RICE IS A STAPLE FOR OVER HALF OF THE WORLD POPULATION AND HAS $1.2B IN U.S. EXPORTS ANNUALLY. SUSTAINABLE PRACTICES TO ENSURE HEALTHY RICE PRODUCTION ARE IMPERATIVE. RICE IS SUBJECT TO ARSENIC (AS) CONTAMINATION DUE TO PADDY SOIL FLOODING. THIS IS EXACERBATED BY EXPANDING RICE CULTIVATION/CONSUMPTION, INCREASING IRRIGATION, AND CONTINUED ENVIRONMENTAL CONTAMINATION.IT HAS BEEN THOUGHT THAT THE IRON OXIDE PLAQUE FORMED ON RICE ROOTS PREVENTS AS UPTAKE, HOWEVER, STUDIES HAVE NOT EXAMINED THE LONG-TERM STABILITY OF ROOT FE PLAQUE OR ITS EFFECTS ON OTHER PLANT NUTRIENTS/CONTAMINANTS. IT IS UNRESOLVED WHETHER/WHEN FE PLAQUE PROMOTES RICE HEALTH. A COMBINATION OF LABORATORY, GREENHOUSE, AND FIELD EXPERIMENTS WILL BE USED TO 1) ANALYZE FE PLAQUE STABILITY; 2) QUANTIFY EFFECTS OF ANION COMPETITION ON FE PLAQUE FORMATION; AND 3) DETERMINE THE MOBILITY OF CONTAMINANTS/NUTRIENTS ADSORBED TO FE PLAQUE.A COLUMN TECHNIQUE WILL BE USED TO MEASURE FE PLAQUE DISSOLUTION KINETICS FROM WELL-CHARACTERIZED RICE ROOTS, AND ROOT MASSES WILL BE INCUBATED POST-HARVEST TO CONFIRM THESE RESULTS AND ACCOMPLISH OBJS. 1 AND 3. RICE WILL BE GROWN IN ARKANSAS AND DELAWARE PADDY SOILS IN A GREENHOUSE WITH MONITORING OF PLAQUE DEVELOPMENT TO ACCOMPLISH OBJ. 2. A SEQUENTIAL EXTRACTION WILL BE DEVELOPED TO ACCOMPLISH OBJ. 2 AND 3. SYNCHROTRON SPECTROSCOPIC TECHNIQUES WILL BE USED TO CONFIRM RESULTS.THESE RESULTS WILL GREATLY ADVANCE FUNDAMENTAL AGRICULTURAL AND ENVIRONMENTAL SCIENCE WHILE PROVIDING NEW TECHNIQUES AND METRICS TO ENSURE HEALTHY RICE PRODUCTION WORLDWIDE. THIS PROJECT ALIGNS WITH THE AFRI EWD PREDOCTORAL FELLOWSHIP GOALS AND PRIORITY AREAS 4 AND 3.