Factors causing the increase in arsenic concentration in brown rice due to high temperatures during the ripening period and its reduction by applying converted furnace slag

It has been pointed out that the concentration of arsenic (As) in brown rice increases due to high temperatures during the ripening period, and fertilization that can reduce As in brown rice even under high-temperature is required. The effectiveness of using converted furnace slag (CFS) to reduce the As concentration in brown rice was investigated. Rice plants were cultivated in Wagner pots (1/5000a) filled with gray lowland soil added CFS under ambient conditions up to 1 week after heading. Those pots were moved to a temperature gradient chamber set at four temperature levels (ambient, mildly-high, moderate-high, and super-high) and kept until harvest. An analysis of covariance using the mean daytime temperature as a covariate showed significant linearity of regression for As concentrations, indicating that high temperature increased the concentration of As in brown rice. The application of 30 g of CFS significantly reduced 20% of the As concentration in the rice, suggesting that CFS can be an effective countermeasure to reduce the As concentration in brown rice under high-temperature conditions. Since inorganic As flows into brown rice through sieve tubes, the cause of the increase in As concentration in brown rice due to high temperature was investigated by comparing the concentrations with carbon dynamics. The significant positive correlation between the As/carbon ratio and the As concentration in brown rice was observed, suggesting that high temperature reduces the rate of carbon translocation which is one of the essential factors in the increase in As concentration in brown rice due to high temperature.