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1.
The photocatalytic inactivation (PCI) of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) was performed using polyoxometalate (POM) as a homogeneous photocatalyst and compared with that of heterogeneous TiO2 photocatalyst. Aqueous suspensions of the microorganisms (107–108 cfu ml−1) and POM (or TiO2) were irradiated with black light lamps. The POM-PCI was faster than (or comparable to) TiO2-PCI under the experimental conditions employed in this study. The relative efficiency of POM-PCI was species-dependent. Among three POMs (H3PW12O40, H3PMo12O40, and H4SiW12O40) tested in this study, the inactivation of E. coli was fastest with H4SiW12O40 while that of B. subtilis was the most efficient with H3PW12O40. Although the biocidal action of TiO2 photocatalyst has been commonly ascribed to the role of photogenerated reactive oxygen species such as hydroxyl radicals and superoxides, the cell death mechanism with POM seems to be different from TiO2-PCI. While TiO2 caused the cell membrane disruption, POM did not induce the cell lysis. When methanol was added to the POM solution, not only the PCI of E. coli was enhanced (contrary to the case of TiO2-PCI) but also the dark inactivation was observed. This was ascribed to the in situ production of formaldehyde from the oxidation of methanol. The interesting biocidal property of POM photocatalyst might be utilized as a potential disinfectant technology. 相似文献
2.
Samples of potassium perfluorooctanesulfonate (PFOSK) from three suppliers were analyzed by LC-ESI-MS/MS for purity and by LC-ESI-MS for the percentage of linear isomer present. Our data indicated that the purity ranged from 80% to 98% and the percentages of linear isomer from 67% to 79%. The proportion of branched isomers present in the samples was also estimated using (19)F NMR. These results agreed quite closely with those found by LC-ESI-MS indicating that there is essentially no difference in overall SIM response factor for the branched isomers vs. that of the linear isomer. Several further observations relevant to the use of standards when analyzing for PFOS were encountered during this study. It appears unlikely that matrix effects attributable to the cation (sodium or potassium) present in PFOSNa or PFOSK internal standards is an issue. In seeking potential matrix effects, it was found that the chromatography was improved substantially when the standard was injected as a solution in 80:20 methanol/water rather than 100% methanol. Notably, in concert with the improvement in chromatography, an increase of about 10% in response was observed. In some closely related studies, when (18)O(2) mass-labeled perfluorohexanesulfonate was used as an internal standard, the actual and theoretical concentration ratios matched closely those for related native sulfonates as long as they did not co-elute. However, when they did co-elute, the peak intensities of the native species were enhanced by about 5%, while those of the labeled compound were suppressed by a similar amount. If this effect were not taken into account, the concentration of the native would be inflated by 10%. 相似文献
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4.
Michael Springborn Boon-Ling Yeo Juhwan Lee Johan Six 《Journal of Environmental Economics and Management》2013
The margin of safety (MOS) approach is an increasingly prevalent tool for ensuring the integrity of market-based programs for providing ecosystem services. Over-crediting is reduced by setting aside mean estimates of uncertain services in favor of a more conservative estimate. Like many environmental policy problems, ecosystem service markets involve the aggregation of uncertainty over multiple scales, e.g. from landowners to market intermediaries to the overall market. We examine how the MOS instrument affects, and is affected by, an ecosystem services market. We show that the common bottom-up approach of imposing risk preferences at a local, disaggregated level—held over from earlier development in the context of toxics and command and control-style health risk regulation—leads to several unintended consequences. Furthermore, discounting landowner services can actually increase their profits, conditional on the elasticity of credit demand. We illustrate theoretical insights with an empirical application to greenhouse gas offset crediting in agriculture. 相似文献
5.
Wang Zhaoqi Jung Soontag Yeo Daseul Park Sunho Woo Seoyoung Seo Yeeun Hossain Md. Iqbal Kim Minji Choi Changsun 《Food and environmental virology》2023,15(1):61-70
Food and Environmental Virology - The performance of dishwashers in removing live viruses is an important informative value in practical applications. Since foodborne viruses are present in... 相似文献
6.
Rates and direction of movement in the sand dollar Peronella lesueuri were measured in summer and winter in Cockburn Sound, a large coastal embayment in south-western Australia. P. lesueuri was found to have a diurnal activity pattern throughout the year and had a greater movement rate in the summer (mean of 5.3 cm h?1, day; 3.9 cm h?1, night) than in the winter (mean of 2.7 cm h?1, day; 2.0 cm h?1, night). Seasonal change in temperature and physiological requirements by the sand dollar are the most likely reason for the seasonal differences. Reasons for diurnal variation were not clear. Direction of movement was found to be random at both times of the year. Based on these movement rates, one sand dollar can bioturbate an approximate area of 0.1 m2 day?1 and 36.4 m2 year?1. At a conservative density estimate of 0.5 sand dollars per m2 it takes approximately 20 days for the sand dollars to rework the entire area of the sediments in the habitats they occupy. 相似文献
7.
Welfare K Flowers TJ Taylor G Yeo AR 《Environmental pollution (Barking, Essex : 1987)》1996,92(3):257-266
Five varieties of rice (Oryza sativa L.) of varying salinity resistance were grown in non-saline and in saline conditions, with and without a repeated exposure to ozone at a concentration of 83 nmol mol(-1) giving an AOT40 (cumulative exposure above 40 nmol mol(-1)) of 3600 nmol mol(-1) h. Salinity caused a substantial reduction in shoot and root dry weight in all varieties, but the effect on root growth was proportionately less than on shoot growth. Ozone reduced root dry weight but the treatment used did not significantly affect shoot dry weight. Both salinity and ozone reduced plant height. The potassium concentration in the leaves of all five varieties was reduced by salinity, and by ozone in both saline and non-saline treatments. Ozone reduced the sodium concentration in plants grown at 50 mM NaCl but had no effect upon the chloride concentration. Carbon dioxide assimilation, transpiration and stomatal conductance were all reduced by salinity and by ozone and there was close quantitative similarity between the effects of ozone and/or salinity upon assimilation, stomatal conductance and transpiration. There were some antagonistic effects but there were additive effects of salinity and of ozone on root dry weight, plant height, shoot potassium concentration, photosynthesis, transpiration and stomatal conductance. The possible basis of the additive effects of salinity and ozone on gas exchange and mineral uptake are discussed. 相似文献
8.
Sock Khim Yeo Chye Peng Ong Hian Kee Lee Sam Fong Yau Li 《Environmental monitoring and assessment》1991,19(1-3):47-53
The applications of Freon-22 (R22) as a mobile phase and as a modifier in supercritical fluid chromatography were investigated. For the purpose of this investigation, the separation of eleven phenols listed by the United States Environmental Protection Agency as priority pollutants was studied. It was found that the use of neat R22 greatly reduced the retention times of the phenols compared with the use of neat carbon dioxide as mobile phase. Satisfactory separation of all the eleven phenols could be achieved using 5% R22 as modifier in carbon dioxide. The promising results obtained in this preliminary investigation indicate the potential for the use of R22 in supercritical fluid separation processes. 相似文献
9.
Seok-Pyo Hong Jong-In Dong Sang-Ku Yeo In-Hee Park Moon-Sik Chung Doo-Il Kim Young-Kwon Park 《Journal of Material Cycles and Waste Management》2011,13(3):186-189
Solid-fuel conversion or gasification study of sewage sludge and energy recovery has become increasingly important because
energy recovery and climate change are emerging issues. Various types of catalysts, such as dolomite, steel slag and calcium
oxide, were tested for tar reduction during the sewage sludge gasification process. For the experiments on sewage sludge gasification
reactions and tar reduction using the catalysts, a fixed bed of laboratory-scale experimental apparatus was set up. The reactor
was made of quartz glass using an electric muffle furnace. The sewage sludge samples used had moisture contents less than
6%. The experimental conditions were as follows: sample weight was 20 g and reaction time was 10 min, gasification reaction
temperature was from 600 to 800°C, and the equivalence ratio was 0.2. The quantity of catalysts was 2–6 g, and temperatures
of catalyst layers were 500–700°C. As the reaction temperature increased up to 800°C, the yields of gaseous products and liquid
products increased, whereas char and tar products decreased, showing effects on gas product compositions. These results were
considered to be due to the increase of the water-gas reaction and Boudouard reaction. In the case of experiments with catalysts,
dolomite (4 g), steel slag (6 g) and calcium oxide (6 g) were used. When the temperature of catalysts increased, the weight
of the tar produced decreased with different cracking performances by different catalysts. Reforming reactions were considered
to occur on the surface of dolomite, steel slag and calcium oxide, causing cracking of the hydrocarbon structure, which eventually
showed reduced tar generation. 相似文献
10.
The aim of this study was to determine the effects of ozone and salinity, singly and in combination, on the growth and ion contents of two chickpea (Cicer arietinum L.) varieties. Chickpea plants were grown in non-saline and saline conditions, with and without a repeated exposure to ozone. Salinity at a concentration of 30 mM NaCl caused a substantial reduction in plant height, number of leaves and the dry weights of the leaves, stems and roots. Biomass allocation to the leaves increased, predominantly at the expense of the roots. Ozone at a concentration of 85 nmol mol(-1) for 6 h per day for 25 days reduced plant height and dry weights but had no effect on leaf number. The results show substantial effects of salinity and ozone on chickpea growth and ion concentrations. When ozonated plants are grown in the presence of salinity, further reductions in growth occur. 相似文献