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- Title
Long term temporal change of sulfur hexafluoride concentration in spring water at a forested headwater catchment.
- Authors
Nagano, Kosuke; Tsujimura, Maki; Sakakibara, Koichi; Sugiyama, Ayumi; Iwagami, Sho; Onda, Yuichi
- Abstract
We monitored the Sulfur hexafluoride (SF6) concentration in the air, the spring and thegroundwater to estimate the residence time of the water from April 2015 through May 2018at a small forested headwater catchment underlain by granite in Fukushima, Japan. The SF6concentration in the air ranged from 9.2 pptv to 14 pptv, and it temporally increased with agradient of 0.5 pptv/year. Also, the SF6 concentration in the spring water ranged from 3.5 fmol/L to 4.6fmol/L during this period, corresponding to the concentration ranging from 9.9pptv to 12.8 pptv in the air with increasing rate of 0.4 pptv/year based on Henry’sequilibrium law between the air and the water. Thus, the temporal change of SF6concentration in the spring water shows the same trend as that of the air in thewatershed with a time lag of a few years. In addition, the apparent SF6 age in the springranged from 2 years to 7 years in the base flow condition except for the rainfall eventperiods. Therefore, the time lag of the temporal change in the SF6 concentrationbetween the air and the spring agrees well with the apparent SF6 age in the springwater. Consequently, these results show that the groundwater flow in the watershedcould be represented displacement piston flow model, and the temporal changepattern of SF6 concentration in the air is conserved well in the groundwater withinthe watershed. Also, the SF6 has a temporal information as two aspects, one isapparent age and the other is conservative temporal pattern such as stable isotopes.
- Subjects
WATER springs; SULFUR hexafluoride; GROUNDWATER flow; STABLE isotopes; SOIL air; GROUNDWATER; AQUIFERS
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article