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Результаты 771-780 из 1,540
Winter Time Concentrations and Size Distribution of Bioaerosols in Different Residential Settings in the UK
2012
Nasir, Zaheer Ahmad | Colbeck, I. (Ian)
The total concentration and size distribution of bioaerosols in three different types of housing (single room in shared accommodation [type I], single bedroom flat in three-storey building [type II] and two- or three-bedroom detached houses [type III]) was assessed during the winter. This research was an extension of a previous study carried out in the summer. The measurement campaign was undertaken in winter 2008 and 30 houses were sampled. Samples were taken from kitchens, living rooms, corridors (only in housing type I) and outdoors with an Anderson 6 stage viable impactor. In housing type I, the total geometric mean concentration was highest in the corridor for both bacteria and fungi (3,171 and 1,281 CFU/m³, respectively). In type II residences, both culturable bacteria and fungi were greatest in the living rooms (3,487 and 833 CFU/m³, respectively). The living rooms in type III residences had largest number of culturable bacteria (1,361 CFU/m³) while fungi were highest in kitchens (280 CFU/m³). The concentrations of culturable bacteria and fungi were greater in mouldy houses than non-mouldy houses. A considerable variation was seen in the size distribution of culturable bacteria in type I residences compared to types II and III. For all housing types more than half of culturable bacterial and fungal aerosol were respirable (<4.7 μm) and so have the potential to penetrate into lower respiratory system. Considerable variation in concentration and size distribution within different housing types in the same geographical region highlights the impact of differences in design, construction, use and management of residential built environment on bioaerosols levels and consequent varied risk of population exposure to airborne biological agents.
Показать больше [+] Меньше [-]Influence of Soil and Climate Conditions on CO2 Emissions from Agricultural Soils
2012
Carbonell-Bojollo, Rosa María | Repullo-Ruibérriz de Torres, Miguel Angel | Rodríguez-Lizana, Antonio | Ordóñez-Fernández, Rafaela
Many of the environmental problems related to agriculture will still be serious over the next 30 years. However, the seriousness of some of those problems may increase more slowly than in the past or even diminish in other cases (FAO 2002). Agriculture plays two different roles in climate change; on one hand, it suffers from the impact of climate change, on the other hand, it is responsible for 14 % of total greenhouse gases (MMA 2008). Nevertheless, agriculture is also part of the solution, as it is capable of mitigating a significant amount of global emissions, according to the FAO (2001). This paper aims to study the influence of edapho-climate conditions on soil CO2 emissions into the atmosphere. In order to do so, we conducted three field trials in different areas in southern Spain, which have different soil textures and different climate conditions. The results show how interaction between the temperature and rainfall recorded has a greater influence on emissions than each of the factors separately. However, at the same time, the texture of the soil at each of the locations was also found to be the most dominant variable in the gas emission process.
Показать больше [+] Меньше [-]Variation of Antioxidant Activity in Dreissena polymorpha Specimens Exposed to 2,2′,4,4′,5,6′-Hexa BDE (BDE-154)
2012
Parolini, Marco | Pedriali, Alessandra | Binelli, Andrea
We evaluated the imbalance of the oxidative status in zebra mussel (Dreissena polymorpha) specimens exposed for 96 h to environmentally relevant concentrations (0.1, 0.5, and 1 μg/L) of the 2,2′,4,4′,5,6′-hexa BDE (BDE-154). The activities of three antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and the phase II detoxifying enzyme glutathione S-transferase (GST), were measured in the cytosolic fraction from a pool of zebra mussels. Significant variations in the activity of each single enzyme were noticed at each treatment, indicating that exposure to BDE-154 was able to impair the oxidative status of treated bivalves through the increase of reactive oxygen species. In detail, SOD and GPx were significantly induced, while CAT and GST were depressed with respect to the baseline levels. These data have confirmed that the raise of oxidative stress is the main cause of the BDE-154-induced genetic damage observed in a previous study on the zebra mussel.
Показать больше [+] Меньше [-]Using Pyrolyzed Rice Husks as an Adsorbent for Purification of Water Basins Polluted with Diesel Fuel
2012
Dimitrov, Aleksandar | Genieva, Svetlana | Petkov, Petko | Vlaev, Lyubomir
Black rice husk ash (BRHA) was obtained by means of thermal degradation of raw rice husks (RRH) on a pilot plant fluidized bed reactor. BRHA was characterized using chemical analyses, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermal analysis. The kinetics was studied using batch adsorption technique and on the basis of prior characterization by X-ray diffraction patterns and scanning electron microscopy. The adsorption capacities of diesel fuel at 288, 293 and 298Â K onto BRHA were determined. Results showed that the material studied has very high adsorption capacity and low cost and may successfully be used as an effective adsorbent to clean up spills of oil products in water basins. The adsorption of diesel fuel onto BRHA proceeds rapidly to reach adsorption equilibrium in about 10Â min. The saturated BRHA can be burnt in incinerators, industrial ovens or steam generators, and through this way ecological and economic benefits are attained.
Показать больше [+] Меньше [-]Experimental Investigation and Artificial Neural Network-Based Modeling of Batch Reduction of Hexavalent Chromium by Immobilized Cells of Newly Isolated Strain of Chromium-Resistant Bacteria
2012
Shetty K., Vidya | L., Namitha | Rao, Shama N. | M., Narayani
The batch bioreduction of Cr(VI) by the cells of newly isolated chromium-resistant Acinetobacter sp. bacteria, immobilized on glass beads and Ca-alginate beads, was investigated. The rate of reduction and percentage reduction of Cr(VI) decrease with the increase in initial Cr(VI) concentration, indicating the inhibitory effect of Cr(VI). Efficiency of bioreduction can be improved by increasing the bioparticle loading or the initial biomass loading. Glass bioparticles have shown better performance as compared to Ca-alginate bioparticles in terms of batch Cr(VI) reduction achieved and the rate of reduction. Glass beads may be considered as better cell carrier particles for immobilization as compared to Ca-alginate beads. Around 90% reduction of 80Â ppm Cr(VI) could be achieved after 24Â h with initial biomass loading of 14.6Â mg on glass beads. Artificial neural network-based models are developed for prediction of batch Cr(VI) bioreduction using the cells immobilized on glass and Ca-alginate beads.
Показать больше [+] Меньше [-]Ecological Environment Protection in Chinese Rural Hydropower Development Practices: A Review
2012
Tang, Xianqiang | Li, Qingyun | Wu, Min | Tang, Wenjian | Jin, Feng | Haynes, Jonathan | Scholz, Miklas
This paper reviews the ecological environment protection measures of Chinese rural hydropower development schemes. China’s rapid economic growth is making great energy demands and developing rural hydropower currently provides 30.4 GW annually. There is a conflict of interest between hydropower development and ecological and environmental protection. Potential problems include changes in hydrological condition, eutrophication, downstream nutrient reduction, sediment deposition, aquatic ecosystem alteration, and ecological water demand variation. Since most of the rural hydropower resources are located in ecologically fragile regions, it is significantly more important that ecological environment protection is being considered. As exploitation of rural hydropower has developed in China, ecological environment protection schemes had to adapt to changing boundary conditions. Due to improvements in environmental protection management, various environmental impact assessment methods have been applied including fuzzy analysis hierarchy process, ecological scheduling, pressure-state-response, and ecological environment evaluation index. The latter index can both qualitatively and quantitatively analyze ecological environment impacts and has become the most frequently used tool in the evaluation of rural hydropower exploitation. To rebalance the interests regarding energy generation and environmental protection, countermeasures originating from different aspects such as engineering design optimization, management improvement, and ecological restoration were recommended to promote ecological environment protection. The review concludes that by taking ecological environment protection into consideration in the whole rural hydropower plan, adopting ecological scheduling to guarantee river ecological water demand and implementing ecological restoration in watershed management are the most effective approaches in furthering sustainable development of rural hydropower.
Показать больше [+] Меньше [-]Potential of Aquatic Macrophytes as Bioindicators of Heavy Metal Pollution in Urban Stormwater Runoff
2012
Ladislas, Séverine | El-Mufleh, Amelène | Gérente, Claire | Chazarenc, Florent | Andrès, Yves | Béchet, Béatrice
The concentrations of heavy metals in water, sediments, soil, roots, and shoots of five aquatic macrophytes species (Oenanthe sp., Juncus sp., Typha sp., Callitriche sp.1, and Callitriche sp.2) collected from a detention pond receiving stormwater runoff coming from a highway were measured to ascertain whether plants organs are characterized by differential accumulations and to evaluate the potential of the plant species as bioindicators of heavy metal pollution in urban stormwater runoff. Heavy metals considered for water and sediment analysis were Cd, Cr, Cu, Ni, Pb, Zn, and As. Heavy metals considered for plant and soil analysis were Cd, Ni, and Zn. The metal concentrations in water, sediments, plants, and corresponding soil showed that the studied site is contaminated by heavy metals, probably due to the road traffic. Results also showed that plant roots had higher metal content than aboveground tissues. The floating plants displayed higher metal accumulation than the three other rooted plants. Heavy metal concentrations measured in the organs of the rooted plants increased when metal concentrations measured in the soil increased. The highest metal bioconcentration factors (BCF) were obtained for cadmium and nickel accumulation by Typha sp. (BCF = 1.3 and 0.8, respectively) and zinc accumulation by Juncus sp. (BCF = 4.8). Our results underline the potential use of such plant species for heavy metal biomonitoring in water, sediments, and soil.
Показать больше [+] Меньше [-]Removal of Anionic Pollutants from Waters and Wastewaters and Materials Perspective for Their Selective Sorption
2012
Lito, Patrícia F. | Aniceto, José P. S. | Silva, Carlos M.
The presence of some anionic species, such as nitrate, nitrite, chloride, sulfide, fluoride, and cyanide, in water supplies may represent a serious environmental problem. In this work, the main sources and harmful effects of their bioaccumulation on living organisms are reviewed, as well as the most adopted technologies for their uptake. The major advantages and disadvantages of each methodology are also listed. In general, ion-exchange has been elucidated as the most suitable removal process. In view of that the most promising materials used to remove anionic pollutants from aqueous solutions are highlighted in this review. In particular, the major efforts towards the development of low-cost and easily available effective sorbents for water decontamination are covered. For instance, natural waste solid materials and derivatives have emerged as promising low-cost exchangers for selective anions uptake. Besides, a number of structural modifications including the introduction of more suitable surface functional groups or compensation species into the sorbent matrix have been investigated in order to enhance sorbents selectivity and capacity for anionic pollutants. The influence of speciation and removal conditions is also focused.
Показать больше [+] Меньше [-]Aerobic Biological Treatment of Chestnut Processing Wastewater
2012
Pirra, António | Lucas, Marco S. | Peres, José A.
Chestnut agro-industrial companies consume a high volume of water for washing and processing fruit, generating a large volume of wastewater. This work studied the biodegradation of chestnut processing wastewater through aerobic assays, varying substrate, and biomass concentrations. In general, this wastewater presents a good biodegradability, especially in experiments with relatively low chemical oxygen demand (COD) (0.4 and 0.6 g O₂ L⁻¹) allowing a COD removal of 85–90 %. The best results were obtained in the reactor initially loaded with 2 g L⁻¹ of biomass and 0.4 or 0.6 g O₂ L⁻¹ of COD. These experiments also showed high COD removal rates: 4.25 and 3.88 g COD g⁻¹ volatile suspended solids (VSS) h⁻¹, respectively. The sedimentation rate, evaluated for different initial values of biomass (1, 2, and 3 g L⁻¹), always presented higher values in the experiments with 2 and 3 g L⁻¹ of biomass, regardless of the initial COD value used. After comparing different kinetic models (Monod, Contois, and Haldane), it was observed that the Haldane inhibition model satisfactorily describes the COD biodegradation. AQUASIM software allowed calculating the kinetic constant ranges: K ₛ, 1.59–6.99 g COD L⁻¹; ν ₘₐₓ, 25–40 g COD g⁻¹ VSS day⁻¹; and K ᵢ values, 0.07–0.11. These kinetic constants corresponds to maximum rates (ν*) between 1.48 and 4.25 g COD g⁻¹ VSS day⁻¹ for substrate concentrations (S*) from 0.38 to 0.88 g COD L⁻¹.
Показать больше [+] Меньше [-]Potential for Phosphate Mitigation from Agricultural Runoff by Three Aquatic Macrophytes
2012
Tyler, H. L. | Moore, M. T. | Locke, M. A.
Phosphate from agricultural runoff is a major contributor to eutrophication in aquatic systems. Vegetated drainage ditches lining agricultural fields have been investigated for their potential to mitigate runoff, acting similarly to a wetland as they filter contaminants. It is hypothesized that some aquatic macrophytes will be more effective at removing phosphate than others. In a mesocosm study, three aquatic macrophyte species, cutgrass (Leersia oryzoides), cattail (Typha latifolia), and bur-reed (Sparganium americanum), were investigated for their ability to mitigate phosphate from water. Mesocosms were exposed to flowing phosphate-enriched water (10 mg L⁻¹) for 6 h, left stagnant for 42 h, and then flushed with non-nutrient enriched water for an additional 6 h to simulate flushing effects of a second storm event. Both L. oryzoides and T. latifolia decreased the load of dissolved phosphate (DP) in outflows by greater than 50 %, significantly more than S. americanum, which only decreased DP by 15 ± 6 % (p ≤ 0.002). All treatments decreased concentrations inside mesocosms by 90 % or more after 1 week, though the decrease occurred more rapidly in T. latifolia and L. oryzoides mesocosms. By discovering which species are better at mitigating phosphate in agricultural runoff, planning the community composition of vegetation in drainage ditches and constructed wetlands can be improved for optimal remediation results.
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