Trace element accumulation in rice: Effects of soil arsenic, irrigation management, cultivar, phosphate application and iron oxide amendment

A concern is growing over the accumulation of trace contaminants in rice, a plant which has been estimated to supply 50% of the caloric intake to the world's population. Contamination with arsenic (As) and other trace elements have been shown in many areas including the U.S. and rice intake poses a potential risk to human health. This research investigated the accumulation of selected trace elements including arsenic (As), selenium (Se), molybdenum (Mo) and cadmium (Cd) in as many as six rice cultivars and two control soils common to the south central U.S. A field study was completed to evaluate the impact of As content in soil, irrigation management and cultivar on total rice grain element accumulation. Results indicated soil amended with monosodium methanearsonate (MSMA) increased the accumulation of As and Se, but decreased Mo accumulation in rice under all irrigation treatments. Grain-Cd increased for most cultivars in MSMA-amended soil. In addition, intermittent flooding significantly decreased total grain-As, Se and Mo, but increased Cd. Greenhouse studies were also completed to evaluate the impact of phosphate application and iron oxide amendments on total grain concentrations of As, Se, Mo and Cd. Correlations between soil-As and grain elements were also studied. Results indicated that grain-As concentration is directly proportional to the soil-As concentration, but phosphate application has no substantial impact on grain element concentration. Iron oxide amendments significantly reduced grain-As accumulation in rice. Results also indicated increasing the soil-As concentration increased grain-As, increased grain-Se and Cd, and decreased grain-Mo accumulation.