关键词: 污染场地, 铬（六价）, 风险管控, 长期管控, 工程措施

Abstract: To understand the performance of long-term risk management in contaminated site, we developed a conceptual model of site risk control according to a study in a chemical plant in southwest China with the risk management from 2004 to 2020. In 2012 and 2020, soil samples, groundwater and water samples were collected to analyze the concentrations of total chromium (Cr) and Cr(VI). Combined with the monitoring data from 2004 to 2020 in wastewater treatment station, we calculated the reduced load of Cr(VI). The Cr concentration in wastewater was 1200 mg·L^-1 in 2004, which decreased significantly and tended to be stable at 400 mg·L^-1  after 2020. Such changes were correlated with implementation of risk control measures since 2004, including the pollution source control transmission process and terminal disposal projects. The groundwater volume in the contaminated site tended to increase to a peak in 2007 and decrease to a stable level after 2010, which varied from 36800 to 256300 m³. From 2004 to 2020, the cumulative volume of the treated wastewater by the groundwater extraction and treatment project was 2160000 m³, with the total reduction of Cr(VI) discharge load was 1376 t. The Cr(VI) concentrations in effluent water have reached the Cr(VI) criteria in the Comprehensive Sewage Discharge Standard (GB 8978-1996) after 2010. Moreover, the Cr(VI) contents in soil samples in 2020 were lower than those in 2012 under the longterm risk management measure. Meanwhile, the Cr(VI) concentrations in sensitive water bodies reached the Cr(VI) criteria in Surface Water Environmental Quality Standard (GB 3838-2002). It can be concluded that long-term implementation of risk control measures on the contaminated site has obtained favorable effect to keep the Cr(VI) in the environment under control. Our results provide a scientific basis for the implementation of long-term risk control measures in Cr(VI) in contaminated sites, and a reference for the risk control of other heavy metals contaminated sites.

Key words: contaminated site, Cr(VI), risk control, long-term implementation, engineering measure