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Résultats 3581-3590 de 5,152
Modeling the exposure time in a tidal system: the impacts of external domain, tidal range, and inflows Texte intégral
2018
Gao, Xueping | Zhao, Guixia | Zhang, Chen | Wang, Yan
Exposure time is an important characteristic for hydrodynamics that has simultaneous impacts on the biochemical processes in tidal systems. To eliminate man-made errors, decrease computational effort, and increase simulation efficiency, exposure time was evaluated under different hydrodynamic conditions for a bay to investigate the impact of the external domain on the accuracy of the computational results for exposure time. The exposure time was explicitly defined and computed using a hydrodynamic model and tracer experiments for a set of ten external domain sizes (EDS), five external domain lengths (EDL), and three special hydrodynamic conditions. The results indicated that the external domain had a significant influence on the exposure time, and the intensity of this influence was related to hydrodynamic conditions. The sensitivity of the exposure time to the external domain increased with increasing tidal range, while freshwater inflows decreased this sensitivity. However, the variation trends for exposure time with different EDS and EDL were independent of the hydrodynamic conditions. Considering the computational efficiency (maximum), the calculated error (minimum) of the exposure time, and the impact of the boundary conditions (minimum), the recommended EDS and EDL range from 9 to 13 times the initial domain size and 1.30 to 1.45 times the length in the bay, respectively. The research regarding exposure time and external domains not only helps to eliminate the errors caused by man-made factors and reduce the computational effort but also provides a reference for understanding the interrelationship between coastal waters, reciprocating flow, and the water environment.
Afficher plus [+] Moins [-]Green light and light stress in moth: influence on antioxidant enzymes in the oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae) Texte intégral
2018
Kim, Kil-Nam | Yun, Chol-Nam | Sin, Un-Chol | Huang, Zhi-Juan | Huang, Qiu-Ying | Lei, Chao-Liang
Recently, light traps equipped with light-emitting diodes (LEDs) have been widely applied for controlling nocturnal pest moths. The oriental armyworm, known as Mythimna separata Walker, is an important insect pest in eastern Asia. The present study aimed to evaluate an influence of green light irradiation on antioxidant enzymes and light stress in M. separata adults. We determined total antioxidant capacity (T-AOC) and an activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione-S-transferase (GST) in the moth bodies according to an exposure time (0 to 180 min) of a green LED light. By our results, we suggested that the green (520 nm) LED light irradiation could induce a weak oxidative stress in M. separata adult moths, and the moths under the green light could restore the damage caused by this light stress. Additionally, we proposed that the adaptive ability to the light stress varied between the moths of different sexes. Our results may provide a theoretical and scientific basis for elucidating a reason of the phototactic behavior of nocturnal moths, including M. separata adults.
Afficher plus [+] Moins [-]Analysis of asymmetries in air pollution with water resources, and energy consumption in Iran Texte intégral
2018
Ashouri, Mohammad Javad | Rafei, Meysam
Iran should pay special attention to its excessive consumption of energy and air pollution due to the limited availability of water resources. This study explores the effects of the consumption of energy and water resources on air pollution in Iran from 1971 to 2014. It utilizes the non-linear autoregressive distributed lag approach to establish a robust relationship between the variables which show that both long- and short-run coefficients are asymmetrical. The positive and negative aspects of the long-run coefficients of energy consumption and water resources were found to be 0.19, − 1.63, 0.18, and 2.36, respectively, while only the negative ones were significant for energy consumption. Based on the cumulative effects, it can be established that there are important and significant differences in the responses of air pollution to positive and negative changes in water productivity and energy consumption. In particular, CO₂ gas emissions are affected by negative changes in H₂O productivity both in terms of the total and the GDP per unit of energy use in Iran. In regard to short-run results, considerable asymmetric effects occur on all the variables for CO₂ emissions. Based on the results obtained, some recommendations are presented, which policymakers can adopt in efforts to address the issues of pollution and consumption.
Afficher plus [+] Moins [-]Spatiotemporal characteristics of hydrochemistry in Asian arid inland basin–a case study of Shiyang River Basin Texte intégral
2018
Yang, Ling | Zhu, Guofeng | Shi, Peiji | Li, Jiafang | Liu, Yuanfeng | Tong, Huali | Hu, Pengfei | Liang, Feng | Pan, Hanxiong | Guo, Huiwen | Zhang, Yu
Inland rivers play a key role in supplying water for domestic and agricultural purposes in Asian arid inland basin. This paper investigates the chemical composition of precipitation, river water, and groundwater, providing evidence for the influencing factors the water composition in the Shiyang River Basin. Water samples were collected and analyzed to determine the content of major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺, and NH+ 4) and anions (HCO– 3, Cl–, NO– 3, NO– 2, F–, and SO2–4), total solid solubility, and pH values. The results showed that precipitation, surface water, and groundwater were mildly alkaline. Ca²⁺ and SO2–4 were the predominant ions. The content of inorganic ions varied largely in the different seasons, with the highest ion concentration observed in spring and the lowest in summer. The seasonal variations in groundwater were less considerable than those in surface water. Furthermore, anion concentrations increased substantially from upstream to downstream. Regional weathering of carbonates and evaporation were established as the major sources of these ions. In addition, we discovered that anthropogenic inputs had led to light pollution of water in some residential districts.
Afficher plus [+] Moins [-]Whole blood and hair trace elements and minerals in children living in metal-polluted area near copper smelter in Karabash, Chelyabinsk region, Russia Texte intégral
2018
Skalny, AnatolyV. | Zhukovskaya, ElenaV. | Kireeva, GalinaN. | Skalnaya, MargaritaG. | Grabeklis, AndreyR. | Radysh, IvanV. | Shakieva, RosaA. | Nikonorov, AlexandrA. | Tinkov, AlexeyA.
The primary aim of the study is assessment of hair and whole blood trace element and mineral levels in children living in a polluted area near a copper smelter (Karabash) and two control locations (Varna, Tomino) using inductively coupled plasma mass spectrometry. The obtained data indicates that both blood and hair As, Pb, and Fe levels in children living in Karabash significantly exceeded the control values. Whole blood levels of copper in children living in Varna exceeded that in Tomino (p = 0.155) and Karabash (p < 0.001) by 16 %. Oppositely, hair concentration of Cu was maximal in children from Karabash. Blood Ca and Mg content in children from Varna exceeded the respective values from Tomino and Karabash by 32 % (p = 0.021) and 42 % (p < 0.001), and 19 % (p < 0.001) and 9 % (p < 0.001), respectively. Similar differences were observed in hair mineral content. Oppositely, children living in Tomino and Karabash were characterized by 10 (p = 0.002) and 23 % (p < 0.001) higher levels of blood phosphorus. At the same time, hair P content was maximal in a polluted area. Therefore, children living in a polluted area near a copper smelter had significantly higher values of heavy metals and decreased Mg and Ca content in biosamples. It is supposed that adverse health effects in persons living near a copper smelter may be associated not only with toxic metal overexposure but also with altered mineral homeostasis.
Afficher plus [+] Moins [-]Large-scale geographic patterns of mercury contamination in Morocco revealed by freshwater turtles Texte intégral
2018
Slimani, Tahar | El Hassani, MohamedSaid | El Mouden, ElHassan | Bonnet, Marine | Bustamante, Paco | Brischoux, François | Brault-Favrou, Maud | Bonnet, Xavier
Large-scale geographic patterns of mercury contamination in Morocco revealed by freshwater turtles Texte intégral
2018
Slimani, Tahar | El Hassani, MohamedSaid | El Mouden, ElHassan | Bonnet, Marine | Bustamante, Paco | Brischoux, François | Brault-Favrou, Maud | Bonnet, Xavier
Mercury (Hg) is a toxic contaminant present in most aquatic ecosystems. High concentrations pose serious threats to organisms and to human health. Because previous studies focused on few countries, environmental hazard due to Hg contamination remains obscure in many geographic areas, and for example limited information is available in North Africa. We examined total Hg contamination in 13 sites in Morocco (12 rivers and one lake) spread over a large area, 400 km north–south and 350 km west–east, that encompasses different biogeographic zones separated by the Atlas Mountains. Due to their longevity and sedentary habits, we used freshwater turtles as biological probes to monitor Hg exposure. Keratinized tissues reflect long-term Hg exposure; thus, we assayed Hg concentration in the claws of > 200 individuals and supplemented these data with blood Hg concentrations of > 60 individuals (a tissue that provides shorter term Hg exposure integration). The results provide the first large-scale picture of Hg contamination in the aquatic freshwater systems of Morocco. Comparisons with previous studies revealed that some of the sites were highly contaminated (e.g. mean Hg concentrations were above 5 μg g⁻¹, a very high level in keratinized tissues) whereas other sites presented moderate or baseline levels. Unexpectedly, all highly contaminated sites were found in less densely populated areas, while more densely urbanized northern sites, even the sewers of large cities, were not highly contaminated. We hypothesize that silver mining activities in the southern High Atlas and in the Anti-Atlas contaminate rivers of the catchment basins over long distances. These findings indicate that fish, water consumption and contamination levels in local people should be further scrutinized.
Afficher plus [+] Moins [-]Large-scale geographic patterns of mercury contamination in Morocco revealed by freshwater turtles Texte intégral
2018
Slimani, Tahar | El Hassani, Mohamed Said | El Mouden, El Hassan | Bonnet, Marine | Bustamante, Paco | Brischoux, Francois | Brault-Favrou, Maud | Bonnet, Xavier | Faculté des Sciences Semlalia [Marrakech] ; Université Cadi Ayyad [Marrakech] (UCA) | Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC) ; Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS) | LIttoral ENvironnement et Sociétés (LIENSs) ; Institut national des sciences de l'Univers (INSU - CNRS)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)
International audience | Mercury (Hg) is a toxic contaminant present in most aquatic ecosystems. High concentrations pose serious threats to organisms and to human health. Because previous studies focused on few countries, environmental hazard due to Hg contamination remains obscure in many geographic areas, and for example limited information is available in North Africa. We examined total Hg contamination in 13 sites in Morocco (12 rivers and one lake) spread over a large area, 400 km north–south and 350 km west–east, that encompasses different biogeographic zones separated by the Atlas Mountains. Due to their longevity and sedentary habits, we used freshwater turtles as biological probes to monitor Hg exposure. Keratinized tissues reflect long-term Hg exposure; thus, we assayed Hg concentration in the claws of > 200 individuals and supplemented these data with blood Hg concentrations of > 60 individuals (a tissue that provides shorter term Hg exposure integration). The results provide the first large-scale picture of Hg contamination in the aquatic freshwater systems of Morocco. Comparisons with previous studies revealed that some of the sites were highly contaminated (e.g. mean Hg concentrations were above 5 μg g⁻¹, a very high level in keratinized tissues) whereas other sites presented moderate or baseline levels. Unexpectedly, all highly contaminated sites were found in less densely populated areas, while more densely urbanized northern sites, even the sewers of large cities, were not highly contaminated. We hypothesize that silver mining activities in the southern High Atlas and in the Anti-Atlas contaminate rivers of the catchment basins over long distances. These findings indicate that fish, water consumption and contamination levels in local people should be further scrutinized.
Afficher plus [+] Moins [-]CFD simulation of copper(II) extraction with TFA in non-dispersive hollow fiber membrane contactors Texte intégral
2018
Amir, Muhammad | Younas, Mohammad | Rezakazemi, Mashallah
This study presents computational fluid dynamics (CFD) simulation of dispersion-free liquid-liquid extraction of copper(II) with trifluoroacetylacetone (TFA) in hollow fiber membrane contactor (HFMC). Mass and momentum balance Navier-Stokes equations were coupled to address the transport of copper(II) solute across membrane contactor. Model equations were simulated using COMSOL Multiphysics™. The simulation was run to study the detailed concentration distribution of copper(II) and to investigate the effects of various parameters like membrane characteristics, partition coefficient, and flow configuration on extraction efficiency. Once-through extraction was found to be increased from 10 to 100% when partition coefficient was raised from 1 to 10. Similarly, the extraction efficiency was almost doubled when porosity to tortuosity ratio of membrane was increased from 0.05 to 0.81. Furthermore, the study revealed that CFD can be used as an effective optimization tool for the development of economical membrane-based dispersion-free extraction processes.
Afficher plus [+] Moins [-]Cytotoxic effect of chlorpyrifos is associated with activation of Nrf-2/HO-1 system and inflammatory response in tongue of male Wistar rats Texte intégral
2018
El-Sayed, NorhanM. | Ahmed, AmalA. M. | Selim, ManarA. A.
Repeated administration of chlorpyrifos (CPF), an organophosphate pesticide, can increase the risk of oral cytotoxicity. The current study was designed to assess the mechanism by which CPF mediates its cytotoxic effect on lingual mucosa of rats. Twenty-four male Wistar rats were used in the present study and divided into three groups: group I: healthy rats (negative control), group II: rats treated with CPF 1/40 LD50 (3.375 mg/kg, orally/daily) for 28 days, group III: rats treated with CPF 1/10 LD50 (13.5 mg/kg, orally/daily) for 28 days. At the end of the experiment, all rats were sacrificed by cervical dislocation under ketamine anesthesia. Tongue samples were dissected out at their base for detection of heme oxygenase-1 (HO-1) and nuclear erythroid 2-related factor 2 (Nrf-2) by western blotting and histopathological and electron microscopic studies. Immunostaining was used to determine cleaved caspase 3 and the nuclear factor kappa B (NF-κB) localization. Structural and ultrastructural examination of treated lingual mucosa with CPF demonstrated degenerative changes that involved both the dorsal and ventral surfaces of the tongue as well as the lingual glands. CPF-treated rats demonstrated a significant increase in the levels of pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor (TNF-α) in addition to a significant dose-dependent activation of NF-κB and cleaved caspase 3. Furthermore, CPF activated HO-1 and Nrf-2 pathway in a dose-dependent manner. In conclusion, this data suggests that the CPF-induced cytotoxicity may be explained by NF-κB activated inflammatory cascade. In addition, CPF triggers an adaptive activation of Nrf-2/HO-1 pathway.
Afficher plus [+] Moins [-]Analysing the accuracy of machine learning techniques to develop an integrated influent time series model: case study of a sewage treatment plant, Malaysia Texte intégral
2018
Ansari, Mozafar | Othman, Faridah | Abunama, Taher | El-Shafie, Ahmed
The function of a sewage treatment plant is to treat the sewage to acceptable standards before being discharged into the receiving waters. To design and operate such plants, it is necessary to measure and predict the influent flow rate. In this research, the influent flow rate of a sewage treatment plant (STP) was modelled and predicted by autoregressive integrated moving average (ARIMA), nonlinear autoregressive network (NAR) and support vector machine (SVM) regression time series algorithms. To evaluate the models’ accuracy, the root mean square error (RMSE) and coefficient of determination (R²) were calculated as initial assessment measures, while relative error (RE), peak flow criterion (PFC) and low flow criterion (LFC) were calculated as final evaluation measures to demonstrate the detailed accuracy of the selected models. An integrated model was developed based on the individual models’ prediction ability for low, average and peak flow. An initial assessment of the results showed that the ARIMA model was the least accurate and the NAR model was the most accurate. The RE results also prove that the SVM model’s frequency of errors above 10% or below − 10% was greater than the NAR model’s. The influent was also forecasted up to 44 weeks ahead by both models. The graphical results indicate that the NAR model made better predictions than the SVM model. The final evaluation of NAR and SVM demonstrated that SVM made better predictions at peak flow and NAR fit well for low and average inflow ranges. The integrated model developed includes the NAR model for low and average influent and the SVM model for peak inflow.
Afficher plus [+] Moins [-]Toxicological effects of chemical constituents from Piper against the environmental burden Aedes aegypti Liston and their impact on non-target toxicity evaluation against biomonitoring aquatic insects Texte intégral
2018
Vasantha-Srinivasan, Prabhakaran | Thanigaivel, Annamalai | Edwin, Edward-Sam | Ponsankar, Athirstam | Senthil-Nathan, Sengottayan | Selin-Rani, Selvaraj | Kalaivani, Kandaswamy | Hunter, WayneB. | Duraipandiyan, Veeramuthu | Al-Dhabi, NaifAbdullah
Dengue is the most rapidly spreading mosquito-borne viral disease in the world. The mosquito, Aedes aegypti, also spreads Yellow fever, Chikungunya, and Zika virus. As the primary vector for dengue, Ae. aegypti now occurs in over 20 countries and is a serious concern with reports of increasing insecticide resistance. Developing new treatments to manage mosquitoes are needed. Formulation of crude volatile oil from Piper betle leaves (Pb-CVO) was evaluated as a potential treatment which showed larvicidal, ovipositional, and repellency effects. Gut-histology and enzyme profiles were analyzed post treatment under in-vitro conditions. The Pb-CVO from leaves of field collected plants was obtained by steam distillation and separated through rotary evaporation. The Pb-CVO were evaluated for chemical constituents through GC-MS analyses revealed 20 vital compounds. The peak area was establish to be superior in Eudesm-7(11)-en-4-ol (14.95%). Pb-CVO were determined and tested as four different concentrations (0.25, 0.5, 1.0, and 1.5 mg/L) of Pb-CVO towards Ae. aegypti. The larvicidal effects exhibited dose dependent mortality being greatest at 1.5 mg Pb-CVO/10 g leaves. The LC₅₀ occurred at 0.63 mg Pb-CVO/L. Larva of Ae. aegypti exposed to Pb-CVO showed significantly reduced digestive enzyme actions of α- and β-carboxylesterases. In contrast, GST and CYP450 enzyme levels increased significantly as concentration increased. Correspondingly, oviposition deterrence index and egg hatch of Ae. aegypti exposed to sub-lethal doses of Pb-CVO demonstrated a strong effect suitable for population suppression. Repellency at 0.6 mg Pb-CVO applied as oil had a protection time of 15–210 min. Mid-gut histological of Ae. aegypti larvae showed severe damage when treated with 0.6 mg of Pb-CVO treatment compared to the control. Non-toxic effects against aquatic beneficial insects, such as Anisops bouvieri and Toxorhynchites splendens, were observed at the highest concentrations, exposed for 3 h. These results suggest that the Pb-CVO may contain effective constituents suitable for development of new vector control agents against Ae. aegypti.
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