Modeling the Fate of Root Exudates and Their Effects on Cesium Partitioning in the Rhizosphere

摘要

A conceptual model is being developed for prediction of cesium (Cs) partitioning between bound (Cs_b), aqueous (Cs_a), and phytoextracted (Cs_p) phases in the rhizosphere. The model categorizes the processes that impact cesium partitioning into six sub-models: geochemistry, physical factors, root density, microorganisms, nutrients, and root exudates. A seventh sub-model (Cs fate) describes Cs movement between the three phases. Functional relationships and parametric values within and between the sub-models are being developed based on literature, field characterization, and laboratory experiments. Sensitivity analyses were conducted to evaluate the effects of root density, microbial population, potassium requirement and concentration, and moisture content on the concentration of root exudates ([E]) and consequently on Cs partitioning. In summary, the model provides a framework for better understanding the fundamental processes that control Cs fate in the rhizosphere. The ability to better understand, predict, and control Cs solubilization could be applied to other metals in the future. Ultimately, the model will be used as a tool for enhancing field implementation of in situ solubilization of metals for a variety of remedial activities.