Effect of nano-hydroxyapatite on Cd chemical speciation in soil and Cd accumulation in rice

The adsorption behavior of Cd on the surface of Nano-hydroxyapatite (nano-HAP) and the effect of nano- HAP on the chemical speciation of Cd in soil and the Cd accumulation in rice were studied by the adsorption isotherm tests and pot experiments. The results showed that nano-HAP had a high adsorption capacity for Cd and the adsorption behavior could be well described by Langumir and Freundlich equations. The results of pot experiments showed that nano- HAP significantly increased the pH of soil solution and inhibited Cd bioavailability. The bioavailability of Cd concentration in the soil decreased by 63.21%, 80.62% and 92.32% under the 0.5%, 1% and 2% nano-HAP treatments, respectively. Nano-HAP significantly reduced the Cd content in rice grain and all rice grain met the edible standards.