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Dou L.,Geological Survey of Guangdong Province | Yang G.-Y.,Guangdong Institute of Eco environmental and Soil Sciences | Yang G.-Y.,Guangdong Key Laboratory of Agro Environment Integrated Control
Huanjing Kexue/Environmental Science | Year: 2015

The contents of 17 Organochlorine pesticides (OCPs) of 605 samples collected from the surface of agriculture land from Pearl River Delta Economic Zone were determined by gas chromatography with electron capture detector (GC-ECD). The residual characteristics, sources and ecological risk of OCPs were also analyzed. The results showed that the detection rate of OCPs was 97.85%. The mean value of residue level was 20.67μg· kg-1, with the highest value of 649.33μg·kg-1. The main contaminants included DDTs, HCHs, endosulfan sulfate and methoxychlor. Compared with the soils of other cities, the levels of HCHs and DDTs in the studied area were arranged from low to middle levels. The OCPs were obviously regionally distributed. High content areas were mainly distributed in the central area with dense population, intense industrial and agricultural activities. The residue levels in different types of lands were significantly different: the arable land>garden land>woodland. Especially, the residue level was the highest in the vegetable land. Source analysis indicated that the HCHs might come from the use of lindane. DDTs in soil mainly came from early residues, but the dicofol might be the important source in partial area. Comparing the contents of HCHs and DDTs with our National Standard (GB 15618-2008), the qualified rates of the first and second standard of HCHs were 97.5% and 100%, respectively, and the DDTs were 95.5% and 97.7%, respectively. According to the risk assessment, DDTs may still have some potential ecological impact on the studied area. ©, 2015, Huanjing Kexue/Environmental Science. All right reserved.

Wu Y.,South China Institute of Environmental Sciences | Wu Y.,Guangdong Key Laboratory of Agro Environment Integrated Control | Han R.,South China University of Technology | Lin B.,South China Institute of Environmental Sciences | And 6 more authors.
Chinese Journal of Environmental Engineering | Year: 2013

The removal effect of low-concentration organic pollutants in a hybrid constructed wetland (HCW) engineering was monitored and studied from May to October. Monod kinetic model was introduced to analyze the treatment effect of low-concentration organic pollutants and verified through three statistical parameters. Correlation of input organics loading vs. removal rates, kinetic coefficients from Monod kinetics against BOD/COD ratio in influent were discussed. The total area of HCW was 5000 m2, and the influent flow rate was 860~1560 m3/d, hydraulic retention time was 1.48~2.69 d, hydraulic loading was 0.17~0.31 m/d. The input organics concentrations were low (BOD5 3.0~25.6 mg/L, COD 22.9~89.8 mg/L). Results showed that the removal efficiencies of BOD5 and COD reached 37.9%~79.0% and 41.0%~68.7% respectively in hybrid constructed wetland. Regressions of Monod kinetics for correlating inlet and outlet organics values in wetland system indicated the difference between actual and predicted value was very slight. The removal efficiencies of BOD5 and COD increased in accord with BOD5 and COD concentrations of the influent, but the increasing tendency became slow. K values derived from Monod model were smaller when organic pollution loads were lower. The efficiencies of organics removal in wetland system appeared to be insensitive to the nature of organic matter when organics pollutants concentrations were low in the influent, whether the organic matter was easily or slowly degradable. This might be related to other factors that promoted removal of organics pollutants in HCW.

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