MICRO X-RAY FLUORESCENCE AS A TOOL FOR UNDERSTANDING SPATIAL DISTRIBUTIONS OF CRITICAL MINERALS IN AQUIC SOILS

Critical minerals, which include trace metals and rare earth elements (REEs), are crucial for maintaining the economy, national security, and the advancement of renewable energy. They are present in soils and their concentration varies due to natural soil formation processes or by contamination of soil by anthropogenic means. We use micro-X-Ray Fluorescence (m-XRF) to explore how enrichment and depletion of these critical minerals affects their spatial distribution in soils. Using this technique, we were able to find cobalt (Co) and cerium (Ce) enrichment in iron (Fe)-manganese (Mn) concretions (FMC). The Co is preferentially enriched in the Fe-portion of the FMC, whereas Ce is co-located with Mn. Unlike bulk geochemical methods which have trouble disentangling the different Ce pools (e.g., lithogenic vs. pedogenic), the m-XRF technique used here shows a direct association between Ce and soil redox processes documented in the FMC. We aim to further explore these associations using aquic soils with varying age and topographic position, which may elucidate the cycling of these critical minerals during soil redox cycles. Understanding how these critical minerals interact with soil is essential for understanding the effects of weathering on the distribution of REEs in soils, and for designing remediation techniques for contaminated soils.