentally promising option for dealing with these problems. An attractive feature is that elimination of essentially all air pollutant emissions is inherent in the process. Current and future air emissions standards should be easily met. Methanol or hydrogen used in fuel cell vehicles (FCV) can help address problems of deteriorating urban air quality due to vehicle pollution and heavy dependence of the transport sector on imported petroleum. Buses are initial targets for commercial application of fuel cells. Coupled with FCVs, MSW could become a major transportation energy resource. For example, less than 25% of New York City's MSW supply would be sufficient to produce the methanol or hydrogen needed to fuel the entire city's bus fleet, if the buses were fuel cell powered. Estimated breakeven tipping fees required for hydrogen or methanol from MSW to compete with the cost of these fuels made from natural gas today are $52 to $89/raw tonne MSW for hydrogen and $64 to $104/raw tonne MSW for methanol (in 1991$), depending on the gasification technology considered. For comparison, the average tipping fee today in New York City is $74/tonne (1991$). Because of the high fuel economies expected for fuel cell buses, total lifecycle costs per bus-km could be lower than for conventional diesel-engine buses. 相似文献
Water samples from streams and springs in the Great Smoky Mountains National Park were analyzed for fecal coliform, fecal streptococcus, and total coliform bacteria. Levels of bacteria were found to be highly variable but related to elevation, time of year, type of water source, and water level of the streams. Visitors did not seem to be major contributors to bacterial contamination. Levels of fecal coliform and total coliform in most water samples were unsuitable for drinking without treatment. Tennessee state standards for body contact recreation (swimming and wading) were exceeded in a few samples but none from streams suitable for swimming. As a result of these findings, park managers increased efforts to inform visitors of the need to treat drinking water and removed improvements at backcountry springs which tended to give the springs the image of safe, maintained water sources. 相似文献
ABSTRACT: Successful stream rehabilitation requires a shift from narrow analysis and management to integrated understanding of the links between human actions and changing river health. At study sites in the Puget Sound lowlands of western Washington State, landscape, hydrological, and biological conditions were evaluated for streams flowing through watersheds with varying levels of urban development. At all spatial scales, stream biological condition measured by the benthic index of biological integrity (B‐IBI) declined as impervious area increased. Impervious area alone, however, is a flawed surrogate of river health. Hydrologic metrics that reflect chronic altered streamflows, for example, provide a direct mechanistic link between the changes associated with urban development and declines in stream biological condition. These measures provide a more sensitive understanding of stream basin response to urban development than do treatment of each increment of impervious area equally. Land use in residential backyards adjacent to streams also heavily influences stream condition. Successful stream rehabilitation thus requires coordinated diagnosis of the causes of degradation and integrative management to treat the range of ecological stressors within each urban area, and it depends on remedies appropriate at scales from backyards to regional storm water systems. 相似文献
Realizing the benefits of environment, health, and safety (EHS) management systems requires more than just rewriting policies and procedures, EHS tasks and activities must be pushed out into all aspects of the organization. The success of this process necessitates an evolving role for EHS managers. For EHS managers, business integration involves the challenge of integrating environment, health, and safety awareness, responsibility, and action into multiple jobs and business processes, leveraging scarce resources to maximize value and minimize costs. Drawing on recent work in the fields of sociology and political science, this article presents conceptual tools for assisting EHS managers to plan and strategize the changing role of the EHS function. By assessing political opportunities, mobilizing structures, and framing processes, EHS managers can maximize the success of EHS programs, while adding value to companies' core operations. 相似文献
Chemical emissions from research and development (R&D) activities are difficult to estimate because of the large number of chemicals used and the potential for continual changes in processes. In this case study, stack measurements taken from R&D facilities at Pacific Northwest National Laboratory (PNNL) were examined, including extreme worst-case emissions estimates and alternate analyses using a Monte Carlo method that takes into account the full distribution of sampling results. The objective of this study was to develop techniques to estimate emissions from stack measurement data that take into account a high degree of variability in the actual emissions. The results from these analyses were then compared to emissions estimated from chemical inventories. Results showed that downwind ambient air concentrations calculated from the stack measurement data were below acceptable source impact levels (ASILs) for almost all compounds, even under extreme worst-case analyses. However, for compounds with averaging periods of a year, the unrealistic but simplifying extreme worst-case analysis often resulted in calculated emissions that were above the lower level regulatory criteria used to determine modeling requirements or to define trivial releases. Compounds with 24-hr averaging periods were nearly all several orders of magnitude below all, including the trivial release, criteria. The alternate analysis supplied a more realistic basis of comparison and an ability to explore effects under different operational modes.
Implications:
Air emissions from research operations are difficult to estimate because of the changing nature of research processes and the small quantity and wide variety of chemicals used. Stack measurements can be used to verify compliance with applicable regulatory criteria. This study shows that while extreme worst-case assumptions can be used for a relatively simple initial comparison, methods that take into account the full range of measurement data are needed to provide a more realistic estimate of emissions for comparison to regulatory criteria, particularly those criteria that define trivial levels of environmental concern.相似文献