Dynamics of transient tracers in the Satoyama spring

-Impact of temperature change on the CFCs and SF₆ concentrations-

Abstract

To understand the dynamics of transient tracers in the spring with small catchment area, a small spring in suburban area, namely Satoyama, nearby Nagoya city was sampled weekly for 1 year and the major dissolved chemical components concentrations, stable isotope ratios, CFCs and SF₆ concentrations were determined. The water chemistry and stable isotope ratio results suggest that the spring water seems to be sourced by the young groundwater with a residence time less than few years. The CFC-12 and SF₆ concentrations show a clear seasonal trend, higher in summer and lower in winter, and the variation range of concentration corresponds to the residence time of 10 years in the spring water. The 10 years variation of residence time is not interpreted reasonably by the hydro-geochemical data. The concentrations of CFC-12 and SF₆ in the spring were negatively correlated with the water temperature, indicating that the spring water is in contact with ambient air through the discharge process. These results suggest that careful consideration should be necessary when applying gaseous tracer method to small-scale springs with fluctuations in water temperature.