Selection of better extractants to indicate Pb bioavailability in lead-contaminated agricultural soils of Zhejiang Province

The accumulation of Pb in the food chain is one of the great concerns as it can cause chronic health problems and the available Pb is easily absorbed by crops. To shed light on Pb bioavailability in lead-contaminated agricultural soils of Zhejiang Province, a series of plant growth experiments were performed in a greenhouse to select more suitable extractants from five commonly used extractants （0.1 M HCl, 1 M NH4OAc, 0.1 M CaCl2, DTPA-TEA and Mehlich 3）. The results showed that 1 M NH4OAc can extract Pb best, indicating the Pb bioavailability, then, DTPA-TEA and 0.1 M HCl in the tested soils. In case 1 M NH4OAc was used as an extractant, the critical Pb concentrations in soils were 50.19 mg/kg, 21.16 mg/kg and 114.00 mg/kg （1 M NH4OAc extracted Pb） in silty loam, yellowish-red soil and purplish soil, respectively. When the values exceed the above ones, the contents of Pb in Chinese cabbage leaves will exceed the Chinese Tolerance Limit of Lead in Foods （GB 14935-94）, as a result, potential ecological risk and hazard to human health via the food chain will appear.