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Resultados 4101-4110 de 5,153
Variation laws and release characteristics of phosphorus on surface sediment of Dongting Lake Texto completo
2018
Zhu, G. (Guangrui) | Yang, Ying
The variation trend and growth rate of P were analyzed by the concentration of the phosphorus fraction on surface sediment of Dongting Lake from 2012 to 2016, to reveal the cumulative effect of P in the actual environment. Meanwhile, the adsorption kinetics and adsorption isotherm were employed to examine the P-release possibility of sediment, which predicts the yearly released sediment phosphorus in Dongting Lake. The actual growth rate of TP (Total Phosphorus) is 53 mg·(kg·year)⁻¹ in East Dongting Lake, 39 mg·(kg·year)⁻¹ in South Dongting Lake, and 29 mg·(kg·year)⁻¹ in West Dongting Lake, while the sum of the phosphorus fraction growth rates has little difference from the rate of TP in sediments of the three areas of Dongting Lake. Furthermore, the Elovich model and the Langmuir crossover-type equations are established to present the adsorption characteristic of sediment in Dongting Lake; the result shows that the sediments play a source role for phosphorus in East and South Dongting Lake from zero equilibrium phosphorus concentration (EPC₀) in the present situation, but an adsorption effect on TP is shown in West Dongting Lake. When the conditions of environment change are ignored, the maximum P-sorption level in sediments of East Dongting Lake will reach in 2040 according to the actual growth rate of sediments, while that in West Dongting Lake and South Dongting Lake will be in 2046 and 2061, respectively.
Mostrar más [+] Menos [-]Nephrotoxicity in Hybrid sparrow (Passer domesticus × Passer hispaniolensis) living near a phosphate treatment factory complex in southern Tunisia: a biochemical and histological study Texto completo
2018
Amri, Nahed | Rebai, Tarek | Jardak, Neila | Badraoui, Riadh
Our study was designed to evaluate impacts of exposure to pollutants, released by the Gabès–Ghannouche factory complex of phosphate treatment, on biochemical biomarkers and histopathological indices in kidney tissues of Hybrid sparrow (Passer domesticus × Passer hispaniolensis) in Gabès city. Our results show evidence of a pronounced impairment in kidney function which is confirmed by remarkable blood chemical alterations in sparrows living in Ghannouche, the most polluted site. Moreover, superoxide dismutase and catalase activities were found to be decreased in birds sampled from the contaminated site when compared to less polluted areas. The population of sparrows feeding in Ghannouche had enhanced renal thiobarbituric acid reactive substance levels, indicating oxidative damage to membrane lipids. Some histopathological alterations were also observed including kidney interstitial dilatations. Overall, our findings demonstrated that the exposure to pollutants released by the factory complex possessed nephrotoxic by depleting renal antioxidant defense system and promoting kidney morphometric damage in sparrows. These results constitute an early warning of an ecological change in relation to human health.
Mostrar más [+] Menos [-]Biochar addition induced the same plant responses as elevated CO2 in mine spoil Texto completo
2018
Zhang, Yaling | Drigo, Barbara | Bai, ShahlaHosseini | Menke, Carl | Zhang, Manyun | Xu, Zhihong
Nitrogen (N) limitation is one of the major constrain factors for biochar in improving plant growth, the same for elevated atmospheric carbon dioxide (CO₂). Hence, we hypothesized that (1) biochar would induce the same plant responses as elevated CO₂ under N-poor conditions; (2) elevated CO₂ would decrease the potential of biochar application in improving plant growth. To test these hypotheses, we assessed the effects of pinewood biochar, produced at three pyrolytic temperatures (650, 750 and 850 °C), on C and N allocation at the whole-plant level of three plant species (Austrostipa ramossissima, Dichelachne micrantha and Isolepis nodosa) grown in the N poor mine spoil under both ambient (400 μL L⁻¹) and elevated (700 μL L⁻¹) CO₂ concentrations. Our data showed that biochar addition (1) significantly decreased leaf total N and δ¹⁵N (P < 0.05); (2) decreased leaf total N and δ¹⁵N more pronouncedly than those of root; and (3) showed more pronounced effects on improving plant biomass under ambient CO₂ than under elevated CO₂ concentration. Hence, it remained a strong possibility that biochar addition induced the same plant physiological responses as elevated CO₂ in the N-deficient mine spoil. As expected, elevated CO₂ decreased the ability of biochar addition in improving plant growth.
Mostrar más [+] Menos [-]Evaluation of larvicidal, adulticidal, and anticholinesterase activities of essential oils of Illicium verum Hook. f., Pimenta dioica (L.) Merr., and Myristica fragrans Houtt. against Zika virus vectors Texto completo
2018
Gomes da Rocha Voris, Diego | dos Santos Dias, Luciana | Alencar Lima, Josélia | dos Santos Cople Lima, Keila | Pereira Lima, José Bento | dos Santos Lima, Antônio Luís
Aedes aegypti is the vector responsible for transmitting pathogens that cause various infectious diseases, such as dengue, Zika, yellow fever, and chikungunya, worrying health authorities in the tropics. Due to resistance of mosquitoes to synthetic insecticides, the search for more effective insecticidal agents becomes crucial. The aim of this study was to verify the larvicidal, adulticidal, and anticholinesterase activities of the essential oils of the Illicium verum (EOIV), Pimenta dioica (EOPD), and Myristica fragrans (EOMF) against Ae. aegypti. The essential oils (EOs) were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The larvicidal and adulticidal activities of EOs were evaluated against third instar larvae and Ae. aegypti adult females, respectively, using the procedures of the World Health Organization (WHO) and the anticholinesterase activity of the EOs by the modified Ellman method. The following major components were identified: (E)-anethole (90.1%) for EOIV, methyl eugenol (55.0%) for EOPD, and sabinene (52.1%) for EOMF. All EOs exhibited larvicidal and adulticidal activity against Ae. aegypti. The highest larval mortality was observed in EOMF with LC₅₀ = 28.2 μg mL⁻¹. Adult mortality was observed after 1 (knockdown) and 24 h exposure, with the highest potential established by the EOIV, KC₅₀ = 7.3 μg mg female⁻¹ and LC₅₀ = 10.3 μg mg female⁻¹. EOIV (IC₅₀ = 4800 μg mL⁻¹), EOMF (IC₅₀ = 4510 μg mL⁻¹), and EOPD (IC₅₀ = 1320 μg mL⁻¹) inhibited AChE. EOMF (4130 μg mL⁻¹) and EOPD (IC₅₀ = 3340 μg mL⁻¹) inhibited BChE whereas EOIV showed no inhibition. The EOs were toxic to larvae and adults of Ae. aegypti, as well as being less toxic to humans than the currently used insecticides, opening the possibility of elaboration of a natural, safe, and ecological bioinsecticide for vector control.
Mostrar más [+] Menos [-]Prevalence of asthma and associated factors among male late adolescents in Tabriz, Iran Texto completo
2018
Ghozikali, MohammadGhanbari | Ansarin, Khalil | Naddafi, Kazem | Nodehi, RaminNabizadeh | Yaghmaeian, Kamyar | Hassanvand, MohammadSadegh | Yunesian, Masud
Asthma is an important chronic disease all over the world. The aim of this study was to determine the prevalence of asthma in a population of male late adolescents and its association with some contributing risk factors in northwest of Iran. This cross-sectional study was carried out in selected high schools of Tabriz, Iran, in 2016. The asthma prevalence and patient background information were examined using a questionnaire that prepared by the ISAAC. One hundred forty-two out of 1134 subjects (12.4%) identified to have asthma, 23.3% had history of current wheeze, and 16.3% had wheezing in the previous year. Family history of asthma was present in 17.1% of the participants; prevalence of active smoking in the study subjects was 3.1%; 25.1% of all subjects had exposure to secondhand tobacco smoke and keeping pets at home was present in 9.1%. Excess weight (overweight and obesity) was positively associated with prevalence of asthma (p < 0.001). No statistically significant associations were observed between asthma and father’s education level (p = 0.570), mother’s education level (p = 0.584), type of birth subjects (p = 0.571), and time spent outdoors during a full day (p = 0.863). Our results suggest that family history of asthma and atopy, exposure to secondhand tobacco smoke, active smoking, amount of automobile traffic around subjects’ home, and keeping pets at homes are important risk factors for asthma, while time spent outdoors, educations of parents, and delivery type (normal vaginal delivery vs. C-section) subjects are not. Therefore, decreased of exposure to some environmental risk factors could be effective to reduce rate of the prevalence of asthma and wheeze.
Mostrar más [+] Menos [-]Adsorption of cadmium ions using the bioadsorbent of Pichia kudriavzevii YB5 immobilized by polyurethane foam and alginate gels Texto completo
2018
Zhao, Wenyu | Zhou, Ting | Zhu, Junxiang | Sun, Xun | Xu, Ying
Pichia kudriavzevii YB5, mutated from Pichia kudriavzevii A16 with a strong ability to remove cadmium ions, was immobilized by polyurethane foam and alginate gels in this work. The immobilization conditions were optimized as follows: sodium alginate concentration of 2% (w/v), calcium chloride concentration of 2% (w/v), biomass dose of 1 × 10⁹ cell/mL, and cross-linking time for 4 h. Then, the results of batch adsorption experiments showed that the removal capacity of prepared bioadsorbent was significantly affected by the pH of media, contact time, and the initial Cd(II) concentration, and a suitable adsorption conditions of Cd(II) could be achieved with a pH value of 6.0 at 20 °C for 90 min. Kinetic and isothermal results indicated the behavior of Cd(II) adsorption onto immobilized P. kudriavzevii YB5 fitted to the pseudo-second-order kinetic equation and the Langmuir adsorption model. Thermodynamic results showed that the Cd(II) adsorption process was endothermic and spontaneous in nature. Besides, the Cd(II) removing capacity of the prepared bioadsorbent was also tested in the oyster hydrolysates, showing an average removal rate of 54.35%. Thus, the immobilized P. kudriavzevii YB5 adsorbent had great potential for application in aquatic products to ensure the food safety.
Mostrar más [+] Menos [-]Characterization and valorization of biomass char: a comparison with biomass ash Texto completo
2018
Trivedi, NikhileshS. | Mandavgane, SachinA. | Chaurasia, Ashish
Organic matter derived from living, or recently living plant and animal, which can be used as fuel is called as biomass. It includes wood and agricultural waste such as dead plant etc. In India, majority of population depends largely upon agriculture as their primary source of income. Following every harvest, a huge amount of biomass is generated. It is mostly discarded as “agro waste”; however, recently, several uses of biomass and its derivatives have been reported. Thermochemical processing of biomass in absence of oxygen produces biomass char and flue gases which are of economic importance. However, it is necessary to characterize the physical and chemical properties of these components so as to utilize their potential benefit to the fullest. In this study, six different biomass remains that include mustard plant, groundnut plant, cotton plant, wheat plant, pigeon peas, and groundnut shell were pyrolyzed at 650 °C, in vertical downdraft fixed-bed biomass reactor. The flue gases were characterized in detail by gas chromatography. X-ray fluorescence, proximate, and ultimate analyses were performed on all BMC (biomass char) samples, and properties such as porosity, particle density, bulk density, point of zero charge, surface pH, surface charges, water-absorption capacity, and BET surface area were determined. SEM and FTIR were also carried out on all BMC samples. Our results showed that the surface area of biomass char varies from 38 to 138 m²/g. The solution pH for all BMC exceeds 8.6, thus confirmed the alkaline nature. Comparison between combustion products produced in the presence (biomass ash) and absence of oxygen (biomass char) is presented. BMC finds applications in agriculture, soil neutralizer, adsorbent, and soil additive. They have high amount of carbon and can act as a rich carbon source for the soil. Flue gases released contain methane and hydrogen which can also improve economic value for the char formation process.
Mostrar más [+] Menos [-]Photodegradation of 2,4-dichlorophenol by supported Pd(X2) catalyst (X = Cl, Br, N3): a HOMO manipulating point of view Texto completo
2018
Tehrani Nejad, Sajedeh | Abolhosseini Shahrnoy, Abdolghafar | Mahjoub, AliReza | Esmaeili Saloumahaleh, Niloufar | Khazaee, Zeynab
Three different palladium(II) complexes with ligands containing nitrogenized aromatic rings were investigated theoretically as model to obtain the computational band gap energies. The results demonstrated promising possibility for designing palladium(II) complexes with photocatalytic properties at visible light irradiation. Deliberated products were synthesized via grafting on the silica-coated Fe₃O₄ magnetic nanoparticles (Fe₃O₄@SiO₂). Formation of complexes on the surface of Fe₃O₄@SiO₂, as insoluble and reusable photocatalysts, was proved by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric (TGA), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), transmission electron microscope (TEM), and scanning electron microscopy (SEM) analyses. The trend of the band gap energies of prepared structures was calculated via experimental and theoretical methods. The photocatalytic capability of these nanoparticles was investigated in degradation of 2,4-dichlorophenol by means of HPLC analysis. A tentative reaction mechanism for the formation of intermediates was proposed. Graphical abstract ᅟ
Mostrar más [+] Menos [-]Accumulation of cadmium in potential hyperaccumulators Chlorophytum comosum and Callisia fragrans and role of organic acids under stress conditions Texto completo
2018
Simek, Jiri | Kovalikova, Zuzana | Dohnal, Vlastimil | Tůma, Jiří
Cadmium (Cd) accumulation, antioxidant activity (AOA), chlorophyll fluorescence (F) and organic acid distribution in Chlorophytum comosum and Callisia fragrans plants exposed to artificially added Cd (40, 160 and 320 mg kg⁻¹) were examined in pot experiment. At the highest Cd concentration, C. comosum accumulated in roots and the aboveground parts up to 1331 and 1054 mg Cd kg⁻¹ DW, and C. fragrans up to 1427 and 1263 mg Cd kg⁻¹ DW, respectively, which are quite near at the level of hyperaccumulator. Cd accumulation in both plant species increased significantly with the increment of soil Cd dosage, and the distribution was roots > shoots > stolons. Values of BC showed rising trend indicating an accumulation potential of both species. The root AOA was positively correlated to Cd addition, especially in C. comosum. Higher values of free SA were found in roots with a significant enhancement at concentrations of 40 and 160 mg kg⁻¹ Cd. It was observed that citric acid significantly reacted in both species, while fumaric acid only in C. comosum in response to Cd which may contribute to Cd chelation. Our data indicate that both species are suitable for phytoextraction of Cd from contaminated soils which increases their value as ornamentals.
Mostrar más [+] Menos [-]Indicators of environmental contamination by heavy metals in leaves of Taraxacum officinale in two zones of the metropolitan area of Mexico City Texto completo
2018
Gómez-Arroyo, Sandra | Barba-García, Arisbel | Arenas-Huertero, Francisco | Cortés-Eslava, Josefina | de la Mora, Michel Grutter | García-Martínez, Rocío
The present study was designed to detect the effect of heavy metals in two zones of the Metropolitan Area of Mexico City (MAMC), the Centro de Ciencias de la Atmósfera (CCA), and the Altzomoni station in the Iztaccíhuatl-Popocatépetl National Park. Taraxacum officinale was selected as the indicator organism of responses to atmospheric contamination by heavy metals. Determinations of heavy metals were performed, and total mRNA was extracted to quantify the expression of microRNA398 (miR398), superoxide dismutase 2 (CSD2), and the amounts of free radicals using the bromide of 3-(4,5-dimethylthiazole-2-ilo)-2,5-diphenyltetrazole (MTT) salts reduction assay. Results from the Altzomoni station showed high concentrations of five heavy metals, especially Aluminum, while three heavy metals were identified in the CCA-UNAM zone, most importantly, Vanadium, both in the dry season; miR398 expression presented subtle changes but was greater in the leaves from the stations with higher concentrations of heavy metals. Observations included a significant expression of CSD2, mainly in the dry season in both study zones, where levels were significant with respect to controls (p < 0.05). Reduced MTT was also higher in the dry season than in the rainy season (p < 0.05). In conclusion, the increase in heavy metals on the leaves of Taraxacum officinale induces increased expression of the CSD2 gene and reduced MTT; thus, they can be used as indicators for biomonitoring heavy metal concentrations.
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