خيارات البحث
النتائج 2571 - 2580 من 4,938
Importance of Organic Matter to the Retention and Transport of Bisphenol A and Bisphenol S in Saturated Soils النص الكامل
2019
Shi, Yanfeng | Sun, Yuanyuan | Gao, Bin | Xu, Hongxia | Wu, Jichun
Bisphenol A (BPA) and bisphenol S (BPS) are frequently detected in soils and groundwater, which may pose threats to public health and the environment. However, the fate and transport of BPA/BPS in the subsurface media are still not clear. In this study, the retention and transport of BPA/BPS in three different natural soils were investigated with column experiments and mathematical modeling. The results showed that both BPA and BPS had high mobility in saturated soil A (Xinjiang soil), medium mobility in soil B (Changshu soil) media, and no mobility in the soil C (Jilin soil). There was a negative correlation between the mobility of BPA/BPS and soil organic matter (SOM) content because of the strong sorption of BPA/BPS on SOM. BPS showed higher mobility than BPA in the three soils. In addition, with the reduction of SOM of the soil B and C (after H₂O₂-treatment), the mobility of BPA/BPS enhanced dramatically. All these suggest that SOM played a significant role in controlling the retention and transport of BPA/BPS in the soil. Furthermore, the two-site kinetic model simulated the BPA/BPS transport experiment results very well.
اظهر المزيد [+] اقل [-]Assessment of Pollution Sources, Fate of Pollutants, and Potential Instream Interventions to Mitigate Pollution of Earthen Canals of Urban to Rural-Urban Fringe النص الكامل
2019
Gomes, Pattiyage I. A. | Fernando, Bothalage A. V. W. | Dehini, Ganegeoda K.
Three representative earthen canals from urban, peri-urban, and rural-urban fringe of Sri Lanka were studied for a 2-year period against different seasons to capture insights important in ecological rehabilitation. Only the canal from rural-urban fringe showed a better water quality in wet season; elucidating, the impact of contaminated catchment runoff in the other canals. At a given sampling session, one or two peaks (relative maxima) were observed in urban and peri-urban canals for pollution representative parameters such as nitrate nitrogen and soluble reactive phosphorus. Those peaks were highly localised, an indication of poor advection. In general, two-dimensional variations of electrical conductivity and turbidity in dry season were uniform in urban and peri-urban canals, an indication of dominant molecular diffusion. This was further evidenced via physical models for different flow stages (low, high, and bankfull). Therefore, fate of contaminants had to be mainly governed by assimilation via sediments. However, grey water footprint analyses showed urban and peri-urban canals have over utilised the natural assimilation capacity of many water quality parameters by several folds. This study proved the importance of inducing attenuation by instream physical heterogeneity similar to natural streams or naturalised canals such as the canal from the rural-urban fringe of this study.
اظهر المزيد [+] اقل [-]Direct and indirect photolysis of the antibiotic enoxacin: kinetics of oxidation by reactive photo-induced species and simulations النص الكامل
2019
Lastre-Acosta, Arlen Mabel | Barberato, Bruna | Parizi, Marcela Prado Silva | Teixeira, Antonio Carlos Silva Costa
The purpose of this study was to investigate the aqueous phase photochemical behavior of enoxacin (ENO), an antibiotic selected as a model pollutant of emerging concern. The second-order reaction rate constants of ENO with hydroxyl radicals (HO●) and singlet oxygen (¹O₂) were determined at pH 3, 7, and 9. Also, the rate constants of the electron transfer reaction between ENO and triplet states of chromophoric dissolved organic matter (³CDOM*) are reported for the first time, based on anthraquinone-2-sulfonate (AQ2S) as CDOM proxy. The sunlight-driven direct and indirect ENO degradation in the presence of dissolved organic matter (DOM) is also discussed. The results show that direct photolysis, which occurs more rapidly at higher pH, along with the reactions with HO● and ³AQ2S*, is the key pathway involved in ENO degradation. The ENO zwitterions, prevailing at pH 7, show kENO, HO●, kENO,₁O₂, and kENO,₃AQ₂S* of (14.0 ± 0.8) × 10¹⁰, (3.9 ± 0.2) × 10⁶, and (61.5 ± 0.7) × 10⁸ L mol⁻¹ s⁻¹, respectively, whose differences at pH 3, 7, and 9 are due to ENO pH-dependent speciation and reactivity. These k values, along with the experimental ENO photolysis quantum yield, were used in mathematical simulations for predicting ENO persistence in sunlit natural waters. According to the simulations, dissolved organic matter and water depth are expected to have the highest impacts on ENO half-life, varying from a few hours to days in summertime, depending on the concentrations of relevant waterborne species (organic matter, NO₃⁻, NO₂⁻, HCO₃⁻).
اظهر المزيد [+] اقل [-]Asymmetric causality among renewable energy consumption, CO2 emissions, and economic growth in KSA: evidence from a non-linear ARDL model النص الكامل
2019
Toumi, Saïd | Toumi, Hassen
This study applies asymmetric causality to renewable energy (REC), carbon dioxide emissions (CE), and real GDP using non-linear broadcasting between these variables through the non-linear autoregressive distributed lag model (NARDL) to examine the short- and long-run asymmetries in the inconsistency of greenhouse gas emissions among the variables and to unpack the asymmetric causality of selective variables through positive and negative shocks for time series data from the Kingdom of Saudi Arabia between 1990 and 2014. The bounds cointegration test shows the existence of long-term dealings among all considered variables in the presence of asymmetry. The non-linear asymmetric causality test shows that negative shocks in carbon dioxide emissions had only positive impacts on real GDP in the long-term but are unobservable in the short-term. Additionally, the short- and the long-term incidences of positive shocks on real GDP are not similar to the negative shock to REC, implying the existence of asymmetric impacts on REC in both short- and long-term forms. Finally, the asymmetric causal relationship from carbon dioxide emissions to REC is neutral in the long-term. Both positive and negative shocks to REC consistently had an adverse effect on CE in the long-term. The presence of asymmetry between economic growth, CE, and REC could be of major substantial for more helpful policymakers and the action plan of sustainable development goals (SDGs) in Saudi Arabia.
اظهر المزيد [+] اقل [-]Acetone adsorption capacity of sulfur-doped microporous activated carbons prepared from polythiophene النص الكامل
2019
Zhu, Junchao | Chen, Ruofei | Zeng, Zheng | Su, Changqing | Zhou, Ke | Mo, Yamian | Guo, Yang | Zhou, Fan | Gao, Jie | Li, Liqing
Sulfur-doped activated carbons (SACs) with high sulfur content and large specific surface area were synthesized from polythiophene for acetone removal. The sulfur content of carbons (3.10–8.43 at.%) could be tunable by adjusting the activation temperature. The BET surface area and pore volume of the obtained samples were 916–2020 m² g⁻¹ and 0.678–1.100 cm³ g⁻¹, with a significant proportion of microporosity (up to 84% and 72% for BET surface area and pore volume, respectively). The resulting SACs show a superior acetone adsorption capacity (i.e., 716.4 mg g⁻¹ at 15 °C and 705 mg g⁻¹ at 25 °C for SAC700). In terms of the adsorption behavior of acetone on the activated carbons, compared to the Langmuir model, the Langmuir-Freundlich model showed better agreement with the adsorption amount. The results reveal that the surface area and micropore volume are the key factors for acetone adsorption, while the sulfur-doped functional groups, especially oxidized sulfur functional groups, can enhance the acetone adsorption capacity at a certain low pressure. Temperature programmed desorption (TPD) experiments were performed to get desorption activation energy of acetone on SAC samples, and the results ranged from 23.54 to 38.71 kJ mol⁻¹. The results of the molecular simulation show that the introduction of sulfur element can increase the binding energy between acetone molecule and carbon surface, and the tri-oxidized sulfur (sulfonic acid) functional group has the highest binding energy of − 0.4765 eV. Graphical abstract
اظهر المزيد [+] اقل [-]Decomposition of 2-Propanol in the Liquid Phase Using a Photocatalyst Immobilized on Nonwoven Fabric and Ozone Microbubbles النص الكامل
2019
Yasui, Fumio | Sekiguchi, Kazuhiko | Tamura, Hajime
2-Propanol (IPA) is a highly water-soluble volatile organic compound that is used in the cleaning and drying processes during semiconductor fabrication. IPA is also used as a disinfectant in the pharmacy field. Water scrubber processing is one of the methods used for IPA collection. However, water scrubbing requires wastewater treatment. In this study, we propose a decomposition system for IPA in the liquid phase based on a TiO₂ photocatalyst immobilized on nonwoven fabric (TiO₂ nonwoven fabric) and ozone microbubbles (MBs). The thick nonwoven fabric with immobilized TiO₂ exhibits a higher IPA removal rate than that exhibited by the pleated fabric. IPA decomposes to produce acetone, which can be further decomposed and possibly undergo mineralization. The entire water tank can be supplied with ozone by introducing the MB-forming ozone, which considerably affects the decomposition of IPA. The efficient decomposition of IPA was achieved by combining ozone MBs, TiO₂ nonwoven fabric, and ultraviolet irradiation, presumably because the photocatalyst promotes the mineralization of the decomposition product. Thus, the OH radicals from the O₃ MBs competitively captured in the decomposition product strongly promote the decomposition of IPA, enhancing the IPA decomposition rate.
اظهر المزيد [+] اقل [-]Simultaneous removal of nitrate/phosphate with bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin النص الكامل
2019
Shen, Zhanhui | Dong, Xinyi | Shi, Jialu | Ma, Yuanhao | Liu, Daoru | Fan, Jing
Given the prevalence of nitrate and phosphate in surface and groundwater, it is important to develop technology for the simultaneous removal of nitrate and phosphate. In this study, we prepared the bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin DOW 3N (D-Fe/Ni and D-Fe/Cu) for removing nitrate and phosphate simultaneously. XPS profiles revealed that Cu has better ability than Ni to increase the stability of Fe nanoparticles and prevent nZVI from oxidation. The results showed that nitrate removal efficiencies by D-Fe/Ni and D-Fe/Cu were 98.7% and 95.5%, respectively and the phosphate removal efficiencies of D-Fe/Cu and D-Fe/Ni were 99.0% and 93.0%, respectively. Besides adsorption and coprecipitation as reported in previous studies, the mechanism of phosphate removal also includes the adsorption of the newly formed polymeric ligand exchanger (PLE). Moreover, in previous studies, the presence of phosphate had significant negative effects on the reduction of nitrate. However, in this study, the removal efficiency of nitrate was less affected with the increasing concentration of phosphate for D-Fe/Cu. This was mainly because D-Fe/Cu had higher adsorption capacity of phosphate due to the newly formed PLE according to the XPS depth profile analysis.
اظهر المزيد [+] اقل [-]Understanding corporate surplus food donation in China: testing the roles of environmental concern, altruism, past experience, and perceived risk النص الكامل
2019
Liao, Chuanhui | Hong, Jin | Zhao, Dingtao
This paper investigates the motives behind corporate giving and determines whether perceived risk plays a major role in corporate surplus food donation intention. A conceptual model is developed from the perspectives of perceived risk, economic concern, past behavior, and moral motives. A questionnaire survey is conducted among food manufacturers and retailers in the Sichuan Province in China. A total of 143 valid observations are used to conduct structural equation modeling analysis. The results show that corporate reputation, legislation, and business risks are the main sub dimensions of risks that corporations perceive. Perceived risk, past behavior, environmental concern, and altruism affect corporate donation intention significantly. Implications of the findings for promoting surplus food donation are also discussed.
اظهر المزيد [+] اقل [-]Exposure index of methyl isocyanate (MIC) gas disaster and a comprehensive spectrum of cytogenetic analysis after 30 years النص الكامل
2019
Ganguly, Bani Bandana
Severity of clinical expression and high mortality could not facilitate establishing exposure index/association following MIC disaster in Bhopal. Mortality-based exposure stratification was critiqued by the International Medical Commission on Bhopal (IMCB). IMCB stratified exposure considering distance as surrogate at 2 km intervals after 10 years. The first follow-up cytogenetic screening of the pre-screened survivors after 30 years has demonstrated chromosome abnormalities (CA). Exposure stratification was attempted considering cytogenetic screening conducted during 1986–1988. Elevation of CA appeared proportional to exposure status and authenticated the initial mortality-based stratification. The one-on-one comparison of the previous and present cytogenetics has described the individual response to MIC exposure over 30 years. Chi-square test has been carried out for checking the cytogenetic changes at the individual level statistically, which revealed that differences of chromosomal aberrations collected immediately post-disaster and 30 years later are nonsignificant. The prominence of interindividual variation was noticed in general. The impact of overall exposure was higher in males. Constitutional abnormalities in 8.5% of the study population, including translocation, inversion, deletion, fragile sites, etc., necessitate screening of blood-linked members. The incidence of acrocentric association was prominent in the study population. Normal karyotype in children born to severely exposed parents with congenital anomalies indicates necessity of molecular karyotyping and/or screening of mutations. The study highlights follow-up of the health of the index cases at shorter (3–6 months) intervals. This comprehensive spectrum of cytogenetic report highlights immediate post-disaster chromosomal aberrations, the changes that occurred over 30 years in conjunction with other environmental factors at the individual level, constitutive genomic aberrations, polymorphic variations, and chromosomal patterns in congenitally malformed children of the survivors, which collectively indicate the possibility of acquisition/persistence of stable aberrations in MIC-exposed lymphocytes through interaction with environmental/biological confounders.
اظهر المزيد [+] اقل [-]Single and combined effects of microplastics and roxithromycin on Daphnia magna النص الكامل
2019
Zhang, Peng | Yan, Zhenhua | Lü, Guanghua | Ji, Yong
There is a rising concern about the pollution of microplastics (plastic particles < 5 mm) in water due to their physicochemical properties, especially their interaction with organic contaminants; however, such knowledge is still limited. The mass production and consumption of medication for the treatment of infectious diseases in human and animals have led to the ubiquity of antibiotics in the environment. We studied the single and joint effects of microplastics (1-μm and 10-μm polystyrene particles, PS) and roxithromycin (ROX) on Daphnia magna through the acute and sublethal toxicity tests. The 48-h median effective concentration (EC₅₀) of 1-μm and 10-μm PS to D. magna was 66.97 mg/L and 199.94 mg/L, respectively, while the value of ROX was 20.28 mg/L. Malondialdehyde (MDA) levels and the activities of four enzymatic biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST), were further detected to assess the oxidative stress caused in D. magna caused. The results showed that 48-h exposure to PS (0.1 mg/L) or ROX (0.01 mg/L) alone activated the activities of CAT and GST and MDA levels. When compared with the ROX alone, the responses of GPx and MDA in D. magna co-exposed to 1-μm PS were significantly decreased, while co-exposure to 10-μm PS significantly decreased the responses of GST and MDA. Furthermore, the integrated biomarker response version 2 (IBRv2) analysis revealed that co-exposure to 1-μm PS and ROX led to the strongest biological responses in D. magna. Our findings underlined that microplastics should be a concern when they interact with the co-existence of pollutants in the aquatic environment.
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