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2007-5-9 EST最新文章和摘要
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Carbon in Black Crusts from the Tower of London Alessandra Bonazza, Peter Brimblecombe,* Carlota M. Grossi, and Cristina Sabbioni Institute ISAC-CNR, Bologna 40129, Italy, and School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK Received for review October 9, 2006 Revised manuscript received March 7, 2007 Accepted April 2, 2007 Abstract: This paper investigates the origin, fluxes, and transformation of carbon compounds within black crusts on the stone walls of the Tower of London. The crusts were analyzed for elemental and organic carbon, including the water soluble fraction. Elemental carbon and low solubility compounds such as oxalates appeared to be conserved because of long residence times. Conversely, more soluble ions, like chloride and formate would be removed from the layers relatively quickly by rainfall. At higher organic carbon concentrations acetic acid may be produced within the crusts from biological transformations. Currently, traffic sources contribute to increasingly organic rich crusts. The deposition of elemental carbon to buildings darkens surfaces and has important aesthetic implications. The increased organic content may have further aesthetic consequence by changing the color of buildings to warmer tones, particularly browns and yellows. Management of historic buildings requires us to recognize the shift away from simple gypsum crusts to those richer in organic materials. -------------------------------------------------------------------------------- Selective Oxidation of Key Functional Groups in Cyanotoxins during Drinking Water Ozonation Gretchen D. Onstad, Sabine Strauch, Jussi Meriluoto, Geoffrey A. Codd, and Urs von Gunten* Swiss Federal Institute of Aquatic Science and Technology, Eawag, Ueberlandstrasse 133, P.O. Box 611, CH-8600 Duebendorf, Switzerland, Department of Biochemistry and Pharmacy, Åbo Akademi University, BioCity, Tykistökatu 6A, 20520 Turku, Finland, Division of Environmental and Applied Biology, College of Life Sciences, University of Dundee, Dundee DD1 4HN, Scotland, U.K., and Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland Received for review October 21, 2006 Revised manuscript received February 9, 2007 Accepted March 23, 2007 Abstract: Chemical kinetics were determined for the reactions of ozone and hydroxyl radicals with the three cyanotoxins microcystin-LR (MC-LR), cylindrospermopsin (CYN) and anatoxin-a (ANTX). The second-order rate constants (kO3) at pH 8 were 4.1 ± 0.1 × 105 M-1 s-1 for MC-LR, ~3.4 × 105 M-1 s-1 for CYN, and ~6.4 × 104 M-1 s-1 for ANTX. The reaction of ozone with MC-LR exhibits a kO3 similar to that of the conjugated diene in sorbic acid (9.6 ± 0.3 × 105 M-1 s-1) at pH 8. The pH dependence and value of kO3 for CYN at pH > 8 (~2.5 ± 0.1 × 106 M-1 s-1) are similar to deprotonated amines of 6-methyluracil. The kO3 of ANTX at pH > 9 (~8.7 ± 2.2 × 105 M-1 s-1) agrees with that of neutral diethylamine, and the value at pH < 8 (2.8 ± 0.2 × 104 M-1 s-1) corresponds to an olefin. Second-order rate constants for reaction with OH radicals (OH), kOH for cyanotoxins were measured at pH 7 to be 1.1 ± 0.01 × 1010 M-1 s-1 for MC-LR, 5.5 ± 0.01 × 109 M-1 s-1 for CYN, and 3.0 ± 0.02 × 109 M-1 s-1 for ANTX. Natural waters from Switzerland and Finland were examined for the influence of variations of dissolved organic matter, SUVA254, and alkalinity on cyanotoxin oxidation. For a Swiss water (1.6 mg/L DOC), 0.2, 0.4, and 0.8 mg/L ozone doses were required for 95% oxidation of MC-LR, CYN, and ANTX, respectively. For the Finnish water (13.1 mg/L DOC), >2 mg/L ozone dose was required for each toxin. The contribution of hydroxyl radicals to toxin oxidation during ozonation of natural water was greatest for ANTX > CYN > MC-LR. Overall, the order of reactivity of cyanotoxins during ozonation of natural waters corresponds to the relative magnitudes of the second-order rate constants for their reaction with ozone and OH. Ozone primarily attacks the structural moieties responsible for the toxic effects of MC-LR, CYN, and ANTX, suggesting that ozone selectively detoxifies these cyanotoxins. -------------------------------------------------------------------------------- High Photocatalytic Capability of Self-Assembled Nanoporous WO3 with Preferential Orientation of (002) Planes Yafeng Guo, Xie Quan,* Na Lu, Huimin Zhao, and Shuo Chen Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental and Biological Science and Technology, Dalian University of Technology, Dalian, China, 116024 Received for review October 23, 2006 Revised manuscript received January 16, 2007 Accepted April 4, 2007 Abstract: Self-assembled nanoporous tungsten oxide (WO3) with preferential orientation (002) planes was successfully synthesized on the tungsten sheet by anodization in a 0.2 wt % NaF and 0.3% (V/V) HF mixture solution in a 1:1 ratio. The pores, of a highly ordered self-assembled structure, had an average size of approximately 70 nm. X-ray diffraction identified a monoclinic WO3 structure and fine preferential orientation of (002) planes. A maximum photoconversion efficiency of 17.2% was obtained for the self-assembled nanoporous WO3 under high-pressure mercury lamp illumination. The photocatalytic (PC) degradation of pentachlorophenol (PCP) in aqueous solution using the self-assembled nanoporous WO3 photocatalyst, performed under both high-pressure mercury lamp and Xe lamp illumination, showed more excellent PC capability than WO3 film and TiO2 nanotube arrays. -------------------------------------------------------------------------------- Effect of Chlorination on Microcystis aeruginosa Cell Integrity and Subsequent Microcystin Release and Degradation Robert I. Daly, Lionel Ho,* and Justin D. Brookes CRC for Water Quality and Treatment, Australian Water Quality Centre, SA Water Corporation, PMB 3, Salisbury, SA 5108, Australia, and School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia Received for review February 7, 2007 Revised manuscript received April 2, 2007 Accepted April 3, 2007 Abstract: The proliferation of cyanobacteria in drinking water sources is problematic for water authorities as they can interfere with water treatment processes. Studies have shown that oxidants such as chlorine can enhance the coagulation of cyanobacteria; however, chlorine can potentially lyse cyanobacterial cells, releasing toxic metabolites. Chlorine also has the potential to effectively degrade these toxins. This study evaluated the effect of chlorine on the cell integrity of toxic Microcystis aeruginosa in reservoir water using flow cytometry. In addition, the effect of chlorine on the subsequent release and degradation of microcystin toxins was systematically assessed. Cell lysis occurred at chlorine exposure values between 7 and 29 mg min/L, which is within the range of normal disinfection practices. Intracellular toxin was shown to be released from damaged cells at a rate three times faster than it was degraded by chlorine. The degradation of extracellular microcystin by chlorine was found to be dependent upon the pH, chlorine exposure, and the presence of cyanobacterial cells. -------------------------------------------------------------------------------- |
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