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261.
Hanzel J Thullner M Harms H Wick LY 《Environmental pollution (Barking, Essex : 1987)》2011,159(4):858-864
Limited information exists on influences of the diffusive transport of volatile organic contaminants (VOC) on bacterial activity in the unsaturated zone of the terrestrial subsurface. Diffusion of VOC in the vapor-phase is much more efficient than in water and results in effective VOC transport and high bioavailability despite restricted mobility of bacteria in the vadose zone. Since many bacteria tend to accumulate at solid-water, solid-air and air-water interfaces, such phase boundaries are of a special interest for VOC-biodegradation. In an attempt to evaluate microbial activity toward air-borne substrates, this study investigated the spatio-temporal interplay between growth of Pseudomonas putida (NAH7) on vapor-phase naphthalene (NAPH) and its repercussion on vapor-phase NAPH concentrations. Our data demonstrate that growth rates of strain PpG7 were inversely correlated to the distance from the source of vapor-phase NAPH. Despite the high gas phase diffusivity of NAPH, microbial growth was absent at distances above 5 cm from the source when sufficient biomass was located in between. This indicates a high efficiency of suspended bacteria to acquire vapor-phase compounds and influence headspace concentration gradients at the centimeter-scale. It further suggests a crucial role of microorganisms as biofilters for gas-phase VOC emanating from contaminated groundwater or soil. 相似文献
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263.
This, our second reply to Östensson, supplements our earlier more technical analysis with a simple intuitive explanation of how investor demand can be driving commodity prices higher even when investor stocks are falling. 相似文献
264.
A new strategy of heavy crude oil removal from contaminated soils was studied. The hexane-acetone solvent mixture was used to investigate the ability of solvent extraction technique for cleaning up soils under various extraction conditions. The mixtures of hexane and acetone (25 vol%) were demonstrated to be the most effective in removing petroleum hydrocarbons from contaminated soils and approx 90% of saturates, naphthene aromatics, polar aromatics, and 60% of nC7-asphaltenes were removed. Kinetic experiments demonstrated that the equilibrium was reached in 5 min and the majority of the oil pollutants were removed within 0.5 min. The effect of the ratio between solvent and soil on the extraction efficiency was also studied and results showed that the efficiency would increase following the higher solvent soil ratio. Then the multistage continuous extraction was considered to enhance the removal efficiency of oil pollutants. Three stages crosscurrent and countercurrent solvent extraction with the solvent soil ratio 6:1 removed 97% oil contaminants from soil. Clearly the results showed that the mixed-solvent of hexane and acetone (25 vol%) with character of low-toxic, acceptable cost and high efficiency was promising in solvent extraction to remove heavy oil fractions as well as petroleum hydrocarbons from contaminated soils. 相似文献
265.
Bourcier L Masson O Laj P Pichon JM Paulat P Freney E Sellegri K 《Journal of environmental radioactivity》2011,102(3):294-301
The atmospheric concentrations of 137Cs, 210Pb, and 7Be were measured over a three-year period at two research stations located less than 12 km apart and at different altitudes (puy de Dôme, 1465 m a.s.l. and Opme, 660 m a.s.l., France). Seasonal trends in all radionuclides were observed at both stations, with high concentration measured during the summer and low concentrations during the winter. The 210Pb concentrations at both stations were similar to each other. Higher concentrations of both 7Be and 137Cs were measured at puy de Dôme than at Opme. These observations can be explained by the stratospheric and upper tropospheric sources of 7Be and the long-range transportation of 137Cs at high altitudes. Air mass origins during sampling periods were classified into several groups by their route to the stations (marine, marine modified, continental and mediterranean). We observed that 7Be concentrations were constant regardless of the air mass origins, unlike 137Cs and 210Pb concentrations that increased when influenced by continental air masses. Higher 7Be concentrations were observed when air masses were arriving from the upper troposphere than from the boundary layer, the opposite was observed for 137Cs. The temporal trend in concentrations of 7Be shows good agreement with previous modelling studies suggesting that there is a good understanding of its sources and the atmospheric vertical mixing of this radionuclide. The sources and mixing of 210Pb, however, seem to be more complex than it appeared to be in previous modelling studies. 相似文献
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267.
Helmut W. Fischer Susanne Ulbrich Daniela Pittauerov Bernd Hettwig 《Journal of environmental radioactivity》2009,100(12):1079-1085
Motivated by the detection of 131I in river sediment in routine long-term surveillance samples, a systematic short-term study of the wastewater treatment chain was planned and conducted. Inflow, effluent and primary sludge were collected on a daily basis during two weeks at a regional wastewater treatment plant. Samples were investigated by gamma spectroscopy. Four medically used isotopes could be identified (131I and 99mTc regularly, 153Sm and 123I sporadically). The concentration levels coincide well with literature data for 131I, and with our own long-term data for 131I and 99mTc for the same plant. Cosmogenic 7Be activity in primary sludge correlated well with rainfall intensity. Surface sediment was sampled at low tide at both shores of the river, up- and downstream of the plant. 131I was identified in all samples, with a sharp maximum (about 100 Bq kg−1 d.m.) at the discharge point of the plant and lower levels elsewhere, decreasing monotonically in downstream direction. 7Be and 137Cs showed the same behaviour, but no peak at the discharge point. Predictions from simple equilibrium models for the transport and sedimentation of 131I show good agreement with the experimental data and suggest that the wastewater treatment plant is the main source for this isotope. 相似文献
268.
Sylwia Wojas Sonia Plaza Oskar Siemianowski Anna Ruszczyńska Danuta M. Antosiewicz 《Environmental pollution (Barking, Essex : 1987)》2009,157(10):2781-2789
Arabidopsis MRPs/ABCCs have been shown to remove various organic and inorganic substrates from the cytosol to other subcellular compartments. Here we first demonstrate that heterologous expression of AtMRP7 in tobacco (Nicotiana tabacum var. Xanthi) modifies cadmium accumulation, distribution and tolerance. Arabidopsis MRP7 was localized both in the tonoplast and in the plasma membrane when expressed in tobacco. Its overexpression increased tobacco Cd-tolerance and resulted in enhanced cadmium concentration in leaf vacuoles, indicating more efficient detoxification by means of vacuolar storage. Heterologous AtMRP7 expression also led to more efficient retention of Cd in roots, suggesting a contribution to the control of cadmium root-to-shoot translocation. The results underscore the use of AtMRP7 in plant genetic engineering to modify the heavy-metal accumulation pattern for a broad range of applications. 相似文献
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270.
等离子喷涂法制备了钛基亚氧化钛电极(Ti/Ti_4O_7),以该电极为阳极,研究了电化学氧化法对水中美托洛尔的去除效果.考察了电流密度(5~25 mA·cm~(-2))、极板间距(5~25 mm)和初始浓度(3~50 mg·L~(-1))对美托洛尔电化学降解效率的影响;分析美托洛尔电化学降解过程中溶液总有机碳(TOC)和毒性的变化,鉴别反应中间产物并计算其毒性.研究表明:Ti/Ti_4O_7阳极电化学降解美托洛尔反应符合一级反应动力学规律(R20.95),降解效率随电流密度的增大而增大,随极板间距和初始浓度的增大而减小;TOC去除率在反应40 min后可达56.5%;反应过程中产生了质合比为266、250、223和207的中间产物,造成美托洛尔溶液的生物毒性在电化学反应过程中先升高后下降. 相似文献