J. Hot Spring Sci. 0* 123* *+* + + - -+. 3 Investigation of ORP (Oxidation-Reduction Potential) Measurement on Sulfur Springs and Its Application on Hot Spring Waters in Nozawa Onsen Takuya M Hidekazu K Shoichi O and Hideyuki O + ORIMOTO + OJIMA KOUCHI NAMI Abstract Although geochemical analysis of hot spring waters is the best way to characterize the chemical condition of hot springs it is not suitable for a multipoint investigation of aged deterioration and route of hot springs from the viewpoint of cost mobility and simplicity. Therefore an exploration with ORP/pH meter which is a handy and mobile device for hot spring research was carried out in order to measure the e# ectiveness of ORP measurement. We studied both acidic sulfur springs containing H S and alkaline sulfur springs containing HS in this paper. The ORP/pH meter measurements revealed aging and changes in water quality of sulfur springs. A practical research was applied for alkaline sulfur springs in Nozawa Onsen and found that there are few di# erences between the hot spring waters at the fountainheads and those at the bathtubs. The result confirms that hot spring waters have been o# ered in good condition to most accommodations in Nozawa Onsen. Moreover the application of ORP measurement has pointed out the problems of some accommodations. After the improvement of their bath facilities the quality of the hot spring waters in Nozawa Onsen was also improved. The result confirms that ORP measurement is an e# ective indicator when we observe the condition of hot springs easily and quickly. Key words : ORP (Oxidation-Reduction Potential) Aging Sulfur spring Nozawa Onsen Management of hot springs +/* *** +3 +/ Nippon Onsen Research Institute +3 +/ Shibuya Shibuya-ku Tokyo +/* *** Japan. +2. 2/2. -1 Faculty of Bio Science and Applied Chemistry Hosei University - 1 Kajino-cho Koganei-shi Tokyo +2. 2/2. Japan. + + 78
0* *+* ORPpH H S HS : + +32 +3. ; +3/3 ; +3/3 ; +312 +2 ORP ph ORP +332 Eh-pH Garrels and Christ +30/ 79
+ ph ph ph +332 ORP AI : Aging index ORP *. 2. *.*.1 ph AIORP ORPORP ORP +** eq eq * ORP Nernst AI HS HS ORP *.-2 *.*.+ ph ORPpH TPX-3* Si ORP / ph - HS HS HS +3/- +3/- ORP Fig. + ph AI 11. 0* m + m + +3/- HS 80
0* *+* Fig. + Tendency of aging of hot spring waters at Yubatake in Kusatsu Onsen viewed from ORP-pH relationship. : Point where spring flows (Upper Yubatake). : Lower Yutaki (Lower Yubatake). : Pouring gate to public bath. + ORP-pH : : : 0 AI 3* +** H S +- mgkg **. +3/- Fig. + H S Fig. km -* m *** ++ A B A H S / 1mgkg B H S mgkg HS Fig. + Fig. 81
Fig. Relationship between ORP and ph at fountainheads in Kawayu Onsen according to various forms of spring flow. Borderline of expected change in quality of hot spring water. ORP-pH - HS - Fig. - Na-Cl-SO - A B C Fig. - A AI + AI B AI -3 Fig. - A AI HS 21. mgkg *-. mgkg C A AI /2 Fig. - A B. 82
0* *+* Fig. - Tendency of aging of alkaline simple hot spring waters viewed from ORP-pH relationship. : Hot spring water at fountainhead. : Hot spring water at pouring gate. - ORP-pH : : Fig. - Fig. + Fig. - -+ **0 +.+ **2 + +/ 22..-3 L 83
Fig.. Relationship between temperature of hot spring water and its electric conductivity at main fountainheads in Nozawa Onsen.. **3. ++ ph 2/. + NaoCloSO..+ 00 **0. +2.1 Fig.. + - +- 2 Fig. / ph + +33- S./ mgkg 84
0* *+* Fig. / ORP-pH relationship of hot spring water at fountainheads which flows to public baths. : Hot spring water in bathtub. / ORP-pH : Fig. / Fig. / AI * AI +* + km AI -* +/ msm +*+ msm -- 2 + Fig. 0 0 + 85
Fig. 0 ORP-pH relationship of hot spring waters between fountainheads and bathtubs of accommodations such as hotels and tourist home. 0 ORP-pH 2 S +* mgkg /3. 3 mgkg +330 /.. + mg kg **/ S AI -* +* /* Fig. 0 AI -* 86
0* *+* -. - Fig. 1 A AI 0* ph CO AI Fig. 1 AI * AI Fig. 0 B Fig. 1 AI -/ AI * Fig. 1 Change in ORP-pH relationship at pouring gate before and after improvement of bath facilities. : Hot spring water at pouring gate before repair. : Hot spring water at pouring gate after repair. 1 ORP-pH : : 87
Fig. 2 Changes in aging of hot spring waters in the transportation routes viewed from ORP-pH relationship. 2 ORP-pH AI +. C AI -1. 0 + km Fig. 2 AI 3. + /.- AI **2 Fig. 3. ORPpH 88
0* *+* Fig. 3 ORP-pH relationships of hot spring waters between fountainheads and bathtubs of accommodations such as hotels and tourist home after improvement of bath facilities. : Hot spring water in bathtub at accommodations after improvement. : Accommodations which didn t make an improvement this time. 3 ORP-pH : : +312 :. /3. Garrels R.M. and Christ C.L. ( +30/ ) : Solutions Minerals and Equilibria. +1 p A Harper International Student Reprint New York. +3/3 : -. 20 3+. +32 : +. 3 pp. +*/ +*0 +3/3 :. -+3---. +3. : 2 + + 1. 89
*** : +332 1+ -/.*. **0 : +332 :.2 3-/. **- : pp. +2 /* **/ :ORP /. +// +0. **2 : /1 +/ /. +3/- : / /* /. **2 3 0 0+ 90