Geochemical and Biogeochemical Processes
Pacific Northwest National Laboratory scientists stand in front of a state-of-the-art molecular beam-surface scattering and kinetics instrument. This unique instrument allows us to investigate the dynamics and kinetics of surface interactions in unprecedented detail. Such interactions are clearly important from an environmental viewpoint, since they form the molecular-level basis for the complex physiochemical processes that take place on the surface of atmospheric aerosols, at the aqueous-mineral geochemical interface, and at the vapor-liquid interface. Enlarged View
The Chemical & Materials Sciences Division has a signature capability in geochemistry and biogoechemistry that is focused on unraveling the fundamental biogeochemical interactions between minerals, solutions, and micro-organisms that occur in geologic environments. The program emphasizes developing a molecular level understanding of these interactions through the use of advanced surface spectroscopies and molecular and thermodynamic modeling simulations.
Understanding the fundamental nature of biogeochemical reactions (e.g., their identity, kinetics, and thermodynamics) is the key to determining the fate and transport of energy-derived contaminants in subsurface systems, developing effective remediation strategies for clean-up of U.S. DOE legacy nuclear production facilities and other contaminated sites, and maintaining global water quality (surface and groundwater) as populations increase. Determining the specific molecular-level mechanisms that determine these reactions as well as the location of contaminants in the environment is our key scientific challenge.
Some questions being addressed by our research include the following:
- What are the structure, molecular architecture, and electrolyte/solvent properties of the mineral-microbe interface?
- How can molecular mechanisms of oxidation/reduction at mineral-water interfaces be determined and how can they be used to predict macroscopic reactivity?
- What factors control the spatial distribution of different functional organism groups in heterogeneous natural materials, and how do spatially distinct organism groups interact to control microscopic and macroscopic geochemical processes?
- What biologic and abiotic molecular interactions/reactions occur at the mineral-microbe interface to regulate energy, chemical, and electron flux to and from microorganisms, and the environmental fate of contaminants?
The research program integrates three "world-class" research disciplines at PNNL: environmental microbiology, geochemistry and mineral surface science, and computational chemistry while drawing heavily on other capabilities in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) to develop a fundamental scientific understanding of how contaminants interact with natural materials. The research includes investigations of molecular biogeochemical mechanisms utilizing the EMSL user facility, experimental geochemistry and biogeochemistry investigations of the mineral-water and mineral-microbe interface supported by BES and OBER, computational geochemical studies of mineral surfaces and contaminant interactions supported by BES and EMSP, and field study of the macroscopic function of these processes in contaminated Hanford subsurface environments that are in dire need of scientific understanding and innovative cleanup techniques.
Future research efforts will build upon new Office of Science investments in nanoscience to determine the role of nanoparticles in natural environments. We will also build upon new microbiological culturing and other techniques developed as part of Genomes to Life research. Computational chemistry will continue to play a central role in unraveling the specific contributions of individual molecular-level processes. These future efforts include
- Development of new culture techniques to allow the quantification of fundamental electron transfer or biomineralization rates in mineral-microbe systems under controlled growth and metabolic conditions that simulate in-situ conditions.
- Development of high-resolution micro-beam spectroscopies and microscopies to enable study of the microscopic structures, chemistries, and architectures of mineral-water and the microbe-mineral interfaces at different stages of chemical reaction.
- Application of microbial genome information to develop research organisms of defined function to test hypotheses on key molecular biogeochemical mechanisms (e.g., the roles of specific membrane-bound cytochromes or proteins used for adhesion).
- Continued development of high-performance computing software and hardware for 1) molecular simulations of solution phase and interfacial structures, and 2) modeling of integrated whole microorganism processes, as well as the inclusion of mechanistic models in field-scale reactive transport simulations.
Molecular Dynamics simulation of the hydration and protonation of the 021 and 110 surfaces of goethite. Enlarged View
The impact of this research is an enhanced understanding of geochemical and biogeochemical controls on contaminant fate and transport on DOE lands; new insights on the local workings of biogeochemical cycles that are driven by interfacial reactions, such as those involving Fe, Mn, and trace metals; and applications for energy production technologies dependent upon oil and gas utilization. Concepts for new environmental technologies or engineered nanoscale machines may emerge from a newfound understanding of the molecular mechanisms of biogeochemical processes that occur in the mineral-microbe interface. Over the long term, this research will add to our understanding for maintaining and preserving the balance of the various biogeochemical cycles that integrate to allow a life-sustaining chemical environment on the earth.