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Resultados 1041-1050 de 2,512
Synthesis and Characterisation of Novel-Activated Carbon from Waste Biomass Pine Cone and Its Application in the Removal of Congo Red Dye from Aqueous Solution by Adsorption Texto completo
2014
Dawood, Sara | Sen, Tushar Kanti | Phan, Chi
This study was undertaken to synthesise a novel biomass-based chemically activated carbon from Australian pine cone and to investigate its effectiveness in the removal of anionic dye Congo red from aqueous solution. The effect of activation parameters such as the concentration of phosphoric acid and temperature were identified as the most efficient parameters for activation in the Congo red removal. The synthesised activated carbon was characterised by Fourier transform infrared and different physical properties, such as bulk density, CHNS analysis, carbon yield, particle size, zeta potential and Brunauer–Emmett–Teller surface area were also determined. Batch adsorption study showed that the amount of adsorption depends on various physico-chemical process parameters, such as solution pH, dye concentration, temperature and adsorbent dose. It was observed that Langmuir maximum adsorption capacity was 500 mg/g at a pH of 3.5. Furthermore, pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion models were fitted to examine the adsorption kinetic and mechanism of adsorption. Equilibrium data were fitted with Langmuir, Freundlich and Tempkin adsorption isotherm models. Thermodynamic parameters such as ΔG⁰, ΔH⁰, and ΔS⁰were also calculated. Finally, a single-stage batch adsorber design for the Congo red adsorption onto activated carbon particles was presented based on the Freundlich isotherm model equation. These results indicated pine cone biomass is a good and cheap precursor for the production of an effective activated carbon adsorbent and alternative to commercial-activated carbon.
Mostrar más [+] Menos [-]Tissue-Specific Variations of Esterase Activities in the Tadpoles and Adults of Pseudis paradoxa (Anura: Hylidae) Texto completo
2014
Attademo, Andrés M. | Peltzer, Paola M. | Lajmanovich, Rafael C. | Basso, Agustín | Junges, Celina
We determined basal levels of cholinesterase (ChE) and carboxylesterase (CbEs; two substrates: α-naphthyl acetate and 4-nitrophenylvalerate) in different tissues of tadpoles and adults of the frog Pseudis paradoxa and evaluated their use as complementary biomarkers of anti-cholinesterase pesticide exposure. ChE and CbEs sensitivity to malaoxon was also evaluated. Adults and tadpoles were collected with sweep net from temporary ponds located in natural riparian forests along the Paraná River (Garay Department, Santa Fe province, Argentina). We found significant differences in B-esterase activities between adults and tadpoles and among different tissues. The in vitro inhibition tests indicated that ChE is more sensitive to inhibition than CbEs. Our results suggest that basal ChE and CbE (α-NA and 4-NPV) activities in different tissues of adult and tadpoles P. paradoxa would be suitable biomarkers of pesticide exposure, and this amphibian species could be used as sentinel in field monitoring.
Mostrar más [+] Menos [-]Application of Controlled-Release Nitrogen Fertilizer Decreased Methane Emission in Transgenic Rice from a Paddy Soil Texto completo
2014
Wenlin, Zhou | Yunsheng, Lou | Lixuan, Ren | Yan, Han | Yan, Meng | Lei, Wu
A pot experiment was conducted to investigate the effect of nitrogen fertilizer on CH₄ emission from a paddy soil under greenhouse conditions. The experiment was designed with two fertilizer types, i.e., controlled-release nitrogen fertilizer (CRNF) and urea (U), and two rice cultivars, i.e., herbicide-resistant transgenic rice (japonica line B2) and its parent conventional rice (japonica cv Xiushui 63). Compared with control (urea), one-time basal application of CRNF increased tiller number, plant height, biomass, and yield in rice and significantly decreased total CH₄ emission from the paddy soil. The total CH₄ emission was significantly lower from the transgenic cultivar than that from the conventional cultivar. It is suggested that CRNF and herbicide-resistant transgenic rice are helpful in mitigating CH₄ emission from the paddy soil.
Mostrar más [+] Menos [-]Burkholderia sp. SCMS54 Triggers a Global Stress Defense in Tomato Enhancing Cadmium Tolerance Texto completo
2014
Dourado, Manuella N. | Souza, Lucas A. | Martins, Paula F. | Peters, Leila P. | Piotto, Fernando A. | Azevedo, Ricardo A.
Cadmium is a toxic element for living organisms. This metal causes different damages to the cell, generating oxidative stress. In order to elucidate cadmium tolerance mechanism and increase tomato plant tolerance by inoculating a Cd-tolerant Burkholderia strain, we analyzed malondialdehyde, hydrogen peroxide content, and the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione S-transferase of two strains, one isolated from a soil contaminated with Cd (strain SCMS54) and the other from a soil without Cd (strain SNMS32). Strains SNMS32 and SCMS54 exhibited different SOD, CAT, and GR isoenzyme profiles in non-denaturing polyacrylamide gel electrophoresis analysis, with strain SCMS54 exhibiting an extra isoenzyme for all enzymes (Mn-SOD, CAT I, and GR IV, respectively). Despite accumulating more Cd, strain SCMS54 did not increase peroxide hydrogen and presented a fast antioxidant response (increasing SOD and CAT after 5 h of Cd exposure). In this way, strain SCMS54 exhibited a higher metabolic diversity and plasticity when compared to strain SNMS32, so it was selected for Cd–Burkholderia–tomato interaction studies. Inoculated tomato plants in the presence of Cd grew more than non-inoculated plants with Cd indicating that the SCMS54 increased tomato Cd tolerance. It appears that the strain isolated from Cd-contaminated soil (SCMS54) triggers a global stress response in tomato increasing plant tolerance, which may enable plants to be cultivated in Cd-contaminated soils.
Mostrar más [+] Menos [-]Exploring the Cr(VI) Phytoremediation Potential of Cosmos bipinnatus Texto completo
2014
Santiago-Cruz, M. A. | Villagrán-Vargas, E. | Velázquez-Rodríguez, A. S. | Vernon-Carter, E. J. | Cruz-Sosa, F. | Orozco-Villafuerte, J. | Buendía-González, L.
Seedlings of Cosmos bipinnatus were cultured in vitro for 30 days on modified Murashige–Skoog medium supplemented with four different concentrations of hexavalent chromium (Cr(VI); 0.0–2.0 mM). Seed germination occurred after 7 days of culture, but was significantly lower when cultured in 2.0 mM Cr(VI) than when cultured without Cr(VI) in the medium. Seedlings were able to survive heavy metal stress condition, irrespectively of the Cr(VI) concentration used. The seedlings showed two metal tolerance mechanisms that were dependent on chromium concentration: (1) metal exclusion at 0.0–0.5 mM and (2) metal accumulation at 1.0–2.0 mM. Regarding the latter mechanism, seedlings showed metal accumulation values considered as characteristic of hyperaccumulator species. The highest bioaccumulation in dry tissue was of 5443 mg Cr kg⁻¹in shoot and 4767 mg Cr kg⁻¹in root for seedlings cultured with 2.0 mM of Cr(VI). These results indicated that substantial Cr translocation from the roots unto shoots took place (translocation factor > 1.14) associated to a bioaccumulation factor for Cr(VI) greater than 98.
Mostrar más [+] Menos [-]Microplastics in the pelagic environment around oceanic islands of the Western Tropical Atlantic Ocean Texto completo
2014
Ivar do Sul, Juliana A. | Costa, Monica F. | Fillmann, Gilberto
Recent evidence suggests that microplastic pollution is widespread in every oceanic basin; however, there is limited data available for the tropical South Atlantic Ocean. The purpose of this study was to examine the distribution, density and characteristics of plastic particles in plankton samples collected in the western tropical Atlantic Ocean. Neustonic tows (N = 160) were conducted near three important insular environments (Fernando de Noronha, Abrolhos and Trindade), and the presence of microplastics in the ocean surface of these areas was confirmed for the first time. The collected microplastic particles included hard plastic fragments, plastic films, paint chips and fibres and strands, which were classified as a secondary source of microplastics. The stock of plastic originates from both land-based and marine-based sources. This type of marine pollution in the tropical Atlantic Ocean is a potential threat to important ecological species.
Mostrar más [+] Menos [-]Modeling the Odor Generation in WWTP: An Integrated Approach Review Texto completo
2014
Carrera-Chapela, Fabio | Donoso-Bravo, Andres | Souto, José A. | Ruiz-Filippi, Gonzalo
Nuisance odors generation from waste and wastewater treatment plants are a cause of public discomfort and complaints. This situation impairs the air quality and represents a growing social and public health problem, especially in developing countries. Several modeling approaches have been developed and successfully implemented in the frame of a wastewater treatment plant for both the biological treatment and physicochemical processes. The mathematical modeling of the odor generation process is still considered a quite complex issue, mainly due to the fact that olfactory nuisance can be caused by many different chemical compounds and the perception of odors is influenced by subjective thresholds. Moreover, the impact of odor sources on air quality is highly conditioned by complex atmospheric dispersion processes. This review presents a critical state-of-art and assessment where information related to odor emissions impact studies as well as modeling applications are compiled and discussed.
Mostrar más [+] Menos [-]Iron Oxide Nanoparticle-Impregnated Alumina for Catalytic Ozonation of para-Chlorobenzoic Acid in Aqueous Solution Texto completo
2014
Park, Hosik | Kim, Jun | Jung, Haeryong | Seo, Jungkwon | Choi, Heechul
A granular media synthesized using iron oxide nanoparticle-coated alumina (IONA) has been demonstrated as an effective solid catalyst in the heterogeneous catalytic ozonation of para-chlorobenzoic acid (pCBA). TEM analysis showed that iron oxide nanoparticles with an average size of 5–20 nm were well-coated onto an alumina surface. It was determined that the iron oxide nanoparticle coating increased the specific surface area by 54 times and the functional group density by 1.5 times. During catalytic ozonation at acidic pH levels, it was clearly observed that IONA increased the degradation of pCBA (98 %) through effective hydroxyl radical formation compared to bare alumina (9 %) under continuous ozonation processes. In comparing the Rcₜvalue, which represents the ratio of ozone exposure to hydroxyl radical exposure, the Rcₜof IONA was approximately four times higher than for bare alumina. In addition, IONA showed good stability for catalytic ozonation of pCBA in the reusability tests.
Mostrar más [+] Menos [-]Pesticides in River and Tap Water in a Rice Production Area of Niigata, Japan Texto completo
2014
Narushima, Terukazu | Sato, Takehiko | Goto, Yusuke | Takahashi, Yukio
Water samples collected in 1995 and 2007 from the Shinano and Agano rivers were examined to determine the types and concentrations of pesticides and their effects on tap water in typical rice production areas of Japan. Tap water originating from the Shinano River was also sampled in 2007, in Niigata City, Japan. Pesticides were present in the river and tap water throughout the year. Comparison of 13 pesticides common to both 1995 and 2007 series revealed that the frequency of individual pesticide occurrence and concentrations were decreasing. Riverine pesticides were classified into five groups according to the period of their appearance and changes in concentration. Pesticides were detected at the time of application to, and drainage from, paddy fields. Pesticide concentrations in tap water showed notable decline following rapid sand-filtration combined with granular activated carbon. The detection index (DI) for tap water and Shinano River water did not exceed a value of 1. Herbicides contributed most to the DI.
Mostrar más [+] Menos [-]Evaluation of Di-1-p-Menthene as Antiozonant on Bel-W3 Tobacco Plants, as Compared with Ethylenediurea Texto completo
2014
Agathokleous, Evgenios | Saitanis, Costas J. | Papatheohari, Yolanda
Tropospheric ozone (O₃) has long been documented to cause an injury to plants, but a plants’ protectant, widely applicable in agronomical practice, does not exist. We evaluated the potential antiozonate efficacy of the antitranspirant di-1-p-menthene (Vapor Gard) compared with ethylenediurea (EDU) on Bel-W3 tobacco plants. Plants were treated either with water, or by EDU (10, 100, and 500 mg dm⁻³), or by vapor (1, 5, 10, and 50 ml dm⁻³) and were exposed either to O₃-enriched (90 ppb) or O₃-free air, for 12 days and 8 h day⁻¹. EDU when applied at 10 mg dm⁻³did not protect the plants against O₃, but when applied at 100 and 500 mg dm⁻³offered a significant protection to the plants. Vapor, when applied at 1 ml dm⁻³did not protect the plants against O₃, neither by terms of foliar visible injury nor by terms of aboveground biomass. In addition, when applied at 10 and 50 ml dm⁻³caused phytotoxicity to all the plants, which it was expressed as necrotic spots on the leaves’ surface, misshaping of the leaves, or short plants' height.It is obvious that vapor does not protect Bel-W3 tobacco plants against O₃. The antiozonate role of di-1-p-menthene is species-specific and probably occurs only under short-term exposures.
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