Earth Sciences Division (ESD) Department of Energy (DOE) Lawrence Berkeley National Laboratory (LBNL)

Geochemistry Department Core Capability:
Molecular Geochemistry and Nanogeoscience

This research field studies the fundamental, molecular-scale phenomena that underpin biogeochemical processes in the natural world and includes a significant effort addressing the properties and environmental roles of natural nanoparticles. Research topics include studies of the surface structure and hydration of environmentally important minerals using x-ray scattering and spectroscopy combined with molecular dynamics (MD) simulation; MD studies of interlayer-solvated cations in clays; ferrihydrite nanoparticle aggregation and sorption reactions; determination of the speciation and formation kinetics of ferric iron oxyhydroxide precipitation on quartz; and studies of the solvation environment of contaminant and nutrient molecules in aqueous solution.

Many of the studies employ newly developed capabilities such as in situ and grazing-incidence synchrotron x-ray methods to study surface structure, heterogeneous nucleation and aggregate formation; time-resolved optical and x-ray methods for following interfacial chemical reactions; and nonlinear laser spectroscopy for studying water at interfaces. In addition to existing Berkeley laboratories, ESD hosts a newly renovated nanogeoscience laboratory for the synthesis and characterization of natural nanomaterials and their analogues. X-ray studies are carried out at Berkeley Lab’s Advanced Light Source as well as other synchrotron sites, electron microscopy is performed at the National Center for Electron Microscopy (NCEM), and MD and ab initio simulations are performed on the dedicated geochemistry computing cluster, as well as the the National Energy Research Scientific Computing (NERSC) facility. Kinetics studies, mainly focusing on heterogeneous precipitation reactions, are also conducted collaboratively with the National Science Foundation Environmental Molecular Science Institute (NSF EMSI) at Pennsylvania State University.

The Earth Sciences Division is leading the construction of a new synchrotron Fourier transform Infrared beamline at the Advanced Light Source.  The new facility will have unprecedented spectra range and will be used for real-time imaging of important biological and environmental processes. This effort involves fundamental studies on the nature of the aqueous solution/mineral interface, the structure and reactivity of minerals at the molecular scale, solvated ions and colloids down to the nanometer scale, and the properties and aggregation behavior of nanoparticles. Current work includes: molecular-dynamics modeling of hydrated interlayers in clays, the aggregation dynamics of iron oxide nanoparticles, the structure of water on mineral surfaces; studies of the diffusion of ions and molecule solvation environment of contaminant and nutrient molecules in aqueous solution; determination of the molecular identity and kinetics of formation of iron oxide precipitates on quartz surfaces; and characterization of the surface chemistry and structure of environmentally important minerals using molecular simulation, x-ray scattering, and x-ray spectroscopy. A new initiative aims at probing redox reactions at mineral surfaces in microsecond to picosecond time regimes, with the aim of better understanding and controlling reductive dissolution and pyrite oxidation processes responsible for acid mine drainage (AMD) pollution.

Many of the studies employ newly developed capabilities such as synchrotron x-ray grazing-incidence methods, a unique (homemade) Hydrothermal Atomic Force Microscope (HAFM), and laser-based phase-sensitive nonlinear optical spectroscopy. Studies of the aqueous behavior of organic species on mineral surfaces and in solution, and on nanoparticle structure, are carried out at the DOE-LBNL Advanced Light Source as well as other DOE synchrotron sites. The group also does extensive collaborative research using the National Center for Electron Microscopy (NCEM) at Berkeley Lab and takes advantage of the National Energy Research Scientific Computing (NERSC) facility (also at Berkeley Lab), as well as other computational sources for large-scale molecular dynamics and ab initio quantum mechanical simulations. Kinetics studies, mainly focusing on heterogeneous precipitation reactions, are also conducted collaboratively with the National Science Foundation Environmental Molecular Science Institute (NSF EMSI) at Pennsylvania State University. In addition, we are studying the kinetics of mineral surface relaxation in response to fluid chemistry changes and the coupling between surface stress and mineral dissolution and growth, including the effect of fluid chemistry and temperature on subcritical crack growth.