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Pore Scale, Darcy Scale, Off-Diagonals: Reactive Transport at the Crossroads

February 25 @ 3:00 pm - 4:30 pm

Dr. Carl I. Steefel
Department Head of Geochemistry

What to Expect

Reactive transport in the Earth and Environmental Sciences is at a crossroads today. The discipline has reached a level of maturity well beyond what could be demonstrated even 15 years ago. This is shown now by the successes with which complex and in many cases coupled behavior have been described in a number of natural Earth environments, ranging from corroding storage tanks leaking radioactive Cs into the vadose zone , to field scale sorption behavior of uranium, to the successful prediction of mineral and pore solution profiles in a 226 ka chemical weathering profile, to the prediction of ion transport in compacted bentonite and clay. Classical “plume” or “Darcy-scale” reactive transport is now considered as almost routine these days, with attention shifting to both the pore and watershed. At the pore scale, the models are driven by data that includes a variety of sources ranging from X-ray synchrotron tomography, to FIB-SEM, to back-scattered electron microscopy used to describe pore structure and mineralogical (reactive) composition. These data, some at very high (micron) resolution, some using averaged values at the micro-continuum scale, are being used to simulate small scale processes that may have an outsized impact in highly heterogeneous systems. At the watershed scale, these highly resolved data streams in time and space drive disparate processes like shallow subsurface biogeochemical processes in hillslopes and floodplains, soil production and chemical export, evapotranspiration regulated by plants, and exchange with the atmosphere. Taken together, these coupled processes result in a complex aggregated behavior at the watershed scale that may be difficult to unravel without a new generation of reactive transport models. In the subsurface, in addition to the focus on the pore scale, interest is now shifting to coupled (chemical-hydrological-mechanical-electrical) systems where off-diagonal contributions to fluxes may become important.

Speaker Bio

Carl Steefel is currently a Senior Scientist at Berkeley Laboratory in the Energy Geosciences Division, Earth and Environmental Sciences Area, serving also as head of the Geochemistry Department. He has over 30 years of experience in developing models for multicomponent reactive transport in porous media and applying them to topics in reactive contaminant transport and water-rock interaction. He is the principal developer of the CrunchFlow software, which won an R&D100 Award in 2017 and was named an AGU Fellow in 2019.


Dr. Hang Deng