Dear Researchers (and Colloid Lovers), We are delighted to invite you to submit your abstracts to Session B025 on “Colloids and Beyond: Insights into biogeochemical colloid processes in the nano-meter to watershed scale” at the 2021 AGU Fall Meeting (New Orleans, LA and online everywhere). Please submit your abstract here - https://agu.confex.com/agu/fm21/prelim.cgi/Session/119451 Description: Colloids play a significant, but poorly understood role in biogeochemical cycles. Owing to their broad size ranges (1 nm – 1 µm), high surface areas, and enhanced surface reactivities, colloids are involved in a multitude of surface-controlled processes. Because they are typically associated with organic matter, micronutrients, and contaminants, colloids may also serve as transport vectors throughout terrestrial and aquatic systems. Identifying the mechanisms controlling colloid fate (formation/transformation/migration) in heterogeneous and dynamic environments can be accomplished by merging information gathered from molecular-scale colloid characterizations, lab-scale controlled experiments, field-scale hydrological colloid studies, and watershed-scale modelling simulations. This session is a multidisciplinary discussion on colloids in near-surface environments, from the nanometer to watershed scale, and invites studies on topics related to colloids and associated organic-, nutrient-, and metal cycling, reaction pathways, transport and migration, characterization and measurement techniques, and modelling efforts. Invited speakers: Jon Chorover (U of Arizona) and Malgorzata Grybos (Université de Limoges) Sincerely, Maya Engel, SLAC National Accelerator Laboratory and Stanford University Aaron Thompson, University of Georgia Dan Kaplan, Savannah River National Laboratory Vincent Noel, SLAC National Accelerator Laboratory John Bargar, SLAC National Accelerator Laboratory John R. Bargar (“he/ him”) Senior Scientist Geosciences group Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory 2575 Sand Hill Rd Menlo Park, CA. 94025 Office: 650-307-4266