In-situ synchrotron X-ray reflectivity measurements at the calcite-water interface

Journal Article · Sun Aug 01 04:00:00 EDT 1993 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(93)90356-2· OSTI ID:5577443

Chiarello, R P; Wogelius, R A; Sturchio, N C ^[1]

---

1. Argonne National Lab., IL (United States)

In-situ synchrotron X-ray reflectivity (SXR) measurements of the calcite-water interface were made. These data were used to model the angstrom-scale interfacial width and electron density profile of the interface. Measurements were made on the (10T4) cleavage surface of Iceland spar calcite in contact with pure N[sub 2], humid N[sub 2], deionized water, and dilute nitric acid solutions at 25[degrees]C. The measurements were performed in an X-ray transparent reaction cell in which fluid pH was monitored during SXR data acquisition. Analysis of the data indicated that the pristine calcite surface in contact with pure N[sub 2] has an interfacial width (statistical roughness) of 2.60 [+-] 0.15 [angstrom]. Exposure to water vapor (humid N[sub 2]) resulted in the deposition of a water film 19.9 [+-] 0.4 [angstrom] thick. There was no evidence from the SXR data that the adsorbed water film caused roughening of the calcite surface. However, when reacted with deionized water the calcite was roughened, yielding an interfacial width of 23.1 [angstrom]. During successive reactions with fluids having decreasing initial pH the calcite/fluid interfacial width increased from 23.1 to 45.3 [angstrom]. The SXR results indicate that intraterrace areas participate in the dissolution of calcite. A linear correlation was observed between interfacial width of the intraterrace areas and the quantity of calcite dissolved. 22 refs., 8 figs., 1 tab.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5577443
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 57:16; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400101* -- Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures
BREMSSTRAHLUNG
CALCITE
CARBONATE MINERALS
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
ENVIRONMENTAL TRANSPORT
FLUIDS
GASES
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INTERFACES
IONIZING RADIATIONS
MASS TRANSFER
MINERALS
NITRIC ACID
OXYGEN COMPOUNDS
RADIATIONS
ROCK-FLUID INTERACTIONS
SPECTROSCOPY
SYNCHROTRON RADIATION
VAPORS
WATER
WATER VAPOR
X RADIATION
X-RAY SPECTROSCOPY