Soil Warming Increases Arsenic Availability in the Rice Rhizosphere

Abstract

Arsenic uptake by rice ( L.) threatens yield and contaminates grain. Climate warming could affect these hazards. We tested the effect of elevated soil temperature on arsenic availability to and uptake by rice plants. Rice was grown in arsenic-amended soil in rhizoboxes that facilitated porewater sampling and synchrotron X-ray fluorescence (XRF) imaging of the rhizosphere. Plants were subjected to similar atmospheric conditions but different soil temperatures. The XRF imaging revealed greater arsenic sequestration in root iron plaques with a warmer soil temperature. Mean and median arsenic concentrations in porewater and root, straw, and husk tissue were positively correlated with average daily maximum soil temperature. Grain arsenic concentrations did not change. Warmer soil temperatures likely increased plant-available arsenic by increasing reductive dissolution of arsenic-bearing iron minerals, but the plants effectively regulated grain arsenic. The impacts of changing environmental conditions on arsenic contamination of rice should be further explored.