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.

In situ stabilization of soil lead using phosphorus.

Abstract: In situ stabilization of Pb-contaminated soils can be accomplished by adding phosphorus. The standard remediation procedure of soil removal and replacement currently used in residential areas is costly and disruptive. This study was carried out to evaluate the influence of P and other soil amendments on five metal-contaminated soils and mine wastes. Seven treatments were used: unamended control; 2,500 mg of P/kg as triple superphosphate (TSP), phosphate rock (PR), acetic acid followed by TSP, and phosphoric acid (PA); and 5,000 mg of P/kg as TSP or PR. A significant reduction in bioavailable Pb, as determined by the physiologically based extraction test (PBET), compared with the control upon addition of P was observed in all materials tested. Increasing the amount of P added from 2,500 to 5,000 mg/kg also resulted in a significantly greater reduction in bioavailable Pb. Phosphate rock was equally or more effective than TSP or PA in reducing bioavailable Pb in four out of five soils tested. Preacidification produced significantly lower bioavailable Pb compared with the same amount of P from TSP or PR in only one material. Reductions in Pb bioavailability as measured by PBET were evident 3 d after treatment, and it may indicate that the reactions between soil Pb and P occurred in situ or during the PBET. No further reductions were noted over 365 d. X-ray diffraction data suggested the formation of pyromorphite-like minerals induced by P additions. This study suggests that P addition reduced bioavailable Pb by PBET and has potential for in situ remediation of Pb-contaminated soils.

Expanded Target-Chemical Analysis Reveals Extensive Mixed-Organic-Contaminant Exposure in U.S. Streams

Abstract: Surface water from 38 streams nationwide was assessed using 14 target-organic methods (719 compounds). Designed-bioactive anthropogenic contaminants (biocides, pharmaceuticals) comprised 57% of 406 organics detected at least once. The 10 most-frequently detected anthropogenic-organics included eight pesticides (desulfinylfipronil, AMPA, chlorpyrifos, dieldrin, metolachlor, atrazine, CIAT, glyphosate) and two pharmaceuticals (caffeine, metformin) with detection frequencies ranging 66–84% of all sites. Detected contaminant concentrations varied from less than 1 ng L–1 to greater than 10 μg L–1, with 77 and 278 having median detected concentrations greater than 100 ng L–1 and 10 ng L–1, respectively. Cumulative detections and concentrations ranged 4–161 compounds (median 70) and 8.5–102 847 ng L–1, respectively, and correlated significantly with wastewater discharge, watershed development, and toxic release inventory metrics. Log10 concentrations of widely monitored HHCB, triclosan, and carbamazepine explain...

Improved method for estimating water solubility from octanol/water partition coefficient

Abstract: Water solubility is a critical property in risk assessments for chemicals, but measured values are often unavailable. The most practical approach to estimating solubility for diverse and complex structures involves regression against the logarithm of the octanol/water partition coefficient (log Kow). However, currently used equations were developed from relatively small training sets (200–300 compounds). Our objective was to upgrade log Kov-based methods by examining a much larger and diverse training set and, if possible, to improve estimation accuracy further by incorporating a series of simple correction factors. We also evaluated the contributions of melting temperature (Tm) and molecular weight (MW). Measured values of water solubility, log Kow and Tm (solids only) were available for all compounds in the training set (n = 1,450). The best equation for this dataset included log Kow, Tm, MW, and 12 correction factors as independent variables, with r2 = 0.970, SD = 0.409, ME = 0.313. Statistics for an independent validation set of 817 compounds were consistent with these results: r2 = 0.902, SD = 0.615, ME = 0.480. We found that Tm contributed significantly to estimation accuracy for solids; addition of MW also increased accuracy; measured values of log Kow and Tm produced more accurate solubility estimates than did estimated values; and the new method outperformed other widely used general-purpose equations based on log Kow.