C and O Stable Isotopic Signatures of Fast-Growing Dripstones on Alkaline Substrates: Reflection of Growth Mechanism, Carbonate Sources and Environmental Conditions

Isotopes Environ Health Stud. 2012 Jun;48(2):354-71. doi: 10.1080/10256016.2012.645540. Epub 2012 Feb 9.

Abstract

Secondary carbonate precipitates (dripstones) formed on concrete surfaces in four different environments--Mediterranean and continental open-space and indoor environments (inside a building and in a karstic cave)--were studied. The fabric of dripstones depends upon water supply, pH of mother solution and carbonate-resulting precipitation rate. Very low δ(13)C (average-28.2‰) and δ(18)O (average-18.4‰) values showed a strong positive correlation, typical for carbonate precipitated by rapid dissolution of CO(2) in a highly alkaline solution and consequent disequilibrium precipitation of CaCO(3). The main source of carbon is atmospheric or biogenic CO(2) in the poorly ventilated karstic cave, which is reflected in even lower δ(13)C values. Statistical analysis of δ(13)C and δ(18)O values of the four groups of samples showed that the governing factor of isotope fractionation is not the temperature, but rather the precipitation rate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon Isotopes / analysis
  • Carbonates / chemistry*
  • Climate*
  • Construction Materials / analysis*
  • Croatia
  • Environmental Monitoring / methods*
  • Geological Phenomena
  • Mediterranean Region
  • Oxygen Isotopes / analysis
  • Slovenia

Substances

  • Carbon Isotopes
  • Carbonates
  • Oxygen Isotopes