K.D. Nelson Lecture – Dr. Li Li

The Department of Earth & Environmental Sciences in the College of Arts and Sciences presents the K.D. Nelson Lecture Series featuring  speaker Dr. Li Li from Penn State University. Her talk is titled: “The shallow and deep hypothesis: linking flow paths, biogeochemical reactions, and stream chemistry in the Critical Zone ”

Hydrological flow and biogeochemical processes in the Critical Zone (CZ) are intimately coupled, yet their respective sciences have often progressed without as much integration. This lack of integration hinders mechanistic understanding and forecasting of earth surface and water response to human- and climate-induced perturbations. This talk will highlight insights gleaned from integrated hydro-biogeochemical measurements and modeling in the CZ. In particular, recent water chemistry data (carbon, nitrogen, and geogenic solutes) and hydro-biogeochemistry modeling has propelled the idea that shallow and deep flow paths connect waters of distinct chemistries at different subsurface depths to streams under variable flow conditions; and that the extent of shallow versus deep chemistry differences shape concentration-discharge relationship in streams. This idea underscores the importance of subsurface structure and vertical hydrological connectivity relative to the extensively studied horizontal connectivity and topography. Broadly, this hypothesis can potentially serve as a conceptual framework that links CZ subsurface structure to its hydrological and biogeochemical functioning under diverse climate, geology, and land cover conditions.