Purification capacity of loess aerated zone on Cd, Pb in the industrial wastewater

For studying the purification capacity of loess aerated zone on Cd, Pb in the industrial wastewater, an in-situ experiment was carried out in the loess aerated zone of the loess plateau in the North Shaanxi Province. In this experiment, the wastewater which contained the pollutants Cd, Pb with respective content of 1.651ug/l, 9.483ug/l was filled into the loess aerated zone. Approximately 565l of wastewater was used in the test, which lasted 333min. Loess samples were collected at 5 discrete depths, 0.2m, 0.4m, 0.6m, 1m, and 1.5m from the surface before, at the end of, and 20 days after the infiltration test. Then the content variation of Cd, Pb in the samples was studied. The test indicates the loess aerated zone has a strong degradation and purification capacity for Cd and Pb. After 565l wastewater with 1.651ug/l of Cd and 9.483ug/l of Pb was applied to test area, the concentration of Cd in the loess samples increased from about 1mg/kg under natural condition to 3mg/kg after the infiltration, and the concentration of Pb also increased, from 1mg/kg under natural condition to above 4mg/kg in the shallow loess samples (<;1.0m) and the maximum (above 6mg/kg) occurred at 0.6m. Twenty days after the infiltration test, the concentration of Cd decreased to about 2mg/kg in all depth range, while the concentration of Pb increased from 1.2mg/kg to 7mg/kg in the loess samples at 1.5m and decreased to 1mg/kg in the shallow loess samples (<;1.0m) with the physical, chemical and biological degradation, showing strong purification capacity for Pb.