关键词: 非正规填埋场, 开挖, 重（类）金属, 绿化用地, 生态风险评估

Abstract: To clarify whether the land resources could be reused safely after excavation in an informal landfill site, a landfill site in Jiashan county was taken as an example. Samples were collected from the excavation area of foundation pit and side wall, and the pH, organic matter and heavy metal （metalloid） concentrations of samples were detected. The results showed that mercury was not detected in the soil at the bottom and side wall of the foundation pit, the cadmium content was close to the background concentration, and the sample content was both below 0.23 mg/kg. The concentration trends of total chromium, copper, lead, and zinc in all samples were the same, and the maximum values were 99.0, 40.2, 43.0, and 201.0 mg/kg, respectively, with approximately 2.43, 1.05, 1.60, and 2.03 times over the background value. However, they were all lower than the requirements of the CJ/T 340—2016 Planting Soil for Green and GB 36600—2018 Soil Environmental Quality Risk Control Standard for Soil Contamination of Development Land, which could meet the requirements for green land use. The pH of the soil in this landfill site ranged from 6.77 to 8.26, with a relatively low organic matter content (average of about 7.96 g/kg) at the bottom of the foundation pit, which was much lower than the green land standard (12 to 80 g/kg). To make the land meet the green land requirements, it was necessary to increase the organic matter content. In addition, according to the Hakanson potential ecological risk assessment of soil heavy metals （metalloids）, the RI value was calculated to be 8.85 (RI<150), indicated that the ecological risk caused by eight heavy metals （metalloids） such as mercury, cadmium, arsenic, lead, copper, chromium, zinc, and nickel in the landfill site was of a mild level.

Key words: irregular landfill sites, excavation, heavy metals （metalloids） , greening land, ecological risk assessment