熱利用のための福井県鯖江盆地地下水系の地球化学的水理解析

抄録

Water quality and flow of shallow groundwaters in the Sabae City, Fukui Prefecture was examined geochemically to apply them to build up a ground source heat pump system (GSHP).Groundwaters and river waters from 25 and 5 sample localities, respectively, were collected five times from June 2014 to July 2015 and analyzed for their chemical and isotopic (D and ¹⁸O) compositions. The results show that groundwaters are mainly of meteoric origin and that the δD and δ¹⁸O are -51.8 to -31.2‰ and -9.6 to -7.4‰, respectively, plotting between two meteoric precipitation lines (δD=8δ¹⁸O+17 in summer and δD=8δ¹⁸O+30 in winter).The chemical compositions of groundwaters in the eastern area are Ca²⁺–HCO₃^- type and those in the western area are Na⁺–HCO₃^- and Ca²⁺–HCO₃^- types. Several groundwaters in the study area have high Fe concentration up to 11 mg/L and are oversaturated with respect to Fe (OH) ₃. This means that cleaning of the heat exchange should be considered when open-type GSHP is used for room air conditioning.