خيارات البحث
النتائج 961 - 970 من 1,546
Electrochemical Degradation of a Real Pharmaceutical Effluent النص الكامل
2012
Domínguez, Joaquín R. | González, Tomás | Palo, P. | Sánchez-Martín, J. | Rodrigo, M. A. | Sáez, C.
In this work, the electrochemical treatment of an effluent from the pharmaceutical industry with boron-doped diamond electrodes was investigated. The electrolyses were carried out in a discontinuous operation mode under galvanostatic conditions, using a bench-scale plant equipped with a single-compartment electrochemical flow cell. The effect of operating conditions, such as current density (from 25.7 to 179.4 mA cm2) and flow rate (from 104.8 to 564.7 cm3 min−1), at residence times between 0 and 570 min, was studied. Design of experiments was used for optimizing the process. The global contribution of operative parameters and evolution of the residence time in TOC removal was studied, and a time of 77 min was obtained in order to evaluate the highest influence of the operative parameters. For this time, ANOVA test reported significance for four of the five involved variables. The current density was found to have a considerable positive effect on TOC removal, whereas the flow rate was found to have a moderate negative effect on target variable.
اظهر المزيد [+] اقل [-]Atmospheric Mercury Fluxes in a Southern Boreal Forest and Wetland النص الكامل
2012
Kyllönen, Katriina | Hakola, Hannele | Hellén, Heidi | Korhonen, Markku | Verta, Matti
Total gaseous mercury (TGM) fluxes from the forest floor and a boreal wetland were measured by a flux chamber technique coupled with an automatic mercury vapour analyser. The fluxes were measured at three sampling sites in southern Finland, 61°14′ N, 25°04′ E in summer 2007, with additionally in situ TGM concentrations in the air at one of the sites and mercury bulk deposition at another. Most of the flux data were collected during the daytime. At one of the sites, diurnal flux behaviour was studied, and a clear cycle with an afternoon maximum and a night minimum was observed. The highest emissions (up to 3.5 ng m−2 h−1) were observed at the forest floor site having a moss and grass cover. At the wetland and litter-rich forest floor sites, the emissions were below 1 ng m−2 h−1 and sometimes negative (down to −1.0 ng m−2 h−1), indicating mercury uptake. The measured average fluxes in August were 0.9 ± 1.1 and 0.2 ± 0.3 ng m−2 h−1 for the forest floor sites and wetland sites, respectively. The flux data were compared with the mercury bulk deposition, which proved to be of the same magnitude, but opposite in sign. At the mossy forest floor site, the extrapolated TGM emissions were 130% of the Hg deposition in August 2007. Comparison with other studies showed that the fluxes in background areas are relatively uniform, regardless of measurement site location and method used. Airborne TGM remained at the background level during the study, with an average value of 1.3 ± 0.2 ng m−3; it frequently showed a diurnal cycle pattern.
اظهر المزيد [+] اقل [-]Redox Stratification and Salinization of Three Kettle Lakes in Southwest Michigan, USA النص الكامل
2012
Koretsky, Carla M. | MacLeod, Andrew | Sibert, Ryan J. | Snyder, Christine
Redox stratification, especially hypolimnetic anoxia resulting from eutrophication, and salinization resulting from application of salts for road deicing is investigated in three kettle lakes in southwest Michigan. Two of the lakes (Asylum and Woods Lakes) are located in urban Kalamazoo, Michigan, and the third (Brewster Lake) is located in rural Hastings, Michigan. In summer, the water columns of all three lakes are distinctly redox stratified, with anoxic hypolimnia and significant accumulation of reduced solutes (e.g., Mn(II), Fe(II), ammonia) in the lake bottom waters. Extremely elevated conductivity, chloride, sodium, and potassium levels are observed in the urban Asylum and Woods Lakes compared to the rural Brewster Lake, presumably due to runoff of road salt deicers applied in the surrounding watershed. These significant changes in water quality are of concern because they may detrimentally impact lake mixing, biodiversity, and ecosystem function in the urban lakes.
اظهر المزيد [+] اقل [-]TiO₂ Immobilized Biodegradable Polymer for Photocatalytic Removal of Chlorophenol النص الكامل
2012
Sivlim, Tuğba | Akkan, Şenay | Altın, İlknur | Koc, Melek | Sökmen, Münevver
This study concentrated on the direct immobilization of anatase nano titanium dioxide particles (TiO₂, 44 nm particle size) into or onto a biodegradable polymer, polycaprolactone, by solvent-cast processes. The photocatalytic properties of the produced materials were tested by photocatalytic removal of organic contaminant 4-chlorophenol. Produced TiO₂ immobilized polymer successfully removed 4-chlorophenol (4-CP, 20 ppm which is equal to 1.56 × 10⁻⁴ M) from aqueous solution without additional pH arrangement employing a UV-A light (365 nm) source. Immobilization of n-TiO₂ onto polycaprolactone (PCL) produced improved 4-CP removal percentages, reaching to nearly 85 %. Increased PCL mass significantly increases the removal percentage of 4-CP. When a UVC lamp emitting 254 nm light is used, the removal percentage reaches to 89 %. UV irradiation did not cause any change in the microstructure of the polymeric material (confirmed with ATR-FTIR analysis). This is an important evidence that the material could be reused for further photocatalytic treatments. Produced material seems to be highly promising for successful removal of organic pollutants beside its biodegradable nature.
اظهر المزيد [+] اقل [-]Energy Basal Levels and Allocation among Lipids, Proteins, and Carbohydrates in Enchytraeus albidus: Changes Related to Exposure to Cu Salt and Cu Nanoparticles النص الكامل
2012
Amorim, Mónica J. B. | Gomes, Susana I. L. | Soares, Amadeu M. V. M. | Scott-Fordsmand, Janeck J.
Energy intake and allocation are mainly used to maintain body functions, such as locomotion, growth, and reproductive output. It has been observed that environmental pollutants can affect the energy allocation either due to a cost of handling toxicants or because the toxicant interacts with the storage processes within the organisms. Less than a handful of studies are available reporting the effect of toxicants on energy reserves in enchytraeids and no studies have dealt with the influence of nanomaterials. The present paper shows results on the basal energy reserves (lipids, carbohydrates, and proteins) in Enchytraeus albidus and the influence of copper (Cu) salt and Cu nanoparticles on these reserves for two exposure durations. The energy allocation levels follow what has been reported for other worm species, although lower carbohydrate levels were observed. There were clear differences between worms exposed to control soils and those exposed to Cu for 3Â weeks, but no difference after 6 weeks exposure. There was no apparent difference between the impacts of the two Cu exposure forms.
اظهر المزيد [+] اقل [-]Advanced Oxidation Processes in Triton X-100 and Wash-up Liquid Removal from Wastewater Using Modified TiO₂/Al ₂O ₃ Photocatalysts النص الكامل
2012
Czech, Bożena | Ćwikła-Bundyra, Wiesława
Photocatalytic methods were applied to remove the recalcitrant or toxic pollutants from the water. The two models of wastewater containing either non-ionic surfactant Triton X-100 or commercially available wash-up liquid were tested in a self-constructed band reactor during the laboratory studies. The photocatalyst, being typed TiO₂, was supported by porous Al₂O₃ and modified by the addition of Cu, Fe, Zn, Ni, Mo or Co. The photocatalysts were characterised by N₂ adsorption–desorption, XRF, XRD, SEM-EDX, Raman and UV–Vis spectroscopy. All catalysts were efficient in the photocatalytic oxidation of surfactants, and they enabled at least 85 % COD reduction. TiO₂/Al₂O₃ photocatalysts modified by the transition metals were efficient only for more complicated compositions of surfactants. The effect of H₂O₂ (0.01 vol.%) addition was also examined and compared with a type of compound and catalyst used—in this case a positive effect for Triton X-100 was only observed over the photocatalyst modified by Ni. When it comes to the wash-up liquid photoremoval, all studied photocatalysts seem to be slightly influenced by H₂O₂ addition. It was also observed that it is not economically justified to conduct such treatment for more than 2 h.
اظهر المزيد [+] اقل [-]Inhibition Kinetics of Ammonia Oxidation Influenced by Silver Nanoparticles النص الكامل
2012
Giao, Nguyen Thanh | Limpiyakorn, Tawan | Siripattanakul-Ratpukdi, Sumana
Silver nanoparticles (AgNPs) have significantly increased in production and use for anti-microbial propose. This agent, after used, is released into sewerage system resulting in possibility to inactivate non-targeted microorganisms in wastewater treatment plants. In this study, the inhibitory effect of AgNPs on ammonia oxidation was investigated using respirometric assay. The initial concentrations of AgNPs and ammonia ranged 0.25–10.00 and 14–280 mg/L, respectively. Half saturation constant (K ₛ) for ammonia oxidation was found to be 15.9 mg N/L. Under the presence of AgNPs, the maximum oxygen uptake rate and K ₛ declined. The effect of AgNPs was proved to follow an uncompetitive-like inhibition kinetic type with the inhibition coefficients (K ᵢ) of 5.5 mg/L. Increasing AgNPs from 0.25 to 10.00 mg/L inhibited 4 to 50 % of ammonia-oxidizing activities at the initial ammonia concentrations from 14 to 280 mg/L. Based on transmission electron microscopic observation, AgNPs could damage the microbial cells. All findings indicated that AgNPs substantially reduced ammonia-oxidizing microorganisms and their activities. Thus, special attention should be made to manage discharge of AgNPs into the environment.
اظهر المزيد [+] اقل [-]Using Pyrolyzed Rice Husks as an Adsorbent for Purification of Water Basins Polluted with Diesel Fuel النص الكامل
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.
اظهر المزيد [+] اقل [-]Modeling of Stomatal Conductance for Estimating Ozone Uptake of Fagus crenata Under Experimentally Enhanced Free-air Ozone Exposure النص الكامل
2012
Hoshika, Yasutomo | Watanabe, Makoto | Inada, Naoki | Koike, Takayoshi
We examined a performance of the multiplicative stomatal conductance model to estimate the stomatal ozone uptake for Fagus crenata. Parameterization of the model was carried out by in-situ measurements in a free-air ozone exposure experiment. The model performed fairly well under ambient conditions, with low ozone concentration. However, the model overestimated stomatal conductance under enhanced ozone condition due to ozone-induced stomatal closure. A revised model that included a parameter representing ozone-induced stomatal closure showed better estimation of ozone uptake. Neglecting ozone-induced stomatal closure induced a 20 % overestimation of the stomatal uptake of ozone. The ozone-induced stomatal closure was closely related to stomatal ozone uptake rather than accumulated concentrations of ozone exceeding 40 nmol mol⁻¹. Our results suggest that ozone-induced stomatal closure should be implemented to stomatal conductance model for estimating ozone uptake for F. crenata. The implementation will contribute to adequate risk assessments of ozone impacts on F. crenata forests in Japan.
اظهر المزيد [+] اقل [-]Effect of Green Waste Compost and Mycorrhizal Fungi on Calcium, Potassium, and Sodium Uptake of Woody Plants Grown Under Salt Stress النص الكامل
2012
Marosz, Adam
Sodium chloride is the most often used chemical to malt ice and snow on the roads and has negative effects on the roadside environment. Searching for ways to improve the conditions for growth of trees and shrubs near the roads becomes an urgent matter. One such method of improving growth conditions for plants under salinity might be to use organic matter (green waste compost) and mycorrhizal fungi. This study studied the effect of application in soil different salts on several trees and shrubs growth in growing media. Also, effect of green waste compost and arbuscular mycorrhiza (AM) added to the growing medium was evaluated in terms of growth and K+, Ca+2, and Na+ uptake. The highest pH of the growing medium was noted when sodium carbonate was used. The pH ranged from 8.7 to 9.0 after eight doses of sodium carbonate. The pH of the growing medium was also significantly higher regardless of whether or not green waste compost or mycorrhizal fungi were used. The type of growing medium had a great effect on the growth of most of the trees, but among shrubs the growing medium was only important for Cornus alba, Sambucus nigra, and Spiraea vanhouttei. Growth of all these plants was much better under salinity when green waste compost or green waste compost with AM fungi was used. In all the cases, when salinity of the growing medium retarded growth of trees and shrubs, sodium chloride was the compound that had the strongest growth retarding effect. Leaf ionic composition was significantly affected by salinity in the growing medium, and in some cases also by micorhizal fungi. The type of growing medium had various effects on sodium uptake, depending on species. In most cases, the addition of green waste compost to the growing medium caused a greater amount of sodium in the leaves of tested plants. The use of mycorrhizal fungi had no effect on the uptake of sodium, compared to the control plants (without AM fungi).
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