Experimental determination of chlorine isotope separation factor by anion-exchange chromatography

Chlorine isotope fractionation factor was determined by strongly basic anion-exchange chromatography with 0.1 mol/l HCl at 25 °C. The magnitude of the factor was calculated as a single-stage separation factor of 1.00030 with analytical precision of 0.00006 (1σ). The results showed that the lighter isotope () was preferentially fractionated into the resin phase, while the heavier one () enriched into the aqueous phase. This trend suggested that the hydrated Cl⁻ ions in the aqueous phase were slightly more stable than the hydrated Cl⁻ ions electrostatically interacting with the ion-exchange groups of the resin.     

Chlorine isotope fractionation associated with volcanic activity at the Kusatsu-Bandaiko hot spring in Japan

Stable chlorine isotope compositions (δ³⁷Cl, per-mil: ‰, vs. a standard sample of sea water) of Kusatsu-bandaiko hot water samples, taken regularly in the years between 1974 and 1995 in the Kusatsu-Shirane volcanic region, Japan, were measured mass-spectrometrically. The results show that the δ³⁷Cl values of the waters taken before 1984 were at around?0.12‰, whereas those after 1984 were at around+0.18‰. The δ³⁷Cl values are thus distinct across 1984, which is consistent with the classification by the Cl to S molar ratio (Cl/S): the higher the Cl/S ratio, the larger the δ³⁷Cl value. The δ³⁷Cl value increased as much as 0.30‰ during 5 years between 1980 and 1984. This isotopic enrichment is likely correlated with increasing Cl/S ratios, suggesting that the heavier isotope (³⁷Cl) may have preferentially increased in the original Cl source of the hot spring across 1984 when volcanic activity likely increased at Mt Kusatsu-Shirane.     

Anion-exchange chromatographic study of the chlorine isotope effect accompanying hydration

The single-stage separation factor for chlorine isotopes ((35)Cl and (37)Cl) was determined to be 1.00034 by anion exchange chromatography on a 4.5-m column operated in reverse breakthrough manner at 25 degrees C. This value is in good agreement with those obtained in our previous works. It was confirmed that the lighter isotope ((35)Cl) was preferentially fractionated into the resin phase, whereas the heavier isotope ((37)Cl) partitioned into the aqueous phase. This observation, however, contradicts the experimental results for Cl isotope fractionation during NaCl precipitation and the recent theoretical results on Cl isotope fractionation: the (37)Cl isotope selectively enriched into the solid phase and not into the aqueous phase. This discrepancy is discussed based on the theory of isotope distribution between two phases. It is suggested that the chromatographic results reflect an isotope effect accompanying hydration rather than an isotope effect due to a phase change, whereas the reverse is the case for the results in the NaCl precipitation study.     

Chlorine isotope fractionation associated with volcanic activity at the Kusatsu-Bandaiko hot spring in Japan

Stable chlorine isotope compositions (delta(37)Cl, per-mil: per thousand, vs. a standard sample of sea water) of Kusatsu-bandaiko hot water samples, taken regularly in the years between 1974 and 1995 in the Kusatsu-Shirane volcanic region, Japan, were measured mass-spectrometrically. The results show that the delta(37)Cl values of the waters taken before 1984 were at around-0.12 per thousand, whereas those after 1984 were at around+0.18 per thousand. The delta(37)Cl values are thus distinct across 1984, which is consistent with the classification by the Cl to S molar ratio (Cl/S): the higher the Cl/S ratio, the larger the delta(37)Cl value. The delta(37)Cl value increased as much as 0.30 per thousand during 5 years between 1980 and 1984. This isotopic enrichment is likely correlated with increasing Cl/S ratios, suggesting that the heavier isotope ((37)Cl) may have preferentially increased in the original Cl source of the hot spring across 1984 when volcanic activity likely increased at Mt Kusatsu-Shirane.