Impacts of Silicon Amendments on Iron Plaque Quantity, Mineral Composition, and Associated Arsenic in Rice (Oryza sativa L.).

Arsenic (As) is a known human carcinogen classified as Group-1 risk and its accumulation in plant tissues represents a major risk to human health. Recent studies have shown that foods are an important source of inorganic As intake by humans, especially rice (Oryza sativa L.), which may contain up to 10 times more than any other cereal. One important mechanism to prevent the uptake of As by rice roots is the formation of iron (Fe) plaques, and varieties that sequester more As in these plaques tend to translocate less to the shoots, and consequently, less accumulation in grain. Another way to prevent the uptake of As by rice is increase the availability of silicon (Si) in paddy fields, because arsenite, As predominant form in flooded soils, and dissolved Si share a root-uptake pathway. The Si can still change the mineralogy of Fe plaques, which can sequester As. Therefore, to decrease the accumulation of arsenic in rice and thus human health risk, it is essential to understand the impacts of management strategies on Fe plaque and associated arsenic. This study evaluated the alteration of the mineralogical composition of Fe plaques extracted from rice plants in three different varieties as well as its association with As after application of different Si amendments using DCB extraction and Synchrotron-based techniques. We show that the presence of Si amendments changed the As concentration on Fe plaques, also indicating a change in the composition of the Fe minerals in plaques. Crystalline phases of Fe were detected by XRD showing, for different treatments, different peaks of iron minerals. The results show that depending on the choice of Si amendment it can improve rice yields.