Release of Cu and Cd from contaminated soil amended by nanoparticle and microparticle hydroxyapatite in the condition of acid deposition

Release characteristics of Cu and Cd from compound contaminated soil under simulated acid rain were studied through a leaching experiment for the untreated soil and hydroxyapatite amended soil with a rate of 1%. EC, pH, Cu and Cd concentration of leaching solution and before and after leaching of soil heavy metal bioavailability were analyzed. The result show that the leaching solution pH order is MHA>NHA>CK, higher than simulated acid rain pH. MHA and NHA treatments increase the leaching solution conductivity (EC), especially for MHA with its leaching solution EC was 10-- 41 times as high as that of CK. Compared with CK, MHA significantly increased Cu concentration of the leaching solution, and had been maintained at a higher level, while the NHA decreased the Cu concentration of the leaching solution, but MHA and NHA both decrease Cd concentration of the leaching solution. Before leaching Cu and Cd bioavailability of MHA treated soil were reduced by 75.0% and 90.7%, respectively, while for NHA treatment the rates were 59.6% and 52.2%, respectively, indicating that MHA can be more effective stabilization of Cu, Cd than NHA. But in MHA treatment Cu and Cd were activated more under simulated acid rain leaching comparing with NHA, showing that MHA stabilized Cu and Cd can easily be reactivated under acid rain condition in south China.