Rice is particularly vulnerable to arsenic uptake because unlike most crops, it grows in flooded conditions with anoxic soil. Microbes that thrive in these anoxic environments release arsenic into the soil’s pore water through normal metabolic reactions. Once liberated from soil particles, this pore water arsenic can be taken up by the rice plant’s roots.
Previous studies have focused mainly on heat stress and its impact on how rice plants grow, possibly making them more likely to concentrate arsenic. What the new research indicates, however, is that “bioavailability may be more important,” [researcher Yasmine] Farhat said.
Farhat’s team grew rice plants in four greenhouses set to daytime temperatures of 25.4°C, 27.9°C, 30.5°C, and 32.9°C… Results showed a strong link between rice grain arsenic concentrations and temperature and confirmed that in hotter conditions, soil pore water contained more arsenic.
The fact that her team used soil low in arsenic is crucial, Farhat said: “Elevated growing temperatures may increase the risk of dietary arsenic exposure in rice systems that were previously considered low risk.”
“If you give the soils time to breathe, or become oxygenated, it is known to reduce arsenic quite a bit,” said Manoj Menon, a soil and environmental scientist at the University of Sheffield… Another potential solution, Menon said, is planting arsenic-resistant varieties of rice.