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Optimization of a laccase-mediator system with natural redox-mediating compounds for pesticide removal Texte intégral
2019
Kupski, Larine | Salcedo, Gabriela M. | Caldas, Sergiane S. | de Souza, Taiana D. | Furlong, Eliana B. | Primel, Ednei G.
This study proposed the optimization of a laccase-mediator system to reduce pesticide levels (bentazone, carbofuran, diuron, clomazone, tebuconazole, and pyraclostrobin) on aqueous medium. Firstly, the mediator concentration of 1 mM was established (average removal of 36%). After that, seven redox-mediating compounds, namely, 2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, caffeic acid, chlorogenic acid, p-coumaric acid, ferulic acid, gallic acid, protocatechuic acid, and vanillin, were compared regarding their removal efficiency. The highest removal (77%) was achieved with the laccase-vanillin system. After this screening, the optimization was carried out by a 2² full factorial design. Variables under study were the enzyme (laccase) activity and vanillin concentration. Maximum removal (53–85%) was achieved with 0.95 U/mL laccase and 1.8 mM vanillin. Pesticide removal in reaction media was fitted to the first-order kinetics equation with an average half-time life of 2.2 h. This is the first study of the use of this natural compound as a mediator in the degradation of the pesticides under investigation. The results of this study contribute, with alternative methods, to decrease pesticide levels since they are highly persistent in aqueous samples and, as a result, mitigate the environmental impact.
Afficher plus [+] Moins [-]Effects of electricity consumption on carbon intensity across Chinese manufacturing sectors Texte intégral
2019
Zhang, Huan
This research aims to study the effect on industrial carbon intensity by decomposing electricity consumption into electricity consumption volume and electric power intensity by using panel data of 27 China’s manufacturing sectors. An improved STIRPAT model is also developed by this article to identify the unexplored potential influencing factors. The research findings suggest that there exists a long-run equilibrium relationship between electricity consumption and carbon intensity and unidirectional causality from electricity consumption volume to carbon intensity. Regression results indicate that electricity consumption volume has a significantly negative effect on industrial carbon intensity for the full sample. However, due to the significantly positive influence that electric power intensity has on carbon intensity, we conclude that energy consumption and industrial economy failed to achieve the decoupling effect. The impacts of electricity consumption volume and electric power intensity have industrial heterogeneity. Electric power intensity impacts carbon intensity the most for resource intensive sectors. The effects of subgroups are further examined for sectors with high/low carbon emission volume and carbon intensity. Foreign direct investment (FDI) is conducive to reducing carbon intensity for sectors with high volume and sectors with high intensity. Industrialization level demonstrates a significantly positive effect on improving carbon intensity for sectors with low volume and sectors with low intensity. Finally, we put forward specific suggestions on the basis of these empirical findings.
Afficher plus [+] Moins [-]Bacterial cellulose/phytochemical’s extracts biocomposites for potential active wound dressings Texte intégral
2019
El-Wakil, Nahla A. | Hassan, Enas A. | Hassan, Mohammad L. | Abd El-Salam, Soheir S.
The present study describes the impregnation of coffee extract (CE) into bacterial cellulose synthesized from kombucha tea fungus (KBC) of different cellulose content, incubated for different incubation periods (2, 4, and 10 days), to prepare biocomposites having the potential for wound healing applications. Total polyphenols in hydroalcoholic extracts from ground roasted coffee and its release from the prepared biocomposites were determined as gallic acid equivalent. The polyphenols content was found to be 13.66 mg/g and the minimum inhibitory concentration (MIC) of the CE was determined using colony-forming unit (CFU) method against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus where the growth inhibition was 86 and 97% respectively. Biocomposites (KBC/CE) with the lowest cellulose and CE content showed the highest wet tensile stress (3.35 MPa), absorption of pseudo extracellular fluid (154.32% ± 4.84), and water vapor transmission rate (3184.94 ± 198.07 g/m²/day), whereas it showed the lowest polyphenols’ release (51.85% ± 2.94)when immersed in PBS buffer of pH 7.4. The impregnation of CE into KBC provided biocomposites that can enlarge the range of BC in the biomedical application.
Afficher plus [+] Moins [-]An experimental study to investigate typical temperature conditions in fuel tanks of European vehicles Texte intégral
2019
Grigoratos, Theodoros | Martini, Giorgio | Carriero, Massimo
Vehicular evaporative emissions have been recognized as an important source of volatile organic compounds to the environment and are of high environmental concern since these compounds have been associated to the formation of surface ozone and secondary organic aerosols. Evaporative emissions occur during any vehicle operation. In Europe, a revised legislative test procedure has been recently introduced to better control evaporative emissions during parking. However, emissions related to normal driving conditions—the so-called running losses—have received less attention compared with the other categories. The current study aims at giving some insights to the prevailing temperature conditions in fuel tanks of typical European vehicles during normal driving operation. The effects of ambient air temperature, trip duration, vehicle speed, and fuel tank level on the temperature reached by the fuel inside the tank under different real-world operating conditions were studied. Tank temperature can exceed 40 °C depending on ambient and driving conditions. Ambient temperature was found to be the most important parameter affecting the tank temperature. Trip duration and driving pattern may also have an influence on the tank temperature particularly when long trips combined with high vehicle speed are examined. Additionally, the difference between tank and ambient temperature was examined during the individual trips and was found to vary between 1 and 10 °C depending on the testing conditions. The most important parameters affecting the delta temperature were found to be the trip duration and the maximum vehicle speed. Finally, the purging strategy of two of the test vehicles was monitored, and the parameters affecting the purging flow rate were investigated. No strong correlation between the canister flow rate with ambient temperature, vehicle speed, or fuel level was observed in either of the tested vehicles. Substantially different canister flow rate levels between the two vehicles point to different purging strategies.
Afficher plus [+] Moins [-]Removal of Heavy Metals Using Rhamnolipid Biosurfactant on Manganese Nodules Texte intégral
2019
Lee, Aleum | Kim, Kyoungrean
The objective of this study is to identify the feasibility of using rhamnolipid biosurfactant to remediate heavy metals contained in manganese nodules collected from the Clarion-Clipperton Fracture Zone, Pacific Ocean. Deep-sea manganese nodules may represent one of the most important future natural resources for heavy metals due to the depletion of resources on land. Since international marine environment guidelines for deep-sea mining will be set up by international organisations in the 2020s, remediation technologies are urgently required for deep-sea mining tailings. We show that rhamnolipid biosurfactant is an environmentally friendly substance and can be successfully used for the remediation of heavy metals in deep-sea mining tailings under various reaction conditions. Rhamnolipids therefore represent a useful extracting agent for heavy metals in deep-sea mining tailings. The removal of nickel (Ni), copper (Cu), and cadmium (Cd) would be enhanced in the presence of rhamnolipids with specific reaction times and concentrations. Future actual remediation technologies should be developed using rhamnolipid biosurfactant on the basis of these results.
Afficher plus [+] Moins [-]Removal of Cu2+ and Ni2+ from Wastewater by Using Modified Alkali-Leaching Residual Wire Sludge as Low-Cost Adsorbent Texte intégral
2019
Kong, Ming | Wang, Longmian | Chao, Jianying | Ji, Zhongxi | Peng, Fuquan | Yang, Fei | Zhang, Yimin
Alkali-leaching residual wire sludge (AWRS) is an abundant by-product in the harmless disposal process of wire rope sludge. In this study, we modified AWRS through thermal treatment to produce a low-cost and highly efficient adsorbent for the removal of Cu²⁺ and Ni²⁺ from wastewater. The results indicated that AWRS calcinated at 700 °C exhibited maximum Cu²⁺ and Ni²⁺ removal capacities (36.48 mg/g and 46.58 mg/g, respectively). The adsorption process was observed to follow the Elovich kinetic model and the Langmuir–Freundlich isotherm model. The sorption of Cu²⁺ and Ni²⁺ on AWRS700 was highly pH dependent and behaved optimally at the solution pH values of 6 and 5, respectively. Column studies and physicochemical analyses (XRD, SEM-EDS, and XPS) indicated that the sorption of Cu²⁺ and Ni²⁺ on AWRS700 was mainly governed by the chemisorption mechanism, and this was attributed to active metal oxides (Fe₂O₃, CaO, and Al₂O₃) in AWRS700. Specifically, Cu²⁺ is mainly adsorbed on AWRS700 in the form of Cu(OH)₂, CuO₂, and CuFeO₂, and Ni²⁺ is mainly adsorbed in the form of NiAlO₄, Ni₂O₃, and Ni(OH)₂. Given the low-cost and high adsorption efficiency of AWRS700, the developed AWRS700 is a promising adsorbent for Cu²⁺ and Ni²⁺ removal from wastewater.
Afficher plus [+] Moins [-]Isolation of Bacterial Consortia that Induced Corrosion of Zirconium Alloys Texte intégral
2019
Stancu, Mihaela Marilena
The aim of the present study was to isolate several bacterial consortia from a soil sample and to establish if they could colonize zirconium-tin alloy, such as Zircaloy-4. Two bacterial consortia containing aerobic heterotrophic bacteria and anaerobic sulfate-reducing bacteria were isolated from a soil sample. The aerobic heterotrophic bacteria exhibited a higher capability to utilize different sole carbon sources, as compared with anaerobic sulfate-reducing bacteria. Based on a morphological, biochemical, and molecular analysis, bacterial isolates were identified as Pseudomonas putida IBBHA₁, Pseudomonas aeruginosa IBBHA₂, Achromobacter spanius IBBHA₃, Citrobacter freundii IBBSR₁, Citrobacter youngae IBBSR₂, and Citrobacter braakii IBBSR₃. Isolated bacterial consortia which possess distinct DNA fingerprints were able to form biofilms and colonize the surface of zirconium-tin alloy coupons, although the colonization of coupons by the aerobic heterotrophic bacteria or anaerobic sulfate-reducing bacteria alone was lower compared with that observed when the coupon was immersed in a mixture of both bacterial consortia. Coupons immersed in these bacterial consortia revealed changes in the surface characteristics, which can facilitate or accelerate zirconium-tin alloy corrosion. The accumulation of corrosion products on coupons surface was less significant when the coupons were immersed solely in aerobic heterotrophic bacteria or anaerobic sulfate-reducing bacteria, compared with that observed when the coupon was immersed in a mixture of both bacterial consortia.
Afficher plus [+] Moins [-]Increased DNA damage is not associated to polymorphisms in OGGI DNA repair gene, CYP2E1 detoxification gene, and biochemical and hematological findings in soybeans farmers from Central Brazil Texte intégral
2019
Godoy, Fernanda Ribeiro | Nunes, Hugo Freire | Alves, Alessandro Arruda | Carvalho, Wanessa Fernandes | Franco, Fernanda Craveiro | Pereira, Rodrigo Roncato | da Cruz, Alex Silva | da Silva, Cláudio Carlos | Bastos, Rogério Pereira | de Melo e Silva, Daniela
Our study evaluated 163 individuals, being 74 soybean farmers, occupationally exposed to pesticides, and 89 individuals from Goias municipalities, Central Brazil, with similar conditions to the exposed group, comprising the control group. Of the 74 soybean farmers, 43 exposed directly to pesticides and 31 exposed indirectly. The exposed group consisted of individuals aged 19 to 63 years, 21 women and 53 men, and the control group had ages ranging from 18 to 64 years, being 36 women and 53 men. 18.9% of the exposed group were poisoned by pesticides, and the most common symptoms were headache and gastrointestinal problems. The genotype frequencies of the rs2031920 (T>C) polymorphism in the CYP2E1 gene present significant differences between the exposed and control groups (p = 0.02), showing that 24.3% of the exposed group were heterozygotes against 6.7% in the control group. For the OGG1 gene, two SNPs, rs1052133 (G>C) and rs293795 (T>C), were evaluated and the genotype frequencies were not statistically different between the exposed and control groups. The DNA damage was distinct (p < 0.05) in the three analyzed comet parameters (tail length, Olive tail moment, %DNA) between groups. However, there was no influence of age and alcohol consumption between the groups associated with the polymorphisms in the CYP2E1 and OGG1 genes and DNA damage. We also did not find altered hematological and biochemical parameters in the exposed group. Thus, this pioneering study at Goias State carried out an overview of the health of soybean farmers. We evaluated classic laboratory exams, associated with exposure markers (comet assay) and susceptibility markers (genetic polymorphisms), emphasizing the need to expand the Brazilian health assessment protocol. We found, in soybean farmers, increased DNA damage and a higher number of heterozygotes in CYP2E1 gene, compared with the control group, despite the lack of association with age, educational level, smoking, drinking habits, and genetic polymorphisms.
Afficher plus [+] Moins [-]Pesticide Dissipation and Enzyme Activities in Ungrassed and Grassed Biomixtures, Composed of Winery Wastes, Used in Biobed Bioremediation Systems Texte intégral
2019
Romero, Esperanza | Delgado-Moreno, Laura | Nogales, Rogelio
The biomixture composition and the presence of a grass layer in a biobed bioremediation system can improve the performance of these systems to minimize pesticide point-source contamination. In this study, a novel biomixture composed with organic wastes from vineyards and wine industries (vermicompost of winery wastes and vine shoots) and top soil (W) was elaborated. The impact of three pesticides, commonly used in vineyards, on its microbial activity and on the development of turfgrass was determined in a short-term experiment. Moreover, the dissipation of the assayed pesticides was evaluated to stablish their distribution patterns between the turfgrass and the biomixture. For comparison, the original biomixture composed with top soil, peat, and straw (P) was also studied. After 15 days of pesticide application, the development of the turfgrass in both biomixtures was similar. However, the oxidoreductases (dehydrogenase and ortho-diphenol oxidase) and the hydrolytic (FDA and β-glucosidase) enzyme activities were greater in W-biomixture than in P-biomixture. The dissipation of metalaxyl and imidacloprid recorded in the W-biomixtures was significantly greater than in the P-biomixtures. The pesticide dissipation in W-biomixtures followed the same order of their octanol water partition coefficients. Except for tebuconazole, the lower biological activity in the P-biomixture would explain the limited pesticide dissipation. In the grassed biomixtures, most (> 83%) of the non-dissipated imidacloprid and tebuconazole remained in the biomixtures, while metalaxyl was rapidly translocated to the aerial part of the turfgrass. Our results show the potential capability of the novel biomixture as an alternative to the original one in a biobed.
Afficher plus [+] Moins [-]Removal of Agrichemicals from Water Using Granular Activated Carbon Filtration Texte intégral
2019
Grant, George A. | Fisher, Paul R. | Barrett, James E. | Wilson, Patrick C.
The objective was to evaluate removal efficacy of agrichemicals from water using a small-scale granular activated carbon (GAC) system. The GAC system consisted of a series of three 1.9- to 4.1-L filter canisters filled with 8 × 30 US mesh (595 to 2380 μm) bituminous coal GAC. In experiment 1, 11 agrichemicals (acephate, bifenthrin, chlorpyrifos, flurprimidol, glyphosate, hydrogen peroxide + peracetic acid, imidacloprid, paclobutrazol, didecyldimethylammonium chloride (DDAC), triclopyr, and uniconazole) used in greenhouse and nursery production were exposed to 0, 12, or 64 s of GAC contact time. Chemical concentrations were prepared at a 1:10 dilution of a recommended label rate for ornamental crops to represent a possible residual concentration found in recaptured irrigation or surface water. In experiment 2, three other chemicals [iron ethylene diamine-N,N′-bis(hydroxy phenyl acetic acid) (iron-EDDHA, a chelated iron fertilizer), soracid blue dye (a fertilizer dye), and sodium hypochlorite (a sanitizing agent)] were also tested with 0, 12, 38, or 64 s of GAC contact time. Agrichemical concentration was reduced with 12 s of GAC contact time compared with the 0 s for all chemicals tested, and in most cases was further increased at 64-s contact time. Chemicals reduced below their minimum detection limits with 64 s GAC included acephate, flurprimidol, paclobutrazol, uniconazole, peracetic acid, DDAC, and chlorine (free and total). Percent reduction for other chemicals with 64 s GAC was 72.2% for bifenthrin, 89% chlorphyrifos, 85.3% imidacloprid, 99% glyphosate, 99.4% triclopyr, 99.3% hydrogen peroxide, 47.6% iron-EDDHA, and 94.6% soracid blue dye. Iron-EDDHA and soracid blue dye could be used as indicator chemicals for onsite monitoring of GAC filter efficacy. Results indicate that GAC filtration can remove a wide range of agrichemical contaminants commonly used in greenhouse and nursery production, although the required contact time in commercial production is expected to be greater than in this research study.
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