United States Environmental Protection Agency

About: United States Environmental Protection Agency is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Population & Environmental exposure. The organization has 13873 authors who have published 26902 publications receiving 1191729 citations. The organization is also known as: EPA & Environmental Protection Agency.

AERMOD: A dispersion model for industrial source applications. Part II: Model performance against 17 field study databases

Abstract: The performance of the American Meteorological Society (AMS) and U.S. Environmental Protection Agency (EPA) Regulatory Model (AERMOD) Improvement Committee’s applied air dispersion model against 17 field study databases is described. AERMOD is a steady-state plume model with significant improvements over commonly applied regulatory models. The databases are characterized, and the performance measures are described. Emphasis is placed on statistics that demonstrate the model’s abilities to reproduce the upper end of the concentration distribution. This is most important for applied regulatory modeling. The field measurements are characterized by flat and complex terrain, urban and rural conditions, and elevated and surface releases with and without building wake effects. As is indicated by comparisons of modeled and observed concentration distributions, with few exceptions AERMOD’s performance is superior to that of the other applied models tested. This is the second of two articles, with the firs...

Fate of PAH compounds in two soil types: influence of volatilization, abiotic loss and biological activity.

Abstract: The fate of 14 polycyclic aromatic hydrocarbon (PAH) compounds was evaluated with regard to interphase transfer potential and mechanisms of treatment in soil under unsaturated conditions. Volatilization and abiotic and biotic fate of the PAHs were determined using two soils not previously exposed to these compounds. Volatilization accounted for approximately 30 and 20% loss of naphthalene and 1-methylnaphthalene, respectively; for the remaining compounds, volatilization was negligible. Abiotic reactions accounted for approximately 2 to 20% of the reduction in concentration in solvent extracts for two- and three-ring PAH compounds; no statistically significant reduction was observed for PAH compounds containing greater than three aromatic rings. Biotic mechanisms were quantified as first-order rate constants corrected for volatilization and abiotic mechanisms. Half-life values increased from approximately 2 to 60 to more than 300 d for two-, three- and four- and five-ring PAH compounds, respectively. In general, biological degradation rates were not significantly different between the two soils. Information concerning interphase transfer potential and mechanisms of treatment provides the basis for a rational approach to remediation of soil contaminated with PAH compounds.

Aspects of basic reproductive biology and endocrinology in the fathead minnow (Pimephales promelas).

Abstract: The fathead minnow (Pimephales promelas) has been proposed as a model species for assessing the adverse effects of endocrine-disrupting chemicals (EDCs) on reproduction and development. The purpose of these studies was to develop baseline reproductive biology and endocrinology data for this species to support interpretation of tests with potential EDCs. Pairs of reproductively-active fathead minnows (n=70) were evaluated with respect to reproductive cyclicity in terms of spawning interval and fecundity. The mode and mean (+/-SE) spawning intervals for the fish in this study were 3.0 and 3.7+/-0.1 days, respectively. The mean number of eggs produced per spawn was 85+/-2.8. Animals were sacrificed at periodic intervals during the established spawning cycle and measurements made of gonadal condition (gonadosomatic index [GSI], histopathology) and plasma concentrations of vitellogenin and sex steroids (beta-estradiol, testosterone, 11-ketotestosterone). The GSI in females varied significantly as a function of spawning interval, with the largest values occurring day 2 post-spawn, just prior to the interval of maximum spawning activity. Plasma beta-estradiol concentrations in females also varied significantly relative to peak values in the GSI and spawning activity. Vitellogenin concentrations in the female, and male GSI and steroid concentrations did not vary significantly relative to position in the spawning cycle. Concentrations of beta-estradiol in females and 11-ketotestosterone in males were positively correlated with testosterone concentrations.