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Huang D.-Y.,CAS Guangzhou Institute of Geochemistry | Huang D.-Y.,Guangdong Institute of Eco environmental and Soil Sciences | Peng P.,CAS Guangzhou Institute of Geochemistry | Xu Y.-G.,CAS Guangzhou Institute of Geochemistry | And 3 more authors.
Atmospheric Research | Year: 2010

We analyzed rainwater collected from multiple sites, Guangzhou, China, from March to August 2005, with the aim to characterize the distribution, regional sources and deposition fluxes of organochlorine pesticides (OCPs) in South China. Eight species of organochlorine pesticide were detected, including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and endosulfans. Volume-weighted mean monthly total concentrations varied from 3.65±0.95 to 9.37±2.63ngL-1, and the estimated total wet deposition flux was about 11.43±3.27μgm-2 during the monitoring period. Pesticides were mainly detected in the dissolved phase. Distribution coefficients between particulate and dissolved phases in March and April were generally higher than in other months. HCHs, p,p'-DDD and p,p'-DDT in precipitation were attributed to both the residues and present usage of insecticides in Pearl River Delta. The concentrations of p,p'-DDD+p,p'-DDT were relatively high from April to August, which were related to the usage of antifouling paints containing DDT for fishing ships in seaports of the South China Sea in summer. In contrast, endosulfans were relatively high in March, which was related to their seasonal atmospheric transport from cotton fields in eastern China by the Asian winter monsoon. The consistency of the variation of endosulfans, p,p'-DDD and p,p'-DDT concentrations with the alternation of summer and winter monsoon suggested that the Asian monsoon played an important role in the long-range transport of OCPs. In addition, the wet deposition of OCPs may influence not only Pearl River water but also the surface land distributions of pesticides in the Guangzhou area, especially for endosulfans, p,p'-DDD and p,p'-DDT. © 2010 Elsevier B.V.

Jia L.,Shanghai JiaoTong University | Jia L.,Shanghai Academy of Public Measurement | Shen Z.,Shanghai JiaoTong University | Su P.,Shanghai JiaoTong University
Journal of Environmental Sciences (China) | Year: 2016

Fenton oxidation is a promising water treatment method to degrade organic pollutants. In this study, 30 different organic compounds were selected and their reaction rate constants (k) were determined for the Fenton oxidation process. Gaussian09 and Material Studio software sets were used to carry out calculations and obtain values of 10 different molecular descriptors for each studied compound. Ferric-oxyhydroxide coagulation experiments were conducted to determine the coagulation percentage. Based upon the adsorption capacity, all of the investigated organic compounds were divided into two groups (Group A and Group B). The percentage adsorption of organic compounds in Group A was less than 15% (wt./wt.) and that in the Group B was higher than 15% (wt./wt.). For Group A, removal of the compounds by oxidation was the dominant process while for Group B, removal by both oxidation and coagulation (as a synergistic process) took place. Results showed that the relationship between the rate constants (k values) and the molecular descriptors of Group A was more pronounced than for Group B compounds. For the oxidation-dominated process, E HOMO and Fukui indices (f(0)x, f(-)x, f(+)x) were the most significant factors. The influence of bond order was more significant for the synergistic process of oxidation and coagulation than for the oxidation-dominated process. The influences of all other molecular descriptors on the synergistic process were weaker than on the oxidation-dominated process. © 2015.

Deng Y.,CAS Guangzhou Institute of Geochemistry | Deng Y.,Shanghai Academy of Public Measurement | Peng P.,CAS Guangzhou Institute of Geochemistry | Ren M.,CAS Guangzhou Institute of Geochemistry | And 2 more authors.
Atmospheric Environment | Year: 2011

Prior studies showed that the polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations in the atmosphere are much higher in the winter than in the summer. This so called winter effect was explained via meteorology-dependent factors such as dispersion, mixing and photo chemical degradation or home heating related formation of PCDDs/Fs. In this study, we took vehicle emission as an example to investigate winter effect on PCDD/Fs formation by fossil fuel combustion. We hypothesized that vehicle emission of PCDDs/Fs may be elevated in the winter season due to the promoted supplies of Cl - (via particular matter) in winter. We collected particulate and gaseous samples from the Pearl River Tunnel and its adjacent open air during spring/summer and winter seasons. Chemical analyses of the tunnel samples showed that the PCDD/F concentrations in the tunnel ranged from 18.6 to 20.4pgm -3 (1.28-1.39pgI-TEQm -3) in the winter, which were 3-5 times higher than in the spring/summer. In the open atmosphere adjacent to the tunnel, the PCDD/F concentrations were much lower than in the tunnel; e.g., approximately one fifth of the tunnel air concentrations during the winter. The emission factors (EFs) calculated based on the tunnel data were 3440 (or 230 I-TEQ) and 1580 (or 27.8 I-TEQ)pgkm -1vehicle -1 in winter and spring/summer season, respectively. The much higher PCDD/F concentrations in the tunnel air and much greater EF value during the winter are likely related to higher content of Cl - associated with small size particulates. This suggests that the winter effect observed in the open atmosphere is not only caused by meteorology-dependent factors and home heating, but also may partly results from much greater PCDD/F formation rates during the combustion processes of fossil fuels such as gasoline- and diesel-fuel in the winter. © 2011 Elsevier Ltd.

Jia L.,Shanghai JiaoTong University | Jia L.,Shanghai Academy of Public Measurement | Shen Z.,Shanghai JiaoTong University | Guo W.,Shanghai JiaoTong University | And 4 more authors.
Journal of the Taiwan Institute of Chemical Engineers | Year: 2015

Fenton oxidation is an advanced treatment process used to remove organic pollutants in wastewater. In this study, quantitative structure activity relationship (QSAR) models for Fenton process were developed with reaction rate constants of organic compounds as the dependent variable. To establish optimum QSAR models, reaction rate constants of 33 kinds of organic substances were determined and 13 molecular descriptors were selected. The molecular descriptors were calculated by Hyperchem, Gaussian 09 and Dmol3 software for each organic compound. The optimum QSAR model for predicting the rate constants consists of three descriptors, SAG, f(0)n and EGAP. Among them, SAG appears most critical in determining rate constants. A set of 26 compounds was used as training set to develop models and 7 compounds was used as test set for external validation. The prediction accuracy of the recommended model was tested using the leave-one-out cross validation procedure, validation through an external test set and the Y-randomization evaluation technique. The domain of applicability was finally determined to identify the reliable predictions. The results indicated that the proposed model proved to have significant predictive potential of reaction rate constants in Fenton process. © 2014.

Rong Z.,Shanghai Academy of Public Measurement | Li K.,Shanghai Academy of Public Measurement | Yin H.,Shanghai Academy of Public Measurement
Environmental Monitoring and Assessment | Year: 2010

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in agricultural soil samples from Shanghai to determine levels and to identify possible dioxin sources. The dioxin level was measured by an enzyme immunoassay method, US EPA 4025 (modified), which provides results as 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) equivalents. The Method 4025m results obtained from 60 soil samples displayed a normal distribution, ranging from 2.8 to 23.4 pg/g 2378-TCDD-equvalents, with an average of 11.0 pg/g. The result also revealed a similar PCDD/Fs concentration among crop usage patterns, but differences by geographic region, low in the southwest of Shanghai and considerably higher in the northwest region. In contrast, the dioxin concentrations on Chongming Island were fairly homogeneous, with a range 10-15 pg/g. This immunoassay method is an effective high throughput screening tool which helps to minimize the need for more expensive analyses. © 2009 Springer Science+Business Media B.V.

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