C and O stable isotopic signatures of fast-growing dripstones on alkaline substrates: reflection of growth mechanism, carbonate sources and environmental conditions.
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.
Department of Environmental Sciences, Jožef Stefan Institute, Ljubljana, Slovenia. sasa.zavadlav@ijs.si
Saša
S
Zavadlav
Darja
D
Mazej
Janez
J
Zavašnik
Aleksander
A
Rečnik
David
D
Dominguez-Víllar
Neven
N
Cukrov
Sonja
S
Lojen
D002247:Carbon Isotopes / Q000032:analysis; D002254:Carbonates / Q000737:chemistry*; D002980:Climate; D003252:Construction Materials / Q000032:analysis*; D017523:Croatia; D004784:Environmental Monitoring / Q000379:methods*; D055593:Geological Phenomena; D019083:Mediterranean Region; D010103:Oxygen Isotopes / Q000032:analysis; D017524:Slovenia
D002247:Carbon Isotopes; D002254:Carbonates; D010103:Oxygen Isotopes