A Study on the Quantitative Recovery of Dissolved Inorganic Carbonates in Ground Water for Radiocarbon Measurement

방사성탄소 측정을 위한 지하수 중에 용존된 무기탄소 화합물의 정량적 회수 연구

  • Received : 1999.03.06
  • Published : 1999.08.25

Abstract

Dissolved inorganic carbonates in ground water were quantitatively recovered by using gas evolution method. Gas evolution method was found to be less time-consuming, less susceptible to the contamination fromatmospheric $CO_2$ and little affected by the sulfate ions in comparison to the direct precipitation method. Extraction efficiency of nearly 99% could be achieved by gas evolution method in two hours using recirculated gas at a sweeping rate of 4 liter per minute. Samples for carbon isotope fractionation study were collected in three fractions with collection times. The evolution time for the first fraction was one hours, and then second and third fractions were collected at intervals of 30 minutes, respectively. A small portion of each fraction was analyzed to evaluate ${\delta}^{13}C$ values, which were measured to be -7.9‰, -3.0‰ and +0,4‰ for the each fraction. The result clearly indicated that gas evolution method generates isotopically lighter carbon at the beginning of the purging process and heavier isotopes at the end. However, this isotope fractionation effect could be neglected by the almost complete recovery of carbonates.

Keywords

ground water;gas evolution method;isotope fractionation;radiocarbon

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Acknowledgement

Supported by : 한국전력연구원