Intriguing unanswered questions about reactions between mineral
surfaces and solutions exist in many subfields of geology. At low
temperatures near Earth's surface, reactions between dissolved and
particulate constituents of natural waters and mineral surfaces control
global and local-scale processes such as weathering, diagenesis, and
mobility of environmental contaminants. A fundamental understanding
of processes and reactions at mineral surfaces is highly relevant
to other disciplines such as materials science and medical science.
|Construction of double-shelled
tanks at U.S. Department of Energy site in Hanford, Washington
(left); salt-cake remaining in single-shelled tank (right)
We focus our research on developing new insights into and quantifying
mechanisms and rates of surface-mediated processes such as dissolution,
growth, and sorption, and then applying our results to a wide variety
of geological and real-world problems. We also work on the chemistry
of systems that occur at extreme limits of the natural world or are
ephemeral on a geologic time-scale but important at the human time-scale.
Currently, we are quantifying reactions pertinent to the interaction
of radioactive solutions leaked from waste tanks with subsurface sediments
at Hanford, Washington; reactions between natural organic matter and
mercury or clay minerals; and reactions specific to the mica-water
and quartz-water interfaces. We use experimental and surface analytical
approaches such as atomic force microscopy and synchrotron X-ray reflectivity
to quantify reaction kinetics and theoretical approaches such as solution
modeling and molecular modeling to guide and interpret experimental
electron microscopy image of the feldspathoid mineral cancrinite
precipitated on quartz reacted with simulated Hanford tank solutions
(Bickmore et al., 2001)
The Hanford studies are addressing how radioactive and toxic contaminants
released during failure of underground storage tanks may be transported
or immobilized in the subsurface. We have focused on understanding
rates and mechanisms of quartz and biotite dissolution and secondary
mineral formation in the high pH, high aluminum, and high nitrate
solutions characteristic of the tank waste. Release of silicon from
quartz contributes to precipitation of secondary aluminosilicates
that can incorporate radioactive contaminants such as cesium. Release
of iron(II) from biotite is considered to be the primary source of
reductant species for conversion of chromate to chromium(III), a relatively
immobile form of this toxic element.
Mercury interactions with natural organic matter control mercury's
bioavailability in the environment. In collaboration with George Aiken
of the U.S. Geological Survey and Joseph Ryan of the University of
Colorado, we study reactions among humic substances, aqueous mercury,
and cinnabar to determine how much mercury is unavailable for uptake
by organisms. We are also investigating how natural organic matter
plays a role in the nucleation of clay minerals.
force microscopy image of iron-oxyhydroxide lepidocrocite particles;
particle size and shape is related to sorption of cadmium (Manceau
et al., 2000)
The structure of an aqueous solution near a mineral surface is central
to understanding empirical observations and theoretical models of
reactions such as sorption, dissolution, or growth. We are investigating
the molecular-scale structure of water and salt solutions at their
interface with mica, an analogue for clay minerals, and quartz. The
work is being performed using X-ray reflectivity at the Advanced
Photon Source , Argonne National Laboratory in collaboration with
Paul Fenter and Neil Sturchio. We also quantify the size and shape
of environmental mineral particles from the nano- to micron-scales
using atomic force microscopy (AFM) and relate surface areas measured
by AFM to reactivity.
Selected Publications (2005-2008):
Lee S. S., Fenter P., Park C.Y. and Nagy K.L., 2008, Fulvic acid sorption on mica as a function of pH and time using in-situ X-ray reflectivity, Langmuir 24, 7817-7829.
Manceau A. and Nagy K. L., 2008, Relationships between Hg(II)-S bond distance and Hg(II) coordination in thiolates, Dalton Transactions, 1421-1425, COVER, DOI: 10.1039/b718372k
Manceau A., Nagy K. L., Marcus M. A., Lanson M., Geoffroy N., Jacquet T., and Kirpichtchikova T., 2008, Formation of metallic copper nanoparticles at the soil-root interface, Environmental Science & Technology, in press, ASAP Article, 10.1021/es072017o.
Soderholm L., Skanthakumar S., Gorman-Lewis D., Jensen M. P., and Nagy K. L., 2008, Characterizing solution and solid-phase amorphous uranyl silicates. Geochimica et Cosmochimica Acta 72, 140-150.
Bickmore B. R., Wheeler J. C., Bates B., Nagy K. L., Eggett D. L., 2008, Reaction Pathways for Quartz Dissolution Determined by Statistical and Graphical Analysis of Macroscopic Experimental Data, Geochimica et Cosmochimica Acta 72, 4521-4536.
Lee S. S., Nagy K. L., and Fenter P., 2007, Distribution of barium and fulvic acid at the muscovite solution interface using in-situ X-ray reflectivity. Geochimica et Cosmochimica Acta 71, 5763-5781.
Park C., Fenter P., Nagy K. L., and Sturchio, N. C., 2006, Hydration and distribution of ions at the mica-water interface. Physical Review Letters 97, 016101.
Schlegel M. L., Nagy K. L., Fenter P., Cheng L., Sturchio N. C., and Jacobsen S. D., 2006, Cation sorption on the muscovite (001) surface in chloride solutions using high-resolution X-ray reflectivity, Geochimica et Cosmochimica Acta 70, 3549-3565.
Bickmore B. R., Nagy K. L., Gray, A. K., and A. R. Brinkerhoff, 2006, The effect of Al(OH)4- on the dissolution rate of quartz, Geochimica et Cosmochimica Acta 70, 290-305.
Waples J. S., Nagy K. L., Aiken G. R., and Ryan J. N., 2005, Dissolution of cinnabar (HgS) in the presence of natural organic matter. Geochimica et Cosmochimica Acta 69, 1575-1588.
Samson S. D., Nagy K. L., and Cotton, Worth B., III., 2005, Transient and steady-state dissolution of biotite at 22-25 °C in high pH, sodium, nitrate, and aluminate solutions. Geochimica et Cosmochimica Acta 69, 399-413.