Speciation of arsenic and concentration of cadmium and arsenic in rice (Oryza sativa L.) cultivated under co-exposure of cadmium/arsenic and different water ponding

• Flooded soil increased tAs in grains, but iAs decreased with Cd co-exposure. • As increased in grains from semi-dry soil, but decreased in dry and flooded soil. • DMA was the predominant As species detected in rice grains. • Water regime significantly impacted As and Cd accumulation in rice. Over three billion people consume rice ( Oryza sativa L), an important cereal in the human diet. It is cultivated typically in flooded soils. However, it is also grown in soils with limited water (upland or dryland). There are few studies on the concomitant translocation of As and Cd from soil to rice in different irrigation systems. The present work aimed to verify the influence of 3 irrigation systems (dry soil, semi-dry, and flooded soil) on the absorption and translocation of arsenic (As) and cadmium (Cd) in the rice cultivar GURI INTA CL. Four different soil treatments were used in each of these irrigation regimes: As 10 mg kg -1 only, Cd 10 mg kg -1 only, 10 mg kg -1 of As + Cd, and the control group (no As/Cd additions). Arsenic treatment affected the agronomic parameters (stem masses and heights and the mass of grains) of the plants cultivated in dry soil and semi-dry soil. It was observed that the co-exposure in flooded soil presented a higher concentration of total As with the lowest percentage of inorganic As (iAs 37.6 %) in grains. Co-exposure or only As had a similar iAs percentage in grains from plants cultivated under other irrigation systems ( ̴ 55 %). The highest Cd concentration was observed in the dry soil irrigation system, for both roots and grains, mainly in co-exposure treatment. Thus, the rice cultivar GURI INTA CL raised in flooded soils absorb higher amounts of As and lesser amounts of Cd. On the contrary, in dry soil there is higher and lesser absorption of Cd and As, respectively. Therefore, this new knowledge on the dynamics of absorption and translocation of As and Cd in Brazilian rice cultivars can provide mitigation strategies for the contamination of rice grains by toxic elements.