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Resultados 3541-3550 de 4,937
Biodegradation aspects of ibuprofen and identification of ibuprofen-degrading microbiota in an immobilized cell bioreactor Texto completo
2019
An enrichment process was employed by applying high ibuprofen concentration in an immobilized cell bioreactor in order to favor the ibuprofen-degrading community present in activated sludge. Experimental data showed the ability of the immobilized cell bioreactor to achieve high ibuprofen removal efficiencies (98.4 ± 0.3%), the tendency of the enriched biomass to acidify the treated liquor, and the inhibition of the nitrification process. Illumina sequencing revealed a massive increase in the relative abundance of Alphaproteobacteria and Gammaproteobacteria (from 29.1 to 80.8%) and a dramatic decrease in the proportion of Bacteroidetes, Planctomycetes, and Verrucomicrobia (from 42.7 to 2.1%) when pure ibuprofen served as the sole carbonaceous feeding substrate. This shift in the feeding conditions resulted in the predominance of Novosphingobium and Rhodanobacter (25.5 ± 10.8% and 25.2 ± 3.0%, respectively) and demonstrated a specialized ibuprofen-degrading bacterial community in activated sludge, which possessed the selective advantage to cope with its degradation. To the best of our knowledge, this bioreactor system was capable of effectively treating the highest ibuprofen concentration applied in wastewater treatment plants.
Mostrar más [+] Menos [-]Adsorption of a textile dye onto piaçava fibers: kinetic, equilibrium, thermodynamics, and application in simulated effluents Texto completo
2019
Marques, Bianca Silva | Frantz, Tuanny Santos | Sant’Anna Cadaval Junior, Tito Roberto | de Almeida Pinto, Luiz Antonio | Dotto, Guilherme Luiz
This research was conducted to evaluate the methylene blue dye adsorption by piaçava fibers. The effects of adsorbent amount, pH, kinetics, equilibrium, and thermodynamics were analyzed, as well as the adsorbent performance in the treatment of synthetic textile effluents. The adsorbent characterization was also performed. Experimental kinetic data were fitted with pseudo-first-order, pseudo-second-order, and Elovich models. The equilibrium tests were done at 298, 308, and 318 K, and the models of Freundlich, Langmuir, Redlich–Peterson, and Sips were used. The adsorption was favored using 0.025 g of adsorbent, pH 10, and 318 K. The Elovich model provided better fit to kinetic data. The equilibrium experimental points were well represented by the Sips model. The maximum experimental adsorption capacity of methylene blue dye was 427.3 mg g⁻¹. It was verified a spontaneous, favorable, and endothermic adsorption. Piaçava fiber was a promising low-cost material to be used for color removal in effluents containing methylene blue.
Mostrar más [+] Menos [-]Effects of perinatal dioxin exposure on development of children: a 3-year follow-up study of China cohort Texto completo
2019
The purpose of this study was to investigate the longitudinal effects of perinatal exposure to dioxin on physical growth in a 3-year follow-up study. In 2015, 27 mother–infant pairs living in an electronic waste (e-waste) dismantling region and 35 pairs living in a control region were enrolled in the present study. Breast milk samples were collected at 4 weeks after birth. Physical growth, including weight, height, and head and chest circumferences, was measured at 6 months and 3 years of age. Dioxin levels in the breast milk were measured by gas chromatography/high-resolution mass spectrometry. Levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin and toxic equivalency values in maternal breast milk of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and PCDDs/PCDFs were significantly higher in women residing in the e-waste dismantling region. In 3-year-old boys, inverse associations were found between height and PCDDs-TEQ. In girls, positive associations were found between height and 2,3,7,8-TetraCDD, PCDDs-TEQ, and PCDDs/PCDFs-TEQ, and for weight and PCDDs-TEQ and PCDDs/PCDFs-TEQ at 3 years of age. In this study, sex-specific differences were observed in children, in whom dioxin exposure decreased growth in boys but increased growth in girls during the first 3 years of life.
Mostrar más [+] Menos [-]Comparison of Jordanian and standard diatomaceous earth as an adsorbent for removal of Sm(III) and Nd(III) from aqueous solution Texto completo
2019
Hamadneh, Imad | Alatawi, Abdulmonem | Zalloum, Ruba | Albuqain, Rula | Alsotari, Shorouq | Khalili, Fawwaz I. | Al-Dujaili, Ammar H.
In this study, Jordanian diatomaceous earth (JDA) and commercial diatomaceous earth (standard diatomaceous earth, SDA) were used for adsorption of samarium (Sm)(III) and neodymium (Nd)(III) ions from aqueous solutions using batch technique as a function of initial concentration of metal ions, adsorbent dosage, ionic strength, initial pH solution, contact time, and temperature. Both adsorbents were characterized by Fourier transform infrared (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface area, and cation exchange capacity (CEC). Maximum metal ion uptake was observed after 100 min of agitation, and the uptake has decreased with increasing temperature and reached a maximum at pH ≈ 5. Different types of adsorption isotherms and kinetic models were used to describe the Nd(III) and Sm(III) ion adsorption. The experimental data fitted within the following isotherms in the order Langmuir > Dubinin–Radushkevich (DR) > Freundlich and the pseudo-second-order kinetic model based on their coefficient of determination (R²), chi-square (χ²), and error function (Fₑᵣᵣₒᵣ%) values. Maximum adsorption uptakes, according to the Langmuir model, were obtained as 188.679 mg/g and 185.185 mg/g for Sm(III) and 169.492 mg/g and 149.254 mg/g for Nd(III) by JDA and SDA, respectively. The results of thermodynamic parameters showed that the adsorption of Sm(III) and Nd(III) ions onto JDA and SDA is a feasible, spontaneous, exothermic, and entropy driven. The best recovery for Sm(III) and Nd(III) was obtained when the 0.05 M EDTA + 0.05 M H₃PO₄ mixture was used as an eluent.
Mostrar más [+] Menos [-]Characteristics, hazards, and control of illegal villa (houses): evidence from the Northern Piedmont of Qinling Mountains, Shaanxi Province, China Texto completo
2019
Li, Chenxi | Gao, Xing | Xi, Zenglei
Unapproved and illegal buildings have sprawled into the Northern Piedmont of the Qinling Mountains. The problem of illegal villas has aroused widespread public opinion and concern. The ecological environment of the Qinling Mountains has been seriously affected by the resurgence of illegal villas. This paper introduces the characteristics and distribution of illegal villas, analyzes the hazards caused by illegal villas, and describes control measures for illegal villas and land consolidation and ecological remediation in the Northern Piedmont of the Qinling Mountains. The results show that illegal planning and illegal development, as well as local governments’ irregularities, including control, governance, punishment, demolition, and compensation for illegal buildings in the expropriation of premises, have caused the problem of illegal construction of villas in the Northern Piedmont of the Qinling Mountains. Control measures for illegal villas are demolition, land consolidation, and ecological remediation. Policy implications for protection of Qinling Mountains are provided.
Mostrar más [+] Menos [-]An evaluation of the levels of organochlorine compounds (OCPs and PCBs) in cultured freshwater and wild sea fish eggs as an exposure biomarker for environmental contamination Texto completo
2019
Atmaca, Enes | Das, Yavuz Kursad | Yavuz, Oguzhan | Aksoy, Abdurrahman
In this study, the eggs of 30 wild Black Sea whiting (Merlangius merlangus euxinus, Nordmann, 1840) and 30 farmed freshwater rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) collected from Samsun Province in Turkey were analyzed to determine the level of contamination by nine organochlorine pesticides (OCPs), namely α-hexachlorocyclohexane (α-HCH), β-HCH, γ-HCH (lindane), hexachlorobenzene (HCB), aldrin, 2,4′-dichlorodiphenyltrichloroethane (DDT), 4,4′-DDT, 2,4′-dichlorodiphenyldichloroethylene (DDE), 4,4′-DDE, and 15 polychlorinated biphenyls (PCBs) (PCB-28, -70, -74, -81, -99, -101, -118, -138, -153, -156, -170, -180, -183, -187, and -208), and their potential use as biomarkers to monitor levels of environmental contamination. OCPs and PCBs in the fat of fish eggs were extracted cryogenically and their concentrations were determined with a gas chromatography-electron capture detector (GC-ECD). The whiting eggs showed high OCP and PCB levels compared to the rainbow trout eggs. The median ∑ DDT values for whiting and rainbow trout eggs were 1601.62 ng g⁻¹ fat (range 824.87–5049.81) and 406.49 ng g⁻¹ fat (range 199.88–588.82); median ∑Indicator PCBs were 1264.24 ng g⁻¹ fat (range 520.05–6140.32) and 82.11 ng g⁻¹ fat (range 2.85–215.97); and median ∑ HCHs were 155.66 ng g⁻¹ fat (range 35.45–330.40) and 13.48 ng g⁻¹ fat (range 4.44–66.44), respectively. In the whiting eggs, the ∑Indicator PCB level was above the maximum residue limit (MRL) of 200 ng g⁻¹ fat stated in the European Commission Regulation (EC) and Turkish Food Codex (TFC). In addition, there was a significant difference between the contamination levels of the eggs of the two species. In conclusion, it appears that fish eggs can serve as a valuable biomarker for the level of contamination of persistent organochlorine contaminants in different aquatic environments.
Mostrar más [+] Menos [-]Differences of Cd uptake and expression of OAS and IRT genes in two varieties of ryegrasses Texto completo
2019
Chi, Sunlin | Qin, Yuli | Xu, Weihong | Chai, Yourong | Feng, Deyu | Li, Yanhua | Li, Tao | Yang, Mei | He, Zhangmi
Pot experiment was conducted to study the difference of cadmium uptake and OAS and IRT genes’ expression between the two ryegrass varieties under cadmium stress. The results showed that with the increase of cadmium levels, the dry weights of roots of the two ryegrass varieties, and the dry weights of shoots and plants of Abbott first increased and then decreased. When exposed to 75 mg kg⁻¹ Cd, the dry weights of shoot and plant of Abbott reached the maximum, which increased by 11.13 and 10.67% compared with the control. At 75 mg kg⁻¹ Cd, cadmium concentrations in shoot of the two ryegrass varieties were higher than the critical value of Cd hyperaccumulator (100 mg kg⁻¹), 111.19 mg kg⁻¹ (Bond), and 133.69 mg kg⁻¹ (Abbott), respectively. The OAS gene expression in the leaves of the two ryegrass varieties showed a unimodal curve, which was up to the highest at the cadmium level of 150 mg kg⁻¹, but fell back at high cadmium levels of 300 and 600 mg kg⁻¹. The OAS gene expression in Bond and Abbott roots showed a bimodal curve. The OAS gene expression in Bond root and Abbott stem mainly showed a unimodal curve. The expression of IRT genes family in the leaves of ryegrass varieties was basically in line with the characteristics of unimodal curve, which was up to the highest at cadmium level of 75 or 150 mg kg⁻¹, respectively. The IRT expression in the ryegrass stems showed characteristics of bimodal and unimodal curves, while that in the roots was mainly unimodal. The expression of OAS and IRT genes was higher in Bond than that in Abbott due to genotype difference between the two varieties. The expression of OAS and IRT was greater in leaves than that in roots and stems. Ryegrass tolerance to cadmium can be increased by increasing the expression of OAS and IRT genes in roots and stems, and transfer of cadmium from roots and stems to the leaves can be enhanced by increasing expression OAS and IRT in leaves.
Mostrar más [+] Menos [-]Biochemical and transcriptomic response of earthworms Eisenia andrei exposed to soils irrigated with treated wastewater Texto completo
2019
In order to ensure better use of treated wastewater (TWW), we investigated the effect of three increasing doses of TWW, 10%, 50%, and 100%, on biochemical and transcriptomic statuses of earthworms Eisenia andrei exposed during 7 and 14 days. The effect of TWW on the oxidative status of E. andrei was observed, but this effect was widely dependent on the dilution degree of TWW. Results showed a significant decrease in the catalase (CAT) activity and an increase in the glutathione-S-transferase (GST) activity, and considerable acetylcholinesterase (AChE) inhibition was recorded after 14 days of exposure. Moreover, malondialdehyde (MDA) accumulation was found to be higher in exposed animals compared to control worms. The gene expression level revealed a significant upregulation of target genes (CAT and GST) during experimentation. These data provided new information about the reuse of TWW and its potential toxicity on soil organisms.
Mostrar más [+] Menos [-]Study on the influence of surface potential on the nitrate adsorption capacity of metal modified biochar Texto completo
2019
Carbon materials, as effective adsorbents to numerous aqueous cationic contaminants, have been hardly applied to remove anions in wastewater. In this work, different modifying agents were used to modify corncob biochars (CC) and the surface potentials of these modified biochars were determined. Based on the findings, modification principle was determined to reveal the relationship between surface potentials of the biochars and their nitrate adsorption capacities. The surface potential was dominated by the metal cations and multivalent cations led to even positive zeta potential. The formation of metal oxide not only led to the augment in surface area but also increase the surface charge. FeCl₃-modified biochar (Fe-CC) with the highest positive surface charge was utilized to remove anions (nitrate) from aqueous solutions. Characterization results confirm that Fe₂O₃ structure were successfully formed on biochar surface. This led to the formation of iron nitrate hydrate (Fe(NO₃)₃·9H₂O), which enabled higher nitrate adsorption performance than that of pristine biochar. Batch experiments showed that nitrate adsorption on the Fe-CC was stable and almost independent of experimental pH and temperature. Based on the Langmuir model results, the maximum nitrate adsorption capacity of Fe-CC was 32.33 mg/g. Coexisting anions had negative influence on the adsorption performance. Findings of this work suggest that the modified biochar can be used in wastewater treatment to remove anions such as nitrate. Graphic abstract ᅟ
Mostrar más [+] Menos [-]Developing an electric vehicle urban driving cycle to study differences in energy consumption Texto completo
2019
This paper develops a methodology for constructing a representative electric vehicle (EV) urban driving cycle as a basis for studying the differences in estimated energy consumption, taking Xi’an as an example. The test route is designed in accordance with the overall topological structure of the urban roads in the study region and the results of a traffic flow survey. Wavelet decomposition and reconstruction are utilized to preprocess the original data. Principal component analysis (PCA) is used to reduce the number of the kinetic parameters. The fuzzy C-means (FCM) clustering algorithm is used to cluster the driving segments. A representative EV urban driving cycle is constructed in accordance with the time proportions of three classes of driving segments and the correlation coefficients of the characteristic parameters. Finally, the differences in energy consumption estimates obtained using the constructed Xi’an EV urban driving cycle (XA-EV-UDC) and the international driving cycles are studied. The comparison shows that when international driving cycles are used to estimate the energy consumption and driving range of EVs, large relative errors will result, with energy consumption errors of 9.65 to 21.17% and driving range errors of 20.10 to 38.14%. Therefore, to accurately estimate energy consumption and driving range of EVs under real-world driving conditions, representative EV driving cycles for each typical city and region should be constructed.
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