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2007-5-1/2 EST最新文章和摘要
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The Impact of Aerosol Composition on the Particle to Gas Partitioning of Reactive Mercury Andrew P. Rutter and James J. Schauer* Environmental Chemistry and Technology Program, 660 North Park Street, University of Wisconsin-Madison, Madison, Wisconsin 53706 Received for review October 11, 2006 Revised manuscript received February 15, 2007 Accepted March 22, 2007 Abstract: A laboratory system was developed to study the gas-particle partitioning of reactive mercury (RM) as a function of aerosol composition in synthetic atmospheric particulate matter. The collection of RM was achieved by filter- and sorbent-based methods. Analyses of the RM collected on the filters and sorbents were performed using thermal extraction combined with cold vapor atomic fluorescence spectroscopy (CVAFS), allowing direct measurement of the RM load on the substrates. Laboratory measurements of the gas-particle partitioning coefficients of RM to atmospheric aerosol particles revealed a strong dependence on aerosol composition, with partitioning coefficients that varied by orders of magnitude depending on the composition of the particles. Particles of sodium nitrate and the chlorides of potassium and sodium had high partitioning coefficients, shifting the RM partitioning toward the particle phase, while ammonium sulfate, levoglucosan, and adipic acid caused the RM to partition toward the gas phase and, therefore, had partitioning coefficients that were lower by orders of magnitude. -------------------------------------------------------------------------------- Perchlorate Behavior in a Municipal Lake Following Fireworks Displays Richard T. Wilkin,* Dennis D. Fine, and Nicole G. Burnett Office of Research and Development, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 919 Kerr Research Drive, Ada, Oklahoma 74820, Shaw Environmental and Infrastructure, P.O. Box 1198, Ada, Oklahoma 74821-1198, and College of Medicine, University of Oklahoma, 900 NE 10th Street, Oklahoma City, Oklahoma 73104 Received for review January 10, 2007 Revised manuscript received March 14, 2007 Accepted March 15, 2007 Abstract: Perchlorate salts of potassium and ammonium are the primary oxidants in pyrotechnic mixtures, yet insufficient information is available regarding the relationship between fireworks displays and the environmental occurrence of perchlorate. Here we document changes in perchlorate concentrations in surface water adjacent to a site of fireworks displays from 2004 to 2006. Preceding fireworks displays, perchlorate concentrations in surface water ranged from 0.005 to 0.081 g/L, with a mean value of 0.043 g/L. Within 14 h after the fireworks, perchlorate concentrations spiked to values ranging from 24 to 1028× the mean baseline value. A maximum perchlorate concentration of 44.2 g/L was determined following the July 4th event in 2006. After the fireworks displays, perchlorate concentrations decreased toward the background level within 20 to 80 days, with the rate of attenuation correlating to surface water temperature. Adsorption tests indicate that sediments underlying the water column have limited (<100 nmol/g) capacity to remove perchlorate via chemical adsorption. Microcosms showed comparatively rapid intrinsic perchlorate degradation in the absence of nitrate consistent with the observed disappearance of perchlorate from the study site. This suggests that at sites with appropriate biogeochemical conditions, natural attenuation may be an important factor affecting the fate of perchlorate following fireworks displays. -------------------------------------------------------------------------------- Structure of the Hydrated (104) Surface of Rhodochrosite (MnCO3) Young-Shin Jun, Sanjit K. Ghose, Thomas P. Trainor, Peter J. Eng,# and Scot T. Martin* School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, Department of Earth and Planetary Sciences, University of California, Berkeley, California 94720, Earth Science Division, Geochemistry Department, Lawrence Berkeley National Laboratory, Berkeley, California 94720, Consortium for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, Alaska 99775, and James Franck Institute, Department of Physics, University of Chicago, Chicago, Illinois 60637 Received for review September 12, 2006 Revised manuscript received March 14, 2007 Accepted March 19, 2007 Abstract: The three-dimensional structure of the hydrated (104) surface of MnCO3 at 90% relative humidity and 295 K is determined from measurements of X-ray scattering along ten crystal-truncation rods (CTRs). The scattering data provide both vertical and lateral information about the interfacial structure. The model that best fits the scattering data is a surface having a first layer of manganese carbonate and an overlayer of oxygen (as water). Within the measurement uncertainty, the overlayer of oxygen (Ow) and the first-layer of manganese (Mn1) have equal occupancies of 0.84. The Mn1-Ow distance between these layers is 2.59 ± 0.04 Å. The overlayer O atoms are displaced laterally by 0.157 Å in the x- and 0.626 Å in the y-direction relative to the first-layer Mn atoms. The first-layer carbonate groups tilt by -4.2 ± 2.1 in phi (toward the surface plane) and -2.6 ± 1.2 in chi (an axis perpendicular to phi). The second-layer carbonate groups do not tilt, at least within measurement uncertainty. The spacing between Mn atom layers remains unchanged within measurement error whereas the spacing between layers of C atoms in carbonate contracts for the top three layers. Knowledge of the detailed atomic structure of the hydrated (104) surface of MnCO3 provides a structural baseline for the interpretation of chemical reactivity. -------------------------------------------------------------------------------- Spatial and Temporal Trends of Chiral Organochlorine Signatures in Great Lakes Air Using Passive Air Samplers T. Gouin, L. Jantunen, T. Harner,* P. Blanchard, and T. Bidleman University of Toronto at Scarborough, Department of Physical and Environmental Sciences, 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada, Centre for Atmospheric Research Experiments, Science and Technology Branch, Environment Canada, 6248 Eighth Line, Egbert, Ontario L0L 1N0, Canada, and Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, ON, M3H 5T4, Canada Received for review December 19, 2006 Revised manuscript received March 20, 2007 Accepted March 22, 2007 Abstract: Passive air samples (PAS) were collected and analyzed to assess the spatial and temporal trends of chiral organochlorine signatures in the Laurentian Great Lakes. Samples were collected from 15 sites and analyzed for the concentrations and enantiomer signature of chlordanes and -hexachlorocyclohexane (-HCH). Levels of the chlordanes were typically 4 times higher in urban areas than what were observed at rural and remote locations, exhibiting strong urban-rural gradients. Near racemic residues were seen for the chlordane enantiomers in samples collected from sites located in Toronto and Chicago, which can be attributed to continued emissions of historical use of the technical chlordane mixture, while the chiral signature observed at sites located in rural and remote locations was indicative of an aged source. Knowledge of the spatial and temporal distribution of the enantiomer signatures of chlordane and -HCH in air is useful for distinguishing sources of these compounds to ambient air. Results suggest that potential sources, such as those associated with Toronto and Chicago, have limited influence over the levels at rural and remote sites within the Great Lakes. Sources that are relatively close to sample sites, however, have a strong influence on levels observed at those sites. For instance, results indicate that Lake Superior continues to act as a source of -HCH to sites located on its shores. Generally, it appears that during the warmer months, local enhanced surface-air exchange influences air concentrations and that during the cooler periods of the year, levels in the atmosphere are more strongly influenced by advective transport from source regions. -------------------------------------------------------------------------------- High-Throughput Determination of Biochemical Oxygen Demand (BOD) by a Microplate-Based Biosensor Hei-Leung Pang, Nga-Yan Kwok, Pak-Ho Chan, Chi-Hung Yeung, Waihung Lo, and Kwok-Yin Wong* Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong SAR, China Received for review January 12, 2007 Revised manuscript received March 13, 2007 Accepted March 30, 2007 Abstract: The use of the conventional 5-day biochemical oxygen demand (BOD5) method in BOD determination is greatly hampered by its time-consuming sampling procedure and its technical difficulty in the handling of a large pool of wastewater samples. Thus, it is highly desirable to develop a fast and high-throughput biosensor for BOD measurements. This paper describes the construction of a microplate-based biosensor consisting of an organically modified silica (ORMOSIL) oxygen sensing film for high-throughput determination of BOD in wastewater. The ORMOSIL oxygen sensing film was prepared by reacting tetramethoxysilane with dimethyldimethoxysilane in the presence of the oxygen-sensitive dye tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) chloride. The silica composite formed a homogeneous, crack-free oxygen sensing film on polystyrene microtiter plates with high stability, and the embedded ruthenium dye interacted with the dissolved oxygen in wastewater according to the Stern-Volmer relation. The bacterium Stenotrophomonas maltophilia was loaded into the ORMOSIL/PVA composite (deposited on the top of the oxygen sensing film) and used to metabolize the organic compounds in wastewater. This BOD biosensor was found to be able to determine the BOD values of wastewater samples within 20 min by monitoring the dissolved oxygen concentrations. Moreover, the BOD values determined by the BOD biosensor were in good agreement with those obtained by the conventional BOD5 method. -------------------------------------------------------------------------------- |
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