خيارات البحث
النتائج 2011 - 2020 من 2,512
Estimated crop yield losses due to surface ozone exposure and economic damage in India النص الكامل
2014
Debaje, S. B.
In this study, we estimate yield losses and economic damage of two major crops (winter wheat and rabi rice) due to surface ozone (O₃) exposure using hourly O₃concentrations for the period 2002–2007 in India. This study estimates crop yield losses according to two indices of O₃exposure: 7-h seasonal daytime (0900–1600 hours) mean measured O₃concentration (M7) and AOT40 (accumulation exposure of O₃concentration over a threshold of 40 parts per billion by volume during daylight hours (0700–1800 hours), established by field studies. Our results indicate that relative yield loss from 5 to 11 % (6–30 %) for winter wheat and 3–6 % (9–16 %) for rabi rice using M7 (AOT40) index of the mean total winter wheat 81 million metric tons (Mt) and rabi rice 12 Mt production per year for the period 2002–2007. The estimated mean crop production loss (CPL) for winter wheat are from 9 to 29 Mt, account for economic cost loss was from 1,222 to 4,091 million US$ annually. Similarly, the mean CPL for rabi rice are from 0.64 to 2.1 Mt, worth 86–276 million US$. Our calculated winter wheat and rabi rice losses agree well with previous results, providing the further evidence that large crop yield losses occurring in India due to current O₃concentration and further elevated O₃concentration in future may pose threat to food security.
اظهر المزيد [+] اقل [-]The removal of uranium (VI) from aqueous solutions onto activated carbon developed from grinded used tire النص الكامل
2014
Belgacem, Ahmed | Rebiai, Rachid | Hadoun, Hocine | Khemaissia, Sihem | Belmedani, Mohamed
In this study, activated carbon was prepared from waste tire by KOH chemical activation. The pore properties including the BET surface area, pore volume, pore size distribution, and average pore diameter were characterized. BET surface area of the activated carbon was determined as 558 m²/g. The adsorption of uranium ions from the aqueous solution using this activated carbon has been investigated. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied by a batch method. The optimum pH for adsorption was found to be 3. The removal efficiency has also been determined for the adsorption system as a function of initial concentration. The experimental results were fitted to Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models. A comparison of best-fitting was performed using the coefficient of correlation and the Langmuir isotherm was found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of uranium ions onto waste tire activated carbon was 158.73 mg/g. The thermodynamic equilibrium constant and the Gibbs free energy were determined and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo-second-order model.
اظهر المزيد [+] اقل [-]The influences of pH and ionic strength on the sorption of tylosin on goethite النص الكامل
2014
Guo, Xuetao | Yang, Chen | Wu, Yinai | Dang, Zhi
As one of the widely used antibiotics in the world, the environmental risks of tylosin (TYL) received more and more attention. In order to assess its environmental fate and ecological effects accurately, it is necessary to understand the sorption properties of TYL on the soils/sediments. The sorption of TYL on goethite at different pH and ionic strength conditions were measured through a series of batch experiments and the sorption data of TYL were fitted by Freundlich and dual-mode sorption models. It was obvious that sorption was strongly dependent on pH and ionic strength. Sorption capacity of TYL increased as the pH increased and ionic strength decreased. The pH and ionic strength-dependent trends might be related with complexation between cationic/neutral TYL species and goethite. The sorption affinity of TYL on goethite decreased as ionic strength increased, which only occurred at higher TYL concentrations, suggested that inner complex might have dominated process at low concentrations and outer complex might occur at higher concentrations of TYL. Spectroscopic evidence indicated that tricarbonylamide and hydroxyl functional groups of TYL might be accounted for the sorption on mineral surfaces. The experimental data of TYL sorption could be fitted by surface complexation model (FITEQL), indicating that ≡FeOH with TYL interaction could be reasonably represented as a complex formation of a monoacid with discrete sites on goethite. The sorption mechanism of TYL might be related with surface complexation, electrostatic repulsion, and H-bounding on goethite. It should be noticed that the heterogeneous of sorption affinity of TYL on goethite at various environment to assess its environment risk.
اظهر المزيد [+] اقل [-]Sources of polycyclic hydrocarbons and pesticides in soluble fraction of deposition samples in Kocaeli, Turkey النص الكامل
2014
Binici, Burcu | Yenisoy-Karakaş, Serpil | Bilsel, Mine | Durmaz-Hilmioğlu, Nilüfer
A wet–dry deposition sampler was located at The Scientific and Technological Research Council of Turkey-National Metrology Institute (TUBITAK-UME) station, and a bulk deposition sampler was placed at the Kadıllı village to determine the atmospheric deposition flux of polycyclic aromatic hydrocarbons (PAHs) and pesticides (organochlorine and organophosphorus) in soluble fraction of samples in Kocaeli, Turkey. The 28 samples for each wet, dry, and total deposition were collected weekly from March 2006 to March 2007. Gas chromatography-tandem mass spectrometry was used to analyze the samples which were prepared by using solid-phase extraction (SPE) method. The sum of volume weighted mean of deposition fluxes was obtained as 7.43 μg m⁻² day⁻¹for wet deposition, 0.28 μg m⁻² day⁻¹for dry deposition and 0.54 μg m⁻² day⁻¹for bulk deposition samples for PAHs and 9.88 μg m⁻² day⁻¹for wet deposition, 4.49 μg m⁻² day⁻¹for dry deposition, and 3.29 μg m⁻² day⁻¹for bulk deposition samples for pesticides. While benzo(a)anthracene had the highest fluxes among PAH compounds for all types of depositions, guthion and phosphamidon had the highest deposition flux compared with the other pesticides. Benzo(ghi)perylene, dibenz(a,h)anthracene, indeno(1,2,3-c,d)pyrene, benzo(a)pyrene, and acenaphthene were not detected in any of the samples. Beta-HCH, gamma-HCH, and endrin aldehyde were the only compounds among 18 organochlorine pesticides to be detected in all deposition samples. The main sources of pesticides were the high number of greenhouses around the sampling stations. However, all of the organophosphorus pesticides were detected in all deposition samples. The pollution sources were identified as coal and natural gas combustion, petrogenic sources, and traffic for TUBITAK-UME station whereas coal and natural gas combustion and traffic were the main sources for Kadıllı station by considering the results of factor analysis, ratios, and wind sector analysis.
اظهر المزيد [+] اقل [-]Effective photodegradation of methomyl pesticide in concentrated solutions by novel enhancement of the photocatalytic activity of TiO2 using CdSO 4 nanoparticles النص الكامل
2014
Barakat, N. A. M. | Nassar, M. M. | Farrag, T. E. | Mahmoud, M. S.
Annihilation of electrons–holes recombination process is the main remedy to enhance the photocatalytic activity of the semiconductors photocatalysts. Doping of this class of photocatalysts by foreign nanoparticles is usually utilized to create high Schottky barrier that facilitates electron capture. In the literature, because nonpolar nanoparticles (usually pristine metals, e.g., Ag, Pt, Au, etc.) were utilized in the doping process, the corresponding improvement was relatively low. In this study, CdSO₄-doped TiO₂nanoparticles are introduced as a powerful and reusable photocatalyst for the photocatalytic degradation of methomyl pesticide in concentrated aqueous solutions. The utilized CdSO₄nanoparticles form polar grains in the TiO₂matrix due to the electrons leaving characteristic of the sulfate anion. The introduced nanoparticles could successfully eliminate the harmful pesticide under the sunlight radiation within a very short time (less than 1 h), with a removal capacity reaching 1,000 mg pesticide per gram of the introduced photocatalyst. Moreover, increase in the initial concentration of the methomyl did not affect the photocatalytic performance; typically 300, 500, 1,000, and 2,000 mg/l solutions were completely treated within 30, 30, 40, and 60 min, respectively, using 100 mg catalyst. Interestingly, the photocatalytic efficiency was not affected upon multiple use of the photocatalyst. Moreover, negative activation energy was obtained which reveals super activity of the introduced photocatalyst. The distinct photocatalytic activity indicates the complete annihilation of the electrons–holes recombination process and abundant existence of electrons on the catalyst surfaces due to strong electrons capturing the operation of the utilized polar CdSO₄nanoparticles. The introduced photocatalyst has been prepared using the sol–gel technique. Overall, the simplicity of the synthesizing procedure and the obtained featured photocatalytic activity strongly recommend the introduced nanoparticles to treat the methomyl-containing polluted water.
اظهر المزيد [+] اقل [-]Impact of gold mining associated with mercury contamination in soil, biota sediments and tailings in Kenya النص الكامل
2014
Odumo, Benjamin Okang’ | Carbonell, Gregoria | Angeyo, Hudson Kalambuka | Patel, Jayanti Purshottam | Torrijos, Manuel | Rodríguez Martín, José Antonio
Impact of gold mining associated with mercury contamination in soil, biota sediments and tailings in Kenya النص الكامل
2014
Odumo, Benjamin Okang’ | Carbonell, Gregoria | Angeyo, Hudson Kalambuka | Patel, Jayanti Purshottam | Torrijos, Manuel | Rodríguez Martín, José Antonio
This work considered the environmental impact of artisanal mining gold activity in the Migori–Transmara area (Kenya). From artisanal gold mining, mercury is released to the environment, thus contributing to degradation of soil and water bodies. High mercury contents have been quantified in soil (140 μg kg⁻¹), sediment (430 μg kg⁻¹) and tailings (8,900 μg kg⁻¹), as expected. The results reveal that the mechanism for transporting mercury to the terrestrial ecosystem is associated with wet and dry depositions. Lichens and mosses, used as bioindicators of pollution, are related to the proximity to mining areas. The further the distance from mining areas, the lower the mercury levels. This study also provides risk maps to evaluate potential negative repercussions. We conclude that the Migori–Transmara region can be considered a strongly polluted area with high mercury contents. The technology used to extract gold throughout amalgamation processes causes a high degree of mercury pollution around this gold mining area. Thus, alternative gold extraction methods should be considered to reduce mercury levels that can be released to the environment.
اظهر المزيد [+] اقل [-]Impact of gold mining associated with mercury contamination in soil, biota sediments and tailings in Kenya النص الكامل
2014
Odumo, B. O. | Carbonell, G. | Angeyo, H. K. | Patel, J. P. | Torrijos Garrido, Manuel | Rodríguez Martín, José Antonio
This work considered the environmental impact of artisanal mining gold activity in the Migori–Transmara area (Kenya). From artisanal gold mining, mercury is released to the environment, thus contributing to degradation of soil and water bodies. High mercury contents have been quantified in soil (140 μg kg−1), sediment (430 μg kg−1) and tailings (8,900 μg kg−1), as expected. The results reveal that the mechanism for transporting mercury to the terrestrial ecosystem is associated with wet and dry depositions. Lichens and mosses, used as bioindicators of pollution, are related to the proximity to mining areas. The further the distance from mining areas, the lower the mercury levels. This study also provides risk maps to evaluate potential negative repercussions. We conclude that the Migori–Transmara region can be considered a strongly polluted area with high mercury contents. The technology used to extract gold throughout amalgamation processes causes a high degree of mercury pollution around this gold mining area. Thus, alternative gold extraction methods should be considered to reduce mercury levels that can be released to the environment. © 2014, Springer-Verlag Berlin Heidelberg.
اظهر المزيد [+] اقل [-]The GMOS cyber(e)-infrastructure: advanced services for supporting science and policy النص الكامل
2014
Cinnirella, S. | D’Amore, F. | Bencardino, M. | Sprovieri, F. | Pirrone, N.
The need for coordinated, systematized and catalogued databases on mercury in the environment is of paramount importance as improved information can help the assessment of the effectiveness of measures established to phase out and ban mercury. Long-term monitoring sites have been established in a number of regions and countries for the measurement of mercury in ambient air and wet deposition. Long term measurements of mercury concentration in biota also produced a huge amount of information, but such initiatives are far from being within a global, systematic and interoperable approach. To address these weaknesses the on-going Global Mercury Observation System (GMOS) project ( www.gmos.eu ) established a coordinated global observation system for mercury as well it retrieved historical data ( www.gmos.eu/sdi ). To manage such large amount of information a technological infrastructure was planned. This high-performance back-end resource associated with sophisticated client applications enables data storage, computing services, telecommunications networks and all services necessary to support the activity. This paper reports the architecture definition of the GMOS Cyber(e)-Infrastructure and the services developed to support science and policy, including the United Nation Environmental Program. It finally describes new possibilities in data analysis and data management through client applications.
اظهر المزيد [+] اقل [-]Bioaccumulation, subcellular, and molecular localization and damage to physiology and ultrastructure in Nymphoides peltata (Gmel.) O. Kuntze exposed to yttrium النص الكامل
2014
Fu, Yongyang | Li, Feifei | Xu, Ting | Cai, Sanjuan | Chu, Weiyue | Qiu, Han | Sha, Sha | Cheng, Guangyu | Xu, Qinsong
Bioaccumulation, subcellular distribution, and acute toxicity of yttrium (Y) were evaluated in Nymphoides peltata. The effects of Y concentrations of 1–5 mg L⁻¹applied for 4 days were assessed by measuring changes in photosynthetic pigments, nutrient contents, enzymatic and non-enzymatic antioxidants, and ultrastructure. The accumulation of Y in subcellular fractions decreased in the order of cell wall > organelle > soluble fraction. Much more Y was located in cellulose and pectin than in other biomacromolecules. The content of some mineral elements (Mg, Ca, Fe, Mn, and Mo) increased in N. peltata, but there was an opposite effect for P and K. Meanwhile, ascorbate, and catalase activity decreased significantly for all Y concentrations. In contrast, peroxidase activity was induced, while initial rises in superoxide dismutase activity and glutathione content were followed by subsequent declines. Morphological symptoms of senescence, such as chlorosis and damage to chloroplasts and mitochondria, were observed even at the lowest Y concentration. Pigment content decreased as the Y concentration rose and the calculated EC₅₀and MPC of Y for N. peltata were 2 and 0.2 mg L⁻¹after 4 days of exposure, respectively. The results showed that exogenous Y was highly available in water and that its high concentration in water bodies might produce harmful effects on aquatic organisms. N. peltata is proposed as a biomonitor for the assessment of metal pollution in aquatic ecosystems.
اظهر المزيد [+] اقل [-]Development of aquatic life criteria in China: viewpoint on the challenge النص الكامل
2014
Jin, Xiaowei | Wang, Yeyao | Giesy, John P. | Richardson, Kristine L. | Wang, Zijian
While more developed countries have a well-established systems to develop water quality criteria (WQC), little research has been done on the adequacy of the current WQC to protect endemic species of China. In order to maintain the health of aquatic ecosystems in China, a series of projects to establish national WQC based on regional characteristics has recently been initiated. However, the establishment of a completely novel methodology would be costly and time consuming. Also, due to the similarities in physiologies and natural histories of classes of aquatic organisms, there is no reason to believe that WQC would not be sufficient to protect unique species in China. This review was undertaken to identify key outstanding issues regarding establishment of aquatic life criteria (ALC) to be applied in China, including prioritization of chemicals, test species, mode of action, field/semi-field data, and methods of aggregating the information and calculating the ALC. This was used to identify the principle issues that need to be addressed in order to better understand the methods for development of criteria for the protection of aquatic life and provide a reference to China and other developing countries committed to the establishment of their own WQC system.
اظهر المزيد [+] اقل [-]Forewarning model for water pollution risk based on Bayes theory النص الكامل
2014
Zhao, Jun | Jin, Juliang | Guo, Qizhong | Chen, Yaqian | Lu, Mengxiong | Tinoco, Luis
In order to reduce the losses by water pollution, forewarning model for water pollution risk based on Bayes theory was studied. This model is built upon risk indexes in complex systems, proceeding from the whole structure and its components. In this study, the principal components analysis is used to screen out index systems. Hydrological model is employed to simulate index value according to the prediction principle. Bayes theory is adopted to obtain posterior distribution by prior distribution with sample information which can make samples’ features preferably reflect and represent the totals to some extent. Forewarning level is judged on the maximum probability rule, and then local conditions for proposing management strategies that will have the effect of transforming heavy warnings to a lesser degree. This study takes Taihu Basin as an example. After forewarning model application and vertification for water pollution risk from 2000 to 2009 between the actual and simulated data, forewarning level in 2010 is given as a severe warning, which is well coincide with logistic curve. It is shown that the model is rigorous in theory with flexible method, reasonable in result with simple structure, and it has strong logic superiority and regional adaptability, providing a new way for warning water pollution risk.
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