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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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Formation and Degradation Kinetics of the Biofumigant Benzyl Isothiocyanate in Soil Anne Louise Gimsing,* Jes Leisgaard Poulsen, Henrik Laurberg Pedersen, and Hans Christian Bruun Hansen Department of Natural Sciences, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark, and Plant Biochemistry Laboratory, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark Received for review August 18, 2006 Revised manuscript received February 2, 2007 Accepted March 30, 2007 Abstract: Glucosinolates (GSLs) are produced by plants of the Capparales order. Upon enzymatic hydrolysis the GSLs can be transformed to the toxic isothiocyanates (ITCs), which can be used as biofumigants for the control of soil-borne pests. The rates of ITC formation and degradation are critical to both biofumigation and the toxicity and leaching of GSLs and ITCs in soil. Degradation kinetics of benzyl GSL and benzyl ITC in a sandy and clayey surface and subsoil at 8-9 C at natural moisture contents were investigated, as was the rate of formation of ITC from the GSL. Degradation of GSL followed logistic kinetics with t1/2 = 0.7-9.1 days. Degradation was faster in clayey soil compared to sandy soil, and faster in surface soil compared to subsoil. In surface soils, up to 25% of added GSL was detected as ITC, while only 1-6% were detected in the subsoils. ITC degradation followed first-order kinetics with t1/2 = 0.3-1.7 days, with faster degradation in subsoils than in surface soils. Based on the data for GSL hydrolysis and ITC degradation, the concentration of ITC following GSL application was successfully modeled assuming complete conversion of glucosinolate to isothiocyanate and first-order degradation of isothiocyanate. -------------------------------------------------------------------------------- Behavioral and Physiological Changes in Daphnia magna when Exposed to Nanoparticle Suspensions (Titanium Dioxide, Nano-C60, and C60HxC70Hx) Sarah B. Lovern, J. Rudi Strickler, and Rebecca Klaper* University of Wisconsin-Milwaukee, Great Lakes WATER Institute, 600 E. Greenfield Avenue, Milwaukee, Wisconsin 53204 Received for review September 8, 2006 Revised manuscript received March 19, 2007 Accepted April 11, 2007 Abstract: Little is known about the impact manufactured nanoparticles will have on aquatic organisms. Previously, we demonstrated that toxicity differs with nanoparticle type and preparation and observed behavioral changes upon exposure to the more lethal nanoparticle suspensions. In this experiment, we quantified these behavioral and physiological responses of Daphnia magna at sublethal nanoparticle concentrations. Titanium dioxide (TiO2) and fullerenes (nano-C60) were chosen for their potential use in technology. Other studies suggest that addition of functional groups to particles can affect their toxicity to cell cultures, but it is unknown if the same is true at the whole organism level. Therefore, a fullerene derivative, C60HxC70Hx, was also used to examine how functional groups affect Daphnia response. Using a high-speed camera, we quantified several behavior and physiological parameters including hopping frequency, feeding appendage and postabdominal curling movement, and heart rate. Nano-C60 was the only suspension to cause a significant change in heart rate. Exposure to both nano-C60 and C60HxC70Hx suspensions caused hopping frequency and appendage movement to increase. These results are associated with increased risk of predation and reproductive decline. They indicate that certain nanoparticle types may have impacts on population and food web dynamics in aquatic systems. -------------------------------------------------------------------------------- Degradation of Well Cement by CO2 under Geologic Sequestration Conditions Barbara G. Kutchko, Brian R. Strazisar,* David A. Dzombak, Gregory V. Lowry, and Niels Thaulow United States Department of Energy, National Energy Technology Laboratory, Pittsburgh, Pennsylvania 15236, Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, and RJ Lee Group, Incorporated, Monroeville, Pennsylvania 15146 Received for review November 29, 2006 Revised manuscript received April 11, 2007 Accepted April 12, 2007 Abstract: Experiments were conducted to assess the durability of cements in wells penetrating candidate formations for geologic sequestration of CO2. These experiments showed a significant variation in the initial degradation (9 days of exposure) based on the curing conditions. The high-temperature (50 C) and high-pressure (30.3 MPa) curing environment increased the degree of hydration and caused a change in the microstructure and distribution of the Ca(OH)2(s) phase within the cement. Cement cured at 50 C and 30.3 MPa (representing sequestration conditions) proved to be more resistant to carbonic acid attack than cement cured at 22 C and 0.1 MPa. The cement cured at 50 C and 30.3 MPa exhibited a shallower depth of degradation and displayed a well-defined carbonated zone as compared to cement cured under ambient conditions. This is likely due to smaller, more evenly distributed Ca(OH)2(s) crystals that provide a uniform and effective barrier to CO2 attack. -------------------------------------------------------------------------------- Current-Use Flame Retardants in the Eggs of Herring Gulls (Larus argentatus) from the Laurentian Great Lakes Lewis T. Gauthier, Craig E. Hebert, D. V. Chip Weseloh, and Robert J. Letcher* Science and Technology Branch, National Wildlife Research Centre, Environment Canada, Carleton University, Ottawa, ON, K1A 0H3, Canada, Department of Chemistry, Carleton University, Ottawa, Ontario, K1S 5B6, Canada, Canadian Wildlife Service, Environment Canada, 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Canada Received for review December 21, 2006 Revised manuscript received April 15, 2007 Accepted April 15, 2007 Abstract: Of the 13, current-use, non-polybrominated diphenyl ether (PBDE) flame retardants (FRs) monitored, hexabromobenzene (HBB), pentabromoethylbenzene (PBEB), pentabromotoluene (PBT), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and - and -isomers of hexabromocyclododecane (HBCD), and the syn- and anti-isomers of the chlorinated Dechlorane Plus (DP) were quantified in egg pools of herring gulls (Larus argentatus) collected in 2004 from six sites in all five of the Laurentian Great Lakes of North America. -HBCD concentrations ranged from 2.1 to 20 ng/g (wet weight (ww)). Other "new" FR levels ranged from 0.004 to 1.4 ng/g ww and were much lower than those of the major BDE congeners that are in technical mixtures (namely BDE-47, -99, -100), where 3PBDE ranged from 186 to 498 ng/g ww. Nineteen hepta-BDEs (hepta = 4.9-11 ng/g ww), octa-BDEs (octa = 2.6-9.1 ng/g ww), and nona-BDEs (nona = 0.12-5.6 ng/g ww) were detectible at all six colonies, while BDE-209 was low but quantifiable (<0.1-0.21 ng/g ww) at two colonies. -DP (syn- and anti-isomers) concentrations in eggs from all sites ranged from 1.5 to 4.5 ng/g ww. Our findings indicate that mother herring gulls are exposed to several, current-use flame retardants via their diet, and in ovo transfer occurred to their eggs. Given the aquatic diet of herring gull, this suggests that there are non-PBDE BFRs present in the gull-associated aquatic food web of the Great Lakes. -------------------------------------------------------------------------------- Biostimulation of PAH Degradation with Plants Containing High Concentrations of Linoleic Acid Haakrho Yi and David E. Crowley* Department of Environmental Sciences, University of California, Riverside, California 92521 Received for review October 6, 2006 Revised manuscript received March 22, 2007 Accepted March 28, 2007 Abstract: Many plant species enhance the biodegradation of polycyclic aromatic hydrocarbons (PAHs), but there is little understanding of the mechanisms by which this occurs. This research identified phytochemicals that stimulate pyrene degradation using crushed root tissues from 43 plants that were screened in soil spiked with 100 ppm pyrene. Among the plants tested, root tissues from Apium graveolens (celery), Raphanus sativus (radish), Solanum tuberosum (potato), and Daucus carota (carrot) were most effective for promoting disappearance of pyrene within 40 days. Experiments with A. graveolens showed that plant culture in soil contaminated with pyrene or benzo[a]pyrene was as effective as addition of crushed root tissues. Comparison of the chemical compositions of the effective plants suggested that linoleic acid was the major substance that stimulated PAH degradation. This hypothesis was supported in experiments examining degradation of pyrene and benzo[a]pyrene in soil amended with linoleate, whereas linolenic and palmitic acids did not stimulate degradation within a 20 day period. Antibiotic inhibitor studies implicated gram positive bacteria as a predominant group responding to linoleic acid. These findings provide insight into the mechanisms by which plants enhance degradation of PAHs, and have practical application for remediation of PAH contaminated soils. -------------------------------------------------------------------------------- Evidence for the Migration of Steroidal Estrogens through River Bed Sediments Pierre Labadie, Andrew B. Cundy, Kevin Stone, Michael Andrews, Sam Valbonesi, and Elizabeth M. Hill* Centre for Environmental Research, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom, and School of the Environment, University of Brighton, Lewes Road, Brighton BN2 4GJ, United Kingdom Received for review December 22, 2006 Revised manuscript received April 4, 2007 Accepted April 16, 2007 Abstract: Estrogenic substances discharged from wastewater treatment plants have been detected in surface sediments of receiving waters, but little is known of their vertical migration through buried sediments and their potential to contaminate subsurface waters. The vertical profiles of estrogenic chemicals were investigated in sediment cores at an alluvial freshwater site (Ditchling) and a clay-rich estuarine site (Lewes), both of which are downstream of wastewater discharges into the River Ouse (Sussex, U.K.). Estrone (E1) was the predominant estrogen detected in surface and buried sediments at both sites and was detected in undisturbed clay sediments >120 years old. Profiles of E1 at Ditchling were characterized by a prominent subsurface peak of E1 at the alluvium/clay interface (-15 cm) at a concentration (28.8 ± 6.0 ng/g of dry wt) that was 9-fold higher than in the surface sediment. In contrast, a steady downcore decline in E1 concentrations was observed in the clay-rich Lewes core. This work provides the first in situ evidence of estrogen migration through river bed sediments and reveals that movement of estrogens through unconsolidated sediment can result in penetration to the underlying substrata and therefore the potential for groundwater contamination. -------------------------------------------------------------------------------- |
11楼2007-05-19 21:51:14
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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