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771.
Yuxin Wu Roelof Versteeg Lee Slater Douglas LaBrecque 《Journal of contaminant hydrology》2009,106(3-4):131-143
Calcium carbonate is a secondary mineral precipitate influencing zero valent iron (ZVI) barrier reactivity and hydraulic performance. We conducted column experiments to investigate electrical signatures resulting from concurrent CaCO3 and iron oxides precipitation under simulated field geochemical conditions. We identified CaCO3 as a major mineral phase throughout the columns, with magnetite present primarily close to the influent based on XRD analysis. Electrical measurements revealed decreases in conductivity and polarization of both columns, suggesting that electrically insulating CaCO3 dominates the electrical response despite the presence of electrically conductive iron oxides. SEM/EDX imaging suggests that the electrical signal reflects the geometrical arrangement of the mineral phases. CaCO3 forms insulating films on ZVI/magnetite surfaces, restricting charge transfer between the pore electrolyte and ZVI particles, as well as across interconnected ZVI particles. As surface reactivity also depends on the ability of the surface to engage in redox reactions via charge transfer, electrical measurements may provide a minimally invasive technology for monitoring reactivity loss due to CaCO3 precipitation. Comparison between laboratory and field data shows consistent changes in electrical signatures due to iron corrosion and secondary mineral precipitation. 相似文献
772.
The application of a mulch biofilm barrier for surfactant enhanced polycyclic aromatic hydrocarbon bioremediation 总被引:1,自引:0,他引:1
Lab scale mulch biofilm barriers were constructed and tested to evaluate their performance for preventing the migration of aqueous and surfactant solubilized PAHs. The spatial distribution of viable PAH degrader populations and resultant biofilm formation were also monitored to evaluate the performance of the biobarrier and the prolonged surfactant effect on the PAH degrading microorganism consortia in the biobarrier. Sorption and biodegradation of PAHs resulted in stable operation of the system for dissolved phenanthrene and pyrene during 150 days of experimentation. The nonionic surfactant could increase the solubility of phenanthrene and pyrene significantly. However, the biobarrier itself couldn't totally prevent the migration of micellar solubilized phenanthrene and pyrene. The presence of surfactant and the resultant highly increased phenanthrene or pyrene concentration didn't appear to cause toxic effects on the attached biofilm in the biobarrier. However, the presence of surfactant did change the structural composition of the biofilm. 相似文献
773.
774.
Y.M. Han S.C. Lee J.J. Cao K.F. Ho Z.S. An 《Atmospheric environment (Oxford, England : 1994)》2009,43(38):6066-6073
A previous study on PM2.5 carbonaceous aerosols measured with the thermal optical reflectance (TOR) method in fourteen Chinese cities is extended by subdividing total EC into char-EC and soot-EC. Average char-EC concentrations show great differences between the fourteen cities and between winter and summer periods, with concentrations of 8.67 and 2.41 μg m?3 in winter and summer, respectively. Meanwhile spatial and seasonal soot-EC variations are small, with average concentrations of 1.26 and 1.21 μg m?3 in winter and summer, respectively. Spatial and temporal distributions of char-EC, similar to EC, are mainly influenced by local fuel consumption, as well as the East Asian monsoon and some meteorological factors such as the mixing height and wet precipitation. The small spatial and seasonal variation of soot-EC is consistent with its regional-to-global dispersion, which may suggest that soot carbon is not local carbon, but regional carbon. Char-EC/soot-EC ratios show summer minimum and winter maximum in all cities, which is in good agreement with the difference in source contributions between the two periods. As OC/EC ratio is affected by the formation of the secondary organic aerosol (SOA), char-EC/soot-EC ratio is a more effective indicator for source identification of carbonaceous aerosol than previously used OC/EC ratio. 相似文献
775.
K.F. Ho Steven Sai Hang Ho S.C. Lee Y. Cheng Judith C. Chow John G. Watson P.K.K. Louie Linwei Tian 《Atmospheric environment (Oxford, England : 1994)》2009,43(40):6343-6351
Real-world vehicle emission factors for seventeen gas and particulate polycyclic aromatic hydrocarbons (PAHs) were quantified in the Shing Mun Tunnel, Hong Kong during summer and winter 2003. Naphthalene, acenaphthylene, and acenaphthene were the most abundant gas PAHs while fluoranthene and pyrene were the most abundant in the particle phase. Most (98%) of the gas PAHs consisted of two- and three-aromatic rings whereas most of the particle-phase PAHs were in four- (~60%) and five-ring (~17%) for fresh exhaust emissions. Average emission factors for the gas- and particle PAHs were 950–2564 μg veh?1 km?1 and 22–354 μg veh?1 km?1, respectively. Good correlations were found between diesel markers (fluoranthene and pyrene; 0.85) and gasoline markers (benzo[ghi]perylene and indeno[1,2,3-cd]pyrene; 0.96). Higher PAH emission factors were associated with a higher fraction of diesel-fueled vehicles (DV) passing through the tunnel. Separate emission factors were determined from diesel and non-diesel exhaust by the regression intercept method. The average PAH emission factor (i.e., sum of gas and particle phases) from DV (3085 ± 1058 μg veh?1 km?1) was ~5 times higher than that from non-diesel-fueled vehicles (NDV, 566 ± 428 μg veh?1 km?1). Ratios of DV to NDV emission factors were high for diesel markers (>24); and low for gasoline markers (<0.4). 相似文献
776.
Chang-Feng Ou Yang Yu-Chi Lin Neng-Huei Lin Chung-Te Lee Guey-Rong Sheu Seak-Hong Kam Jia-Lin Wang 《Atmospheric environment (Oxford, England : 1994)》2009,43(40):6449-6453
Three CO instruments, i.e., vacuum ultraviolet resonance fluorescence (VUV-RF), gas chromatography/reduction gas detection (GC/RGD), and non-dispersive infrared (NDIR) spectrometry, were inter-compared at a background site, i.e., Lulin Atmospheric Baseline Station (LABS) in central Taiwan. For a period of 18 days of continuous measurements, highly coherent results were observed between the three instruments. Calibration of the GC/RGD and VUV-RF was based on the same batch of CO standards, producing results that agreed within 4%. Nevertheless, NDIR displayed a significant bias with a large offset compared to the other two instruments (about ?63.1 ppb), due mainly to its over-simplified calibration procedure. The NDIR bias was then removed by aligning the NDIR data to those of GC/RGD in a process termed “post-run correction”. Through this practice, the NDIR was linked to the same calibration scale as that of GC/RGD. As a result, by simultaneously exploiting both GC/RGD and NDIR to measure background CO, both time-resolution and accuracy can be secured. 相似文献
777.
Jinsang Jung Hanlim Lee Young J. Kim Xingang Liu Yuanhang Zhang Jianwei Gu Shaojia Fan 《Journal of environmental management》2009,90(11):3231-3244
Optical and chemical aerosol measurements were obtained from 2 to 31 July 2006 at an urban site in the metropolitan area of Guangzhou (China) as part of the Program of Regional Integrated Experiment of Air Quality over Pearl River Delta (PRIDE-PRD2006) to investigate aerosol chemistry and the effect of aerosol water content on visibility impairment and radiative forcing. During the PRIDE-PRD2006 campaign, the average contributions of ammonium sulfate, organic mass by carbon (OMC), elemental carbon (EC), and sea salt (SS) to total PM2.5 mass were measured to be 36.5%, 5.7%, 27.1%, 7.8%, and 3.7%, respectively. Compared with the clean marine period, (NH4)2SO4, NH4NO3, and OMC were all greatly enhanced (by up to 430%) during local haze periods via the accumulation of a secondary aerosol component. The OMC dominance increased when high levels of biomass burning influenced the measurement site while (NH4)2SO4 and OMC did when both biomass burning and industrial emissions influenced it. The effect of aerosol water content on the total light-extinction coefficient was estimated to be 34.2%, of which 25.8% was due to aerosol water in (NH4)2SO4, 5.1% that in NH4NO3, and 3.3% that in SS. The average mass-scattering efficiency (MSE) of PM10 particles was determined to be 2.2 ± 0.6 and 4.6 ± 1.7 m2 g−1 under dry (RH < 40%) and ambient conditions, respectively. The average single-scattering albedo (SSA) was 0.80 ± 0.08 and 0.90 ± 0.04 under dry and ambient conditions, respectively. Not only are the extinction and scattering coefficients greatly enhanced by aerosol water content, but MSE and SSA are also highly sensitive. It can be concluded that sulfate and carbonaceous aerosol, as well as aerosol water content, play important roles in the processes that determine visibility impairment and radiative forcing in the ambient atmosphere of the Guangzhou urban area. 相似文献
778.
Carlos Sanchez Tze-San Lee Stacy Young Dahna Batts Jefferson Benjamin Josephine Malilay 《Disasters》2009,33(4):705-720
This study examines health effects resulting from landslides in Chuuk during Tropical Storm Chata'an in July 2002, and suggests strategies to prevent future mortality. In August 2002, we conducted a cross-sectional survey to identify risk factors for mortality during landslides, which included 52 survivors and 40 surrogates for 43 decedents to identify risk factors for death. Findings suggest that 1) females had a higher mortality rate from this event than males, and 2) children aged 5–14 years had a 10-fold increase in mortality when compared with annual mortality rates from all causes. Awareness of landslides occurring elsewhere and knowledge of natural warning signs were significantly associated with lower risks of death; being outside during landslides was not associated with reduced mortality. In Chuuk, improving communication systems during tropical storms and increasing knowledge of natural warnings can reduce the risk for mortality during landslides. 相似文献
779.
湖南长株潭城市群灾害应急管理能力评价 总被引:4,自引:2,他引:2
以城市应急管理能力及其内涵为基础,运用层次分析法,对湖南长株潭城市群灾害应急管理能力进行综合评价.结果表明:①从时间上看,长株潭灾害应急管理能力综合评分值由2005年的5.67、3.66、3.34分别增加到2006年的5.82、4.20、3.98,说明长株潭灾害应急管理能力均有所增强,这是因为应急管理能力是随城市社会经济的发展而增强的;②从空间上看,长株潭灾害应急管理能力存在一定的区域差异;③从整体上看,长株潭的灾害应急管理能力排名为长沙市>株洲市>湘潭市,其主要是由城市化水平及经济实力的差异所致. 相似文献
780.
Analysis and evaluation of chlorinated persistent organic compounds and PAHs in sludge in Korea 总被引:4,自引:0,他引:4
The concentrations of 12 POPs listed in the Stockholm convention, chlorophenols (CPs) and PAHs were investigated in sludge samples from wastewater and sewage treatment plants (WWTPs and STPs). The concentrations of PCDD/Fs in the wastewater sludge ranged from 0.189 to 1092 ng-TEQkg(-1) dry wt., and most of the sludge samples had levels below the EU guideline for the land application of PCDD/Fs (<100 ng-TEQkg(-1) dry wt.) except one sample. Co-PCB congeners were analyzed from four WWTPs, with total concentrations ranging from 0.265 to 26.6 ng-TEQkg(-1) dry wt., which were similar to the results obtained from previous studies. The levels of PCDD/Fs and Co-PCBs varied according to the main source of the influent to each WWTP and the paper industry was the main source of these compounds in the sludge due to the chlorine bleaching process. In case of OCPs, HCB and p,p'-DDE were detected at relatively high levels in the sludge samples compared to other target compounds, ranging from 1.30 to 21.5 microg kg(-1) dry wt. and 0.758 to 14.8 microg kg(-1) dry wt., respectively. Different OCP distribution patterns were observed according to sludge types, with HCB and DDTs being dominant in the sludge from WWTPs and STPs, respectively. The total levels of PAHs and CPs ranged from 1.24 to 44.9 mg kg(-1) dry wt. and 0.340 to 3.85 mg kg(-1) dry wt., respectively. The PAHs and CPs were also shown to have various distribution patterns, possibly due to the different wastewater sources to the WWTPs. 相似文献