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Resultados 2641-2650 de 4,935
Biodegradation and Detoxification of Benzalkonium Chloride in Synthetic and Industrial Effluents in Upflow Biofilm Aerobic Reactors Texto completo
2019
Fortunato, María Susana | Baroni, Sabina | González, Ana Julieta | Álvarez Roncancio, Jesús David | Storino, Alejandra | Parise, Claudia | Planes, Estela | Gallego, Alfredo | Korol, Sonia Edith
A previously isolated indigenous strain of Pseudomonas sp. was used to treat effluents, a synthetic and an industrial-containing benzalkonium chloride (BAC), in continuous upflow biofilm aerobic reactors. The reactor used to treat the synthetic effluent was constructed from Plexiglas® and filled with hollow polyvinyl chloride (PVC) cylinders as support material, whereas the one used to treat the industrial effluent was constructed from PVC and had a high recirculation flow rate and lightweight expanded clay aggregate (LECA®) as support material. Biodegradation was evaluated by spectrophotometry, HPLC, and microbial growth. Detoxification was evaluated by using Vibrio fisheri, Pseudokirchneriella subcapitata, and Lactuca sativa as test organisms. Maximal BAC influent concentrations were of 383.4 and 1172.0 mg L⁻¹ respectively, which corresponds to a maximal organic load of 49.8 and 146.5 g BAC m⁻³ day⁻¹. The efficiency of the reactors was higher than 99.3% in terms of compound removal and 97.0% in terms of COD removal. Complete detoxification of the effluent was demonstrated for the synthetic effluent, whereas a toxicity removal higher than 97% was reached in the case of the industrial effluent. The promising behavior of the isolated indigenous strain to degrade BAC in continuous reactors allows us to suggest its possible use in remediation processes.
Mostrar más [+] Menos [-]Increased Mortality, Delayed Hatching, Development Aberrations and Reduced Activity in Brown Trout (Salmo trutta) Exposed to Phenethyl Isothiocyanate Texto completo
2019
White, Asa B. | Pernetta, Angelo P. | Joyce, Chris B. | Crooks, Neil
Plants of the order Brassicaceae have evolved a chemical defence against herbivory: the glucosinolate-myrosinase system. Mechanical damage to plant tissues, such as grazing, initiates the production of phenethyl isothiocyanate (PEITC), a compound toxic to invertebrates. Mechanical damage caused during biofumigation and the harvesting and washing of watercress presents routes for PEITC release into waterbodies, such as the chalk stream spawning sites of brown trout (Salmo trutta). This laboratory study exposed developing S. trutta embryos to PEITC at concentrations of 0.01, 0.1 and 1 μg/L. S. trutta exposed to 1 μg/L PEITC during embryonic development resulted in 100% mortality after four dose days. Exposure to 0.1 μg/L PEITC resulted in an approximate fourfold increase in mortality relative to the controls, while exposure to 0.01 μg/L PEITC had a negligible effect on embryo mortality. Embryos exposed to 0.1 μg/L PEITC showed a significant delay in hatching and produced alevins with significantly shorter total lengths, lighter body weights and an approximate threefold increase in spinal deformities relative to those exposed to the controls and 0.01 μg/L PEITC. The results of a motor activity assay demonstrate that alevins exposed to PEITC showed a significant decrease in swimming activity compared with control animals during periods of illumination. The increased mortality, teratogenic effects and impaired behaviour in S. trutta following embryonic exposure to relatively low concentrations of PEITC highlight a need to accurately quantify and monitor environmental levels of PEITC.
Mostrar más [+] Menos [-]Genetic and systemic toxicity induced by silver and copper oxide nanoparticles, and their mixture in Clarias gariepinus (Burchell, 1822) Texto completo
2019
Ogunsuyi, Olusegun I. | Fadoju, Opeoluwa M. | Akanni, Olubukola O. | Alabi, Okunola A. | Alimba, Chibuisi G. | Cambier, Sébastien | Eswara, Santhana | Gutleb, Arno C. | Adaramoye, Oluwatosin A. | Bakare, Adekunle A.
Unanticipated increase in the use of silver (Ag) and copper oxide (CuO) nanoparticles (NPs) due to their antimicrobial properties is eliciting environmental health concern because of their coexistence in the aquatic environment. Therefore, we investigated the genetic and systemic toxicity of the individual NPs and their mixture (1:1) using the piscine micronucleus (MN) assay, haematological, histopathological (skin, gills and liver) and hepatic oxidative stress analyses [malondialdehyde (MDA), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT)] in the African mud catfish, Clarias gariepinus. The fish were exposed to sublethal concentrations (6.25–100.00 mg/L) of each NP and their mixture for 28 days. Both NPs and their mixture induced significant (p < 0.05) increase in MN frequency and other nuclear abnormalities. There was significant decrease in haemoglobin concentration, red and white blood cell counts. Histopathological lesions observed include epidermal skin cells and gill lamellae hyperplasia and necrosis of hepatocytes. The levels of MDA, GSH and activities of SOD and CAT were impacted in C. gariepinus liver following the exposure to the NPs and their mixture. Interaction factor analysis of data indicates antagonistic genotoxicity and oxidative damage of the NPs mixture. These results suggest cytogenotoxic effects of Ag NPs, CuO NPs and their mixture via oxidative stress in Clarias gariepinus.
Mostrar más [+] Menos [-]Does agricultural value added induce environmental degradation? Empirical evidence from an agrarian country Texto completo
2019
Agboola, Mary Oluwatoyin | Bekun, Festus Victor
This study empirically investigates the agriculture-induced environmental Kuznets curve (EKC) hypothesis in an agrarian framework. Annual time series data from 1981–2014 was employed using augmented Dickey–Fuller and the Phillips–Perron (PP) unit root test complemented by the Zivot and Andrews unit root that accounts for a single structural break to ascertain stationarity properties of variables under consideration. For the cointegration analysis, an autoregressive distributive lag methodology and the recent novel Bayer and Hanck combined cointegration technique are employed. For the direction of causality, the Granger causality test is used as estimation technique. Empirical findings lend support for the long-run equilibrium relationship among the variables under consideration. This study also validates the inverted U-shaped pattern of EKC for the case of Nigeria, affirming that Nigeria remains at the scale-effect stage of its growth trajectory. Further empirical results show that foreign direct investment attraction helps mitigate carbon emissions in Nigeria. Based on these results, several policy prescriptions on the Nigeria energy mix and agricultural operations in response to quality of the environment were suggested for policymakers, stakeholders, and environmental economists that formulate and design environmental regulations and strategies to realise the goal 7 of sustainable development (SDG).
Mostrar más [+] Menos [-]Activity of Phosphatases in Soil Contaminated with PAHs Texto completo
2019
Lipińska, Aneta | Kucharski, Jan | Wyszkowska, Jadwiga
Polycyclic aromatic hydrocarbons (PAHs) upset the basic biological parameters of the soil, such as enzymatic activity, which can be used to identify the direction and intensity of organic and mineral substance transformation in the soil environment. The aim of this study was to determine the impact of soil contamination with naphthalene, phenanthrene, anthracene and pyrene at rates of 0–4000 mg kg⁻¹ DM (dry matter) of soil on the activity of acid phosphatase and alkaline phosphatase. An analysis was also conducted on how some organic substances, such as cellulose, sucrose and compost at rates of 0 and 9 g kg⁻¹ DM alleviate the PAH impact on the enzymes under study. The experiment was carried out in a laboratory with loamy sand as the soil material. Phosphatase resistance (RS) and soil resilience (RL) were calculated. The enzyme activity was found to depend significantly on the PAH rate, time of PAH deposition in soil and the type of organic substance added to the soil. The activity of acid and alkaline phosphatase increased with the degree of soil contamination with PAHs. Naphthalene had the greatest stimulating effect on enzyme activity. Biostimulation of soil with cellulose, sucrose and compost had a positive effect on acid and alkaline phosphatase activity, with cellulose and compost being the most effective in boosting acid and alkaline phosphatase activity, respectively. Naphthalene had the greatest effect on acid and alkaline phosphatase resistance and pyrene had the least effect. Low RL indices indicate that the presence of PAHs permanently disturbed the activity of acid and alkaline phosphatase.
Mostrar más [+] Menos [-]Evaporation and concentration of desulfurization wastewater with waste heat from coal-fired power plants Texto completo
2019
Zheng, Hao | Zheng, Chenghang | Li, Xiang | Xu, Shiguo | Liu, Shaojun | Zhang, Youngxin | Weng, Weiguo | Gao, Xiang
The reduction of wet desulfurization wastewater is one of the important tasks of coal-fired power plants, and it is important for achieving “zero emissions.” Evaporation and concentration (E&C) with waste heat is an effective way to reduce wastewater. Here, two typical types of industrial desulfurization wastewater are used to study the change rule of pH and total dissolved solids during wastewater concentration in a circulating evaporation tower. The results indicate that with the increase of concentration ratio, the pH of desulfurization wastewater is decreased rapidly and then is gradually stabilized at 2–3 when SO₂ or SO₃ is contained in flue gas, and the increase in conductivity is less for wastewater with higher SO₄²⁻ content. The characteristics of various ions are also analyzed, and the composition and microscopic morphology of the precipitates are characterized during concentration. The growth pattern of Ca²⁺ concentration is dependent on the ratio of Ca²⁺ and SO₄²⁻ in raw wastewater. When the concentration ratio is 7.21, the insoluble and slightly soluble substances undergo precipitation and the solid content is approximately 20%, which can help realize the concentration and reduction of desulfurization wastewater.
Mostrar más [+] Menos [-]Temporal investigation of radionuclides and heavy metals in a coastal mining area at Ierissos Gulf, Greece Texto completo
2019
Pappa, Filothei K. | Tsabaris, Christos | Patiris, Dionisis L. | Eleftheriou, Georgios | Ioannidou, Alexandra | Androulakaki, Effrosini G. | Kokkoris, Michael | Vlastou, Roza
Vertical variations of radionuclides, trace metals, and major elements were determined in two sediment cores, which were collected in the marine environment of Ierissos Gulf near Stratoni’s mining area. The enrichment factors (EFs) were also estimated and provided moderately severe to extremely severe enrichment for most trace elements and Mn, describing the anthropogenic influence in the gulf during the previous century. According to the applied dating models based on ²¹⁰Pb and ¹³⁷Cs, the effect in the marine sediment due to the exploitation of pyrite for the production of sulfuric acid during 1912–1920 was observed. Additionally, the decrease of mining activity during 1935–1945 due to the Second World War and the type of ore exploitation, the alteration of the exploited ores, and the construction and operation of Olympiada’s floatation plant during 1950–1970 were identified. The end of tailing discharging into the marine environment during 1980–2010 was also noted.
Mostrar más [+] Menos [-]Ameliorative effect of Bacillus subtilis, Saccharomyces boulardii, oregano, and calcium montmorillonite on growth, intestinal histology, and blood metabolites on Salmonella-infected broiler chicken Texto completo
2019
Abudabos, Alaeldein M. | Alhouri, Hemiar A.A. | Alhidary, Ibrahim A. | Nassan, Mohammed A. | Swelum, Ayman A.
This study evaluated the effects of Bacillus subtilis, Saccharomyces boulardii, oregano, and calcium montmorillonite on the physical growth, intestinal histomorphology, and blood metabolites in Salmonella-challenged birds during the finisher phase. In this study, a total of 600 chicks (Ross 308) were randomly distributed into the following dietary treatments: basal diet with no treatment; infected with Salmonella; T1, infected + avilamycin; T2, infected + Bacillus subtilis; T3, Saccharomyces boulardii; T4, infected + oregano; T5, infected + calcium montmorillonite. Our results indicated that feed consumption, body weight gain, total body weight, and feed conversion ratio increased significantly (P < 0.01) in T1 and T2. Villus width increased significantly (P < 0.01) in T1 while the total area was significantly (P < 0.01) higher in T1 and T2 among the treatment groups. Blood protein was significantly (P < 0.01) high in T3 and T4; however, the glucose concentration was significantly (P < 0.01) high in T2, T3, and T4. The treatments increased significantly (P< 0.01) in the treatment groups compared to the negative control. Aspirate aminotransferase (AST) was significantly (P < 0.05) low in T3 compared to the positive control. In conclusion, the results indicated that supplementation of Bacillus subtilis and calcium montmorillonite improved the production performance compared to other feed additives in broiler chicks infected with Salmonella during the finisher phase.
Mostrar más [+] Menos [-]Electrochemical modification of activated carbon fiber as 3-D particle electrodes: characterization and enhancement for the degradation of m-cresol Texto completo
2019
Liu, Weijun | Hu, Xiang | Sun, Zhirong | Duan, Pingzhou
Commercial activated carbon fiber (ACF) has been employed as particle electrodes to degrade aqueous m-cresol in 3-D electrode systems. To enhance the electrooxidation performance, three types of new ACF modification modes (anodic oxidation, cathodic reduction, and aqueous oxidation with concentrated HNO₃) were introduced in this paper. These pretreated samples were characterized by N₂ adsorption, scanning electron microscopy (SEM), cyclic voltammetry (CV), temperature-programmed desorption mass (TPD-MS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). It was revealed that the two new modification methods could efficiently modify the surface morphology as well as the chemical property. Eight types of surface oxygen groups (SOGs) were identified on the surface of ACF, and the types and amount of SOGs might be related to the oxidation effect of ACF on the 3-D electrodes. The effect and mechanism of these SOGs on electrooxidation performance were discussed with the aid of the frontier molecular orbital theory. It was demonstrated that the H₂O₂–·OH reaction mechanism was improved in the 3-D electrode system and the mechanism was elucidated.
Mostrar más [+] Menos [-]Comparison and optimization of different methods for Microcystis aeruginosa’s harvesting and the role of zeta potential on its efficiency Texto completo
2019
Geada, Pedro | Oliveira, Francisca | Loureiro, Luís | Esteves, Diogo | Teixeira, José A. | Vasconcelos, Vítor | Vicente, António A. | Fernandes, Bruno D.
This study has compared the harvesting efficiency of four flocculation methods, namely, induced by pH, FeCl₃, AlCl₃ and chitosan. No changes were observed on M. aeruginosa cells. Flocculation assays performed at pH 3 and 4 have shown the best harvesting efficiency among the pH-induced tests, reaching values above 90% after 8 h. The adjustment of zeta potential (ZP) to values comprised between − 6.7 and − 20.7 mV enhanced significantly the settling rates using flocculant agents, being FeCl₃ the best example where increments up to 88% of harvesting efficiency were obtained. Although all the four methods tested have presented harvesting efficiencies above 91% within the first 8 h after the optimization process, the highest performance was obtained using 3.75 mg L⁻¹ of FeCl₃, which allowed reaching 92% in 4 h.
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