KONG Xiangsheng1, MIAO Ying1, LUAN Rijian2, QIN Suni1
(1.Institude of Karst Geology, Chinese Academy of Geological Science(CAGS)/Key Open Laboratory of Karst Ecosystem and Rocky Desertification Control, CAGS, Guilin 541004, China;
2. Shandong Testing Center of China Metallurgical Geology Bureau, Jinan 250014, China)
Abstract: In order to understand contamination of persistent organic pollutants（POPs) in the offshore groundwater in Nanning City, China caused by polluted rivers, Chaoyangxi River was selected to study as a typical polluted river. Methods of field survey and drilling engineering were taken to study hydrogeology in this area, and then groundwater, surface water, soils and sediment samples were collected and tested. The characteristics of hexachlorocyclohexane (HCHs), and fluoranthene and pyrene in the offshore groundwater before and after rainfall were also discussed. Results show that average concentrationsof fluoranthene and pyrene in groundwater before and after the rainfall are 24.11ng/L and 7.98ng/L, respectively. The average concentrations of HCHs are 19.75ng/L and 13.24ng/L, respectively. The detection rates and concentrations of fluoranthene, pyrene and HCHs after rainfall are higher than those before. Concentrations of fluoranthene and pyrene gradually increase with increasing distance away from Chaoyangxi River, but those of HCHs are the opposite. This study speculates that hydrophobic stronger fluoranthene and pyrene are strongly adsorbed by suspended solids in the aquifer and the bottom sediment of river because of the difference of physical and chemical properties, so that they are not detected in groundwater near the offshore. However, hydrophobic weaker HCHs have higher concentrations due to residual, form pollution source, and result in a "secondary release" of HCHs in aquifer. Overall, rainfall has dilution effect on organic pollutants in groundwater, but HCHs at some local area are disturbed by rainfall to release. Relationship between the concentrations of fluoranthene and pyrene and the suspended material in the groundwater shows a negative moderate correlation, while that of HCHs concentrations and the suspended solids shows a very strong correlation, so the "filtering effect" of fluoranthene and pyrene of the suspended solids in the aquifer is higher than HCHs. Thus, this study suggests that the impact factors of POPs migration in the offshore groundwater are closely related with the structures of vadose zone and aquifer, hydrogeological conditions, and locations of pollution sources
Keywords: river pollution; offshore groundwater; persistent organic pollutants (POPs); hexachlorocyclohexane; fluoranthene; pyrene
EARTH AND ENVIRONMENT Vol.44, No.4 Tot No.312, 2016, Page 406-413
