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Resultados 3621-3630 de 6,560
Removal and Recovery of Phosphorus from Contaminated Water Using Novel, Reusable, Renewable Resource-Based Aluminum/Cerium Oxide Nanocomposite Texto completo
2020
Nakarmi, Amita | Moreira, Rebecca | Bourdo, Shawn E. | Watanabe, Fumiya | Toland, Alan | Viswanathan, Tito
The combination of cerium oxide and aluminum oxide nanocomposites in quaternary ammonium–modified wood has been shown to be excellent for phosphorus (as phosphate) removal from contaminated waters. The results are better than using single metal oxides in the nanocomposite based on the adsorption capacity and kinetic rate. The mixed metal oxide nanocomposite on pine wood chips (a renewable resource) represent a green technology for phosphorus remediation. The process of preparation of nanocomposite of this material is straightforward, economically feasible, and environmentally friendly. There are no harmful chemicals or petroleum reagents used during the synthesis. In this study, adsorption isotherms (Langmuir and Freundlich, Temkin and Dubinin-Radushkevich) and kinetic studies (Lagergren pseudo-first and pseudo-second order, Elovich and Weber-Morris) were performed to determine the adsorption capacity and mechanism of the phosphorus removal by the nanocomposite. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area, and Fourier-transfer infrared (FTIR) spectroscopy were analyzed to determine the size and structure of the nanocomposite as well as elements present on the surface of the wood chips. The maximum adsorption capacity was found to be 70.42 mg/g. The results from this study demonstrate that phosphorus levels in polluted water can be reduced from 10,000 parts per billion to 10 parts per billion. We also demonstrated that the phosphorus could be desorbed and the media regenerated for repeated use without loss of efficiency.
Mostrar más [+] Menos [-]Study of the Performance of a Composite Bioreactor on Removal of High Concentrations of Formaldehyde Texto completo
2020
Wen, Haoren | Wang, Jie | Yang, Changliang | Bi, Xiaoyi | Zou, Ping
Controlling high concentrations of industrial formaldehyde pollution has become a hot issue in recent years. This problem needs to be solved, where formaldehyde, which is highly soluble in water, in biofilm packed towers led to the reduction of removal performance of the packed towers. This paper presented a new method which is based on the biofilm packed tower, a liquid-phase treatment device consisting of an aeration tank and a sedimentation tank that was added to construct a composite bioreactor system. Moreover, this study investigated the effects of the composite bioreactor on the removal of formaldehyde under different operation conditions and the structural succession characteristics of the dominant bacterial communities in the composite biological system. The results indicated that even if the operating conditions including meteorological formaldehyde concentrations at the inlet, gas flow, and circulating liquid flow were changed, the B (amount of biochemically degraded formaldehyde in waste gas per unit time in a unit volume) in the composite bioreactor was also higher than that of the blank biofilm packed tower. Also, at the genus level, the microbial community structures of the two systems were not the same, where the dominant genera of the biofilm packed tower (blank group) included Pseudomonas, Methyloversatilis, Cupriavidus, and Hyphomicrobium. After the addition of the liquid-phase treatment device, the composite bioreactor promoted three aerobic bacteria including Ensife, Acidimicrobiales_norank, and Anaerolineaceae_norank to become the dominant genera. In the two systems, the relative abundances of the formaldehyde-degrading bacteria including Pseudomonas, Methyloversatilis, Methylophilus, and Methylobacterium increased with time and gradually became stabilized.
Mostrar más [+] Menos [-]Study of occupational exposure to brick kiln emissions on heavy metal burden, biochemical profile, cortisol level and reproductive health risks among female workers at Rawat, Pakistan Texto completo
2020
David, Mehwish | Qurat-Ul-Ain, | Afzal, Muhammad | Shoaib, Muhammad | Aman, Faiza | Cloete, Karen J. | Turi, Naheed | Jahan, Sarwat
The present study was planned to understand the heavy metal burden and its possible actions in blood of occupational females working at brick kilns at Rawat, Pakistan. A total of 232 women were included in the study, of which 114 presented control subjects. Apart from collection of demographic data, fertility indicators and body mass index (BMI), blood was collected from subjects that was later used for the determination of heavy metal concentrations using atomic absorption spectroscopy and haematological profile. Blood was centrifuged and plasma was obtained and stored at − 20° to study biochemical variables (sodium dismutase, peroxidase, reactive oxygen species, thiobarbituric acid reactive species, protein estimation), lipid profile and cortisol concentrations among the two groups. Analysis of heavy metal in blood showed elevated levels of cadmium (3.09 ± 0.01 μg/dl), chromium (4.20 ± 0.02 μg/dl) and nickel (5.59 ± 0.03 μg/dl) in worker’s group as compared with control. Increased platelet count; decreased antioxidant enzyme and increased oxidants level; increased total cholesterol, low-density lipoprotein (LDL) and triglyceride (TG); decreased total protein and high-density lipoprotein (HDL); and increased cortisol levels were evident among workers as compared with the control group. The study concluded that occupational workers experience increased heavy metals burden in blood and, therefore, pose a risk to human health by causing reduction in antioxidant enzymes concentration and increase in stress conditions.
Mostrar más [+] Menos [-]Epiphytic bacterial community enhances arsenic uptake and reduction by Myriophyllum verticillatum Texto completo
2020
Zhen, Zhuo | Yan, Changzhou | Zhao, Yuan
Microbes play an important role in the biotransformation of arsenic (As) speciation in various environments. Nevertheless, whether epiphytic bacteria that attached on submerged macrophytes have the potential to influence As speciation still remains unclear. In this study, sterile or nonsterile Myriophyllum verticillatum was cultured with arsenite (As(III)) or arsenate (As(V)) to investigate the impact of epiphytic bacterial community on As uptake, transformation, and efflux. Results showed that both sterile and nonsterile M. verticillatum did not display substantial As(III) oxidation, suggesting that neither M. verticillatum nor epiphytic bacterial community has the capacities of As(III) oxidation. However, sterile M. verticillatum exhibited capacity for As(V) reduction, and the presence of epiphytic bacterial community substantially enhanced the proportions of As(III) in the medium (from 39.91 to 98.44%), indicating that epiphytic bacterial community contributes significantly to As(V) reduction in the medium. The presence of epiphytic bacterial community elevated As accumulation (by up to 2.06-fold) in plants when exposed to As(V). Results also showed that epiphytic bacterial community contributed little to As(III) efflux. Quantitative PCR of As metabolism genes revealed the dominance of the respiratory As(V) reductase genes (arrA) in epiphytic bacterial community, which might play a significant role in As(V) reduction in aquatic environments. Phylogenetic analysis of the arrA genes revealed the widely distribution and diversity of As(V)-respiring bacteria. These results highlighted the substantial impact of the epiphytic bacterial community associated with submerged aquatic macrophytes on As biogeochemistry in wetland and water environments.
Mostrar más [+] Menos [-]The impact of natural disasters on China’s macroeconomy Texto completo
2020
Pu, Chengyi | Liu, Zhen | Pan, Xiaojun | Addai, Bismark
This study attempts to construct an econometric model using China’s natural disaster losses and macro-industry development data from 1980 to 2017 to explore the macroeconomic fluctuations caused by natural disasters. The structural vector autoregressive (SVAR) and the seemingly unrelated regression (SUR) models are employed in estimating the impact of natural disasters on China’s macroeconomy and how the disasters specifically affect the three sectors of the economy: primary, secondary, and tertiary. This study concludes that even though natural disasters in China do not significantly affect the overall real GDP, they have adverse impacts on the production in the primary industry, causing a sudden reduction in the means of production in the market and directly affecting various industries, but the impact on the secondary and tertiary industries is weak. This study also shows that the effect of natural disasters on the primary sector reduced significantly following industry restructuring after China’s accession to the World Trade Organization (WTO). The impact of natural disasters on the primary industry could be reduced by adjusting the industrial structure to deal with macroeconomic shocks caused by natural disasters in order to promote macroeconomic stability of both regional and national economies. Finally, national aid policy should focus on the primary industry since that sector is significantly affected by natural disasters shocks.
Mostrar más [+] Menos [-]Influence of Outdoor Air Pollution on Cardiovascular Diseases in Madeira (Portugal) Texto completo
2020
Camacho, Irene | Camacho, Jaime | Camacho, Roberto | Góis, André | Nóbrega, Vítor
Previous studies suggest that human exposure to atmospheric pollution can trigger cardiovascular diseases (CVDs). This study aimed at assessing the influence of short-term exposure to atmospheric pollution in the occurrence of CVD and mortality in Madeira. A single-centre retrospective study was conducted during 2005–2011. Air pollutant data and meteorological parameters were gathered. Daily admissions at the emergency service due to CVD and markers levels for cardiac function were obtained from a public hospital. Exploratory and correlation analysis of all variables were performed, and the CVD relative risk (RR) of hospital admissions and mortality was calculated. During the study, mean annual concentrations of the air pollutants varied greatly, with NOₓ and O₃ showing the highest annual average concentrations. Two hundred ten thousand five hundred forty patients were admitted at the emergency service, 74% of them due to cardiovascular causes. Hospital admissions were positively correlated with PM₂.₅, and SO₂. A positive and significant association between PM₂.₅ with creatine kinase myocardial band and B-type natriuretic peptides markers was found, whilst SO₂ was positively associated with Creatine kinase myocardial band. The RR seemed to increased with PM₂.₅ and NOₓ exposure. Traffic-related pollutants were weakly but statistically associated to hospital admissions due to CVD and mortality. PM₂.₅ and SO₂ were related with higher hospital admissions which in turn seemed to increase the serum markers. The risk of mortality was mainly associated with O₃ and average air temperature. Adults and elders seem to be more susceptible to atmospheric pollutants, particularly in the winter.
Mostrar más [+] Menos [-]Seasonal variation of biomarker responses in Cantareus aspersus and physic-chemical properties of soils from Northeast Algeria Texto completo
2020
Douafer, Louiza | Zaidi, Nedjoua | Soltani, Noureddine
This study belongs to the biomonitoring program of soil qualities using a land snail, Cantareus aspersus, as bioindicator. The metal-soil contamination in some sites (National Park of El Kala (NPK), El Bouni, Sidi Amar, Nechmaya, and Guelma) located in Northeast Algeria were determined during two seasons (winter and spring 2015, 2016). Glutathione (GSH) content and acetylcholinesterase (AChE) activity were significantly decreased in snails collected during spring as compared with those noticed during winter under bioclimate change. In addition, a significant difference between various sites was observed, depending on the proximity to pollution sources. The significant variation of biomarker levels is a function of the physic-chemical properties of soils when they positively correlated with EC, H, and OM, and negatively correlated with all metallic elements. Moreover, Fe and Al₂O₃ are the most abundant in all the sites, and the most polluted site was found as that of El Bouni, followed by Sidi Amar, Nechmaya, and Guelma, since NPK is the less polluted site and considered a reference site. The tested biomarkers are sensitive oxidative parameters in snails exposed to pollution correlated significantly with the soil physic-chemical properties and metallic element contents in soil. Indeed, C. aspersus could be used as sentinel species in field monitoring of Mediterranean climate regions.
Mostrar más [+] Menos [-]Green mitigation of microbial corrosion by copper nanoparticles doped carbon quantum dots nanohybrid Texto completo
2020
Kalajahi, Sara Taghavi | Rasekh, Behnam | Yazdian, Fateme | Neshati, Jaber | Taghavi, Lobat
Recently, nanomaterials have been introduced as a new generation of inhibitors to control the microbiologically influenced corrosion (MIC). In this study, copper nanoparticles doped carbon quantum dots (Cu/CQDs) nanohybrid was used as an inhibitor to reduce the MIC. FESEM, EDS, FTIR, and XRD were used to characterize the nanohybrid. The dose-response test was performed to evaluate the inhibitory effect of Cu/CQDs against SRB. Design-Expert software was used to design the matrix of experiment and analyze the result. Cu/CQDs showed significant inhibitory effect against SRB compared to the copper nanoparticles (CuNPs) and carbon quantum dots (CQDs), at 50 ppm. Moreover, corrosion behavior of X60 steel was evaluated via electrochemical impedance spectroscopy (EIS) and Tafel polarization techniques in the presence of SRB and Cu/CQDs. The fitted result of EIS showed that the charge transfer resistance (Rcₜ) value increased in the presence of Cu/CQDs owing to the enhancement in the thickness of the electrical double layer, indicating that Cu/CQDs is able to provide significant corrosion protection to X60 steel in the presence of SRB. In addition, FESEM, EDS, and XRD were used to study the formed corrosion products and biofilm on the surface of X60 steel. Corrosion test results indicated that the addition of the Cu/CQDs reduced the surface damage of X60 steel in the presence of SRB. It is attributed to the carbon dots adsorption film formation, which possessed a significant protective ability to inhibit the corrosion of steel in the presence of SRB.
Mostrar más [+] Menos [-]Potentially toxic elements in the Middle East oldest oil refinery zone soils: source apportionment, speciation, bioaccessibility and human health risk assessment Texto completo
2020
Mokhtarzadeh, Zeinab | Keshavarzi, Behnam | Moore, Farid | Marsan, Franco Ajmone | Padoan, Elio
In this research, fifteen potentially toxic elements (PTEs) (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Sc and Zn) were analysed and quantified in samples collected at 44 sites in an urban area of Iran. Sources were apportioned using enrichment factors (EFs), modified pollution index (MPI), principal component analysis (PCA), multivariate linear regression of absolute principal component scores (MLR-APCS) and speciation, with a focus on anthropogenic PTEs in the urban and industrial soils of the Arvand Free Zone area, an oil-rich zone in the country. Furthermore, the bioaccessibility and the human health risks of PTEs were investigated. The EF revealed a significant enrichment for elements such as Cd, Cu, Hg, Mo, Pb, Sb and Zn. Values of MPI showed that Abadan industrial district and Abadan petrochemical complex are the most polluted sites in the study area.The PCA/MLR analysis revealed four main sources: natural sources, fossil fuel combustion, traffic and oil derivatives and petroleum waste. The relative contribution of each source to PTE concentration varied from 32.3% of the natural sources to 30.6% of traffic and from 20.1% of petroleum waste to 17% of fossil fuel combustion. The source apportionment of metals generated using MLR-APCS receptor modelling revealed that 85.0% of Hg was generated by oil products. Chemical speciation results were compatible with the results obtained from PCA. Bioaccessibility of PTEs decreased from gastric to intestinal phase except Mo and Sb due to their different geochemical characteristics. Hazard index (HI) for non-cancer risk of PTEs for both children and adults based on total element concentrations was estimated to range from 2-fold to more than 10-fold higher than that of bioaccessible phases.
Mostrar más [+] Menos [-]Platelet-rich plasma and/or sildenafil topical applications accelerate and better repair wound healing in rats through regulation of proinflammatory cytokines and collagen/TGF-β1 pathway Texto completo
2020
Gad, Shereen B. | Hafez, Mona H. | El-Sayed, Yasser S.
Platelet-rich plasma (PRP) composites of various cytokines and growth factors which have the potential to activate and speed the process of wound repair. Sildenafil also is a potent stimulator of angiogenesis which favors its potential effects on wound healing in several models. Existing work planned to examine the effectiveness of topical application of PRP and/or sildenafil citrate hydrogel (SCH) in a non-splinted excision skin wound model. Adult male rats were allocated into control, PRP, SCH, and PRP/SCH groups. On the 7th and 14th days, blood and tissue samples were collected for hematobiochemical, histopathological, and immunohistochemistry analyses. PRP and/or SCH topical treatments caused an enhancement of wound healing parameters, including a rapid switch from inflammatory phase to connective tissue stage evident by less systemic hematological changes and decreased values of proinflammatory cytokines (IL-6, TNF-α, and IL-1β) and C-reactive protein (CRP) on the 7th or 14th days post-wounding. Also, tissue hydroxyproline, collagen, nitrite, and total protein contents were higher in therapeutically handled wounded rats. Histologically, PRP- and/or SCH-treated wounded rats exhibited less necrosis, inflammation, and fibrin with a higher level of granulation tissue formation on the 7th day post-wounding and abundant collagen remodeling, epithelization, and vascularization on the 14th day relative to control. Interestingly, combined PRP and SCH treatment was more efficient in wound healing scoring with less inflammation, more collagen remodeling, and more epithelization. Our findings confirm the effectiveness of PRP and/or SCH as a topical wound healing treatment, with better skin wound healing with their combination.
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