Arsenic transfer and accumulation in the soil-rice system with sulfur application and different water managements

Abstract

Rice (Oryza sativa L.) can readily accumulate arsenic (As), owing to its high capacity to take up As and special flooding cultivation, which poses a potential risk to human health. Although sulfur (S) can influence As accumulation in rice, its behavior in the rice-soil system is not clear under practical water management conditions. In this study, the transfer and soil solution dynamics of As in the whole soil-rice system was investigated under continuous flooding or intermittent drainage, either with S addition or not. The results showed that intermittent drainage effectively reduced As concentration in soil solution regardless of S conditions, and it only reduced As content in rice without S addition. Exogenous S decreased As concentration in soil solution and rice, except in the roots of mature rice, under continuous flooding. Sulfur addition significantly decreased the total As and As(III) contents in rice grains, by 62% and 79% under continuous flooding and by 50% and 76% under intermittent drainage, respectively. Moreover, the addition of S resulted in impaired iron plaque and inhibited binding of As. Sulfur also reduced As translocation from rice roots to shoots. Therefore, S could alleviate the crisis of excessive accumulation of As in rice grains caused by flooded environment through various adjustments to the soil-rice system.

Keywords: As speciation; Continuous flooding; Intermittent drainage; Iron plaque; Paddy field; Rice.