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.

Effects of Enhanced Solar Ultraviolet Radiation on Aquatic Ecosystems

Abstract: The photosynthetic production of organic biomass using solar energy is the almost exclusive source of energy for life on our planet. The amount of carbon in the form of its dioxide incorporated annually into organic molecules exceeds 100 gigatons which can be visualized by the load filling 10 coal trains spanning the distance from the earth to the moon (Hader et al., 1989). However, only about one third of this enormous production is accounted for by terrestrial plants — forests, savannas, crop plants etc. — while the majority is produced by the phytoplankton organisms (primary producers) in aquatic habitats, especially in the world oceans. The marine phytoplankton communities represent by far the largest ecosystem on earth (Schneider, 1989); therefore even a small percentage decrease in the populations would result in enormous losses in the biomass productivity of these organisms, which could have dramatic effects both for the intricate ecosystem itself and for humans, who depend on this system in many ways (Hader et al., 1989).

Developing a Social Cost of Carbon for US Regulatory Analysis: A Methodology and Interpretation

Abstract: The US government recently developed a range of values representing the monetized global damages associated with an incremental increase in carbon dioxide (CO2) emissions, commonly referred...

DDT, DDD, and DDE Dechlorination by Zero-Valent Iron

Abstract: Traditionally, destruction of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] for environmental remediation required high-energy processes such as incineration. Here, the capability of powdered zero-valent iron to dechlorinate DDT and related compounds at room temperature was investigated. Specifically, DDT, DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane], and DDE [2,2-bis(p-chlorophenyl)-1,1-dichloroethylene] transformation by powdered zero-valent iron in buffered anaerobic aqueous solution was studied at 20 °C, with and without the presence of nonionic surfactant Triton X-114. The iron was successful at dechlorinating DDT, DDD, and DDE. The rates of dechlorination of DDT and DDE were independent of the amount of iron, with or without surfactant. The rates with surfactant present were much higher than without. Initial first-order transformation rates for DDT, DDD, and DDE were determined. For example, the initial first-order rate of DDT dechlorination was 1.7 ± 0.4 and 3.0 ± 0.8 day-1 or, normalized...

Distribution of total mercury and methyl mercury in water, sediment, and fish from south Florida estuaries.

Abstract: Concentrations of total mercury and methyl mercury were determined in sediment and fish collected from estuarine waters of Florida to understand their distribution and partitioning. Total mercury concentrations in sediments ranged from 1 to 219 ng/g dry wt. Methyl mercury accounted for, on average, 0.77% of total mercury in sediment. Methyl mercury concentrations were not correlated with total mercury or organic carbon content in sediments. The concentrations of total mercury in fish muscle were between 0.03 and 2.22 (mean: 0.31) μg/g, wet wt, with methyl mercury contributing 83% of total mercury. Methyl mercury concentrations in fish muscle were directly proportional to total mercury concentrations. The relationship of total and methyl mercury concentrations in fish to those of sediments from corresponding locations was fish-species dependent, in addition to several abiotic factors. Among fish species analyzed, hardhead catfish, gafftopsail catfish, and sand seatrout contained the highest concentrations of mercury. Filtered water samples from canals and creeks that discharge into the Florida Bay showed mercury concentrations of 3–7.4 ng/L, with methyl mercury accounting for <0.03–52% of the total mercury. Consumption of fish containing 0.31 μg mercury/g wet wt, the mean concentration found in this study, at rates greater than 70 g/day, was estimated to be hazardous to human health.