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Showing papers by "United States Environmental Protection Agency published in 1994"


Journal ArticleDOI
14 Jan 1994-Science
TL;DR: Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon.
Abstract: Forest systems cover more than 4.1 x 109 hectares of the Earth9s land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 ± 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 ± 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 ± 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.

3,175 citations


Journal ArticleDOI
TL;DR: In this article, the authors present an analytical model that distributes point measurements of monthly and annual precipitation to regularly spaced grid cells in midlatitude regions, using a combination of climatological and statistical concepts to analyze orographic precipitation.
Abstract: The demand for climatological precipitation fields on a regular grid is growing dramatically as ecological and hydrological models become increasingly linked to geographic information systems that spatially represent and manipulate model output. This paper presents an analytical model that distributes point measurements of monthly and annual precipitation to regularly spaced grid cells in midlatitude regions. PRISM (Precipitation-elevation Regressions on Independent Slopes Model) brings a combination of climatological and statistical concepts to the analysis of orographic precipitation. Specifically, PRISM 1) uses a digital elevation model (DEM) to estimate the “orographic” elevations of precipitation stations; 2) uses the DEM and a windowing technique to group stations onto individual topographic facets; 3) estimates precipitation at a DEM grid cell through a regression of precipitation versus DEM elevation developed from stations on the cell's topographic facet; and 4) when possible, calculates...

2,770 citations


Journal ArticleDOI
TL;DR: The data suggest an association between aspirin consumption and decreased cancer incidence at several cancer sites and are not readily explained by potentially confounding factors.
Abstract: A large body of experimental data and several recent epidemiologic studies indicate that aspirin use may decrease cancer risk. The experimental studies found effects at many anatomic sites, whereas the epidemiologic studies saw the greatest effect on mortality from digestive cancers. To provide further human data, we examined the association between aspirin use and cancer risk using data from the National Health and Nutrition Examination Survey I (NHANES I) and the NHANES I Epidemiologic Follow-up Studies (NHEFS). Characterization of aspirin use was based on questions in the baseline interview asking whether subjects used aspirin during the previous 30 days. Data were available from 12,668 subjects age 25-74, at time of initial examination for NHANES I, who were followed for an average of 12.4 years. Among these subjects, 1,257 were diagnosed with cancer more than 2 years after their NHANES I examination. Incidence of several cancers was lower among persons who reported aspirin use: the incidence rate ratios (and 95% confidence intervals) for all sites combined were 0.83 (0.74-0.93), lung cancer 0.68 (0.49-0.94), breast cancer in women 0.70 (0.50-0.96), and colorectal cancer in younger men 0.35 (0.17-0.73). These findings were not readily explained by potentially confounding factors. The data suggest an association between aspirin consumption and decreased cancer incidence at several cancer sites.

751 citations


Book
01 Feb 1994
TL;DR: A broad overview of current research in the emerging field of environmental aquatic and surface photochemistry can be found in this paper, where selected reviews and current research articles are blended to provide an in-depth treatment of various aspects of this research area.
Abstract: Aquatic and Surface Photochemistry provides a broad overview of current research in the emerging field of environmental aquatic and surface photochemistry. Selected reviews and current research articles are blended to provide an in-depth treatment of various aspects of this research area. The first part of the text deals with photochemistry in the environment, covering recent research on the following topics: aquatic photochemistry of organic pollutants and agrochemicals, photochemical cycling of carbon and transition metals (especially iron), photochemical formation of reactive oxygen species in natural waters, photoreaction in cloud and rain droplets, and photoreactions on environmental surfaces (soil, ash, metal, oxide). The second part provides discussions and data on both heterogeneous photocatalytic and homogeneous processes, with topics ranging from applications to mechanistic studies. These chapters illustrate the wide diversity of pollutant classes that are degradable by photochemical techniques and the effects of various reaction conditions on the rates and efficiency of the techniques. Current kinetic studies are presented, which provide new information about the role of adsorption and the nature of the reactive oxidizing species that mediate these photoremediation processes. This book will interest civil, chemical, and environmental engineers, as well as chemists, soil scientists, geochemists, and atmospheric chemists.

530 citations


Journal ArticleDOI
TL;DR: The observation of perinatal-induced agenesis of the prostate and blocked testicular descent, a pattern of malformations nearly identical to that reported for the antiandrogen flutamide, is consistent with other recent evidence that this fungicide is an androgen-receptor antagonist.

468 citations


Journal ArticleDOI
TL;DR: This work compares qualitative structure-activity relationships for PCBs with the limited information on the related non-coplanar chlorinated diphenyl ethers, providing further insights into the nature of the molecular recognition processes and support for the structural relationship of PCBs to thyroid hormones.
Abstract: Among the environmental chemicals that may be able to disrupt the endocrine systems of animals and humans, the polychlorinated biphenyls (PCBs) are a chemical class of considerable concern. One possible mechanism by which PCBs may interfere with endocrine function is their ability to mimic natural hormones. These actions reflect a close relationship between the physicochemical properties encoded in the PCB molecular structure and the responses they evoke in biological systems. These physicochemical properties determine the molecular reactivities of PCBs and are responsible for their recognition at biological acceptors and receptors, as well as for triggering molecular mechanisms that lead to tissue response. "Coplanarity" of PCB phenyl rings and "laterality" of chlorine atoms are important structural features determining specific binding behavior with proteins and certain toxic responses in biological systems. We compare qualitative structure-activity relationships for PCBs with the limited information on the related non-coplanar chlorinated diphenyl ethers, providing further insights into the nature of the molecular recognition processes and support for the structural relationship of PCBs to thyroid hormones. Steroidlike activity requires conformational restriction and possibly hydroxylation. We offer some simple molecular recognition models to account for the importance of these different structural features in the structure-activity relationships that permit one to express PCB reactivities in terms of dioxin, thyroxine, and estradiol equivalents. The available data support the involvement of PCBs as mimics of thyroid and other steroidal hormones. The potential for reproductive and developmental toxicity associated with human exposure to PCBs is of particular concern.(ABSTRACT TRUNCATED AT 250 WORDS)

319 citations


Journal ArticleDOI
TL;DR: The role of reduced glutathione in the metabolism of arsenic is consistent with the previously described effects of this agent on the organismic toxicity of arsenic.

292 citations


Journal ArticleDOI
TL;DR: Investigation of the acute and subchronic immunotoxicity and endocrine effects of a commercial pentabromodiphenyl either mixture, DE-71, in female C57BL/6 mice found significant suppression of the anti-SRBC response was seen only in mice exposed subchronically to 1000 mg DE- 71/kg, an exposure that also resulted in decreased thymus weight.

274 citations


Journal ArticleDOI
01 Jan 1994-Nature
TL;DR: The data indicate that if elevated atmos-pheric CO2 and altered climate stressors alter mycorrhizal colonization in forests, the role of forests in sequestering carbon could be altered.
Abstract: PLANTS and soils are a critically important element in the global carbon–energy equation. It is estimated that in forest ecosystems over two-thirds of the carbon is contained in soils and peat deposits1. Despite the importance of forest soils in the global car-bon cycle, fluxes of carbon associated with fundamental processes and soil functional groups are inadequately quantified, limiting our understanding of carbon movement and sequestration in soils. We report here the direct measurement of carbon in and through all major pools of a mycorrhizal (fungus-root) coniferous seedling (a complete carbon budget). The mycorrhizal symbiont reduces over-all retention of carbon in the plant–fungus symbiosis by increasing carbon in roots and below-ground respiration and reducing its retention and release above ground. Below ground, mycorrhizal plants shifted allocation of carbon to pools that are rapidly turned over, primarily to fine roots and fungal hyphae, and host root and fungal respiration. Mycorrhizae alter the size of below-ground carbon pools, the quality and, therefore, the retention time of carbon below ground. Our data indicate that if elevated atmos-pheric CO2 and altered climate stressors alter mycorrhizal colonization in forests, the role of forests in sequestering carbon could be altered.

271 citations


Journal ArticleDOI
TL;DR: There was no evidence that other measures of particulate pollution including aerosol acidity were preferable to PM10 in predicting incidence of respiratory symptoms, and significant associations were found between incidence of coughing symptoms and incidence of lower respiratory symptoms and PM10.
Abstract: A daily diary of respiratory symptoms was collected from the parents of 1,844 school children in six U.S. cities to study the association between ambient air pollution exposures and respiratory illness. A cohort of approximately 300 elementary school children in each of six communities were asked to keep a daily log of the study child's respiratory symptoms for one year. Daily measurements of ambient sulfur dioxide, nitrogen dioxide, ozone, inhalable particles (PM10), respirable particles (PM2.5), light scattering, and sulfate particles were made, along with integrated 24-h measures of aerosol strong acidity. The analyses were limited to the five warm season months between April and August. Significant associations were found between incidence of coughing symptoms and incidence of lower respiratory symptoms and PM10, and a marginally significant association between upper respiratory symptoms and PM10. There was no evidence that other measures of particulate pollution including aerosol acidity were prefera...

237 citations



Journal ArticleDOI
TL;DR: A protocol is offered that suggests that radiation therapy patients with implanted pacemakers be planned so as to limit accumulated dose to the pacemaker to 2 gray, suggesting that this is not a serious problem around most contemporary radiation therapy equipment.
Abstract: Contemporary cardiac pacemakers can fail from radiation damage at doses as low as 10 gray and can exhibit functional changes at doses as low as 2 gray. A review and discussion of this potential problem is presented and a protocol is offered that suggests that radiation therapy patients with implanted pacemakers be planned so as to limit accumulated dose to the pacemaker to 2 gray. Although certain levels and types of electromagnetic interference can cause pacemaker malfunction, there is evidence that this is not a serious problem around most contemporary radiation therapy equipment.

Journal ArticleDOI
TL;DR: In this paper, the size-segregated speciation of trace metals in pulverized coal-fired power plant effluents has been investigated and new theoretical results interpreting existing data are presented.

Journal ArticleDOI
TL;DR: Dietary vitamin C intake was positively and significantly associated with the level of FEV1 and this data are consistent with the hypothesis thatitamin C intake has a protective effect on pulmonary function.

Journal ArticleDOI
TL;DR: The Non-Occupational Pesticide Exposure Study was designed to assess total human exposures to 32 pesticides and pesticide degradation products in the non-occupational environment; however, the study focused primarily on inhalation exposures.
Abstract: The Non-Occupational Pesticide Exposure Study, funded by the U.S. Environmental Protection Agency, was designed to assess total human exposures to 32 pesticides and pesticide degradation products in the non-occupational environment; however, the study focused primarily on inhalation exposures. Two sites—Jacksonville, Florida (USA) and Springfield/Chicopee, Massachusetts (USA)—were studied during three seasons: Summer 1986 (Jacksonville only), Spring 1987, and Winter 1988. Probability samples of 49 to 72 persons participated in individual site/seasons. The primary environmental monitoring consisted of 24-hr indoor, personal, and outdoor air samples analyzed by gas chromtography/mass spectrometry and gas chromatography/electron capture detection. Indoor and personal air concentrations tended to be higher in Jacksonville than in Springfield/Chicopee. Concentrations tended to be highest in summer, lower in spring, and lowest in winter. Indoor and personal air concentrations were generally comparable and were usually much higher than outdoor air concentrations. Inhalation exposure exceeded dietary exposure for cyclodiene termiticides and for pesticides used mainly in the home. Dietary exposures were greater for many of the other pesticides. Inhalation risks were uncertain for termiticides (depending on rates of degradation) but were negligible for other pesticides. The data were insufficient to support risk assessments for food, dermal contact, or house dust exposures.

Journal ArticleDOI
TL;DR: Because most exposure to these persistent chemicals is via food, changes in dietary habits and/or reduced contamination of the food supply may be required.
Abstract: Recent reports have suggested that environmental chemicals may be associated with endocrine alterations in people, wildlife, and experimental animals. Pharmacological investigations as well as natu...

Journal ArticleDOI
TL;DR: The data from this study suggest that under normal conditions, the Trad-MCNBioassay is an efficient and reliable short-term bioassay for clastogens, suitable for the rapid screening of chemicals, and also is specially qualified for in situ monitoring of ambient pollutants.
Abstract: Four coded chemicals, azidoglycerol (AG), N-methyl-N-nitrosourea (MNU), sodium azide (NaN3), and maleic hydrazide (MH), were tested with the Tradescantia micronucleus (Trad-MCN) bioassay by five independent laboratories from five different countries. The purpose of this international collaborative study was to evaluate four plant bioassays, of which the Trad-MCN assay was one, for their sensitivity, efficiency and reliability. The study was carried out under the sponsorship of the International Programme on Chemical Safety. All laboratories adhered to a standard Trad-MCN protocol which suggested that three replicate tests be conducted with each chemical. The results reported by all laboratories, although not equal, showed good agreement among the laboratories. In fact, all five laboratories obtained positive results with MH and MNU, while four of the five laboratories achieved positive results with NaN3. AG was tested in only three laboratories. Two reported negative results, while one reported positive results but only at a single high dose. The data from this study suggest that under normal conditions, the Trad-MCN bioassay is an efficient and reliable short-term bioassay for clastogens. It is suitable for the rapid screening of chemicals, and also is specially qualified for in situ monitoring of ambient pollutants.

Journal ArticleDOI
TL;DR: In this article, a more mechanistic explanation for the prediction of photo-induced toxicity of polycyclic aromatic hydrocarbons (PAHs) was proposed, which is the result of competing processes such as stability and light absorbance which interact to produce a complex, multilinear relationship between toxicity and chemical structure.

Journal ArticleDOI
TL;DR: The divergence in the 16S ribosomal RNA sequences between the new isolate and Thermodesulfobacterium commune suggests that these two thermophilic sulfate-reducing bacteria represent different genera, and these two bacteria depict a lineage that branches deeply within the Bacteria domain and which is clearly distinct from previously defined phylogenetic lines.
Abstract: A thermophilic sulfate-reducing vibrio isolated from thermal vent water in Yellowstone Lake, Wyoming, USA is described. The gram-negative, curved rod-shaped cells averaged 0.3 micrometer wide and 1.5 micrometers long. They were motile by means of a single polar flagellum. Growth was observed between 40 degrees and 70 degrees C with optimal growth at 65 degrees C. Cultures remained viable for one year at 27 degrees C although spore-formation was not observed. Sulfate, thiosulfate and sulfite were used as electron acceptors. Sulfur, fumarate and nitrate were not reduced. In the presence of sulfate, growth was observed only with lactate, pyruvate, hydrogen plus acetate, or formate plus acetate. Pyruvate was the only compound observed to support fermentative growth. Pyruvate and lactate were oxidized to acetate. Desulfofuscidin and c-type cytochromes were present. The G + C content was 29.5 mol%. The divergence in the 16 S ribosomal RNA sequences between the new isolate and Thermodesulfobacterium commune suggests that these two thermophilic sulfate-reducing bacteria represent different genera. These two bacteria depict a lineage that branches deeply within the Bacteria domain and which is clearly distinct from previously defined phylogenetic lines of sulfate-reducing bacteria. Strain YP87 is described as the type strain of the new genus and species Thermodesulfovibrio yellowstonii.

Journal ArticleDOI
TL;DR: An index was developed for estuarine macrobenthos in the Gulf of Mexico that discriminated between areas with degraded environmental conditions and areas with undegraded or reference conditions and was used to evaluate the spatial patterns of degraded benthic resources.
Abstract: An index was developed for estuarine macrobenthos in the Gulf of Mexico that discriminated between areas with degraded environmental conditions and areas with undegraded or reference conditions. Test sites were identified as degraded or reference based on criteria for dissolved oxygen levels, sediment toxicity tests, and sediment contamination. Discriminant analysis was used to identify a suite of measures of benthic community composition and diversity that would most successfully distinguish degraded from undegraded sites. The resultant benthic index was composed of a linear combination of three factors: the Shannon-Wiener diversity index, the proportion of total benthic abundance as tubificid oligochaetes, and the proportion of total benthic abundance as bivalve molluscs. This index was used to evaluate the spatial patterns of degraded benthic resources in the Gulf of Mexico.

Journal ArticleDOI
TL;DR: In this paper, the authors show that the degree of char devolatilization has a profound influence on both the yield of N2O during char oxidation, and on the apparent mechanism.

Journal ArticleDOI
TL;DR: A global analysis of biologic and economic data from 94 nations representing diverse climatic and edaphic conditions reveals a range of integrated land-use systems which could be used to establish and manage vegetation on marginal or degraded lands.
Abstract: Degraded or sub-standard soils and marginal lands occupy a significant proportion of boreal, temperate and tropical biomes. Management of these lands with a wide range of existing, site-specific, integrated, agroforest systems represents a significant global opportunity to reduce the accumulation of greenhouse gases in the atmosphere. Establishment of extensive agricultural, agroforest, and alternative land-use systems on marginal or degraded lands could sequester 0.82–2.2 Pg carbon (C) per year, globally, over a 50-year time-frame. Moreover, slowing soil degradation by alternative grassland management and by impeding desertification could conserve up to 0.5–1.5 Pg C annually. A global analysis of biologic and economic data from 94 nations representing diverse climatic and edaphic conditions reveals a range of integrated land-use systems which could be used to establish and manage vegetation on marginal or degraded lands. Promising land-use systems and practices identified to conserve and temporarily store C include agroforestry systems, fuelwood and fiber plantations, bioreserves, intercropping systems, and shelterbelts/windbreaks. For example, successful establishment of low-intensity agroforestry systems can store up to 70 Mg C/ha in boreal, temperate and tropical ecoregions. The mean initial cost of soil rehabilitation and revegetation ranges from $500–3,000/ha for the 94 nations surveyed. Natural regeneration of woody vegetation or agro-afforestation establishment costs were less than $1000/ha in temperate and tropical regions. The costs of C sequestration in soil and vegetation systems range from $1-69/Mg C, which compares favorably with other options to reduce greenhouse gas emissions to the atmosphere. Although agroforestry system projects were recently established to conserve and sequester C in Guatemala and Malaysia, constraints to wide-spread implementation include social conditions (demographic factors, land tenure issues, market conditions, lack of infrastructure), economic obstacles (difficulty of demonstrating benefits of alternative systems, capital requirements, lack of financial incentives) and, ecologic considerations (limited knowledge of impacts and sustainability of some systems).

Journal ArticleDOI
TL;DR: Two approaches for BMD estimation with each other and with corresponding statistically derived NOAELS are compared, with observed conservatism of the QBMD values relative to the corresponding CBMD values attributed to two factors, lower maximum likelihood estimates for the quantal model and wider confidence intervals around the maximum likelihood estimate.

Journal ArticleDOI
TL;DR: In this paper, potential scenarios of global and regional equilibrium changes in vegetation leaf area index and terrestrial water balance under 2 x CO2 climate from five different general circulation models (GCMs) are presented.
Abstract: . A biogeographic model, MAPSS (Mapped Atmosphere-Plant-Soil System), predicts changes in vegetation leaf area index (LAI), site water balance and runoff, as well as changes in biome boundaries. Potential scenarios of global and regional equilibrium changes in LAI and terrestrial water balance under 2 x CO2 climate from five different general circulation models (GCMs) are presented. Regional patterns of vegetation change and annual runoff are surprisingly consistent among the five GCM scenarios, given the general lack of consistency in predicted changes in regional precipitation patterns. Two factors contribute to the consistency among the GCMs of the regional ecological impacts of climatic change: (1) regional, temperature-induced increases in potential evapo-transpiration (PET) tend to more than offset regional increases in precipitation; and (2) the interplay between the general circulation and the continental margins and mountain ranges produces a fairly stable pattern of regionally specific sensitivity to climatic change. Two areas exhibiting among the greatest sensitivity to drought-induced forest decline are eastern North America and eastern Europe to western Russia. Regional runoff patterns exhibit much greater spatial variation in the sign of the response than do the LAI changes, even though they are deterministically linked in the model. Uncertainties with respect to PET or vegetation water use efficiency calculations can alter the simulated sign of regional responses, but the relative responses of adjacent regions appear to be largely a function of the background climate, rather than the vagaries of the GCMs, and are intrinsic to the landscape. Thus, spatial uncertainty maps can be drawn even under the current generation of GCMs.

Journal ArticleDOI
TL;DR: Phylogenetic relationships between isolates defined by 16S rRNA sequence divergence represent a selection clearly different from the multi-enzyme activities responsible for the PLFA patterns.
Abstract: Twenty-five isolates of dissimilatory sulfate-reducing bacteria were clustered based on similarity analysis of their phospholipid ester-linked fatty acids (PLFA). Of these, 22 showed that phylogenetic relationships based on the sequence similarity of their 16S rRNA directly paralleled the PLFA relationships. Desulfobacter latus and Desulfobacter curvatus grouped with the other Desulfobacter spp. by 16S rRNA comparison but not with the PLFA analysis as they contained significantly more monoenoic PLFA than the others. Similarly, Desulfovibrio africanus clustered with the Desulfovibrio spp. by 16S rRNA but not with them when analyzed by PLFA patterns because of higher monoenoic PLFA content. Otherwise, clustering obtained with either analysis was essentially congruent. The relationships defined by PLFA patterns appeared robust to shifts in nutrients and terminal electron acceptors. Additional analyses utilizing the lipopolysaccharide-lipid A hydroxy fatty acid patterns appeared not to shift the relationships based on PLFA significantly except when completely absent, as in Gram-positive bacteria. Phylogenetic relationships between isolates defined by 16S rRNA sequence divergence represent a selection clearly different from the multi-enzyme activities responsible for the PLFA patterns. Determination of bacterial relationships based on different selective pressures for various cellular components provides more clues to evolutionary history leading to a more rational nomenclature.

Journal ArticleDOI
TL;DR: Inhalation exposure to styrene, mixed xylene, toluene, and 1,1,2-trichloroethylene resulted in hearing dysfunction only in the mid-frequency range and spared function at lower and higher frequencies, indicating that for those solvents reported thus far to cause hearing loss, the deficit is restricted to mid-frequencies in rats.

Journal ArticleDOI
TL;DR: In this paper, an extensive literature survey was conducted to evaluate the carbon dynamics of agroforestry practices and assess their potential to store carbon, and the limited survey information available substantiated the concept that implementing agro forestry practices can help reduce deforestation.
Abstract: The process of land degradation is a local phenomenon that occurs field by field. Because of the extent at which it is occurring, however, it also has a global dimension. Agroforestry represents a link between the local and global scales. From the farmer's perspective, agroforestry can be a way to increase crop yields and the diversity of products grown. An additional benefit is the creation of a carbon sink that removes carbon dioxide from the atmosphere. Successful agroforestry systems will also reduce land clearing and maintain carbon in existing vegetation. An extensive literature survey was conducted to evaluate the carbon dynamics of agroforestry practices and to assess their potential to store carbon. Data on tree growth and wood production were converted to estimates of carbon storage. Surveyed literature showed that median carbon storage by agroforestry practices was 9 tC/ha in semi-arid, 21 tC/ha in sub-humid, 50 tC/ha in humid, and 63 tC/ha in temperate ecozones. The limited survey information available substantiated the concept that implementing agroforestry practices can help reduce deforestation.

Journal ArticleDOI
TL;DR: In this article, a conceptual model for the uptake of anthropogenic organic chemicals into plants is presented, describing the dynamic uptake from soil, solution, or atmosphere, and the metabolism and accumulation of xenobiotic chemicals in roots, stems, leaves, and fruits.
Abstract: This paper documents a conceptual model for the uptake of anthropogenic organic chemicals into plants. The model describes the dynamic uptake from soil, solution, or atmosphere, and the metabolism and accumulation of xenobiotic chemicals in roots, stems, leaves, and fruits. The goal was to develop an easy and rapid tool that would be numerically stable and require only a few well-known input data. The model is applicable to different plant species and most (nondissociating) organic chemicals. Processes considered are (a) diffusive exchange, soil/roots, and air/leaves; (b) mass flows in xylem and phloem; and (c) metabolism. The model is tested with laboratory studies on the uptake of the herbicide bromacil under various controlled conditions. No adjustments to the parameter values were required for successful simulations.

Journal ArticleDOI
TL;DR: In this paper, the authors developed a test apparatus and procedure to quantify the fractional filtration efficiency of air cleaners over the 0.1 to 0.5 μm diameter size range.
Abstract: The filtration efficiency of ventilation air cleaners is highly particle-size dependent over the 0.01 to 3 μm diameter size range. Current standardized test methods, which determine only overall efficiencies for ambient aerosol or other test aerosols, provide data of limited utility. Because particles in this range are respirable and can remain airborne for prolonged time periods, measurement of air cleaner fractional efficiency is required for application to indoor air quality issues. The objectives of this work have been to 1) develop a test apparatus and procedure to quantify the fractional filtration efficiency of air cleaners over the 0.01 to 3 μm diameter size range and 2) quantify the fractional efficiency of several induct air cleaners typical of those used in residential and office ventilation systems. Results show that efficiency is highly dependent on particle size, flow rate, and dust load present on the air cleaner. A minimum in efficiency was often observed in the 0.1 to 0.5 μm diameter size range. The presence of a dust load frequently increased an air cleaner's efficiency; however, some air cleaners showed little change or a decrease in efficiency with dust loading. The common furnace filter had fractional efficiency values of less than 10% over much of the measurement size range.

Journal ArticleDOI
TL;DR: In this article, the authors summarized reports prepared for the U.S. Environmental Protection Agency (EPA) by researchers at Oak Ridge National Laboratory (ORNL) and presented conclusions from a Biomass Energy Strategies Workshop conducted at ORNL.
Abstract: This paper summarizes reports prepared for the U.S. Environmental Protection Agency (EPA) by researchers at the U.S. Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL). It also presents conclusions from a Biomass Energy Strategies Workshop conducted at ORNL. The Biofuels Feedstock Development Program (BFDP) has largely concentrated on the development of dedicated biomass feedstocks, referred to as energy crops. Two general types of energy crops have received the most attention—short-rotation woody crops (SRWC) and herbaceous energy crops (HEC). These cropping systems use traditional food production technologies as a means of maximizing the production of biomass per unit of land. Research focuses on the development of new crops and cropping technologies. The reports prepared for EPA and summarized by this article include discussions of crop production technologies, available land, economic considerations and environmental trade-offs. The discussion of other sources of biomass occurs only in the context of the workshop on biomass energy strategies. [The views expressed in this paper are those of the authors and do not necessarily represent the views of the U.S. Environmental Protection Agency or the U.S. Department of Energy.]