Effect of Mixed Application of Biomass Power Plant Ash and Sodium Sulphide on Cd Accumulation in Rice

<p indent="0mm">Rice consumption is a significant source of cadmium (Cd) exposure for the population in China and rice with high Cd has become an important environmental issue in China. Soil addition of passivators is one of the important measures to reduce the Cd accumulation in rice. It is also an effective strategy to minimize the risk of Cd exposure to the populations. In this study, we investigated the effects of adding varying amounts of lime and biomass ash from power plant compounded with sodium sulfide with mass ratio of 7:3 (DSO) to the soils on the Cd uptake by rice by means of soil incubation tests, pot tests (early and late season rice), and field experiments. The results showed that DSO reduced the bioavailable Cd concentrations in soils by 42% in the soil incubation test, which was higher than the lime treatment group. Both the lime and DSO effectively reduced the Cd concentrations in brown rice by 46%-66% and 67%-68% in the early rice pot test. Meanwhile, lime and DSO reduced the brown rice Cd concentrations by 43%-66% and 69%-78% in the late rice test, respectively; whereas, 0.1%, 0.2%, and 0.4% additions of DSO reduced the Cd concentrations by 68%, 68% and 67% in early brown rice and 78%, 78%, and 69% in late brown rice, respectively. In the field experiment, the application of 0.2% and 0.3% DSO reduced the brown rice Cd concentrations by 16% and 42%, respectively. The results suggested that DSO application was more effective than lime in Cd reduction in brown rice and the reduction of Cd in brown rice was more effective than those of the other treatments when DSO was applied at a rate of 0.3% (w/w) and with a 7:3 ratio of biomass power plant ash to sodium sulfide.