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2007-5-4 EST最新文章和摘要
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Thermodynamic Properties of Malonic, Succinic, and Glutaric Acids: Evaporation Rates and Saturation Vapor Pressures Ismo K. Koponen, Ilona Riipinen, Anca Hienola, Markku Kulmala, and Merete Bilde Department of Chemistry and Physical Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark, and Department of Physical Sciences, University of Helsinki, P.O. Box 64, FI-00014, Helsinki, Finland Received for review May 11, 2006 Revised manuscript received September 28, 2006 Accepted March 28, 2007 Abstract: This work provides thermodynamic data, in particular, liquid-state saturation vapor pressures of three common slightly water soluble secondary organic aerosol components, namely, malonic, succinic, and glutaric acids. A modified tandem differential mobility analyzer system was used to measure evaporation rates of nanometer sized aqueous malonic, succinic, and glutaric acid droplets at relative humidities and temperatures relevant in the lower troposphere. Liquid phase saturation vapor pressures and other thermodynamic properties were derived from the measure ments using a binary condensation model. The obtained expressions for liquid phase saturation vapor pressures compare well with extrapolated literature data. The importance of the choice of method for calculating activity coefficients is discussed. -------------------------------------------------------------------------------- Effects of Fuel Ethanol Content and Volatility on Regulated and Unregulated Exhaust Emissions for the Latest Technology Gasoline Vehicles Thomas D. Durbin,* J. Wayne Miller, Theodore Younglove, Tao Huai, and Kathalena Cocker College of Engineering, Center for Environmental Research and Technology, University of California, Riverside, California 92521, and Statistical Consulting Collaboratory, Department of Statistics, University of California, Riverside, California 92521 Received for review July 26, 2006 Revised manuscript received December 18, 2006 Accepted March 29, 2007 Abstract: Oxygenate content and fuel volatility (distillation) variables are important parameters affecting vehicle exhaust emissions, and data on their effects on the latest technology vehicles are quite limited. For this study, 12 California-certified LEV to SULEV vehicles were tested on a matrix of 12 fuels with varying levels of ethanol concentration (0, 5.7, and 10 vol %), T50 (195, 215, and 235 F), and T90 (295, 330, and 355 F). There were statistically significant interactions between ethanol and T90 for NMHC, ethanol, and T50 for CO and ethanol and T50 for NOx. NMHC emissions increased with increasing ethanol content at the midpoint and high level of T90 but were unaffected at the low T90 level. CO emissions decreased as the ethanol content increased from the low to the midpoint level for all levels of T50, but between the 5.7 and 10% ethanol levels, CO showed only an increase for the high level of T50. NOx emissions increased with ethanol content for some conditions. Non-methane organic gases (NMOG) and toxic emissions were examined for only a subset of fuels with the highest T90 level, with NMOG, acetaldehyde, benzene, and 1-,3-butadiene all found to increase with increasing ethanol content. -------------------------------------------------------------------------------- In Situ Spectroscopic Evidence for Neptunium(V)-Carbonate Inner-Sphere and Outer-Sphere Ternary Surface Complexes on Hematite Surfaces Yuji Arai,* P. B. Moran, B. D. Honeyman, and J. A. Davis Department of Entomology, Soils and Plant Sciences, 270 Poole Agricultural Center, Clemson University, Clemson, South Carolina 29634-0315, Department of Environmental Science & Engineering, Colorado School of Mines, Coolbaugh Hall, Golden, Colorado 80401-1887, and Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, 1500 Illinois Street, Golden, Colorado 80401 Received for review October 14, 2006 Revised manuscript received March 7, 2007 Accepted March 28, 2007 Abstract: Np(V) surface speciation on hematite surfaces at pH 7-9 under pCO2 = 10-3.45 atm was investigated using X-ray absorption spectroscopy (XAS). In situ XAS analyses suggest that bis-carbonato inner-sphere and tris-carbonato outer-sphere ternary surface species coexist at the hematite-water interface at pH 7-8.8, and the fraction of outer-sphere species gradually increases from 27 to 54% with increasing pH from 7 to 8.8. The results suggest that the heretofore unknown Np(V)-carbonato ternary surface species may be important in predicting the fate and transport of Np(V) in the subsurface environment down gradient of high-level nuclear waste respositories. -------------------------------------------------------------------------------- SOA Formation by Biogenic and Carbonyl Compounds: Data Evaluation and Application Barbara Ervens* and Sonia M. Kreidenweis Atmospheric Science Department, Colorado State University, Fort Collins, Colorado 80523 Received for review August 13, 2006 Revised manuscript received November 23, 2006 Accepted March 28, 2007 Abstract: The organic fraction of atmospheric aerosols affects the physical and chemical properties of the particles and their role in the climate system. Current models greatly underpredict secondary organic aerosol (SOA) mass. Based on a compilation of literature studies that address SOA formation, we discuss different parameters that affect the SOA formation efficiency of biogenic compounds (-pinene, isoprene) and aliphatic aldehydes (glyoxal, hexanal, octanal, hexadienal). Applying a simple model, we find that the estimated SOA mass after one week of aerosol processing under typical atmospheric conditions is increased by a few g m-3 (low NOx conditions). Acid-catalyzed reactions can create >50% more SOA mass than processes under neutral conditions; however, other parameters such as the concentration ratio of organics/NOx, relative humidity, and absorbing mass are more significant. The assumption of irreversible SOA formation not limited by equilibrium in the particle phase or by depletion of the precursor leads to unrealistically high SOA masses for some of the assumptions we made (surface vs volume controlled processes). -------------------------------------------------------------------------------- Trichloroethylene Removal from Groundwater in Flow-Through Columns Simulating a Permeable Reactive Barrier Constructed with Plant Mulch Hai Shen and John T. Wilson* Office of Research and Development, U.S. Environmental Protection Agency, Robert S. Kerr Environmental Research Center, 919 Kerr Research Drive, Ada, Oklahoma 74820 Received for review October 31, 2006 Revised manuscript received March 23, 2007 Accepted March 29, 2007 Abstract: Groundwater contaminated with TCE is commonly treated with a permeable reactive barrier (PRB) constructed with zero-valence iron. The cost of iron has driven a search for less costly alternatives, and composted plant mulch has been used as an alternative at several sites. A column study was conducted that simulated conditions in a PRB at Altus Air Force Base, Oklahoma. The reactive matrix was 50% (v/v) shredded tree mulch, 10% cotton gin trash, and 40% sand. The mean residence time of groundwater in the columns was 17 days. The estimated retardation factor for TCE was 12. TCE was supplied at concentrations near 20 M. Over 793 days of operation, concentrations of TCE in the column effluents varied from 0.1% to 2% of the column influents. Concentrations of cis-DCE, vinyl chloride, ethylene, ethane, and acetylene could account for l% of the TCE that was removed; however, up to 56% of 13C added as [1,2-13C] TCE in the column influents was recovered as 13C in carbon dioxide. After 383 and 793 d of operation, approximately one-half of the TCE removal was associated with abiotic reactions with FeS that accumulated in the reactive matrix. -------------------------------------------------------------------------------- |
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Comparison of Cd(II), Cu(II), and Pb(II) Biouptake by Green Algae in the Presence of Humic Acid Cristina Lamelas and Vera. I. Slaveykova* Environmental Biophysical Chemistry, Environmental Science and Technology Institute, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 2, 1015 Lausanne, Switzerland Received for review December 31, 2006 Revised manuscript received March 21, 2007 Accepted March 29, 2007 Abstract: The present study examines the role of humic acid, as a representative of dissolved organic matter, in Cd(II), Cu(II), and Pb(II) speciation and biouptake by green microalgae. Cellular and intracellular metal fractions were compared in the presence of citric and humic acids. The results demonstrated that Cd and Cu uptake in the presence of 10 mg L-1 humic acid was consistent with that predicted from measured free metal concentrations, while Pb biouptake was higher. By comparing Cd, Cu, and Pb cellular concentrations in the absence and presence of humic acid, it was found that the influence of the increased negative algal surface charge, resulting from humic acid adsorption, on cellular metal was negligible. Moreover, the experimental results for all three metals were in good agreement with the ternary complex hypothesis. Given that metal has much higher affinity with algal sites than humic acid adsorbed to algae, the contribution of the ternary complex to metal bioavailability was negligible in the case of Cd (II) and Cu (II). In contrast, the ternary complex contributed to over 90% of total cellular metal for Pb(II), due to the comparable affinity of Pb to algal sites in comparison with humic acid adsorbed to algae. Therefore, the extension of the biotic ligand model by including the formation of the ternary complex between the metal, humic acid, and algal surface would help to avoid underestimation of Pb biouptake in the presence of humic substances by green algae Chlorella kesslerii. -------------------------------------------------------------------------------- Distribution of Organochlorine Pesticides in the Northern South China Sea: Implications for Land Outflow and Air-Sea Exchange Gan Zhang,* Jun Li, Hairong Cheng, Xiangdong Li, Weihai Xu, and Kevin C. Jones State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China, Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, and Lancaster Environmental Centre and Department of Environmental Sciences, Lancaster University, Lancaster LA1 4YQ, UK Received for review January 10, 2007 Revised manuscript received March 16, 2007 Accepted March 22, 2007 Abstract: The South China Sea (SCS) is surrounded by developing countries in Southeast Asia, where persistent organic pollutants (POPs), such as organochlorine pesticides (OCPs), are still used legally or illegally, and are of concern. Yet little is known about the distribution of OCPs in the water and atmosphere over SCS, as well as their air-sea equilibrium status and time trends. In this study, ship-board air samples and surface seawater collected in the northern SCS between September 6 and 22, 2005 were analyzed for selected OCPs. The measured OCP concentra tions in the atmosphere over the northern SCS were influenced by proximity to source regions and air mass origins. The highest atmospheric OCP concentrations were found at sampling sites adjacent to continental South China. OCPs in surface seawater showed significant spatial variations, with the highest concentration observed in a water sample from off Vietnam. The coastal currents were suggested to play a key role in the delivery of waterborne OCPs in the northern SCS. Time trend, land outflow, and air-sea exchange of selected OCPs in the SCS were investigated, by comparison of this dataset with historical data. -------------------------------------------------------------------------------- Contributions of Toluene and -Pinene to SOA Formed in an Irradiated Toluene/-Pinene/NOx/ Air Mixture: Comparison of Results Using 14C Content and SOA Organic Tracer Methods John H. Offenberg,* Charles W. Lewis, Michael Lewandowski, Mohammed Jaoui, Tadeusz E. Kleindienst, and Edward O. Edney National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, 27511, and Alion Science and Technology, Box 12313, Research Triangle Park, North Carolina, 27709 Received for review January 12, 2007 Revised manuscript received March 26, 2007 Accepted March 29, 2007 Abstract: An organic tracer method, recently proposed for estimating individual contributions of toluene and -pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydrocarbon, toluene, and the biogenic monoterpene, -pinene, was irradiated in air in the presence of NOx to form SOA. The contributions of toluene and -pinene to the total SOA concentration, calculated using the organic tracer method, were compared with those obtained with a more direct 14C content method. In the study, SOA to SOC ratios of 2.07 ± 0.08 and 1.41 ± 0.04 were measured for toluene and -pinene SOA, respectively. The individual tracer-based SOA contributions of 156 g m-3 for toluene and 198 g m-3 for -pinene, which together accounted for 82% of the gravimetrically determined total SOA concentration, compared well with the 14C values of 182 and 230 g m-3 measured for the respective SOA precursors. While there are uncertainties associated with the organic tracer method, largely due to the chemical complexity of SOA forming chemical mechanisms, the results of this study suggest the organic tracer method may serve as a useful tool for determining whether a precursor hydrocarbon is a major SOA contributor. -------------------------------------------------------------------------------- Substrate-Enhanced Microbial Fuel Cells for Improved Remote Power Generation from Sediment-Based Systems Farzaneh Rezaei, Tom L. Richard, Rachel A. Brennan, and Bruce E. Logan* Department of Agricultural and Biological Engineering and Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 Received for review February 19, 2007 Revised manuscript received March 27, 2007 Accepted March 28, 2007 Abstract: A sediment microbial fuel cell (MFC) produces electricity through the bacterial oxidation of organic matter contained in the sediment. The power density is limited, however, due in part to the low organic matter content of most marine sediments. To increase power generation from these devices, particulate substrates were added to the anode compartment. Three materials were tested: two commercially available chitin products differing in particle size and biodegradability (Chitin 20 and Chitin 80) and cellulose powder. Maximum power densities using chitin in this substrate-enhanced sediment MFC (SEM) were 76 ± 25 and 84 ± 10 mW/m2 (normalized to cathode projected surface area) for Chitin 20 and Chitin 80, respectively, versus less than 2 mW/m2 for an unamended control. Power generation over a 10 day period averaged 64 ± 27 mW/m2 (Chitin 20) and 76 ± 15 mW/m2 (Chitin 80). With cellulose, a similar maximum power was initially generated (83 ± 3 mW/m2), but power rapidly decreased after only 20 h. Maximum power densities over the next 5 days varied substantially among replicate cellulose-fed reactors, ranging from 29 ± 12 to 62 ± 23 mW/m2. These results suggest a new approach to power generation in remote areas based on the use of particulate substrates. While the longevity of the SEM was relatively short in these studies, it is possible to increase operation times by controlling particle size, mass, and type of material needed to achieve desired power levels that could theoretically be sustained over periods of years or even decades. -------------------------------------------------------------------------------- High-Resolution In Situ Analysis of Nitrate and Phosphate in the Oligotrophic Ocean Lori R. Adornato, Eric A. Kaltenbacher, Danielle R. Greenhow, and Robert H. Byrne* College of Marine Science, University of South Florida, 140 Seventh Avenue South, St. Petersburg, Florida 33701 and SRI International, 140 Seventh Avenue South, COT 100, St. Petersburg, Florida 33701 Received for review January 12, 2007 Revised manuscript received March 29, 2007 Accepted April 2, 2007 Abstract: Accurate, high-resolution profiles of nitrate and phosphate distributions in the open ocean are difficult to obtain using conventional techniques. Concentrations typically range from low nanomolar levels in the stratified euphotic zone to micromolar levels below the nutricline. With multiple pumps, a heating cartridge, a long-path-length cell, and a multiwavelength spectrometer, the reconfigured Spectrophotometric Elemental Analysis System (SEAS) provides the capability to fully ascertain the distributions of nitrate and phosphate in the upper 200 m of the oligotrophic ocean. By utilizing a 15 cm path length and multiple wavelength spectrophotometry, SEAS can detect nitrate concentrations from 2 nM to 20 M and, with a 50 cm path length, can accurately measure phosphate concentrations from 1 nM to 1 M. SEAS is capable of collecting auxiliary data from up to four separate instruments, including a CTD, a fluorometer, a PAR sensor, and a second SEAS instrument. Sampling frequency depends on peripheral instrument selection and ranges from 0.4 to 0.75 Hz. -------------------------------------------------------------------------------- Detoxification of 2,4-dinitrotoluene by Transgenic Tobacco Plants Expressing a Bacterial Flavodoxin Vanesa B Tognetti, Mariela R Monti, Estela M Valle, Nestor Carrillo, and Andrea M Smania* Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, División Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, S2002LRK Rosario, Argentina, Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, X5000HUA Córdoba, Argentina, and Biochemie und Physiologie der Pflanzen, Fakultät für Biologie der Universität Bielefeld, D-33615 Bielefeld, Germany Received for review January 3, 2007 Revised manuscript received March 13, 2007 Accepted March 30, 2007 Abstract: Significant effort has been directed in recent times to the use of plants to extract and detoxify nitroaromatics from polluted industrial facilities. We have explored the possibility of overcoming the phytotoxicity of the highly toxic and recalcitrant nitroderivative 2,4-dinitrotoluene (2,4-DNT) by expressing a cyanobacterial flavodoxin (Fld) in tobacco plants. We demonstrate here that transformants accumulating Fld in plastids display a remarkable increase in the ability to tolerate, take up, and transform 2,4-DNT, as compared to their wild-type siblings. We also show that Fld mediates one-electron reduction of 2,4-DNT in the presence of oxygen and especially in anaerobiosis. Moreover, Fld-loaded chloroplasts are able to convert 2,4-DNT into its aminoderivatives in the presence of light. The results suggest that expression of Fld in landscape plants could facilitate effective cleanup of sites contaminated with this class of pollutants. -------------------------------------------------------------------------------- Strong Sorption of Phenanthrene by Condensed Organic Matter in Soils and Sediments Yong Ran,* Ke Sun, Yu Yang, Baoshan Xing,* and Eddy Zeng State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China, Department of Plant, Soil, and Insect Sciences, University of Massachusetts, Amherst, Massachusetts 01003, and Graduate School, Chinese Academy of Sciences, Beijing 100049, China Received for review December 10, 2006 Revised manuscript received March 19, 2007 Accepted March 30, 2007 Abstract: The nonhydrolyzable carbon (NHC) and black carbon (BC) in three contaminated soils and seven sediments from the Pearl River Delta and Estuary, China, were isolated upon treatments with an acid hydrolysis method and with a combustion method at 375 C, respectively, and their sorption isotherms for phenanthrene (Phen) were established. It was found that NHC is chemically and structurally different from the biopolymer and humic substances and consists mainly of aliphatic and aromatic carbon using elemental analysis, 13C nuclear magnetic resonance spectroscopy (13C NMR), and Fourier transformed infrared spectroscopy (FTIR). All the sorption isotherms are nonlinear and are well fitted by the Freundlich model. The single-point organic carbon-normalized distribution coefficient (Koc) measured for the isolated NHC is 1.3-7.7 times higher than that for the bulk samples at the same aqueous concentration of Phen. The NHC fractions play a dominant role to the overall sorption in the bulk samples. The bulk soils and their NHC fractions have lower sorption capacity than the bulk sediments and their NHC fractions, relating to the different source of organic matter between soils and sediments. The Phen sorption capacity in the NHC samples is related significantly to H/C ratios and aliphatic carbon, but negatively to aromatic carbon, demonstrating the important role of aliphatic carbon to the Phen sorption and the fate in the investigated soils and sediments. -------------------------------------------------------------------------------- |
2楼2007-05-04 21:26:08
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Sources of Parameter Uncertainty in Predicting Treatment Performance: The Case of Preozonation in Drinking Water Engineering Marc B. Neumann, Urs von Gunten, and Willi Gujer* Swiss Federal Institute of Aquatic Science and Technology, Eawag, 8600 Dübendorf, Switzerland, Institute of Environmental Engineering, ETH Zurich, 8093 Zurich, Switzerland, and Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland Received for review October 26, 2006 Revised manuscript received March 30, 2007 Accepted April 2, 2007 Abstract: This study investigates the factors that determine parameter uncertainty when applying predefined, existing models to predict the performance of a full scale treatment system from environmental engineering. The analysis is performed for ozonation of surface water, a technology applied in drinking water treatment for disinfection and oxidation of micropollutants. The pseudo first order rate constant of ozone decay kO3 is characterized as a time dependent parameter and estimated from data obtained from three experimental setups representing upscaling stages in engineering design. To obtain meaningful uncertainty estimates, various factors need to be acknowledged: uncertainty about the model structure, uncertainty of other model parameters, uncertainty due to non-representative sampling, and errors in chemical analysis. It is concluded that an on-site automated sequencing batch reactor is best suited for estimating kinetics during operation of the full scale system. Furthermore, the transferability of information in upscaling from laboratory experiments to the full scale system is found to be critical. Although uncertainty analysis enhances the understanding of the system, it is also shown to be a subjective process depending on the knowledge and assumptions of the modeler and the availability and quality of data. -------------------------------------------------------------------------------- |
3楼2007-05-04 21:26:20