Combined climate change and arsenic pollution increases rice cadmium with little effect on micronutrients

(Background and Aims) Rice production faces the dual threat of increasing soil As contamination and climate change. Each stressor can alter micronutrient (e.g. Fe, Zn) and toxin (e.g., Cd) plant uptake and internal translocation. Yet, the combined effects of soil As contamination and climate change factors on the nutritional quality and safety of rice grain remain poorly elucidated. (Methods) A full-factorial pot experiment growing rice under two soil As levels (low-As, high-As) and four climate conditions (today; elevated CO2 (+435 ppm CO 2 ); elevated temperature (+5° C); future (combined elevated CO 2 and temperature)) was performed. (Results) Grain Fe decreased slightly with soil As contamination and was barely altered by future climate conditions. Grain Zn and Cd both decreased with soil As contamination and increased with future climate. For grain Zn, the decrease with As contamination led to an overall decrease (by 25%) with combined soil As contamination and future climate. For Cd, increased concentrations under future climate outweighed the effect of soil As, leading to two-fold increased grain concentrations with As contamination and future climate combined. (Conclusion) Our results provide insight into the processes controlling Fe, Zn, and Cd in rice grown in polluted systems threatened by climate change, and highlight the critical importance of multifactorial, mechanistic studies.