Effect of an acid rain environment on limestone surfaces
As part of a study to assess mineralogical alterations in building stone caused by acid rain, Salem limestone samples were exposed for one year in several urban and one rural environments. Samples exposed in the rural location were chemically indistinguishable from the freshly quarried limestone (control material). All samples collected from urban exposure sites developed gypsum stains on the grounding surfaces, where the stones were unwashed by precipitation. However, the bulk chemistry of the urban samples (not including the stain) was virtually identical to that of the control stone. Sulfur (in the form of sulfate) was disseminated over the calcite grain surfaces to a depth less than 10 nanometer in the freshly quarried limestone; an identical sulfate layer was found on the calcite grains after the 1-y exposure period. Mass balance calculations and sulfur isotope patterns indicate that the gypsum stain on the protected surfaces consists of adventitious sulfur. A model, involving the attack of SO/sub 2/ on dry calcite, was used to define the conditions for stain formation on dry, protected surfaces. This suggests that under arid conditions, once the surface has been saturated with gypsum, the quantity of stain deposited on an unwashed surface is independent of atmospheric SO/sub 2/ concentration. On rain-washed surfaces experiencing gas-solid attack during intermittent dry periods, the quantity of gypsum produced by a gas-solid reaction mechanism should strongly correlate with both the frequency of rain events and the atmospheric SO/sub 2/ level, provided that the rain events are frequent and clearly delimited by periods of dryness.
- Research Organization:
- US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 (USA)
- OSTI ID:
- 5310640
- Journal Information:
- Mater. Performance; (United States), Vol. 26:11
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
54 ENVIRONMENTAL SCIENCES
LIMESTONE
CORROSION
ENVIRONMENTAL EFFECTS
SULFATES
CORROSIVE EFFECTS
WASHOUT
ACID RAIN
CALCITE
ENVIRONMENTAL TRANSPORT
GYPSUM
ISOTOPE RATIO
POLLUTANTS
SULFUR DIOXIDE
SURFACE FINISHING
ALKALINE EARTH METAL COMPOUNDS
ATMOSPHERIC PRECIPITATIONS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CALCIUM SULFATES
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHALCOGENIDES
CHEMICAL REACTIONS
MASS TRANSFER
MINERALS
OXIDES
OXYGEN COMPOUNDS
PRECIPITATION SCAVENGING
RAIN
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SULFATE MINERALS
SULFUR COMPOUNDS
SULFUR OXIDES
360604* - Materials- Corrosion
Erosion
& Degradation
500200 - Environment
Atmospheric- Chemicals Monitoring & Transport- (-1989)