Porosity in Reactive Geochemical Systems

Despite the importance of geochemical reactions in many natural and engineered systems, we have not been able to measure geochemical reaction-rate constants in the laboratory in such a way to be consistent with field observations. Laboratory measured mineral dissolution rates are often two to six orders of magnitude faster than effective reaction rates measured in field systems, partly due to the impact of heterogeneity and fluid flow on geochemical reactions in field systems that are not accurately represented in laboratory experiments. To advance our ability to predict geochemical processes and their products in field systems we need a better understanding of how fluid flow and geochemical reactions are coupled at scales ranging from pores to watersheds. Recent advances in experimental techniques to quantify surface area and porosity at nanometer to micron length scales using neutron scattering are described that provide an opportunity to advance our understanding of coupled reactive transport at the pore scale.