Mitigation of cadmium and arsenic in rice plant by soil application of steel slag and/or biochar with water management

Simultaneous mitigation of cadmium(Cd) and arsenic(As) in rice grain has been a great challenge, in contaminated paddy soilrice system. Here, a soil column experiment and a field experiment were conducted to investigate the optimal mitigation strategies on Cd and As contaminated paddy soil by soil application of steel slag and/or biochar with water managements. Soil column experimental results showed that continuous flooding(CF) decreased Cd but increased As concentrations in soil solutions. Soil application of steel slag(SS) significantly increased soil pH but decreased soil Eh. Meanwhile, SS treatment reduced the Fe/Cd concentrations but increased Mn/As concentrations in soil solutions. The field trial data showed that there was a significant negative correlation (R=-0.838, P<0.05) between brown rice Cd and brown rice As. The results indicate that aerobic condition could not reduce Cd accumulation in rice grain. However, soil application of steel slag and biochar with continuous flooding condition (CF + SS+BC) had the best mitigation effect on both Cd and As concentrations (rice Cd reduced by 80% and rice As kept unchanged) in rice grain simultaneously. Hence it could be one of the effective strategies to mitigate Cd and As accumulation in rice plant.