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2007-5-3 EST最新文章和摘要
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Sensitive Detection of Anaerobic Monochlorobenzene Degradation Using Stable Isotope Tracers Ivonne Nijenhuis,* Nicole Stelzer, Matthias Kästner, and Hans-H. Richnow Departments of Isotope Biogeochemistry (ISOBIO) and Bioremediation (BIOREM), UFZ Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany Received for review September 13, 2006 Revised manuscript received February 13, 2007 Accepted March 28, 2007 Abstract: Microbial degradation of monochlorobenzene (MCB) under anaerobic conditions was investigated using a stable isotope tracer under in and ex situ conditions. In situ microcosms were incubated directly in an anoxic aquifer and carbon derived from [13C6]-MCB was found to be incorporated into the microbial biomass. In laboratory microcosms, amended with [13C6]-MCB, anaerobic mineralization of MCB was indicated by the production of 13CO2. Further, recovery of the 13C-label in the fatty acids confirmed the assimilation of MCB-derived carbon into microbial biomass. The described approach may be applied to various other organic groundwater contaminants of concern using carbon (13C) as well as other stable isotope tracers, such as nitrogen (15N), allowing direct and sensitive detection of biodegradation. -------------------------------------------------------------------------------- Effects of Relative Humidity on Chloroacetanilide and Dinitroaniline Herbicide Desorption from Agricultural PM2.5 on Quartz Fiber Filters Wenli Yang and Britt A. Holmén* Environmental Engineering Program, University of Connecticut, Storrs, Connecticut 06269-2037 Received for review November 10, 2006 Revised manuscript received March 9, 2007 Accepted March 23, 2007 Abstract: This study quantified the release of seven relatively polar preemergence herbicides to the gas phase from soil-generated PM2.5-loaded quartz fiber filters (QFFs) and bare QFF as a function of relative humidity (RH). A 48-hour desorption fraction, F48, was defined to evaluate the relative desorption behavior of herbicides from two families, chloroacetanilide (alachlor, butachlor, metolachlor, and propachlor) and dinitroaniline (pendimethalin, prodiamine, and trifluralin) using temperature- (8 C) and humidity- (10-64% RH) controlled air at a flow rate of 4 L/min. With increasing RH, an increase in F48 by a factor of 2-8 was observed for all herbicides, except metolachlor and butachlor, which showed significantly strong sorption to both sorbents. The conjugate carbonyl oxygen and amide nitrogen in the chloroacetanilide structure enables stronger specific interactions with the sorbents, leading to lower desorption compared to the dinitroaniline herbicides. Desorption of chloroacetanilides decreased in the order propachlor > alachlor > metolachlor ~ butachlor, and desorption of dinitroanilines decreased in the order trifluralin > pendimethalin > prodiamine. These orders are consistent with the different substituents in the herbicide molecules for each family and their relative tendencies to coordinate with surface moieties as indicated by electron-donating capacity. Henry's law constant and Abraham's H-acceptor parameter were found to be useful empirical parameters for describing the F48 desorption behavior for all seven herbicides. -------------------------------------------------------------------------------- Polychlorinated Biphenyls in Chinese Surface Soils Nanqi Ren, Mingxue Que, Yi-Fan Li,* Yu Liu, Xinnan Wan, Diandou Xu,# Ed Sverko,$ and Jianmin Ma International Joint Research Center-For Persistent Toxic Substances (IJRC-PTS), Harbin Institute of Technology, China, IJRC-PTS, Harbin Engineering University, China, Science and Technology Branch, Environment Canada, Toronto, Canada, IJRC-PTS, Dalian Maritime University, China, IJRC-PTS, Chengdu University of Technology, China, IJRC-PTS, Institute of High Energy Physics, Chinese Academy of Sciences, China, and IJRC-PTS, McMaster University, Canada Received for review December 18, 2006 Revised manuscript received March 15, 2007 Accepted March 31, 2007 Abstract: Polychlorinated biphenyl (PCB) concentrations in surface soil samples (0-20 cm) from 52 sites (4 background, 39 rural, and 9 urban) across China in 2005 are presented. The average concentration of total PCBs among all the sites was 515 pg/g dry weight (dw), approximately one-tenth of that in global background soil in 1998. Differences of less than 1 order of magnitude were found between all background and rural sites, indicating a generally uniform distribution of PCBs in Chinese background/rural surface soil. While the major PCB homologue group in global background soil is hexa-PCB followed by penta-PCB, the major PCB homologue group in Chinese background/rural soil is tri-PCB followed by di-PCB, indicating a rather fresh signature in comparison to the much weathered PCBs in global surface soil. The correlation between PCBs and also each PCB homologue group per soil organic carbon (SOC) content in background/rural soil with longitude from 80 to 122 East was studied. The results indicated the strong influence of PCBs concentrations in Chinese background/rural soil by proximity to source region and SOC content, and also provided evidence for urban fractionation effect of PCBs in soil in the city of Shanghai and the longitudinal fractionation of PCBs in Chinese background/rural soil from east to west. This work is the first comprehensive and spatial study of its kind for PCBs in Chinese surface soil on a national scale, and the data presented in this study can provide baseline information for establishing a long-term PCBs monitoring program in China. -------------------------------------------------------------------------------- A Terrestrial Food-Chain Bioaccumulation Model for POPs James M. Armitage and Frank A. P. C. Gobas* School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 Received for review January 9, 2007 Revised manuscript received March 28, 2007 Accepted April 2, 2007 Abstract: Mechanistic bioaccumulation models for fish and piscivorous food-webs are widely used to assess the environmental hazard and risk of commercial chemicals, develop water quality criteria and remediation objectives, and conduct exposure assessment of pesticides in aquatic systems. Similar models for mammals and terrestrial food-webs are largely absent. As a result, the hazards and risks of bioaccumulative substances in mammals, birds, and humans remain unrecognized by regulators, and current globally used criteria for identifying bioaccumulative substances only apply to water-breathing organisms and are inadequate for protecting air-breathing organisms including mammals, birds, and human beings. In this paper, we develop and test a modeling framework that can be used to estimate the biomagnification potential and the organism-soil bioaccumulation factor of organic commercial chemicals in terrestrial food-chains. We test the model for the soil-earthworm-shrew food-chain and apply the model to illustrate that (i) chemicals with an octanol-air partition coefficient (KOA) < 105.25 do not biomagnify even if the KOW is high and optimal for biomagnification in fish; (ii) chemicals with a KOA 105.25 and a KOW between 101.75 and 1012 have a biomagnification potential unless they are metabolized at a sufficiently rapid rate (e.g., in excess of 0.3 d-1 or a half-life time of 2.5 d for shrews). -------------------------------------------------------------------------------- 1,1,2,2-Tetrachloroethane Reactions with OH-, Cr(II), Granular Iron, and a Copper-Iron Bimetal: Insights from Product Formation and Associated Carbon Isotope Fractionation Martin Elsner,* David M. Cwiertny, A. Lynn Roberts, and Barbara Sherwood Lollar Stable Isotope Laboratory, University of Toronto, 22 Russell Street, Toronto, Ontario M5S 3B1, Canada, and Department of Geography and Environmental Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore Maryland 21218 Received for review December 21, 2006 Revised manuscript received February 28, 2007 Accepted March 1, 2007 Abstract: Despite widespread implementation of zero-valent iron remediation schemes, the manner and order of chemical bond cleavage in iron-mediated organohalide transformations remains imperfectly understood. We present insights from carbon isotope fractionation for the dehalogenation of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) and 1,1,1-trichloroethane (1,1,1-TCA) by various reactants. Elimination of HCl by OH- gave isotope fractionation in 1,1,2,2-TeCA of = -25.6”, KIEC = 1.02 to 1.03 per carbon center, consistent with a concerted (E2) mechanism. In contrast, 1,1,1-TCA reduction by Cr(II), Fe(0), and Cu-plated iron (Cu/Fe) resulted in = -13.6” to -15.8” indicating the initial involvement of a single C-Cl bond (KIEC 1.03). 1,1,2,2-TeCA reduction by Cr(II), Fe(0), and Cu/Fe yielded = -18.7”, -19.3”, and -17.0”, respectively. In the two latter cases, depletion of the minor product TCE by 26” indicated its formation via nonreductive dehydrohalogenation. The major 1,1,2,2-TeCA reduction products, cis- and trans-DCE, differed by 2.3” ± 1.0” in Cr(II) systems, but were equivalent in Fe(0) and Cu/Fe systems. In contrast, the ratio of cis-DCE to trans-DCE concentration was 2.5 for reduction with Cr(II) and Fe(0), but ~3.8 with Cu/Fe. Complementary isotope and concentration data therefore suggest differences in the transition state geometry and/or reaction intermediates in each reductant system. -------------------------------------------------------------------------------- |
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