Impacts of biochar and silicate fertilizer on arsenic accumulation in rice (Oryza sativa L.).


Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, PR China; Institute of Eco-Chongming, East China Normal University, Shanghai, 200241, PR China. Electronic address: [Email]


Human exposure to arsenic (As) through rice consumption is a global food safety issue, especially in Southeast Asia. To investigate the impacts of biochar amendment (rice husk and smooth cordgrass-derived biochar) and/or silicate fertilizer on As mobility/phytoavailability in soil and on As accumulation in rice, pot and microcosm experiments were conducted. The results showed that both single application of low doses of biochar (0.5%, w/w) and coapplication of biochar with silicate fertilizer decreased As levels in grain (brown rice) by 14-16%, but not in straw and roots. The biodilution of As in grain resulting from increased grain biomass (by 6-21%) could be mainly a response to the decline in grain As levels with biochar and/or silicate fertilizer amendment. However, both applications exerted limited effects to decrease the overall As uptake by rice grain and straw, potentially due to the small changes in As mobility/phytoavailability in amended soil relative to the control, although plant-available silicon (Si) from amendment could potentially inhibit As uptake. Furthermore, microcosm-based anaerobic incubation experiments demonstrated that As levels in soil solution increased (up to 11-14-fold) with increasing doses of biochar amendment (up to 5%, w/w), possibly due to biochar enhancing the reductive dissolution of iron (oxyhydr) oxides via an increase in the total number of iron-reducing bacteria (up to 1.6-3.2-fold). Our findings suggested that a low application rate of biochar may not be a very effective approach for mitigating As accumulation in rice, while a high application rate could enhance the health risk of As in As-contaminated flooded soil.



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