Inorganic calcite precipitation in Tartare karstic spring (Lazio, central Italy): field measurements and theoretical prediction on depositional rates.

Autor: Bono, P., Dreybrodt, W., Ercole, S., Percopo, C., Vosbeck, K.
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Zdroj: Environmental Geology; Dec2001, Vol. 41 Issue 3/4, p305-313, 9p
Abstrakt: Precipitation rates of calcite, the hydro-chemistry of the stream water and flow conditions along a travertine depositing perennial karstic stream were investigated along a stream of 100 m in length. Four sites were selected, where marble tablets of 3×3×0.3 cm3 were mounted. At each site tablets were placed into fast flowing water at the top of rimstone dams and into stagnant water in the pool nearby. Precipitation rates were obtained from the weight increase after the samples had been immersed for 4 days. Temperature, pH, electrical conductivity, and the concentrations of Ca2+, Mg2+, HCO-3, PO3-4, NO-3 atm at the spring to 6×10-4 atm 100 m downstream enhancing precipitation of CaCO3 downstream. The precipitation rates measured are compared with theoretical rates derived from the hydrochemistry and flow conditions. This confirms earlier findings on the dependence of travertine deposition on the hydrodynamic flow conditions. Deposition rates in fast flow are higher by a factor of about four compared with those in still water. Although phosphate is present in the spring water, precipitation is only moderately inhibited. Finally, a simple test procedure is presented to select sites where precipitation is likely to be active. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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