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2007-5-10 Metabolic Profile Biomarkers of Metal Contamination in a Sentinel Terrestrial Species Are Applicable Across Multiple Sites Jacob G. Bundy,* Hector C. Keun, Jasmin K. Sidhu, David J. Spurgeon, Claus Svendsen, Peter Kille, and A. John Morgan Department of Biomolecular Medicine, Division of Surgery, Oncology, Reproductive Biology and Anaesthetics (SORA), Faculty of Medicine, Sir Alexander Fleming Building, Imperial College London, London SW7 2AZ, Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon PE28 2LS, and Cardiff School of Biosciences, Main Building, Cardiff University, Park Place, Cardiff CF10 3TL, Wales, United Kingdom Received for review January 5, 2007 Revised manuscript received March 15, 2007 Accepted March 21, 2007 Abstract: In this study, we addressed the question of whether an omic approach could genuinely be useful for biomarker profile analysis across different field sites with different physicochemical characteristics. We collected earthworms (Lumbricus rubellus) from seven sites with very different levels of metal contamination and prevailing soil type and analyzed tissue extracts by 1H nuclear magnetic resonance spectroscopy. Pattern recognition analysis of the data showed that both site- and contaminant-specific effects on the metabolic profiles could be discerned. Zinc was identified as the probable major contaminant causing a metabolic change in the earthworms. Individual sites could be resolved on the basis of NMR spectral profiles by principal component analysis; these site differences may also have been caused by additional abiotic factors such as soil pH. Despite an inevitable degree of confounding between site and contaminant concentrations, it was possible to identify metabolites which were correlated with zinc across all different sites. This study therefore acts as a proof of principle for the use of NMR-based metabolic profiling as a diagnostic tool for ecotoxicological research in polluted field soils. -------------------------------------------------------------------------------- Emissions from Laboratory Combustion of Wildland Fuels: Emission Factors and Source Profiles L.-W. Antony Chen,* Hans Moosmüller, W. Patrick Arnott, Judith C. Chow, John G. Watson, Ronald A. Susott, Ronald E. Babbitt, Cyle E. Wold, Emily N. Lincoln, and Wei Min Hao Division of Atmospheric Sciences, Desert Research Institute, Nevada System of Higher Education, Reno, Nevada, and Fire Sciences Laboratory, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana Received for review October 4, 2006 Revised manuscript received February 23, 2007 Accepted March 22, 2007 Abstract: Combustion of wildland fuels represents a major source of particulate matter (PM) and light-absorbing elemental carbon (EC) on a national and global scale, but the emission factors and source profiles have not been well characterized with respect to different fuels and combustion phases. These uncertainties limit the accuracy of current emission inventories, smoke forecasts, and source apportionments. This study investigates the evolution of gaseous and particulate emission and combustion efficiency by burning wildland fuels in a laboratory combustion facility. Emission factors for carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbon (THC), nitrogen oxides (NOx), PM, light extinction and absorption cross sections, and spectral scattering cross sections specific to flaming and smoldering phases are reported. Emission factors are generally reproducible within ±20% during the flaming phase, which, despite its short duration, dominates the carbon emission (mostly in the form of CO2) and the production of light absorption and EC. Higher and more variable emission factors for CO, THC, and PM are found during the smoldering phase, especially for fuels containing substantial moisture. Organic carbon (OC) and EC mass account for a majority (i.e., >60%) of PM mass; other important elements include potassium, chlorine, and sulfur. Thermal analysis separates the EC into subfractions based on analysis temperature demonstrating that high-temperature EC (EC2; at 700 C) varies from 1% to 70% of PM among biomass burns, compared to 75% in kerosene soot. Despite this, the conversion factor between EC and light absorption emissions is rather consistent across fuels and burns, ranging from 7.8 to 9.6 m2/gEC. Findings from this study should be considered in the development of PM and EC emission inventories for visibility and radiative forcing assessments. -------------------------------------------------------------------------------- Lateral and Longitudinal Variation of Hyporheic Exchange in a Piedmont Stream Pool Robert J. Ryan and Michel C. Boufadel* Department of Civil and Environmental Engineering, Temple University, 1947 North 12th Street, Philadelphia, Pennsylvania 19122 Received for review July 6, 2006 Revised manuscript received March 24, 2007 Accepted April 2, 2007 Abstract: A conservative solute tracer experiment was conducted in Indian Creek, a small urban stream in Philadelphia, PA, to investigate the role of subsurface properties on the exchange between streamwater and the hyporheic zone (subsurface surrounding the stream). Sodium bromide (NaBr) was used as a conservative tracer, and it was monitored in the surface water and in the bed sediments of a 15 m long pool. Subsurface sampling occurred at 12 locations in the upper layer sediments (extending from 7.5 to 10 cm below the streambed) and 13 locations in the lower layer sediments (extending from 10 to 12.5 cm below the streambed). The hydraulic conductivity (K) of the upper bed sediments and the lower bed sediments was measured in situ. Several locations within the streambed exhibited an increase in tracer concentration with depth, suggesting the presence of horizontal flow paths within this small pool. Over the entire pool, the influence of K heterogeneity on hyporheic exchange was masked by the groundwater head gradient and the morphology of the stream. Together, the groundwater head gradient and stream morphology induced a generally high tracer concentration and fast hyporheic exchange on the left side and center of the channel and low concentrations and slower exchange on the right side. Although the reach-scale effects on the surface water concentration were small, groundwater greatly influenced the local-scale hyporheic exchange in the pool. Understanding how physical stream characteristics control the location and extent of hyporheic exchange pathways will lead to a better understanding of biogeochemical cycling of nutrients and contaminants. -------------------------------------------------------------------------------- |
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A Novel Test for Measuring and Managing Potential Phosphorus Loss from Dairy Cattle Feces Zhengxia Dou,* Charles F. Ramberg, Jr., Lydie Chapuis-Lardy, John D. Toth, Yu Wang, Robert J. Munson, Zhiguo Wu, Larry E. Chase, Richard A. Kohn, Katharine F. Knowlton, and James D. Ferguson Section of Animal Production Systems, School of Veterinary Medicine, University of Pennsylvania, 382 West Street Road, Kennett Square, Pennsylvania 19348, Institut de Recherche pour le Développement, 213 Rue La Fayette, 75 480 Paris, Cedex 10 France, Cornell University, Ithaca, New York 14853, University of Maryland, College Park, Maryland 20742, and Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Received for review December 20, 2006 Revised manuscript received March 18, 2007 Accepted April 11, 2007 Abstract: Pollution of waters resulting from phosphorus (P) runoff from agricultural land receiving long-term manure application is one of the most serious threats to water quality in many regions of the world. Of various approaches to alleviate the problem, reducing P surplus on animal farms through optimizing P intake and minimizing P excretion in manure offers a great opportunity. Here, we present a fecal P test method that has the potential to identify over-feeding of P in dairy cattle. Previous research has suggested that water-extractable P in dairy cow feces closely reflects dietary P changes and may indicate the animal's P status (adequate vs excessive). However, the notion was somewhat confounded when a subsequent study found other factors (pH and Ca content as well as sample handling method) also affecting P extractability in water. In the present work, we hypothesize that the impact of those factors on P extractability can be overcome by selecting dilute acid solutions to replace deionized water as the extractant. Using samples from 25 commercial dairy farms, we tested an array of acid solutions (including HCl, citric acid, and acetic acid) and found that 0.1% HCl is the most suitable extractant. Inorganic P (Pi) released in 0.1% HCl closely reflected dietary P changes among the farms (R2 = 0.69) and was independent of pH, Ca, or sample handling method. Knowledge of P metabolism and partitioning in dairy cows and our experimental data suggest that excess P intake by the animal leads to greater amounts of bioavailable but unabsorbed P, which is excreted in feces. Its relative magnitude may be estimated by measuring Pi extractable in 0.1% HCl. This novel and simple fecal P test could potentially be used as an indicator of the animal's P supply utilization status and thus serve as a screening tool for the presence of P over-feeding on dairy farms. -------------------------------------------------------------------------------- SO2 Retention by Reactivated CaO-Based Sorbent from Multiple CO2 Capture Cycles Vasilije Manovic and Edward J. Anthony* CANMET Energy Technology Centre-Ottawa, Natural Resources Canada, 1 Haanel Drive, Ottawa, Ontario, Canada K1A 1M1 Received for review December 12, 2006 Revised manuscript received March 22, 2007 Accepted April 4, 2007 Abstract: This paper examines the reactivation of spent sorbent, produced from multiple CO2 capture cycles, for use in SO2 capture. CaO-based sorbent samples were obtained from Kelly Rock limestone using three particle size ranges, each containing different impurities levels. Using a thermogravimetric analyzer (TGA), the sulfation behavior of partially sulfated and unsulfated samples obtained after multiple calcination-carbonation cycles in a tube furnace (TF), following steam reactivation in a pressurized reactor, is examined. In addition, samples calcined/sintered under different conditions after hydration are also examined. The results show that suitably treated spent sorbent has better sulfation characteristics than that of the original sorbent. Thus for example, after 2 h sulfation, >80% of the CaO was sulfated. In addition, the sorbent showed significant activity even after 4 h when >95% CaO was sulfated. The results were confirmed by X-ray diffraction (XRD) analysis, which showed that, by the end of the sulfation process, samples contained CaSO4 with only traces of unreacted CaO. The superior behavior of spent reactivated sorbent appears to be due to swelling of the sorbent particles during steam hydration. This enables the development of a more suitable pore surface area and pore volume distribution for sulfation, and this has been confirmed by N2 adsorption-desorption isotherms and the Barrett-Joyner-Halenda (BJH) method. The surface area morphology of sorbent after reactivation was examined by scanning electron microscopy (SEM). Ca(OH)2 crystals were seen, which displayed their regular shape, and their elemental composition was confirmed by energy-dispersive X-ray (EDX) analysis. The improved characteristics of spent reactivated sorbent in comparison to the original and to the sorbent calcined under different conditions and hydrated indicate the beneficial effect of CO2 cycles on sorbent reactivation and subsequent sulfation. These results allow us to propose a new process for the use of CaO-based sorbent in fluidized bed combustion (FBC) systems, which incorporates CO2 capture, sorbent reactivation, and SO2 retention. -------------------------------------------------------------------------------- Hydroxylated Metabolites of - and -Hexachlorocyclohexane: Bacterial Formation, Stereochemical Configuration, and Occurrence in Groundwater at a Former Production Site Vishakha Raina, Andrea Hauser, Hans Rudolf Buser,* Daniel Rentsch, Poonam Sharma, Rup Lal, Christof Holliger, Thomas Poiger, Markus D. Müller, and Hans-Peter E. Kohler Environmental Microbiology, Swiss Federal Institute for Aquatic Science and Technology (Eawag), CH-8600 Dübendorf, Switzerland, Agroscope Changins-Wädenswil, Research Station ACW, CH-8820 Wädenswil, Switzerland, Laboratory for Functional Polymers, EMPA, Swiss Federal Laboratories for Materials Testing and Research, CH-8600 Dübendorf, Switzerland, Department of Zoology, University of Delhi, Delhi-110007, India, and EPFL, ENAC-ISTE, Laboratory of Environmental Biotechnology, CH-1015, Lausanne, Switzerland Received for review December 7, 2006 Revised manuscript received April 5, 2007 Accepted April 9, 2007 Abstract: Although the use of hexachlorocyclohexane (HCH), one of the most popular insecticides after the Second World War, has been discontinued in many countries, problems remain from former production and waste sites. Despite the widespread occurrence of HCHs, the environmental fate of these compounds is not fully understood. In particular, environmental metabolites of the more persistent -HCH and -HCH have not been fully identified. Such knowledge, however, is important to follow degradation and environmental fate of the HCHs. In the present study, several hydroxy metabolites that formed during incubation of - and -HCH with the common soil microorganism Sphingobium indicum B90A were isolated, characterized, and stereochemically identified by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The metabolites were identified as isomeric pentachlorocyclohexanols (B1, D1) and tetrachlorocyclohexane-1,4-diols (B2, D2); -HCH additionally formed a tetrachloro-2-cyclohexen-1-ol (D3) and a trichloro-2-cyclohexene-1,4-diol (D4), most likely by hydroxylation of -pentachlorocyclohexene (-PCCH), initially formed by dehydrochlorination. The dehydrochlorinase LinA was responsible for conversion of -HCH into -PCCH, and the haloalkane dehalogenase LinB was responsible for the transformation of -HCH and -HCH into B1 and D1, respectively, and subsequently into B2 and D2, respectively. LinB was also responsible for transforming -PCCH into D3 and subsequently into D4. These hydroxylations proceeded in accordance with SN2 type reactions with initial substitution of equatorial Cls and formation of axially hydroxylated stereoisomers. The apparently high reactivity of equatorial Cls in - and -HCH toward initial hydroxylation by LinB of Sphingobium indicum B90A is remarkable when considering the otherwise usually higher reactivity of axial Cls. Several of these metabolites were detected in groundwater from a former HCH production site in Switzerland. Their presence indicates that these reactions proceed under natural environmental conditions and that the metabolites are of environmental relevance. -------------------------------------------------------------------------------- |
8楼2007-05-16 21:51:22
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HCB, p,p'-DDE and PCB Ontogenetic Transfer and Magnification in Bluefin Tuna (Thunnus thynnus) from the Mediterranean Sea Simonetta Corsolini,* Gianluca Sarà, Nicoletta Borghesi, and Silvano Focardi G. Sarfatti Department of Environmental Sciences, University of Siena, via P.A. Mattioli, 4, I-53100 Siena, Italy, and Animal Biology Department, University of Palermo, via Archirafi, 18, I-90123 Palermo, Italy Received for review October 11, 2006 Revised manuscript received March 31, 2007 Accepted April 8, 2007 Abstract: The bluefin tuna, Thunnus thynnus (Linnaeus 1758), is biologically and economically important in the Atlantic-Mediterranean ecosystems. Bluefin tuna feed on diverse food items depending on their age, thus they occupy different trophic levels during their lifespan. Hexachlorobenzene (HCB), p,p'-DDE and polychlorinated biphenyls (PCBs) are well-known persistent organic pollutants (POPs) in the Mediterranean basin. The relationship between stable isotopes of nitrogen (N) and the POP residue levels in tissues has recently increased knowledge on the link between the trophic levels and the contaminant accumulation. Trophic levels were estimated by using 15N/14N ratio (15N) and HCB, p,p'-DDE, and forty-three PCBs were quantified in bluefin tuna from the southern Tyrrhenian Sea. Results showed that changes in PCB and p,p'-DDE concentrations were a function of size and trophic level, while no correlations were observed for HCB. Apart from HCB and PCB nos. 101, 207, 95, 158, and 60 + 56, which did not show any significant increase per trophic level, the other PCBs and the p,p'-DDE increased significantly. The ontogenetic magnification factor of PCBs was 6.6 ± 0.5, which was significantly (12 times) higher (p < 0.05) than the values found for p,p'-DDE (1.4) and HCB (1.4). -------------------------------------------------------------------------------- Removal of Polycyclic Aromatic Hydrocarbons from Contaminated Soil by Aqueous DNA Solution Ronald R. Navarro, Hiroyasu Ichikawa, Yosuke Iimura, and Kenji Tatsumi* National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan Received for review October 13, 2006 Revised manuscript received February 9, 2007 Accepted March 26, 2007 Abstract: An aqueous DNA solution was applied for the extraction of polycyclic aromatic hydrocarbons (PAHs) from a spiked soil. Solubilities of 0.56, 11.78, and 11.24 mg L-1 for anthracene, phenanthrene, and pyrene, respectively, were achieved after 1 day equilibration in 1% DNA. Using a spiked soil that contained 72 mg kg-1 anthracene, 102 mg kg-1 phenanthrene, and 99 mg kg-1 pyrene, extractions of close to 88, 78, and 94%, respectively, were attained with 5% DNA at a 1:50 soil/extractant ratio. Maximum PAH dissolution occurred after 4-6 h. Comparative tests showed the main advantage of DNA over methyl-- and -cyclodextrins and Tween 80 for pyrene removal. An ionic strength of 0.1 M NaCl was found necessary for maximum PAH dissolution and extraction. The performance of hexane regenerated DNA also remained stable after three stages of recycling. These results show the huge potential of DNA as an aqueous washing agent for PAH-contaminated soil. -------------------------------------------------------------------------------- Copper(II) Binding to Dissolved Organic Matter Fractions in Municipal Solid Waste Incinerator Bottom Ash Leachate Susanna Olsson,* Joris W. J. van Schaik, Jon Petter Gustafsson, Dan Berggren Kleja, and Patrick A. W. van Hees Department of Land and Water Resources Engineering, KTH (Royal Institute of Technology), 100 44 Stockholm, Sweden, Department of Soil Sciences, Swedish University of Agricultural Sciences, Box 7014, 750 07 Uppsala, Sweden, and Man-Technology Environment Research Center, Department of Natural Science, Örebro University, 701 82 Örebro, Sweden Received for review December 13, 2006 Revised manuscript received March 26, 2007 Accepted April 2, 2007 Abstract: Information on Cu speciation in municipal solid waste incineration (MSWI) bottom ash leachate is needed for Cu leaching predictions and toxicity estimates. The complexation of Cu with dissolved organic matter (DOM) in leachates from a stored MSWI bottom ash was studied potentiometrically using a Cu-ion selective electrode. More than 95% of the copper was bound to DOM in the hydrophilic fraction of the leachate, indicating that the hydrophilic acids contribute to Cu complex formation. The hydrophilic acids constituted 58% of the dissolved organic carbon in the ash leachate. Comparisons between experimental results and speciation calculations with the NICA-Donnan model and the Stockholm humic model indicated differences between the ash DOM and the natural DOM for which the models have been calibrated. The ratio of carboxylic binding sites to phenolic binding sites was 2 times larger in ash DOM, and the Cu-binding affinity of the former was stronger than accounted for by the generic Cu-binding parameters. The Cu-binding affinity of the phenolic sites, on the other hand, was weaker. When these parameters were adjusted, a good description of the experimental data was obtained. -------------------------------------------------------------------------------- Stable Carbon Isotope Fractionation of Chloroethenes by Dehalorespiring Isolates Patrick K. H. Lee, Mark E. Conrad, and Lisa Alvarez-Cohen* Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, and Earth Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 Received for review November 20, 2006 Revised manuscript received March 5, 2007 Accepted March 28, 2007 Abstract: Stable carbon isotope fractionation during the reductive dechlorination of chloroethenes by two bacterial strains that dechlorinate to ethene, Dehalococcoides ethenogenes 195 and Dehalococcoides sp. strain BAV1 as well as Sulfurospirillum multivorans and Dehalobacter restrictus strain PER-K23, isolates that do not dechlorinate past DCE, are reported. Fractionation by a Dehalococcoides-containing enrichment culture is also measured for comparison to the isolates. All data adequately fit the Rayleigh model and results are presented as enrichment factors. For strain 195, the measured enrichment factors were -9.6 ± 0.4, -21.1 ± 1.8, and -5.8 ± 0.5 when degrading TCE, cDCE, and 1,1-DCE, respectively. Strain BAV1 exhibited enrichment factors of -16.9 ± 1.4, -8.4 ± 0.3, -21.4 ± 0.9, and -24.0 ± 2.0 for cDCE, 1,1-DCE, tDCE, and VC, respectively. The surprisingly large differences in enrichment factors caused by individual reductases (RDases) reducing different chloroethenes is likely the result of chemical structure differences among the chloroethenes. For TCE reduction, S. multivorans and D. restrictus strain PER-K23 exhibited enrichment factors of -16.4 ± 1.5 and -3.3 ± 0.3, respectively. While all of the organisms studied here utilize RDases that require corrinoid cofactors, the biotic TCE enrichment factors varied widely from those reported for the abiotic cobalamin-catalyzed reaction, indicating that additional factors affect the extent of fractionation in these biological systems. The enrichment factors measured for the Dehalococcoides-containing enrichment culture did not match well with those from any of the isolates, demonstrating the inherent difficulties in predicting fractionation factors of undefined communities. Although compound-specific isotope fractionation is a powerful tool for evaluating the progress of in situ bioremediation in the field, given the wide range of enrichment factors associated with functionally similar and phylogenetically diverse organisms, caution must be exercised when applying enrichment factors for the interpretation of dechlorination data. -------------------------------------------------------------------------------- |
3楼2007-05-11 23:02:11
4楼2007-05-12 13:18:15
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Modeling Atmospheric Vegetation Uptake of PBDEs Using Field Measurements Annick D. St-Amand, Paul M. Mayer, and Jules M. Blais* Department of Chemistry, University of Ottawa, 10 Marie-Curie, Ottawa, Ontario, K1N 6N5, and Department of Biology, University of Ottawa, 30 Marie-Curie, Ottawa, Ontario, K1N 6N5 Received for review October 12, 2006 Revised manuscript received March 8, 2007 Accepted April 4, 2007 Abstract: Polybrominated diphenyl ethers (PBDEs) are flame retardants used in a variety of consumables. Models indicate that air-vegetation exchange plays an important role in their global distribution. The present study surveyed PBDEs in spruce needles and air (gaseous and particulate-bound) over an annual cycle to model accumulation of PBDEs in vegetation. Air-particulate distributions revealed that penta and higher BDE congeners were mainly associated with particulates even in warmer temperatures, whereas for the tri- and tetra-BDE congeners, a significant temperature dependence was observed. Using measured vegetation and atmospheric concentrations from bud burst 2004 to June 2005, a modeling concept was developed to determine PBDE deposition velocities to vegetation. Particulate-bound deposition velocity was calculated to be 3.8 m/h. Net gaseous transfer velocities ranged from 2.4 to 62.2 m/h and correlated significantly with log KOA. These derived values were used to model PBDE accumulation by vegetation through time, and these agreed well with measured values. This study provides the necessary background for modeling PBDE transport between air and coniferous vegetation globally. -------------------------------------------------------------------------------- Mechanistic Studies of the Photocatalytic Degradation of Methyl Green: An Investigation of Products of the Decomposition Processes Chiing-Chang Chen* and Chung-Shin Lu Department of General Education, National Taichung Nursing College, Taichung 403, Taiwan, ROC Received for review October 14, 2006 Revised manuscript received March 20, 2007 Accepted April 3, 2007 Abstract: The methyl green (MG) dye dissolves into an alkaline solution when the pH value is too high (pH 9). The cationic MG dye molecules are converted into the colorless carbinol base (CB) and produce crystal violet (CV) dye and ethanol by hydroxide anion. Thirty-three intermediates of the process were separated, identified, and characterized by HPLC-ESI-MS technique in this study and their evolution during the photocatalytic reaction is presented. Moreover, the other intermediates formed in the photocatalytic degradation MG processes were separated and identified by HPLC-PDA technique. The results indicated that the N-de-methylated degradation of CV dye took place in a stepwise manner to yield N-de-methylated CV species, and the N-de-alkylated degradation of CB also took place in a stepwise manner to yield N-de-alkylated CB species generated during the processes. Moreover, the oxidative degradation of the CV dye (or CB) occurs to yield 4-(N,N-dimethylamino)phenol (DAP), 4-(N,N-dimethylamino)-4'-(N',N'-dimethylamino)benzophenone (DDBP) and their N-de-methylated products [or to yield 4-(N-ethyl-N,N-dimethyl)aminophenol (EDAP), DDBP, 4-(N-ethyl-N,N-dimethylamino)-4'-(N',N'-dimethylamino)benzophenone (EDDBP), DAP, and their N-de-alkylated products], which were found for the first time. A proposed degradation pathway of CV and CB is presented, involving mainly the N-de-alkylation and oxidation reaction. -------------------------------------------------------------------------------- Supercritical Preparation of a Highly Active S-Doped TiO2 Photocatalyst for Methylene Blue Mineralization Hexing Li,* Xinyu Zhang, Yuning Huo, and Jian Zhu Department of Chemistry, Shanghai Normal University, Shanghai 200234, P. R. China Received for review November 8, 2006 Revised manuscript received February 25, 2007 Accepted February 26, 2007 Abstract: Sulfur-modification of the TiO2 was achieved by treating the TiO2 precursor (xerogel) under supercritical conditions in CS2/ethanol fluid. Nuclear magnetic resonance, X-ray photoelectron spectroscopy and Fourier transform infrared spectra demonstrated that the TiO2 was modified by the S-species incorporated into the TiO2 network by forming S-Ti-O bonds rather than by the adsorbed CS2. During liquid-phase photocatalytic degradation of methylene blue (MB) under visible light irradiation (>420 nm), the as-prepared S-doped TiO2 exhibited much higher activity than the undoped TiO2 obtained via either supercritical treatment or direct calcinations and even the N-doped TiO2 obtained via supercritical treatment. The promoting effects of both the supercritical treatment and S-modification on the photocatalytic activity were discussed by considering the high surface, large porous channels, well crystallized anatase phase, excellent thermal stability, and strong absorbance for visible lights, corresponding to the high quantum efficiency. The maximum activity was obtained at 1.8% S/Ti molar ratio, nearly 8 times higher than that of the commercially available P25 TiO2. -------------------------------------------------------------------------------- Kinetic Gas-Water Transfer and Gas Accumulation in Porous Media during Pulsed Oxygen Sparging Gerd U. Balcke, Stefan Meenken, Carsten Hoefer, and Sascha E. Oswald* UFZ, Helmholtz Centre for Environmental Research, Department of Hydrogeology, Permoserstr. 15, 04318 Leipzig, Germany Received for review December 5, 2006 Revised manuscript received March 27, 2007 Accepted March 28, 2007 Abstract: Gas-water mass transfer and the transport of dissolved gases in variably saturated porous media are key processes for in-situ remediation by pulsed gas sparging. In this context, gas dissolution tests were conducted during pulsed oxygen gas injection into sand columns. The columns were recharged with anoxic water, effluents were analyzed for dissolved O2, and tracer tests were performed to detect accumulation of trapped gas. In a second series oxygen gas was blended with sulfur hexafluoride (SF6), and O2 and SF6 breakthrough curves were recorded. To interpret experimental results, a numerical model was applied that simulates multi-species kinetic mass transfer during gas dissolution. The model predicted breakthrough curves of dissolved gas species and delivered spatially resolved values for gas phase accumulation and composition, which are not directly accessible experimentally. It was shown how dissolved nitrogen accumulates increasingly in trapped gas phase and inhibits its complete dissolution, in case the pulsed gas injections were operated based on O2 breakthrough only. Accumulation of nitrogen also retarded dissolved oxygen transport and thus oxygen breakthrough. Experiments plus modeling demonstrated that SF6 measurements are highly sensitive to the gas dissolution processes, and provide a more sensitive criterion for determining gas injection frequencies during pulsed biosparging. -------------------------------------------------------------------------------- Accumulation, Whole-Body Depletion, and Debromination of Decabromodiphenyl Ether in Male Sprague-Dewley Rats Following Dietary Exposure Janice K. Huwe* and David J. Smith: Degradation of Methylene Blue by Three-Dimensionally Ordered Macroporous Titania Madhavi Srinivasan* and Tim White School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 Received for review January 22, 2007 Revised manuscript received March 20, 2007 Accepted March 30, 2007 Abstract: Accelerated photodegradation of methylene blue (MB) over three-dimensionally ordered macroporous (3DOM) titania (pore sizes: 0.5 and 1 m) is demonstrated. The catalysts were synthesized by colloidal crystal templating against polystyrene spheres using a metal alkoxide precursor. The 3DOM titania walls which are predominantly anatase (>98%) were decorated homogeneously with gold nanoparticles (5-7 nm) by pH-controlled precipitation of Au from HAuCl4 using sodium hydroxide. A combination of powder X-ray diffraction (XRD), analytical transmission electron microscopy (ATEM) and X-ray photoelectron spectroscopy (XPS) confirmed the deposition of Au(0) on the 3DOM titania macroporous walls. Photocatalytic activity was monitored by following the degradation of MB with activity benchmarked against commercial P25 (Degussa) and powder titania prepared by hydrolysis of titanium ethoxide. Macroporous 3DOM titania with pore diameter 0.5 m had the highest first-order rate constant of 0.042 min-1 for decomposition of MB, compared to 0.025 min-1 for P25 titania. Deposition of gold on the 3DOM titania surfaces decreased the reaction rate by covering the surface active sites. -------------------------------------------------------------------------------- |
5楼2007-05-12 22:06:48