In this study, the degradation kinetics and transformation mechanism of oxytetracycline (OTC) by UV-254 nm and UV-254 nm/H2O2 were investigated. The removal of OTC increased with increasing initial H2O2 dosage while excess H2O2 acted as an inhibitor of HO. The observed UV fluence based pseudo first-order rate constant of OTC (k(obs), cm(2) mJ(-1)) decreased while the degradation rate at the initial 13 min (mu M min(-1)) increased with increasing initial OTC concentrations. Presence of different water constituents in the reaction system had a different degree of influence on the degradation efficiency of OTC. Though after 10 h irradiation, there was only a limited elimination of total organic carbon (TOC), successful transformation of OTC was demonstrated by the detection of thirty-one degradation byproducts in the UV/H2O2 system. Potential degradation mechanisms for OTC were proposed exhibiting five main pathways, including hydroxylation (+16 Da), secondary alcohol oxidation (-2 Da), demethylation (-14 Da), decarbonylation (-28 Da) and dehydration (-18 Da). This study indicates that UV-254 nm/H2O2 is an effective technology for the removal of OTC from an aquatic environment. (c) 2015 Elsevier B.V. All rights reserved.
Liu, Yiqing;He, Xuexiang;Fu, Yongsheng;Dionysiou, Dionysios D
Journal of hazardous materials,2016年305:229-239 ISSN：0304-3894
Dionysiou, Dionysios D.
[Fu, Yongsheng; Liu, Yiqing] Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China;[He, Xuexiang; Liu, Yiqing] Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States;[Dionysiou, Dionysios D] Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States. Electronic address: email@example.com
Oxytetracycline (OTC), an important broad-spectrum antibiotic, has been detected extensively in various environmental systems, which may have a detrimental impact on ecosystem and human health through the development of drug resistant bacteria and pathogens. In this study, the degradation of OTC was evaluated by UV-254 nm activated persulfate (PS). The observed UV fluence based pseudo first-order rate constant (Robs) was found to be the highest at near neutral pH conditions (pH 5.5-8.5). Presence of various natural water constituents had different effects on OTC degradation, with a significant enhancement in the presence of bicarbonate or Cu2+. Limited elimination of total organic carbon (TOC) and PS was observed during the mineralization of OTC. Transformation byproducts in the presence and absence of hydroxyl radical scavenging agent tert-butanol (t-BuOH) were identified using ultra-high definition accurate mass quadrupole time-of-flight liquid chromatography/mass spectrometer (LC-QTOF/MS). Potential OTC degradation mechanism was subsequently proposed revealing four different reaction pathways by SO4 center dot-reaction including hydroxylation (+16 Da), demethylation (-14 Da), decarbonylation (-28 Da) and dehydration (-18 Da). This study suggests that UV-254 nm/PS is a promising treatment technology for the control of water pollution caused by emerging contaminants such as OTC. (C) 2015 Elsevier B.V. All rights reserved.
This paper presents a multi-objective optimization model for a green supply chain management scheme that minimizes the inherent risk occurred by hazardous materials, associated carbon emission and economic cost. The model related parameters are capitalized on a big data analysis. Three scenarios are proposed to improve green supply chain management. The first scenario divides optimization into three options: the first involves minimizing risk and then dealing with carbon emissions (and thus economic cost); the second minimizes both risk and carbon emissions first, with the ultimate goal of minimizing overall cost; and the third option attempts to minimize risk, carbon emissions, and economic cost simultaneously. This paper provides a case study to verify the optimization model. Finally, the limitations of this research and approach are discussed to lay a foundation for further improvement. (C) 2016 Elsevier Ltd. All rights reserved.
[Liu, Chengliang] East China Normal Univ, Sch Urban & Reg Sci, Shanghai, Peoples R China.;[Wang, Jiaqi] Hubei Univ, Fac Resource & Environm Sci, Wuhan, Hubei, Peoples R China.;[Zhang, Hong] Southwest Jiaotong Univ, Fac Geosci & Environm Engn, Chengdu, Sichuan, Peoples R China.;[Liu, Chengliang] 3663 North Zhongshan Rd, Shanghai 200062, Peoples R China.;[Zhang, Hong] 111,North Sect 1,Second Ring Rd, Chengdu 610031, Sichuan, Peoples R China.
[Liu, Chengliang] 3663 North Zhongshan Rd, Shanghai 200062, Peoples R China.;[Zhang, Hong] 111,North Sect 1,Second Ring Rd, Chengdu 610031, Sichuan, Peoples R China.
Global maritime network;spatial heterogeneity;hierarchical structure;weighted average centrality rank;weighted ego network analysis
More extensive attention has been paid to the heterogeneity of maritime transport network in topological rather than in spatial aspects. However, the importance of links and the roles of neighbors of a node has been ignored if not all. To fill this gap, this article introduced the approach of weighted ego network analysis (WENA) to visualize the spatial heterogeneity of the maritime network at global and local levels. The topological connectivity graph of the global marine network was derived, and its structural properties were analyzed. It is found out that the values of the degree of ports follow power-law distribution, which indicates that the global marine network is scale-free, that is, there are few well-connected ports and a majority of less connected ports. The spatial disparities of the network can be described by a core-periphery pattern. In global, most of the hubs or ports with extremely high values of degree locate in the big-three maritime regions including Far East, North America, and West Europe. Along the peripheral belts of the three regions, there are lots of less connected small ports. A different hierarchical structure of six continents was captured by WENA. It is found that Europe, Asia, North America, and Africa showcase a pyramid-shaped hierarchical structure with a scale-free feature similar to the entire network, while South America and Oceania exhibit the fusiform hierarchy like small-world networks. It is proposed that such spatial inequality and heterogeneity were caused by the geographical environments such as the hub-and-spoke organization, the embedded trade pattern, and the proximity of location. These findings help us to understand the characteristics of the international trade pattern and shed light on the strategies of development for the industry stakeholders.