Concentrations and Health Implications of As, Hg, and Cd and Micronutrients in Rice and Emissions of CH4 From Variably Flooded Paddies
Date
2025-08-13
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GeoHealth
Abstract
The flooded soil conditions under which rice is typically grown are beneficial for boosting yield and decreasing herbicide inputs but may pose a food safety and environmental health risk. Flooded soils lead to reducing conditions and anaerobic metabolisms of soil microorganisms, which mobilizes arsenic from soil into soil solution, where it can be absorbed by rice roots and transported to grain. These conditions also promote the production and emission of methane (CH4)—a potent greenhouse gas. To evaluate how water management affects metal(loid) grain concentrations and CH4 emissions, we conducted a 2-year field study in which rice paddy water was managed under a range of soil redox conditions that spanned from flooded to non-flooded. We observed that growing rice under less flooded conditions decreased CH4 emissions and concentrations of grain total As, grain inorganic As, grain total Hg, and grain inorganic Hg relative to flooded conditions, with more reductions observed as conditions were drier; grain organic As and Hg (MeHg) species also decreased with drier conditions particularly in Year 1. However, the driest conditions tested led to a 50%–97% increase in grain Cd concentrations that exceeded the CODEX limit and grain yield reductions as high as 25% and 40% in Year 1 and 2, respectively. While concentrations of toxic metal(loid)s could be manipulated by water management, micronutrient concentrations were similar or decreased with drier conditions, potentially increasing grain Cd bioaccessibility to humans. Because practices for rice water management are gaining momentum, more research should monitor grain Cd levels along with micronutrients.
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This article was originally published in [Journal Name]. The version of record is available at: https://doi.org/10.1029/2025GH001410
© 2025 The Author(s). GeoHealth published by Wiley Periodicals LLC on behalf of American Geophysical Union.This is an open access article under theterms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
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Citation
Seyfferth, A. L., Limmer, M. A., Jackson, B. P., & Runkle, B. R. K. (2025). Concentrations and health implications of As, Hg, and Cd and micronutrients in rice and emissions of CH4 from variably flooded paddies. GeoHealth, 9, e2025GH001410. https://doi.org/10.1029/2025GH001410