Seasonal and Spatial Variability of Arsenic in Rice Across a Climate Gradient in Vietnam

Abstract

Arsenic (As) accumulation in rice poses a significant, worldwide threat to food safety. Arsenic uptake is highly sensitive to climate and environmental factors; however, a comprehensive understanding of how diverse climatic conditions influence As dynamics and subsequent grain accumulation remains elusive. To fill this gap, we investigated As in soil and rice grain across 243 floodplain paddy sites along a ~2000 km longitudinal transect in Vietnam (8° N to 22° N), which is part of the world's largest rice-growing belt in Asia. The median levels of As in soils ranged from 8.3 to 9.9 mg kg⁻¹, and the consequent median levels of As in straw and grain were 0.85 mg kg⁻¹ and 163.5 μg kg⁻¹, respectively. Our findings reveal a clear tendency for rice grain As accumulation to vary with climate and cropping season. Particularly, data from contrasting seasons show that warmer temperatures promote higher As uptake in rice grains and enhance the accumulation of inorganic As species. These results underscore an urgent need to establish new, proactive mitigation strategies and sustainable land management practices in response to accelerating global warming to safeguard the global rice supply.