Home About us Contact
|
Home About us Contact | ||
|
|
||
United States Environmental Protection Agency (united + states_environmental_protection_agency)
Selected AbstractsAnalyzing weather effects on airborne particulate matter with HGLMENVIRONMETRICS, Issue 7 2003Yoon Dong Lee Abstract Particulate matter is one of the six constituent air pollutants regulated by the United States Environmental Protection Agency. In analyzing such data, Bayesian hierarchical models have often been used. In this article we propose the use of hierarchical generalized linear models, which use likelihood inference and have well developed model-checking procedures. Comparisons are made between analyses from hierarchical generalized linear models and Daniels et al.'s (2001) Bayesian models. Model-checking procedure indicates that Daniels et al.'s model can be improved by use of the log-transformation of wind speed and precipitation covariates. Copyright © 2003 John Wiley & Sons, Ltd. [source] Developmental toxicity evaluation of inhaled tertiary amyl methyl ether in mice and ratsJOURNAL OF APPLIED TOXICOLOGY, Issue 6 2003Frank Welsch Abstract This evaluation was part of a much more comprehensive testing program to characterize the mammalian toxicity potential of the gasoline oxygenator additive tertiary amyl methyl ether (TAME), and was initiated upon a regulatory agency mandate. A developmental toxicity hazard identi,cation study was conducted by TAME vapor inhalation exposure in two pregnant rodent species. Timed-pregnant CD®(Sprague-Dawley) rats and CD-1® mice, 25 animals per group, inhaled TAME vapors containing 0, 250, 1500 or 3500 ppm for 6 h a day on gestational days 6,16 (mice) or 6,19 (rats). The developmental toxicity hazard potential was evaluated following the study design draft guidelines and end points proposed by the United States Environmental Protection Agency. Based on maternal body weight changes during pregnancy, the no-observable-adverse-effect level (NOAEL) was 250 ppm for maternal toxicity in rats and 1500 ppm for developmental toxicity in rats using the criterion of near-term fetal body weights. In mice, more profound developmental toxicity was present than in rats, at both 1500 and 3500 ppm. At the highest concentration, mouse litters revealed more late fetal deaths, signi,cantly reduced fetal body weights per litter and increased incidences of cleft palate (classi,ed as an external malformation), as well as enlarged lateral ventricles of the cerebrum (a visceral variation). At 1500 ppm, mouse fetuses also exhibited an increased incidence of cleft palate and the dam body weights were reduced. Therefore, the NOAEL for the mouse maternal and developmental toxicity was 250 ppm under the conditions of this study. Copyright © 2003 John Wiley & Sons, Ltd. [source] An Evaluation of Qualitative Indexes of Physical Habitat Applied to Agricultural Streams in Ten U.S. States,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2010Robert M. Hughes Hughes, Robert M., Alan T. Herlihy, and Philip R. Kaufmann, 2010. An Evaluation of Qualitative Indexes of Physical Habitat Applied to Agricultural Streams in Ten U.S. States. Journal of the American Water Resources Association (JAWRA) 46(4): 792-806. DOI: 10.1111/j.1752-1688.2010.00455.x Abstract:, Assessment of stream physical habitat condition is important for evaluating stream quality globally. However, the diversity of metrics and methods for assessing physical habitat condition confounds comparisons among practitioners. We surveyed 51 previously sampled stream sites (0.0-6.3 m wide) located in regions of row-crop agriculture in Oregon, California, North Dakota, South Dakota, Nebraska, Iowa, Minnesota, Pennsylvania, Maryland, and West Virginia to evaluate the comparability of four indexes of physical habitat condition relative to each other. We also compared the indexes to previously calculated indexes of fish and macroinvertebrate condition. The physical habitat indexes included the Stream Visual Assessment Protocol Version 2 of the Natural Resources Conservation Service, the qualitative habitat evaluation index of the Ohio Environmental Protection Agency, the rapid bioassessment protocol of the United States Environmental Protection Agency (USEPA), and a qualitative physical habitat index based on USEPA quantitative physical habitat measurements. All four indexes were highly correlated with each other, but low-to-moderately correlated with biotic index scores for fish and macroinvertebrate assemblages. Moderately high correlations occurred between some macroinvertebrate biotic index scores and quantitative metrics. We conclude that additional research is needed to increase the predictive and diagnostic capabilities of qualitative physical habitat indexes. [source] Bound and unextractable pesticidal plant residues: chemical characterization and consumer exposurePEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2004Heinrich Sandermann Jr Abstract Plants are well known to incorporate pesticides into bound and unextractable residues that resist solubilization in common laboratory solvents and are therefore not accessible to standard residue analysis. A characterization of such residues has been proposed for incorporation rates above trigger values of 0.05 mg kg,1 parent pesticide equivalents, or percentage values of 10% (United States Environmental Protection Agency, 1995) or 25% (Commission of the European Communities, 1997) of the total radioactive residue. These trigger values are often exceeded. The present review describes the current status of the chemical characterization and animal bioavailability of bound and unextractable residues that may be xenobiotic in nature or result from natural recycling of simple degradation products. The latter case represents a mechanism of detoxification. Bound residues have been shown to be covalent or non-covalent in nature. With regard to the plant matrix molecules involved, incorporation into proteins, lignins, pectins, hemicelluloses and cutins has been demonstrated, and four covalent linkage types are known. Animal feeding experiments have revealed cases of low as well as high bioavailability. Many of the studies are limited by experimental uncertainties and by results only being reported as relative percentage values rather than absolute exposure. A preliminary value of absolute exposure from bound and unextractable residues is derived here for the first time from eight case studies. The mean exposure (ca 1.5 mg kg,1 pesticidal equivalents) exceeds some of the existing maximum residue levels (MRLs) of residual free pesticides that are typically in the range of 0.05,1 mg kg,1. A mathematical framework for the correction of current maximum residue levels is presented for cases of highly bioavailable bound residues. As bound pesticidal residues in food plants could represent a source of significant consumer exposure, an experimental test scheme is proposed here. It consists of basic chemical characterization, model digestibility tests and, in exceptional cases, animal bioavailability and additional toxicological studies. Copyright © 2004 Society of Chemical Industry [source] Planning-level source decay models to evaluate impact of source depletion on remediation time frameREMEDIATION, Issue 4 2005Charles J. Newell A recent United States Environmental Protection Agency (US EPA) Expert Panel on Dense Nonaqueous Phase Liquid (DNAPL) Source Remediation concluded that the decision-making process for implementing source depletion is hampered by quantitative uncertainties and that few useful predictive tools are currently available for evaluating the benefits. This article provides a new planning-level approach to aid the process. Four simple mass balance models were used to provide estimates of the reduction in the remediation time frame (RTF) for a given amount of source depletion: step function, linear decay, first-order decay, and compound. As a shared framework for assessment, all models use the time required to remediate groundwater concentrations below a particular threshold (e.g., goal concentration or mass discharge rate) as a metric. This value is of interest in terms of providing (1) absolute RTF estimates in years as a function of current mass discharge rate, current source mass, the remediation goal, and the source- reduction factor, and (2) relative RTF estimates as a fraction of the remediation time frame for monitored natural attenuation (MNA). Because the latter is a function of the remediation goal and the remaining fraction (RF) of mass following remediation, the relative RTF can be a valuable aid in the decision to proceed with source depletion or to use a long-term containment or MNA approach. Design curves and examples illustrate the nonlinear relationship between the fraction of mass remaining following source depletion and the reduction in the RTF in the three decay-based models. For an example case where 70 percent of the mass was removed by source depletion and the remediation goal (Cg/C0) was input as 0.01, the improvement in the RTF (relative to MNA) ranged from a 70 percent reduction (step function model) to a 21 percent reduction (compound model). Because empirical and process knowledge support the appropriateness of decay-based models, the efficiency of source depletion in reducing the RTF is likely to be low at most sites (i.e., the percentage reduction in RTF will be much lower than the percentage of the mass that is removed by a source-depletion project). Overall, the anticipated use of this planning model is in guiding the decision-making process by quantifying the relative relationship between RTF and source depletion using commonly available site data. © 2005 Wiley Periodicals, Inc. [source] Using the Triad Approach to expedite the acquisition of an Abbott district school siteREMEDIATION, Issue 2 2004Fred Ellerbusch The Triad Approach was field-tested to determine if characterization objectives could be met for a brownfields property that had been identified as a future elementary school site. The new school is in response to a New Jersey Supreme Court ruling (the Abbott decision) that directed the state of New Jersey to fund school construction in poorer districts to expand physical facilities to relieve overcrowding. The Triad Approach is promoted by the United States Environmental Protection Agency as a process that has the potential to improve the timeliness and efficiency of site characterization, and the New Jersey Department of Environmental Protection (NJDEP) recently issued a policy statement supporting its potential. Aggressive school construction deadlines are contingent on property acquisitions that are relatively faster than the traditional investigatory process. In addition, given the future sensitive population, the investigations must be thorough. This case study is among the first studies to document the use of the Triad Approach for a future school site. The Triad Approach was used to define site conditions for six areas of concern in a two-month time frame (from the start of the planning process to completed investigation). © 2004 Wiley Periodicals, Inc. [source] Treatment technology for remediation of wood preserving sites: OverviewREMEDIATION, Issue 3 2000Edward R. Bates This is the first in a series of five articles describing the applicability, performance, and cost of technologies for the remediation of contaminated soil and water at wood preserving sites. Site-specific treatability studies conducted under the supervision of the United States Environmental Protection Agency (US EPA), National Risk Management Research Laboratory (NRMRL), from 1995 through 1997 constitute much of the basis for the evaluations presented, although data from other treatability studies, literature sources, and actual site remediations have also been included to provide a more comprehensive evaluation of remediation technologies. This article provides an overview of the wood preserving sites studied, including contaminant levels, and a summary of the performance of the technologies evaluated. The subsequent articles discuss the performance of each technology in more detail. Three articles discuss technologies for the treatment of soils, including solidification/stabilization, biological treatment, solvent extraction and soil washing. One article discusses technologies for the treatment of liquids, water and nonaqueous phase liquids (NAPLS), including biological treatment, carbon adsorption, photolytic oxidation, and hydraulic containment. The reader should be aware that other technologies including, but not limited to, incineration, thermal desorption, and base catalyzed dehalogenation, also have application for treating contaminants on wood preserving sites. They are not discussed in these five articles since the focus was to evaluate lesser known and hopefully lower cost approaches. However, the reader should include consideration of these other technologies as part of any evaluation or screening of technologies applicable to remediation of wood preserving sites. [source] Interregional comparisons of sediment microbial respiration in streamsFRESHWATER BIOLOGY, Issue 2 2000B. H. Hill Summary 1The rate of microbial respiration on fine-grained stream sediments was measured at 371 first to fourth-order streams in the Central Appalachian region (Maryland, Pennsylvania, Virginia, and West Virginia), Southern Rocky Mountains (Colorado), and California's Central Valley in 1994 and 1995. 2Study streams were randomly selected from the United States Environmental Protection Agency's (USEPA) River Reach File (RF3) using the sample design developed by USEPA's Environmental Monitoring and Assessment Program (EMAP). 3Respiration rate ranged from 0 to 0.621 g O2 g -1 AFDM h -1 in Central Appalachian streams, 0-0.254 g O2 g -1 AFDM h -1 in Rocky Mountain streams, and 0-0.436 g O2 g -1 AFDM h -1 in Central Valley streams. 4Respiration was significantly lower in Southern Rocky Mountain streams and in cold water streams (< 15 °C) of the Central Appalachians. 5Within a defined index period, respiration was not significantly different between years, and was significantly correlated with stream temperature and chemistry (DOC, total N, total P, K, Cl, and alkalinity). 6The uniformity of respiration estimates among the three study regions suggests that sediment microbial respiration may be collected at any number of scales above the site-level for reliable prediction of respiration patterns at larger spatial scales. [source] Evaluation of a vertical frozen soil barrier at oak ridge national laboratoryREMEDIATION, Issue 3 2000Stanley W. Lynn Arctic Foundations, Inc. (AFI), of Anchorage, Alaska, has developed a freeze barrier system designed to hydraulically isolate a contaminant source area. The system can be used for long-term or temporary containment of groundwater until appropriate remediation techniques can be applied. The technology was evaluated under the United States Environmental Protection Agency's (EPA's) Superfund Innovative Technology Evaluation (SITE) program at the United States Department of Energy's (DOE's) Oak Ridge National Laboratory (ORNL) facility in Oak Ridge, Tennessee. For the demonstration, an array of freeze pipes called "thermoprobes" was installed to a depth of 30 feet below ground surface around a former waste collection pond and keyed into bedrock. The system was used to establish an impermeable frozen soil barrier to hydraulically isolate the pond. Demonstration personnel collected independent data to evaluate the technology's performance. A variety of evaluation tools were used,including a groundwater dye tracing investigation, groundwater elevation measurements, and subsurface soil temperature data,to determine the effectiveness of the freeze barrier system in preventing horizontal groundwater flow beyond the limits of the frozen soil barrier. Data collected during the demonstration provided evidence that the frozen soil barrier was effective in hydraulically isolating the pond. [source] | ||||||||||