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Результаты 1801-1810 из 2,513
Visible-light driven oxidation of gaseous aliphatic alcohols to the corresponding carbonyls via TiO₂ sensitized by a perylene derivative Полный текст
2014
Guarisco, Chiara | Palmisano, Giovanni | Calogero, Giuseppe | Ciriminna, Rosaria | Di Marco, Gaetano | Loddo, Vittorio | Pagliaro, Mario | Parrino, Francesco
Sensitized P25 TiO₂ was prepared by wet impregnation with a home-prepared perylene dye, i.e., N,N′-bis(2-(1-piperazino)ethyl)-3,4,9,10-perylene-tetracarboxylic acid diimide dichloride (PZPER). Energy levels of PZPER were found to be compatible with those of TiO₂ allowing fast electron transfer. The obtained catalyst has been characterized and used in the gas-phase partial oxidation of aliphatic primary and secondary alcohols, i.e., methanol, ethanol, and 2-propanol. The reaction was carried out under cut-off (λ > 400 nm) simulated solar radiation in O₂ atmosphere. The perylene derivative allowed a good absorbance of visible radiation thanks to its low optical energy gap (2.6 eV) which was evaluated by cyclic voltammetry. The optimal organic sensitizing amount was found to be 5.6 % w/w in terms of yield in carbonyl derivatives. Moreover, no change in reactivity/selectivity was observed after 10-h irradiation thus confirming the catalyst stability. Yields into formaldehyde, acetaldehyde, and acetone were 67, 70, and 96 %, respectively. No significant amounts of organic byproducts were detected but for methanol oxidation, whereas a minor amount of the substrate degraded to CO₂.
Показать больше [+] Меньше [-]Effects of diethylphthalate and di-(2-ethyl)hexylphthalate on the physiology and ultrastructure of cucumber seedlings Полный текст
2014
Zhang, Ying | Wang, Lei | Du, Na | Ma, Guangpeng | Yang, Aimin | Zhang, Hui | Wang, Zhigang | Song, Qiuxia
Phthalic acid esters (PAEs) are one kind of persistent organic pollutants. This study was conducted to investigate the effects of diethylphthalate (DEP) and di(2-ethyl)hexylphthalate (DEHP) with different concentrations (0, 30, 50, 100, and 200 mg L⁻¹) on early seedling growth of Cucumis sativus L. Physiological, biochemical, and ultrastructure of seedling leaves were examined for 7-day exposure. The three antioxidant enzymes’ activities was stimulated at low-DEP treatments and decreased under higher levels (>200 mg L⁻¹) compared to the controls. Furthermore, MDA and H₂O₂gradually enhanced with the elevation of DEP and DEHP concentration. Significant impact on the chloroplast and mitochondrion was visible, possibly as a consequence of free radical generation. DEP induced bigger and more starch grains in chloroplasts than DEHP. This study concluded that the effects of DEP and DEHP on cucumber seedlings represented the adverse impacts of DEP and DEHP on the ecosystem and agricultural production. The environmental harm caused by DEP was severer than DEHP.
Показать больше [+] Меньше [-]Filter materials for metal removal from mine drainage—a review Полный текст
2014
Westholm, Lena Johansson | Repo, Eveliina | Sillanpää, Mika
A large number of filter materials, organic and inorganic, for removal of heavy metals in mine drainage have been reviewed. Bark, chitin, chitosan, commercial ion exchangers, dairy manure compost, lignite, peat, rice husks, vegetal compost, and yeast are examples of organic materials, while bio-carbons, calcareous shale, dolomite, fly ash, limestone, olivine, steel slag materials and zeolites are examples of inorganic materials. The majority of these filter materials have been investigated in laboratory studies, based on various experimental set-ups (batch and/or column tests) and different conditions. A few materials, for instance steel slag materials, have also been subjects to field investigations under real-life conditions. The results from these investigations show that steel slag materials have the potential to remove heavy metals under different conditions. Ion exchange has been suggested as the major metal removal mechanisms not only for steel slag but also for lignite. Other suggested removal mechanisms have also been identified. Adsorption has been suggested important for activated carbon, precipitation for chitosan and sulphate reduction for olivine. General findings indicate that the results with regard to metal removal vary due to experimental set ups, composition of mine drainage and properties of filter materials and the discrepancies between studies renders normalisation of data difficult. However, the literature reveals that Fe, Zn, Pb, Hg and Al are removed to a large extent. Further investigations, especially under real-life conditions, are however necessary in order to find suitable filter materials for treatment of mine drainage.
Показать больше [+] Меньше [-]Genotoxicity and cytotoxicity induced by municipal effluent in multiple organs of Wistar rats Полный текст
2014
da Silva, Victor Hugo Pereira | de Moura, Carolina Foot Gomes | Ribeiro, Flavia Andressa Pidone | Cesar, Augusto | Pereira, Camilo Dias Seabra | Silva, Marcelo Jose Dias | Vilegas, Wagner | Ribeiro, Daniel Araki
The aim of this study was to evaluate cytotoxicity and genotoxicity in multiple organs of rats induced by municipal effluent released by submarine outfall in city of Santos. A total of 20 male Wistar rats were exposed to effluents by drinking water ad libitum at concentrations of 0, 10, 50, and 100 % for 30 days. Microscopic analysis revealed severe lesions such as necrosis and hemorrhagic areas in liver and kidney from animals exposed to effluent at 50 and 100 % concentration. DNA damage in peripheral blood, liver, and kidney cells were detected by comet assay at higher concentrations of effluent. Moreover, a decrease DNA repair capacity was detected in liver cells. Significant statistical differences (p < 0.05) for micronucleated cells from liver were noticed at 50 % concentration of effluent. Taken together, our results demonstrate that municipal effluent is able to induce cytotoxicity and genotoxicity in multiple organs of Wistar rats.
Показать больше [+] Меньше [-]Electrolytic removal of Rhodamine B from aqueous solution by peroxicoagulation process Полный текст
2014
Nidheesh, Puthiya Veetil | Gandhimathi, Rajan
Peroxicoagulation treatment of aqueous solution containing hazardous dye, Rhodamine B, with commercially available graphite as cathode and iron as anode has been studied. The effect of various operational parameters such as solution pH, applied voltage, electrode area, other ions, etc. on the dye removal was investigated. The experimental result showed that pH-regulated peroxicoagulation system is an efficient process for the dye removal. Ninety-five percent of the dye was removed after 180 min of electrolysis. Anions such as carbonate, bicarbonate, chloride and sulphate negatively affected the efficiency of peroxicoagulation system. From the present study, it can be concluded that peroxicoagulation process is an efficient tool for dye removal from aqueous solution.
Показать больше [+] Меньше [-]Deposition and regional distribution of HCHs and p,p′-DDX in the western and southern Tibetan Plateau: records from a lake sediment core and the surface soils Полный текст
2014
Tao, Yu-Qiang | Lei, Guo-Liang | Xue, Bin | Yao, Shu-Chun | Pu, Yang | Zhang, Hu-Cai
Tibetan Plateau is the world’s highest plateau, which provides a unique location for the investigation of global fractionation of organochlorine pesticides (OCPs). In this study, deposition and regional distribution of HCHs and p,p′-DDX in the western and southern Tibetan Plateau were investigated by the records from a sediment core of Lake Zige Tangco and 24 surface soils. Concentration of ΣHCHs in the surface soils of the western Tibetan Plateau was much higher than that of the southern part. Maximum fluxes of α-, β-, and δ-HCH in the sediment core were 9.0, 222, and 21 pg cm⁻² year⁻¹, respectively, which appeared in the mid-1960s. Significant correlations were observed between concentrations of α- and β-HCH in both the surface soils and the sediment core. Concentrations of both α- and β-HCH increased with the inverse of the average annual temperature of these sites. γ-HCH became the dominant isomer of HCHs after the late 1970s, and reached the maximum flux of 160 pg cm⁻² year⁻¹in the early 1990s. There were no significant correlations between concentrations of γ-HCH and the other isomers in both the surface soils and the sediment core. The results suggested that there was input of Lindane at scattered sites in this area. In contrast to ΣHCHs, concentration of Σp,p′-DDX in the surface soils of the southern part was much higher than that of the western part. Maximum flux of Σp,p′-DDX was 44 pg cm⁻² year⁻¹, which appeared in the mid-1960s. Local emission of p,p′-DDT was found at scattered sites. This study provides novel data and knowledge for the OCPs in the western and southern Tibetan Plateau, which will help understand the global fractionation of OCPs in remote alpine regions.
Показать больше [+] Меньше [-]Fate of pharmaceutical compounds and steroid hormones in soil: study of transfer and degradation in soil columns Полный текст
2014
Salvia, Marie-Virginie | Experton, Julie | Geandel, Claire | Cren-Olivé, Cécile | Vulliet, Emmanuelle
Numerous chemical products are dispersed into the environment, and the consequences can be sometimes harmful to humans and ecosystems. Pharmaceutical compounds and hormone steroids are among these substances that concern the scientific community. Currently, little data are available on the presence and fate of these compounds in the environment and, in particular, for solid matrices. Therefore, the aim of this work was to perform soil column experiments to evaluate the accumulation, transfer and degradation of these substances in soil. The analyses were based on efficient sample preparation followed by sensitive and selective liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). For this purpose, 23 compounds were chosen including both pharmaceutical compounds as well as steroid hormones. In addition, this experiment was performed on two soils with different properties (% clay, pH, etc.). To the best of our knowledge, no soil column experiments have been performed previously on a large number of pharmaceutical compounds and steroid hormones. Significant transfer was observed only for sulphonamides that can be justified by their polarity (log K ₒw < 3). Furthermore, some compounds have a cationic characteristic and are likely to be not much mobiles in soil due to cation exchange process. However, it was observed that the migration of the substances depends on the soil characteristics, such as the amount of clay and the pH values. Regarding the degradation, it was noticed that substances degraded rapidly in the two soils. Indeed, for most substances, their half-lives were lower than 20 days. Furthermore, it was observed that the degradation rate depended on the soil.
Показать больше [+] Меньше [-]Seasonal variations in the chemical composition of particulate matter: a case study in the Po Valley. Part I: macro-components and mass closure Полный текст
2014
Perrino, C. | Catrambone, M. | Dalla Torre, S. | Rantica, E. | Sargolini, T. | Canepari, S.
The seasonal variability in the mass concentration and chemical composition of atmospheric particulate matter (PM₁₀and PM₂.₅) was studied during a 2-year field study carried out between 2010 and 2012. The site of the study was the area of Ferrara (Po Valley, Northern Italy), which is characterized by frequent episodes of very stable atmospheric conditions in winter. Chemical analyses carried out during the study allowed the determination of the main components of atmospheric PM (macro-elements, ions, elemental carbon, organic matter) and a satisfactory mass closure was obtained. Accordingly, chemical components could be grouped into the main macro-sources of PM: soil, sea spray, inorganic compounds from secondary reactions, vehicular emission, organics from domestic heating, organics from secondary formation, and other sources. The more significant seasonal variations were observed for secondary inorganic species in the fine fraction of PM; these species were very sensitive to air mass age and thus to the frequency of stable atmospheric conditions. During the winter ammonium nitrate, the single species with the highest concentration, reached concentrations as high as 30 μg/m³. The intensity of natural sources was fairly constant during the year; increases in natural aerosols were linked to medium and long-range transport episodes. The ratio of winter to summer concentrations was roughly 2 for combustion product, close to 3 for secondary inorganic species, and between 2 and 3 for organics. The winter increase of organics was due to poorer atmospheric dispersion and to the addition of the emission from domestic heating. A similar winter to summer ratio (around 3) was observed for the fine fraction of PM.
Показать больше [+] Меньше [-]Application of activated M/ZnO (M = Mn, Co, Ni, Cu, Ag) in photocatalytic degradation of diazo textile coloring dye Полный текст
2014
Milenova, K. | Avramova, I. | Eliyas, A. | Blaskov, V. | Stambolova, I. | Kassabova, Nikoleta
Activated ZnO powder has been prepared by procedures involving first its dissolution in nitric acid, then simultaneous treatment by adding NH₄OH and CO₂ bubbling leading to precipitation as Zn(OH)CO₃ (ZH) and further thermal decomposition of ZH at 400 °C. The gas evolution leads to formation of pores and increase in the specific surface area. Chemically activated M/ZnO powders doped with Mn, Co, Ni, Cu, and Ag have been obtained by the impregnation method. The samples have been characterized by ultraviolet-visible (UV-Vis) spectroscopy, diffuse reflectance (DR) UV-Vis, X-ray diffraction (XRD), single point Brunauer–Emmet–Teller (BET), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) methods. The experiments have shown that metal-doped activated ZnO powders possess higher photocatalytic activities in oxidative discoloration of model contaminant textile coloring dye Reactive Black 5 in slurry reactor compared to that of the pure ZnO. The XRD and XPS data have shown the presence of defects, nonstoichiometricity implying the formation of solid solutions. Copper-doped (1.5 wt%) activated ZnO (Cu²⁺ replaces Zn²⁺) is outstanding in its photocatalytic performance in discoloration of the dye due to the higher specific surface area and improved charge carrier separation.
Показать больше [+] Меньше [-]Mercury in the Mediterranean. Part 2: processes and mass balance Полный текст
2014
Žagar, Dušan | Sirnik, Nataša | Četina, Matjaž | Horvat, Milena | Kotnik, Jože | Ogrinc, Nives | Hedgecock, Ian M. | Cinnirella, Sergio | De Simone, Francesco | Gencarelli, Christian N. | Pirrone, Nicola
Mass balance of contaminants can provide useful information on the processes that influence their concentrations in various environmental compartments. The most important sources, sinks and the equilibrium or non-equilibrium state of the contaminant in individual environmental compartments can also be identified. Using the latest mercury speciation data, the results of numerical models and the results of recent studies on mercury transport and transformation processes in the marine environment, we have re-evaluated the total mercury (HgT) mass balance in the Mediterranean Sea. New calculations have been performed employing three distinct marine layers: the surface layer, the thermocline and the deep sea. New transport mechanisms, deep water formation and density-driven sinking and upwelling, were included in the mass balance calculations. The most recent data have even enabled the calculation of an approximate methylmercury (MeHg) mass balance. HgT is well balanced in the entire Mediterranean, and the discrepancies between inputs and outputs in individual layers do not exceed 20 %. The MeHg balance shows larger discrepancies between gains and losses due to measurement uncertainties and gaps in our knowledge of Hg species transformation processes. Nonetheless, the main sources and sinks of HgT (deposition and evasion) and MeHg (fluxes from sediment, outflow through the Gibraltar Strait) are in accordance with previous studies on mercury in the Mediterranean Basin. Mercury in the Mediterranean fish harvest is the second largest MeHg sink; about 300 kg of this toxic substance is consumed annually with sea food.
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