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Resultados 4411-4420 de 4,924
Heavy metal concentrations in drinking water in a country heavily reliant on desalination
2019
Barnett-Itzhaki, Zohar | Eaton, Jarrod | Hen, Irit | Berman, Tamar
Desalination is an important strategy for adapting to the global shortage in safe drinking water. Israel relies heavily on desalinated water (over 50% of supplied drinking water). However, desalinated water may be more corrosive than water from other sources and may cause leaching of heavy metals from materials in contact with water. In this study, we measured heavy metal concentrations (copper, iron, lead) in 1379 drinking water samples in educational institutions in Israel and compared heavy metal concentrations in drinking water from different sources (desalination, groundwater, desalinated and groundwater mixture). 99.9% of the samples met the standard for copper (1400 μg/l), 99.7% for iron (1000 μg/l), and 99.6% for lead (10 μg/l). As expected, heavy metal concentrations were higher in first flush samples compared to flushed samples (significant findings for lead, copper, and iron). Heavy metal concentrations were not higher in desalinated water, or desalinated and groundwater mixture, compared to groundwater. In first flush samples, lead concentrations in groundwater were significantly higher than in desalinated-groundwater mixtures (p = 0.005). In flushed samples, lead concentrations in groundwater were higher than in desalinated-groundwater mixtures but the difference was not significant (p = 0.07). We suggest that regulatory requirements for stabilization of desalinated water and restrictions on lead content of plumbing materials appear to have been effective in preventing increased exposure to lead in desalinated drinking water in Israel. Further study should focus on potential heavy metal leaching in pure desalinated water samples.
Mostrar más [+] Menos [-]Distinctive fingerprints of genotoxicity induced by As, Cr, Cd, and Ni in a freshwater fish
2019
Singh, Meenu | Khan, Huma | Verma, Yeshvandra | Rana, Suresh Vir Singh
Genotoxicity of three toxic elements (chromium, cadmium, nickel) and a metalloid (arsenic) has been studied in a freshwater fish, Channa punctatus using micronuclei (MN) test, comet assay, and erythrocyte nuclear alterations (ENAs) as fingerprints of genotoxicity. These tests yielded different results suggesting involvement of different mechanisms for their genotoxicity. While highest frequency of blebbed nuclei was observed in chromium-treated fish (6.5 ± 0.76), lowest was observed in cadmium-treated fish (4.0 ± 1.0). Maximum number of notched nuclei was recorded in arsenic-treated fish (5.5 ± 1.15) whereas highest numbers of lobed nuclei were found in cadmium-treated fish (4.5 ± 0.13). These differences might be attributed to selective bioaccumulation and chemodynamics of each element. Other parameters used to determine genotoxicity viz.: lipid peroxidation and DNA damage also suggested different mechanisms of their genotoxicity. It is suggested that an integrative approach, using a battery of tests for determining genotoxicity, should be made while making environmental health risk assessment and ecotoxicological studies of these toxic elements.
Mostrar más [+] Menos [-]Particulate matter in the cultivation area may contaminate leafy vegetables with heavy metals above safe levels in Korea
2019
Noh, Kyungdeok | Thi, Luc The | Jeong, Byoung Ryong
Among air pollutants, particulate matter (PM) has been identified as a major cause of environmental pollutants due to the advancement of industrial development and the generation of smaller particles. Particulate matter, in particular, is defined only by the size of particles and thus is not enough to study its composition yet. However, edible crops grown in contaminated atmospheres can be contaminated with heavy metals contained in particulate matter in the atmosphere, which can seriously damage food safety. In this study, we investigated the influence of the accumulation of particulate matter on leafy vegetables cultivated at areas with different levels of PM in atmosphere. Four districts of Gyeongsangnam-do were chosen to conduct this experiment: outdoor spaces of three respectively located in industrial, near-highway, and rural areas were considered, and research plant growth chambers at Gyeongsang National University were used as the control. After 3 weeks of cultivation in those conditions, the results showed that Pb in milligrams per kilogram of fresh weight (FW) was 0.383 in Chrysanthemum coronarium and 0.427 in Spinacia oleracea that were grown near the highway, which exceeded the 0.3 mg kg⁻¹ FW standard set by the Republic of Korea, EU, and CODEX. However, when those vegetables were sufficiently washed with tap water, it was confirmed that the heavy metal content fell into the safety standard range.
Mostrar más [+] Menos [-]Alpine accentors as monitors of atmospheric long-range lead and mercury pollution in alpine environments
2019
Janiga, Marián | Haas, Martina
Mercury and lead are deposited in the West Carpathians as long-range transported air pollution. The Alpine accentor (Prunella collaris) was recognized as a cost-effective biomonitor, and used to investigate the bioavailability of contaminants in large alpine areas. The outer tail feathers and blood of the alpine accentors were used for assessment of atmospheric mercury and lead contamination, respectively. Mean mercury levels in feathers of accentors averaged at 1.15 μg/g (SE = 0.105, n = 40). There were no temporal variations in mercury concentrations. Mean blood lead levels were at 5.2 μg/dL (SE = 0.5, n = 27), showing a slight decreasing trend from July to October. Juveniles were not more susceptible to lead accumulation than adults. Bone lead concentrations that increase with age reflect a bioaccumulation effect. A statistically significant negative correlation was found between the length of erythrocytes and the concentration of lead, which may show the first symptoms of microcytosis. In comparison to aquatic ecosystems, the biogeochemical factors that influence methylmercury availability in alpine habitats are not yet completely known and require further investigation. Our findings show that birds in alpine terrestrial ecosystems may contain surprisingly high levels of methylmercury. The mercury levels in the feathers of accentors probably indicate that alpine autotrophs make sufficient amounts of mercury available to the terrestrial food web. The blood lead levels of accentors likely approach the threshold level for further hematological effects. We found a clear tendency in erythrocytes to change their shape from ellipsoid to smaller and rounder with increasing amounts of lead in their blood. The shape of bird erythrocytes appears to be a very sensitive indicator of critical levels of lead in the alpine environment.
Mostrar más [+] Menos [-]Levels of organochlorine pesticide residues in fresh water fishes of three bird sanctuaries in Tamil Nadu, India
2019
Samidurai, Jayakumar | Subramanian, Muralidharan | Venugopal, Dhananjayan
Organochlorine pesticide (OCP) residues were determined in nine species of fresh water fishes caught from three bird sanctuaries in Tamil Nadu, India. A total of 302 fishes were analyzed for various types of OCPS. OCPs, namely hexachlorocyclohexane (HCH), dichloro diphenyl trichloroethane (DDT), heptachlor epoxide, endosulfan, and dieldrin were detected among various species of fishes. Among the various OCPs analyzed, HCH was the most frequently detected pesticides. Among the HCH isomers, β HCH contributed more than 50% to the Σ HCH. p,p’ DDT, the metabolites of DDT, had high percentage of occurrence. Among the cyclodiene insecticide residues, endosulfan was detected in more than 60% of the fishes. Varying levels of ΣOCPs (a sum of Σ HCH, Σ DDT, Σ endosulfan, heptachlor epoxide, and dieldrin) were detected in various fish species, although it was not significant (p > 0.05). However, significant variations in OCPs were observed among location and between seasons (p < 0.05). However, continuous monitoring is recommended to facilitate the early identification of risks not only to the fishes, but also to fish-eating birds breeding in these sanctuaries.
Mostrar más [+] Menos [-]Regeneration of 4-chlorophenol from spent powdered activated carbon by ultrasound
2019
Zhang, Tingting | Yang, Yanling | Li, Xing | Wang, Nan | Zhou, Zhiwei
Ultrasound-assisted regeneration of powdered activated carbon (PAC) saturated with 4-chlorophenol (4-CP) was investigated in this work. The variables, i.e., acoustic frequency, density levels, regenerating solution species, spent PAC mass, and the number of repeated cycle, were optimized. The UV–Vis spectra, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and pore structure analysis were used to characterize the regenerated PAC as compared to the virgin and spent PAC. The adsorption experiments indicated that the adsorption kinetics of 4-CP fitted well with the pseudo-second-order model, and the main chemisorption process was nonlinear and heterogeneous. The desorption results showed that the optimized regenerated conditions were identified as 40 kHz of frequency, 0.18 W/mL of sonication intensity, 0.1 M NaOH and 50% (v/v) ethyl alcohol mixture of regeneration solution, and 1 g/L of saturated PAC mass. Under this condition, the regeneration efficiency reached up to 86.81%. Hydroxylated oxidation products especially benzoquinone and hydroquinone were formed during ultrasound regeneration. Ultrasound mainly acted on surface functionalities, mesopores, and macropores of PAC through the hydroxyl radical oxidization resulted from the cavitation effect.
Mostrar más [+] Menos [-]Aryl hydrocarbon receptor-mediated potencies in field-deployed plastics vary by type of polymer
2019
Schönlau, Christine | Larsson, Maria | Lam, Monika M. | Engwall, Magnus | Giesy, John P. | Rochman, Chelsea | Kärrman, Anna
Plastic is able to sorb environmental pollutants from ambient water and might act as a vector for these pollutants to marine organisms. The potential toxicological effects of plastic-sorbed pollutants in marine organisms have not been thoroughly assessed. In this study, organic extracts from four types of plastic deployed for 9 or 12 months in San Diego Bay, California, were examined for their potential to activate the aryl hydrocarbon receptor (AhR) pathway by use of the H4IIE-luc assay. Polycyclic aromatic hydrocarbons (PAH), including the 16 priority PAHs, were quantified. The AhR-mediated potency in the deployed plastic samples, calculated as bio-TEQ values, ranged from 2.7 pg/g in polyethylene terephthalate (PET) to 277 pg/g in low-density polyethylene (LDPE). Concentrations of the sum of 24 PAHs in the deployed samples ranged from 4.6 to 1068 ng/g. By use of relative potency factors (REP), a potency balance between the biological effect (bio-TEQs) and the targeted PAHs (chem-TEQs) was calculated to 24–170%. The study reports, for the first time, in vitro AhR-mediated potencies for different deployed plastics, of which LDPE elicited the greatest concentration of bio-TEQs followed by polypropylene (PP), PET, and polyvinylchloride (PVC).
Mostrar más [+] Menos [-]Synthesis of carbon nano-onion embedded metal–organic frameworks as an efficient adsorbent for cadmium ions: kinetic and thermodynamic studies
2019
Hassan, Asaad F.
Carbon nano-onions (CNOs), metal–organic frameworks (MOF-199), and carbon nano-onion embedded metal–organic frameworks (CMOF-199) were synthesized from garlic peels as a green source of carbon atoms while MOF-199 was prepared by solvothermal interaction between 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate. All the prepared solid materials were characterized by nitrogen adsorption/desorption isotherm, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), point of zero charge (pHPZC), and Fourier transform infrared spectroscopy (FTIR). Adsorption of cadmium ions from aqueous solution was investigated onto all prepared solid materials considering different application conditions such as adsorbent dosage, pH, contact time, initial concentration of Cd⁺², and temperature. Adsorption of Cd⁺² was investigated by Langmuir, Freundlich, Temkin, and Dubinin–Radhushkevich adsorption isotherm models. Maximum adsorption capacity (113.3 mg g⁻¹) was achieved by CMOF-199 at 40 °C. The adsorption of Cd⁺² obeys pseudo-second-order kinetic model. Thermodynamic studies confirmed that the adsorption process is spontaneous, favorable, endothermic, and physisorption. Adsorption results proved that carbon nano-onion embedded metal–organic frameworks are promising solid adsorbents for cadmium ion adsorption.
Mostrar más [+] Menos [-]The combination of Luffa cylindrical fibers and metal oxides offers a highly performing hybrid fiber material in water decontamination
2019
Kesraoui, Aida | Bouzaabia, Sarra | Seffen, Mongi
The present investigation aims to prepare a hybrid material from Luffa cylindrica and metal oxides (ZnO, Al₂O₃) by precipitation for different percentages of zinc and aluminum (1, 2, and 4%) with a determined amount of biomass (a diameter of 250 μm). Physicochemical characterization of “Luffa cylindrica” and “Luffa cylindrica-metal oxides” was carried out by Boehm titration, pHPZC determination, scanning electron microscopy (SEM), and FTIR spectroscopic analysis. The process was optimized according to the adsorbed amount of methylene blue: MB (cationic dye) and methyl orange: MO (anionic dye) onto Luffa cylindrica and hybrid materials prepared. The results demonstrated the efficiency of the designed hybrid materials in removing MB and MO, accelerating the biosorption process and improving the performance of Luffa cylindrica fibers. The highest quantities adsorbed of dyes were obtained by the hybrid material prepared using 4% ZnO. Finally, the Brouers-Sotolongo mathematical modeling of kinetics was used in order to describe the pollutants retention process.
Mostrar más [+] Menos [-]Exploring the driving forces for emission reduction strategies in Henan by combining spectral clustering with two-layer LMDI decomposition
2019
Wen, Lei | Li, Zhenkai
To comprehend city-level driving mechanisms of carbon emissions, this paper utilizes spectral cluster and two-layer LMDI (logarithmic mean divisia index) method to systematically assess the contribution values of correlative factors from each cluster to Henan’s carbon emissions increments, and accordingly comes up with more strategies about how to reduce carbon emissions for each cluster on the basis of driving forces of carbon emissions. The results of clustering and the decomposition are as follows: (1) the 18 prefecture-level cities in Henan were divided into five categories by spectral clustering, and there are similar development patterns within each category, so they can learn from each other to improve their own defects of development; (2) this paper utilizes the two-layer LMDI method to divide the factors affecting each cluster of carbon emissions into four types, which includes energy structure, energy intensity, per capita GDP, and population, and calculates the contribution value of each factor. It was concluded that the contribution value of per capita GDP dominantly drove up carbon emissions, while energy intensity played a significant role in offsetting them. Therefore, it is important for Henan’s low-carbon development to control the expansion of economic activity and improve energy efficiency in the future.
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