Arsenic Coordination in Naturally Occurring Minerals and Salts
EMSL Project ID
21390
Abstract
Arsenic is ubiquitous in soils and marine sediments, is a frequent by-product of smelting operations and coal-fired powerplants, is a common component of wood preservatives, and was traditionally used in pesticides. Chronic exposure to ppm levels of arsenic has been linked to cancer (particularly skin cancer), arteriosclerosis and other cardiovascular diseases, chronic liver disease, and in some cases genetic mutation. While arsenic speciation and toxicity have been studied for many years, there are few data regarding the molecular-level dynamic behavior of arsenic in soil systems and at mineral surfaces. Our goal is to understand the structural and dynamical behavior of arsenic species sorbed by phyllosilicates, crystalline and amorphous oxyhydroxide surfaces, and layered double-hydroxide materials using high field NMR. Solid-state arsenic NMR studies have been quite limited due to the large quadrupole moment of 75As (0.314 x 10-28 m2), which reportedly leads to quadrupole couplings of greater than 50 MHz in some amorphous systems. As previously demonstrated by numerous authors, the reduced central transition line-width provided by stable high magnetic fields combined with a frequency-stepped quadrupolar Carr-Purcell-Meiboom-Gill (QCPMG) experiment is an appropriate, time efficient, and generally applicable approach to solid-state NMR of challenging nuclei such as 75As. In our initial efforts, we will interrogate the arsenic coordination environment in salts and naturally occurring arsenic minerals with arsenic in the As(III) and As(V) oxidation states. This research will provide a foundation for continued studies of arsenic sequestration, speciation, and dynamics in soil constituents. Completion of our overall objectives will certainly involve subsequent visits to PNNL and will result in a number of publications.
Project Details
Project type
Capability Research
Start Date
2006-12-01
End Date
2007-03-20
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bowers GM, RJ Kirkpatrick. 2007. "High Field 75As NMR Study of Arsenic Oxysalts." Journal of Magnetic Resonance 188: 311-321.
Bowers GM, RJ Kirkpatrick. 2007. "High-field 75As NMR Study of Arsenic Oxysalts." Journal of Magnetic Resonance, in press.
H2O and cation structure and dynamics in expandable clays: H-2 and K-39 NMR investigations of hectorite Author(s): Bowers GM, Bish DL, Kirkpatrick RJ Source: JOURNAL OF PHYSICAL CHEMISTRY C Volume: 112 Issue: 16 Pages: 6430-6438 Published: APR 24 2008