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231.
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233.
Arthur H. Johnson 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1049-1054
Red spruce have died in abnormal numbers in the high elevation forests of New York and New England during the past two decades while spruce in the southern Appalachians remain healthy. Investigations of insect damage, fungal pathogens, successional dynamics, competitive status, climate and weather patterns and possible pollutant effects indicate that the decline was triggered by abiotic stress during the dry years of the 1960s. Tree response, as recorded in the pattern of annual rings, and the wide range of soil conditions in which spruce are declining, suggest drought or dry summers as key factors. Hypotheses regarding the role of acid deposition induced stress have been offered, but at present there is not evidence which clearly links acid deposition to spruce decline. Indirect effects of acid deposition on soils, direct effects of acid deposition on foliage, and interactions of acid deposition and drought stress are possible but unproven pathways by which acid deposition could be involved. 相似文献
234.
Allen L. Jakway Arthur M. Sterling Vic A. Cundy Charles A. Cook Alfred N. Montestruc 《Journal of the Air & Waste Management Association (1995)》2013,63(11):877-885
Abstract For the first time, velocities were measured inside a fieldscale rotary kiln incinerator. Combustion gas velocities and temperatures were measured at multiple points across a quadrant of the kiln near its exit using a bidirectional pressure probe and suction pyrometer. To accommodate the new bidirectional probe and gain access to the upper portion of the kiln, a lighter and stiffer positioning boom was designed. The kiln was directly fired using natural gas in a steady state mode. Results indicate strong vertical stratification of both velocity and temperature, with the highest values corresponding to the top of the kiln. Access restraints prevented the lower region of the kiln from being mapped. Horizontal variations in both temperature and velocity were insignificant. Operating conditions were varied by adjusting the amount of ambient air added to the front of the kiln. Increasing the flow of ambient air into the front of the kiln reduced the measured temperatures as expected, but did hot have as significant an effect on measured velocities. The quality of the results is examined by performing mass balances across the incinerator and by comparison to an existing numerical model. Both methods indicate that the experimental results are reasonable. 相似文献
235.
C. Andrew Miller George Hidy Jeremy Hales Charles E. Kolb Arthur S. Werner Bernd Haneke 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1115-1129
Abstract Although emission inventories are the foundation of air quality management and have supported substantial improvements in North American air quality, they have a number of shortcomings that can potentially lead to ineffective air quality management strategies. Major reductions in the largest emissions sources have made accurate inventories of previously minor sources much more important to the understanding and improvement of local air quality. Changes in manufacturing processes, industry types, vehicle technologies, and metropolitan infrastructure are occurring at an increasingly rapid pace, emphasizing the importance of inventories that reflect current conditions. New technologies for measuring source emissions and ambient pollutant concentrations, both at the point of emissions and from remote platforms, are providing novel approaches to collecting data for inventory developers. Advances in information technologies are allowing data to be shared more quickly, more easily, and processed and compared in novel ways that can speed the development of emission inventories. Approaches to improving quantitative measures of inventory uncertainty allow air quality management decisions to take into account the uncertainties associated with emissions estimates, providing more accurate projections of how well alternative strategies may work. This paper discusses applications of these technologies and techniques to improve the accuracy, timeliness, and completeness of emission inventories across North America and outlines a series of eight recommendations aimed at inventory developers and air quality management decision-makers to improve emission inventories and enable them to support effective air quality management decisions for the foreseeable future. 相似文献
236.
Michael J. McFarland Glenn R. Palmer Scott Peters Arthur C. Olivas Tim M. Nelson 《Journal of the Air & Waste Management Association (1995)》2013,63(3):365-372
Abstract To effectively reduce the environmental compliance costs associated with meeting specific requirements under the Aerospace Manufacturing and Rework Facility’s National Emission Standard for Hazardous Air Pollutants rule, the U.S. Environmental Protection Agency’s (EPA) Data Quality Objective (DQO) process has been proposed as a suitable framework for developing a scientifically defensible surface compliance monitoring program. By estimating the variability associated with the air cap pressure of high-volume, low-pressure (HVLP) surface-coating spray equipment, the number of monitoring samples necessary for an affected facility to claim compliance with a desired statistical confidence level was established. Using data taken from the pilot test facility, the DQO process indicated that the mean of at least 21 HVLP air cap pressure samples taken over the compliance period must be ≤10 pounds per square inch (psig) gauge for the facility to claim regulatory compliance with 99.99% statistical confidence. Fewer compliance samples could be taken, but that decision would lead to a commensurate reduction in the compliance confidence level. Implementation of the DQO-based compliance sampling plan eliminates the need for an affected facility to sample all regulated HVLP surface-coating processes while still maintaining a high level of compliance assurance. 相似文献
237.
Impacts of climatic and atmospheric changes on carbon dynamics in the Great Smoky Mountains National Park 总被引:1,自引:0,他引:1
Zhang C Tian H Chappelka AH Ren W Chen H Pan S Liu M Styers DM Chen G Wang Y 《Environmental pollution (Barking, Essex : 1987)》2007,149(3):336-347
We used the Dynamic Land Ecosystem Model (DLEM) to estimate carbon (C) storage and to analyze the impacts of environmental changes on C dynamics from 1971 to 2001 in Great Smoky Mountain National Park (GRSM). Our simulation results indicate that forests in GRSM have a C density as high as 15.9kgm(-2), about twice the regional average. Total carbon storage in GRSM in 2001 was 62.2Tg (T=10(12)), 54% of which was in vegetation, the rest in the soil detritus pool. Higher precipitation and lower temperatures in the higher elevation forests result in larger total C pool sizes than in forests at lower elevations. During the study period, the CO(2) fertilization effect dominated ozone and climatic stresses (temperature and precipitation), and the combination of these multiple factors resulted in net accumulation of 0.9Tg C in this ecosystem. 相似文献
238.
239.
Walter R. Hill Michael G. Ryon John G. Smith S. Marshall Adams Harry L. Boston Arthur J. Stewart 《Environmental management》2010,45(3):563-576
The effects of pollutants on primary producers ramify through ecosystems because primary producers provide food and structure
for higher trophic levels and they mediate the biogeochemical cycling of nutrients and contaminants. Periphyton (attached
algae) were studied as part of a long-term biological monitoring program designed to guide remediation efforts by the Department
of Energy’s Y-12 National Security Complex on East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee. High concentrations of
nutrients entering EFPC were responsible for elevated periphyton production and placed the stream in a state of eutrophy.
High rates of primary production at upstream locations in EFPC were associated with alterations in both invertebrate and fish
communities. Grazers represented >50% of the biomass of invertebrates and fish near the Y-12 Complex but <10% at downstream
and reference sites. An index of epilithic periphyton production accounted for 95% of the site-to-site variation in biomass
of grazing fish. Analyses of heavy metals in EFPC periphyton showed that concentrations of zinc, cadmium, copper and nickel
in periphyton decreased exponentially with distance downstream from Y-12. Zinc uptake by periphyton was estimated to reduce
the concentration of this metal in stream water ~60% over a 5-km reach of EFPC. Management options for mitigating eutrophy
in EFPC include additional reductions in nutrient inputs and/or allowing streamside trees to grow and shade the stream. However,
reducing periphyton growth may lead to greater downstream transport of contaminants while simultaneously causing higher concentrations
of mercury and PCBs in fish at upstream sites. 相似文献
240.
Katherine R. M. Mackey Tanya Rivlin Arthur R. Grossman Anton F. Post Adina Paytan 《Marine Biology》2009,156(8):1531-1546
The spring bloom in seasonally stratified seas is often characterized by a rapid increase in photosynthetic biomass. To clarify
how the combined effects of nutrient and light availability influence phytoplankton composition in the oligotrophic Gulf of
Aqaba, Red Sea, phytoplankton growth and acclimation responses to various nutrient and light regimes were recorded in three
independent bioassays and during a naturally-occurring bloom. We show that picoeukaryotes and Synechococcus maintained a “bloomer” growth strategy, which allowed them to grow quickly when nutrient and light limitation were reversed.
During the bloom picoeukaryotes and Synechococcus appeared to have higher P requirements relative to N, and were responsible for the majority of photosynthetic biomass accumulation.
Following stratification events, populations limited by light showed rapid photoacclimation (based on analysis of cellular
fluorescence levels and photosystem II photosynthetic efficiency) and community composition shifts without substantial changes
in photosynthetic biomass. The traditional interpretation of “bloom” dynamics (i.e., as an increase in photosynthetic biomass)
may therefore be confined to the upper euphotic zone where light is not limiting, while other acclimation processes are more
ecologically relevant at depth. Characterizing acclimation processes and growth strategies is important if we are to clarify
mechanisms that underlie productivity in oligotrophic regions, which account for approximately half of the global primary
production in the ocean. This information is also important for predicting how phytoplankton may respond to global warming-induced
oligotrophic ocean expansion. 相似文献