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2007-4-24 EST最新文章和摘要
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Role of Temperature and Enzyme Induction in the Biotransformation of Polychlorinated Biphenyls and Bioformation of Hydroxylated Polychlorinated Biphenyls by Rainbow Trout (Oncorhynchus mykiss) Andrea H. Buckman, Scott B. Brown, Jeff Small, Derek C. G. Muir, Joanne Parrott, Keith R. Solomon, and Aaron T. Fisk* Department of Environmental Biology, University of Guelph, Guelph, ON, Canada N1G 2W1, National Waters Research Institute, Environment Canada, Burlington, ON, Canada L7R 4A6, and Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, Canada N9B 3P4 Received for review October 11, 2006 Revised manuscript received March 16, 2007 Accepted March 21, 2007 Abstract: Hydroxylated PCBs (OH-PCBs) are metabolites of polychlorinated biphenyls (PCBs) that have recently been found in the plasma of Great Lakes fish. Studies have shown that the ability of laboratory-held rainbow trout (Oncorhynchus mykiss) to bioform OH-PCBs from dietary mixtures of PCB congeners is complex and may be attributed to factors such as temperature and/or enzyme induction. Past studies have also suggested that CYP1A- and 2B-like enzymes are the likely mechanism for forming OH-PCBs, but this has not been directly studied in a controlled setting. To address these issues, we exposed rainbow trout (~80 g) to dietary concentrations of a mixture of three Aroclors (1248, 1254, and 1260), at three water temperatures (8, 12, and 16 C), as well as additional PCBs known to induce CYP1A- and CYP2B-like isoforms in mammals. PCB half-lives in trout were inversely related to water temperature, but biotransformation of PCBs was positively related to water temperature. Thirty-one OH-PCBs were observed in trout plasma after 30 days of dietary exposure to the Aroclor mixtures, although approximately 40% of the OH-PCBs concentrations were OH-PCB for which no standards were available. Concentration of OH-PCBs in the trout plasma increased with increasing temperature and with the addition of CYP2B-like inducing congeners but not with the addition of CYP1A-inducing congeners to food. The results of this study provide the first in vivo evidence that rainbow trout are responsive to CYP2B-like induction by PCBs and that this enzyme system can influence PCB concentrations and OH-PCB formation in fish. -------------------------------------------------------------------------------- Predicted Secondary Organic Aerosol Concentrations from the Oxidation of Isoprene in the Eastern United States Timothy E. Lane and Spyros N. Pandis* Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, and Department of Chemical Engineering, University of Patras, Patra, 26500, Greece Received for review June 1, 2006 Revised manuscript received October 16, 2006 Accepted February 27, 2007 Abstract: Isoprene, the most abundant non-methane hydrocarbon emitted into the troposphere, has generally not been considered a major source of SOA due to the relatively high volatility of its oxidation products. In this study, the SOA formed from the oxidation of isoprene is predicted using a three-dimensional chemical transport model, PMCAMx, across the eastern U.S. for July, October, January, and April 2001-2002. The variability of the measured SOA yields in the available smog chamber studies is captured by combining the base case scenario with upper and lower bound estimates of the measurements. For the base case simulation, the predicted annual average isoprene SOA concentration in the southeast is 0.09 g m-3 (bounds 0.04-0.23 g m-3). Isoprene is predicted to produce 70% less SOA across the entire domain for spring and fall than during the summer and negligible amounts of SOA during the winter. During the summer, the average concentrations in the northeast are predicted to be 0.11 g m-3 (bounds 0.04-0.31 g m-3) and in the southeast 0.19 g m-3 (bounds 0.11-0.58 g m-3). PMCAMx predictions are compared to available measurements of some isoprene SOA components in North Carolina and New York State. These modeling results suggest that on an annual basis isoprene oxidation is a small but non-negligible organic aerosol source in the eastern U.S. Its contribution is relatively more important during the summer and in the southeast U.S. -------------------------------------------------------------------------------- |
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