The shallow and deep hypothesis: linking flow paths, biogeochemical reactions, and stream chemistry in the Critical Zone - Li Li, Penn State University

Li Li, Professor, Department of Civil and Environmental Engineering, Penn State University

Abstract: 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.

About the Speaker: Dr. Li Li is a professor in Environmental Engineering at Penn State University. Li received a bachelor and master’s degree in environmental chemistry from Nanjing University in China and a doctoral degree in environmental engineering and water resources from Princeton University. She worked at the Lawrence Berkeley National Laboratory as a postdoc and as a research scientist before joining faculty at Penn State University. Her group asks questions on how external drivers and internal structure regulate water flow paths and biogeochemical processes at the watershed scale under diverse climate, geology, and land use conditions. She is active in the Critical Zone community, and collaborates broadly with biogeochemists, hydrologists, ecologists, and geologists. She has been promoting woman scientists’ work via the Women Advancing River Research (WARR) seminar series.



Start date
Tuesday, Sept. 14, 2021, 3 p.m.