Chemical evolution of a travertine-depositing stream: geochemical processes and mass transfer reactions
This field study focuses on quantitatively defining the chemical changes occurring in Falling Spring Creek, a travertine-depositing stream located in Alleghany County, Virginia. The processes of CO/sub 2/ outgassing and calcite precipitation or dissolution control the chemical evolution of the stream. The observed chemical composition of the water was used with the computerized geochemical model WATEQF to calculate aqueous speciation, saturation indices, and CO/sub 2/ partial pressure values. Mass balance calculations were performed to obtain mass transfers of CO/sub 2/ and calcite. Reaction times, estimated from stream discharge, were used with the mass transfer results to calculate rates of CO/sub 2/ outgassing and calcite precipitation between consecutive sampling points. The stream, which is fed by a carbonate spring, is supersaturated with respect to CO/sub 2/ along the entire 5.2-km flow path. Outgassing of CO/sub 2/ drives the solution to high degrees of supersaturation with respect to calcite. Metabolic uptake of CO/sub 2/ by photosynthetic plants is insignificant, because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic CO/sub 2/ outgassing to occur. Calcite precipitation is kinetically inhibited until near the crest of a 20-m vertical waterfall. Calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of CO/sub 2/. Physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1.0 km below the falls. Net calcite precipitation occurs at all times of the year but is greatest during low-flow conditions in the summer and early fall.
- Research Organization:
- Univ. of Virginia, Charlottesville (USA)
- OSTI ID:
- 6682598
- Journal Information:
- Water Resour. Res.; (United States), Vol. 24:9
- Country of Publication:
- United States
- Language:
- English
Similar Records
Geochemical and petrographic analyses of travertine-precipitating waters and travertine deposits, Arbuckle Mountains, Oklahoma
Calcite precipitation rates in the field: Measurement and prediction for a travertine-depositing stream
Related Subjects
CALCITE
PRECIPITATION
CARBON DIOXIDE
MASS TRANSFER
STREAMS
GEOCHEMISTRY
TRAVERTINE
DEPOSITION
COMPUTERIZED SIMULATION
DISSOLUTION
VIRGINIA
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHALCOGENIDES
CHEMISTRY
FEDERAL REGION III
LIMESTONE
MINERALS
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SIMULATION
SURFACE WATERS
USA
520200* - Environment
Aquatic- Chemicals Monitoring & Transport- (-1989)