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Using Pyrolyzed Rice Husks as an Adsorbent for Purification of Water Basins Polluted with Diesel Fuel Texto completo
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.
Mostrar más [+] Menos [-]Modeling of Stomatal Conductance for Estimating Ozone Uptake of Fagus crenata Under Experimentally Enhanced Free-air Ozone Exposure Texto completo
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.
Mostrar más [+] Menos [-]Effect of Green Waste Compost and Mycorrhizal Fungi on Calcium, Potassium, and Sodium Uptake of Woody Plants Grown Under Salt Stress Texto completo
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).
Mostrar más [+] Menos [-]Structural, Transport and Adsorptive Properties of Lantana camara-Reinforced Ethylene Vinyl Acetate Composites Texto completo
2012
Dlamini, Derrick S. | Mishra, Ajay K. | Mamba, Bhekie B.
This paper presents for the first time the technological potential of novel Lantana camara-reinforced ethylene vinyl acetate (EVA) composites fabricated via the melt-blending technique. The composite and L. camara were characterized using X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and deferential scanning calorimeter. L. camara was found to drastically reduce the crystallinity of EVA from 44.3 % to a minimum of 1.16 %. Immersion of the composite specimens in de-ionised water showed that moisture absorption was less significant for composites with L. camara contents less than 15 % (w/w). A maximum sorption capacity of 1.20 mol% was recorded in 42 h which is remarkable considering the hydrophobic nature of EVA with 9 % vinyl acetate. L. camara and the composite removed 96 % and 88 % para-nitrophenol from water, respectively.
Mostrar más [+] Menos [-]Assessment of s-Triazine Catabolic Potential in Soil Bacterial Isolates Applying atz Genes as Functional Biomarkers Texto completo
2012
Fajardo, Carmen | Saccà, Maria Ludovica | Gibello, Alicia | Martinez-Iñigo, María José | Nande, Mar | Lobo, Carmen | Martín Velasco, Margarita
Fluorescence in situ hybridization (FISH) technique and qPCR analyses, targeting atz genes, were applied to detect the presence of simazine-degrading bacteria in an agricultural soil with a history of herbicide application. atzB-targeted bacteria detected by FISH represented 5% of total soil bacteria with potential capability to metabolize the herbicide. The soil natural attenuation capacity was confirmed in soil microcosms by measuring simazine degradation. Moreover, four bacterial strains were isolated from the soil and identified as Acinetobacter lwoffii, Pseudomonas putida, Rhizobium sp. and Pseudomonas sp. The isolates were able to grow using different s-triazine compounds and related metabolites as the sole carbon source. Growth parameters in presence of simazine were calculated using the Gompertz model. Rhizobium sp. showed the highest simazine degradation (71.2%) and mineralization (38.7%) rates, whereas the lowest values were found to A. lwoffii—50.4% of degradation and 22.4% of mineralization. Results from qPCR analyses of atzA, atzB and atzC genes revealed their presence in Rhizobium sp. and A. lwoffii, being atzB and atzC the most abundant functional genes. Rhizobium sp. showed a higher amount of the three biomarkers compared to A. lwoffii: the atzA, atzB and atzC gene copy number per microlitre were, respectively, 101, 102 and 103-fold higher in the former. Therefore the proposed molecular approaches based on the use of atz genes as biomarkers can be considered as useful tools to evaluate the presence and potential capability of degrading-s-triazines soil microorganisms.
Mostrar más [+] Menos [-]A Comparison of Two Collectors for Monitoring Precipitation Chemistry Texto completo
2012
Kelly, Victoria R. | Weathers, Kathleen C. | Lovett, Gary M. | Likens, Gene E.
Comparison of event-based precipitation collected during 1 year showed that samples from a Yankee Environmental Systems collector had significantly higher volume, higher concentrations, and higher deposition of all ions analyzed except PO 4 3− and NH 4 + compared to samples collected simultaneously with an Aerochem Metrics collector.
Mostrar más [+] Menos [-]Aerobic Biological Treatment of Chestnut Processing Wastewater Texto completo
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.
Mostrar más [+] Menos [-]Arsenic Uptake from Arsenic-Contaminated Water Using Hyperaccumulator Pteris vittata L.: Effect of Chloride, Bicarbonate, and Arsenic Species Texto completo
2012
Guo, Huaming | Zhong, Zhennan | Lei, Mei | Xue, Xiaolei | Wan, Xiaoming | Zhao, Junying | Chen, Tongbin
High As groundwater normally contained high concentrations of Cl⁻ and HCO ₃ ⁻ . This study examined the effects of Cl⁻, HCO ₃ ⁻ , and As species on As uptake by hyperaccumulator Pteris vittata. Plants were exposed hydroponically to 5.0 mg/L As(III) or As(V) in the presence of 0, 0.5, 1, 2, 5, 10, and 20 mM of Cl⁻ or HCO ₃ ⁻ for 10 days. Addition of high Cl⁻ concentrations (>10 mM) slightly inhibited P. vittata growth (biomass), while generally had no significant effect on plant As uptake. High solution pH resulted in reduced plant growth and As uptake, which attributed to the inhibitory effects in HCO ₃ ⁻ treatments with the high pH of the high HCO ₃ ⁻ concentration. It was speculated that addition of HCO ₃ ⁻ (<20 mM) would have no significant effect on plant growth and As uptake. The inhibitory effect of HCO ₃ ⁻ on As translocation was less apparent in the As(III) solutions than the As(V) solutions. For the high As groundwater with As(III) as the predominant species, high pH, instead of high concentrations HCO ₃ ⁻ and Cl⁻, was expected to inhibit As uptake. The results suggested that optimum plant growth and maximum As hyperaccumulation could be achieved by adjusting solution pH in the growth media (around 7.2).
Mostrar más [+] Menos [-]Kinetic, Isotherm and Thermodynamic Analysis on Adsorption of Cr(VI) Ions from Aqueous Solutions by Synthesis and Characterization of Magnetic-Poly(divinylbenzene-vinylimidazole) Microbeads Texto completo
2012
Kara, Ali | Demirbel, Emel
The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53–212 μm) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N2 adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin–Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol−1, which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field.
Mostrar más [+] Menos [-]Arbuscular Mycorrhizal Fungal Infectivity in Two Soils as Affected by Atmospheric Phenanthrene Pollution Texto completo
2012
Desalme, Dorine | Chiapusio, Geneviève | Bernard, Nadine | Gilbert, Daniel | Toussaint, Marie-Laure | Binet, Philippe
Arbuscular mycorrhizal fungi (AMF) hold a crucial role in ecosystems because they are involved in nutrient cycling between soil and plants. This work aimed at evaluating the impacts that atmospheric pollution by polycyclic aromatic hydrocarbons may have on infectivity of indigenous AMF in soils. Two agricultural soils (Maconcourt, La Bouzule) were exposed for 2 weeks to ambient air (control, C) or to atmospheric phenanthrene (PHE) deposition (180 μg m−3 air). After exposure, soils were divided into a top (0–1 cm) and a bottom (1–15 cm) layer fraction. AMF infectivities of soils were determined after 2 weeks of atmospheric exposition using leek (Allium porum) as bioassay plant. Atmospheric PHE was mainly recovered in the top layer of soil (500–1,350 μg kg−1) of both soils and did not readily diffuse into the depth. Atmospheric contamination led to decreases in AMF infectivities of the top layer in both soils and affected the growth of leeks. Our results not only report evidence that infectivity of indigenous AMF is sensitive to PHE in soils but also emphasize that AMF are primary affected by the soil layer regardless to the pollution level.
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