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761.
762.
Jason W Sahl Junko Munakata-Marr Michelle L Crimi Robert L Siegrist 《Water environment research》2007,79(1):5-12
For sites contaminated with chloroethene non-aqueous-phase liquids, designing a remediation system that couples in situ chemical oxidation (ISCO) with potassium permanganate (KMnO4) and microbial dechlorination may be complicated because of the potentially adverse effects of ISCO on anaerobic bioremediation processes. Therefore, one-dimensional column studies were conducted to understand the effect of permanganate oxidation on tetrachloroethene (PCE) dechlorination by the anaerobic mixed culture KB-1. Following the confirmation of PCE dechlorination, KMnO4 was applied to all columns at a range of concentrations and application velocities to simulate varied distances from oxidant injection. Immediately following oxidation, reductive dechlorination was inhibited; however, after passing several pore volumes of sterile growth medium through the columns after oxidation, a rebound of PCE dechlorination activity was observed in every inoculated column without the need to reinoculate. The volume of medium required for a rebound of dechlorination activity differed from 1.1 to 8.1 pore volumes (at a groundwater velocity of 4 cm/d), depending on the specific condition of oxidant application. 相似文献
763.
The effect of exposure to sodium arsenite during development was tested on adult fluctuating asymmetry (FA) in sternopleural bristle number, bristle number, body size and survivorship in Drosophila melanogaster. Three genetic strains of flies were used, CT-106, PVM and Oregon-R, and arsenite concentrations ranged from relatively mild, sub-lethal doses, to concentrations with pronounced negative effects on survivorship. At arsenite concentrations of 1.0 and 0.125 mM, mortality was on average 38% greater than in controls, and surviving flies emerged significantly smaller and had fewer bristles than controls. Neither the effect of arsenite or the genotype x environment interaction on asymmetry were significant. However, given the high mortality, any increase in FA could have been masked by the outcome of developmental selection against developmentally unstable phenotypes. We tested for this effect by contrasting FA values between (1) flies reared at the highest concentrations used previously, (2) flies reared at sub-lethal dosage, and (3) controls. Positional fluctuating asymmetry (PFA), which is expected to be a sensitive indicator of underlying developmental stability, was significantly reduced among flies reared at the highest concentration, and at which flies suffered significant mortality. Moreover, the slope of the regression relating mean PFA to emergence per bottle was significantly positive. These data support the hypothesis that developmental selection occurred in this experiment, and that the expected positive relationship between asymmetry and stress may be altered when the stressor eliminates individuals from the population. In contrast, FA of flies reared at sub-lethal dosage did not differ from that in controls, a result that fails to support the hypothesis that arsenite disrupts developmental stability. Our results call for caution in FA-based biomonitoring, especially of potentially lethal forms of stress, because in the presence of developmental selection, and under the common assumption that FA should increase under stress, erroneous conclusions may be drawn about the health and well being of a population. It is suggested that FA-based biomonitoring efforts integrate the use of FA with other bioindicators, and experimentally validate any expected FA-stress relationship before attempting to infer the presence of environmental stress. 相似文献
764.
Moine C Gloaguen V Gloaguen JM Granet R Krausz P 《Journal of environmental science and health. Part. B》2004,39(4):627-640
Esterification of hemicelluloses of the xylan family was performed in order to produce hydrophobic films. Acylation reactions were carried out with lauroyl chloride in the N,N-dimethylacetamide/lithium chloride homogeneous system using 4-dimethylaminopyridine as activator and were induced by microwave irradiation. In the experimental conditions used, 108 and 172% mass ratios were obtained for the dodecyl-grafted xylan and heteroxylan, respectively. The degrees of substitution (DS) were 1.3 (maximum 2) for xylan and 1.2 (maximum 2.1) for heteroxylan. These products were further characterized by FT-IR spectroscopy. The mechanical and thermomechanical behavior of this new family of hydrophobic films were analyzed and compared to those obtained from cellulose with a similar DS by the means of tensile tests. Our results indicate that the dodecyl-grafted xylan film presents the best rigidity-resistance to traction ratio. 相似文献
765.
Development of GC capillary column for isomer-specific separation of toxic isomer of PCDDs and PCDFs in environmental samples 总被引:1,自引:0,他引:1
Analysis of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) has been performed using gas chromatography mass spectrometry (GC-MS). Analysis of the most toxic isomers, in particular, 2,3,7,8-substituted PCDD/PCDF in the presence of other isomers requires a special isomer specific capillary column or high performance liquid chromatography (HPLC) fractionation prior to GC-MS analysis. Commercially available long (>50 m) polar columns can separate 2,3,7,8-TCDD from other tetra isomers. However, those columns are not satisfactory for the analyses of total PCDD/PCDF in the environmental samples. Gas chromatography -high resolution mass spectrometry (GC-HRMS) and GC-MS/MS techniques are not helpful in the analysis of 2,3,7,8-TCDD unless it is separated from the other tetra isomers. The analysis of 2,3,7,8-TCDD and total PCDD and PCDF in a single GC-MS run can ease the laborious techniques presently used. In this study we have developed a new stationary phase for the GC capillary column. The capillary column developed using this new stationary phase showed unsurpassed selectivity for the separation of 2,3,7,8-TCDD from other tetra isomers. There are several advantages of the newly developed GC capillary column. 相似文献
766.
Solvent Yellow 33 and a Solvent Green 3 mixture (30:70 mixture of Solvent Yellow 33 and Solvent Green 3) were not acutely toxic to seven of nine freshwater species when tested at the solubility limits of the dyes in freshwater. A solubility limit solution of the Solvent Green 3 mixture killed 50% of the rainbow trout tested for 96 h but was non-toxic when diluted by 50%. Both dyes caused a reduction in green algal growth at solubility limits. The Solvent Green 3 mixture was the most detrimental causing a 98–99% reduction in growth after 5 days of exposure. 相似文献
767.
A complete separation of PDDD and PCDF from a complex sample matrix by a two-step HPLC clean-up procedure shows the feasibility of analysis of PCDD and PCDF using less expensive instruments. This is demonstrated by a comparison of quantitative results of PCDD and PCDF in a complex flyash sample analyzed using GC/FID, GC/ECD, and GC/MSD. 相似文献
768.
Toward a high-rate enhanced biological phosphorus removal process in a membrane-assisted bioreactor.
Alessandro Monti Eric R Hall Fred A Koch Robert N Dawson Hadi Husain Harlan G Kelly 《Water environment research》2007,79(6):675-686
A membrane enhanced biological phosphorus removal (MEBPR) process was studied to determine the impact of hydraulic retention time (HRT) and solids retention time (SRT) on the removal of chemical oxygen demand (COD), nitrogen, and phosphorus from municipal wastewater. The MEBPR process was capable of delivering complete nitrification independent of the prevailing operating conditions, whereas a significant improvement in COD removal efficiency was observed at longer SRTs. In the absence of carbon-limiting conditions, the MEBPR process was able to achieve low phosphorus concentrations in the effluent at increasingly higher hydraulic loads, with the lowest HRT being 5 hours. The MEBPR process was also able to maintain optimal phosphorus removal when the SRT was increased from 12 to 20 days. However, at higher suspended solids concentrations, a substantial increase was observed in carbon utilization per unit mass of phosphorus removed from the influent. These results offer critical insights to the application of membrane technology for biological nutrient removal systems. 相似文献
769.
Longauer R Gömöry D Paule L Blada I Popescu F Mankovska B Müller-Starck G Schubert R Percy K Szaro RC Karnosky DF 《Environmental pollution (Barking, Essex : 1987)》2004,130(1):85-92
The effects of air pollution on the genetic structure of Norway spruce, European silver fir and European beech were studied at four polluted sites in Slovakia, Romania and Czech Republic. In order to reduce potential effects of site heterogeneity on the health condition, pair-wise sampling of pollution-tolerant and sensitive trees was applied. Genotypes of sampled trees were determined at 21 isozyme gene loci of spruce, 18 loci of fir and 15 loci of beech. In comparison with Norway spruce, fewer genetic differences were revealed in beech and almost no differentiation between pollution-tolerant and sensitive trees was observed in fir. In adult stands of Norway spruce, sensitive trees exhibited higher genetic multiplicity and diversity. The decline of pollution-sensitive trees may result thus in a gradual genetic depletion of pollution-exposed populations of Norway spruce through the loss of less frequent alleles with potential adaptive significance to altered stressing regimes in the future. Comparison of the subsets of sensitive and tolerant Norway spruce individuals as determined by presence or absence of discolorations ("spruce yellowing") revealed different heterozygosity at 3 out of 11 polymorphic loci. 相似文献
770.
Durbin TD Sauer CG Pisano JT Rhee SH Huai T Miller JW MacKay GI Robbins J Gamble H Hochhauser AM Ingham MC Gorse RA Beard LK 《Journal of the Air & Waste Management Association (1995)》2004,54(3):258-268
The impact of the sulfur (S) content in lubricating oil was evaluated for four ultra-low-emission vehicles and two super-ultra-low-emission vehicles, all with low mileage. The S content in the lube oils ranged from 0.01 to 0.76%, while the S content of the gasoline was fixed at 0.2 ppmw. Vehicles were configured with aged catalysts and tested over the Federal Test Procedure, at idle and at 50-mph cruise conditions. In all testing modes, variations in the S level of the lubricant did not significantly affect the regulated gas-phase tailpipe emissions. In addition to the regulated gas-phase emissions, a key element of the research was measuring the engine-out sulfur dioxide (SO2) in near-real-time. This research used a new methodology based on a differential optical absorption spectrometer (DOAS) to measure SO2 from the lubricants used in this study. With the DOAS, the contribution of SO2 emissions for the highest-S lubricant was found to range from less than 1 to 6 ppm on a gasoline S equivalent basis over the range of vehicles and test cycles used. The development and operation of the DOAS is discussed in this paper. 相似文献