International Journal of GEOMATE, Oct., 2019 Vol.17, Issue 62, pp. 158 - 166 ISSN: 2186-2982 (P), 2186-2990 (O), Japan, DOI: https://doi.org/10.21660/2019.62.7156 Special Issue on Science, Engineering & Environment CHARACTERISTIC OF WATER CHEMISTRY FOR ARIMA TYPE DEEP THERMAL WATER IN THE KINOKAWA RIVER CATCHMENT, KII PENINSULA, JAPAN *Hiroyuki Ii1, Hiroki Kitagawa2, Takuma Kubohara2 and Isao Machida3 1Faculty of Systems Engineering, Wakayama University, Japan; 2 Graduate School of Systems Engineering, Wakayama University, Japan; 3 Geological Survey of Japan, Japan *Corresponding Author, Received: 10 March.2019, Revised: 01April. 2019, Accepted: 20 April. 2019 ABSTRACT: All soluble substances for coastal shallow well waters were higher than those for the inland well waters in the Kinokawa River catchment along the Median Tectonic Line in Wakayama Prefecture, Japan. Coastal areas were thought to have been contaminated by sewage wastewater due to a high population. Shallow groundwater is thought to have derived from precipitation because all shallow groundwater is on the Global Meteoric Water Line. There are many hot springs in the Kinokawa River catchment along the Median Tectonic Line in Wakayama. Most hot spring waters are thought to originate from mixing of shallow groundwater and Arima type deep thermal water because of their δ18O and δD values. High Li+ concentration water was found for Arima type deep thermal water. In particular, Li+ concentration of Nohan No.5 borehole, 1100m in depth, in the center of Kinokawa River catchment reached 100 mg/l and this value was the highest in Japan. However, both δ18O and δD values for hot spring waters did not always increase with Li+ and - 18 + - + HCO3 concentrations although both δ O and δD values increased with Na and Cl concentrations. Li - concentration for hot springs increased with HCO3 concentration. Therefore, the Li source was determined not to be different from Na+ and Cl- source. Keywords: Hot spring, Median Tectonic Line, Thermal water, Metamorphic dehydrated fluid, Kinokawa 1. INTRODUCTION comparing surface and deep groundwater. Groundwater is widely used for agriculture, industry or domestic purposes. Therefore, it is necessary to conserve groundwater sources around the globe as well as determine their origins. Precipitation is the main source for groundwater. However, seawater is also an important source of groundwater near the sea. In recent years, the origin for saline hot spring water has been studied and some hot spring origin is now thought to be metamorphic dehydrated fluid, not precipitation or modern seawater[1]. The study area, the Kinokawa River catchment, Fig.1 Study area lies along the Median Tectonic Line[2]. In and around the Median Tectonic Line, certain 2. STUDY AREA metamorphic water is known as Arima type deep thermal water, which shows a high salt type (Na- Fig.1 shows the location of the study area in Cl type)[3], has been found even in areas far from northern Wakayama Prefecture. The Kinokawa volcanic areas[4,5]. However, there are few reports River, approximately 136 km long, flows from east which mention the influence of Arima type deep to west in the area. The river flow rate is estimated thermal water on the hot springs in Kinokawa at 37.4 m3/s on average[6]. The Median Tectonic River catchment[2]. Therefore, in this study, Line (MTL) is at the center of the Kinokawa River detailed sampling for hot spring and shallow catchment[2]. The center of the Kinokawa River groundwater was performed. The purpose of this catchment was composed of alluvial sediments on study was to clarify the characteristics of the Sambagawa metamorphic rocks. At the north groundwater chemistry in the Kinokawa River and south parts of the Kinokawa River catchment catchment along the Median Tectonic Line and were the Izumi Group sedimentary rocks and the groundwater chemistry changes with depth by Sambagawa metamorphic rocks. The Median 158 International Journal of GEOMATE, Oct., 2019 Vol.17, Issue 62, pp. 158 - 166 Tectonic Line (MTL) is the boundary between the In the early period of those studies, one of the Izumi group and alluvial sediments. Most shallow most important characteristics of Global Meteoric wells and hot springs are found within these Water was found[7]. Generally, δ18O and δD alluvial sediments. values in rain water are located in the vicinity of the Global Meteoric Water Line of equation (3) [7]. δD = 8 δ18O+10 (3) 57~60 1 9 31~35 42 44~47 56 3 4 5 6 7 8 36~ 10 43 -30 -4 41 40 48~50 2 1213 1415 51~55 δD 18 17 18 19 16 31 δ O 20 -35 -5 21 27 23 24 25 26 28 29 30 -40 -6 O(‰) 18 δD(‰) δ Fig.2 Shallow house well sampling points in the -45 -7 Kinokawa River catchment -50 -8 -55 -9 0 10 20 30 40 50 60 well No. Fig.4 Distribution of δ18O and δD values for shallow groundwater. Fig.3 Hot spring sampling points in the Kinokawa 120 River catchment Cl- 100 Na+ 3. METHOD 80 There are numerous private house wells and mg/l 60 hot springs in the Kinokawa River catchment. Fig.2 and Fig.3 show each sampling point of 40 shallow house wells and hot springs. Sampling was performed from April 2012 to November 2016. 20 The depth of shallow wells and hot springs were 0 less than 10 m and 10 to 1500 m. Soluble 0 10 20 30 40 50 60 substances were measured by ion exchange well No. - chromatography. The concentration of HCO3 for Fig.5 Distribution of Na+ and Cl- concentrations the sampled water was measured with a TOC for shallow groundwater. analyzer. Stable hydrogen and oxygen isotopic ratios were measured by a mass spectrometer (Sercon Geo Wet System) with dual inlet and 280 70 equilibrium with CO and H gas method. HCO3- Ca2+ 2 2 240 60 Generally, oxygen and hydrogen isotope ratios are 18 expressed as δ O and δD. They are presented as 200 50 per mil (‰) of the standard average seawater 160 40 (mg/l) (SMOW: Standard Mean Ocean Water)[7]. The (mg/l) - 3 formulas are shown in equation (1) and (2). δ18O 2+ 120 30 Ca and δD of SMOW are denoted as (D/H)SMOW, HCO 18 16 18 ( O/ O)SMOW and δD and δ O of the sample are 80 20 18 16 denoted as (D/H)Sample, ( O/ O)Sample. The measurement error of δD is ±1.0‰ and 40 10 18 measurement error of δ O is ±0.1‰. 0 0 0 10 20 30 40 50 60 δD= [ (D/H)Sample/(D/H)SMOW-1]×1000 (1) well No. 2+ - Fig.6 Distribution of Ca and HCO3 18 18 16 18 16 δ O= [( O/ O)Sample/( O/ O)SMOW-1]×1000 (2) concentrations for shallow groundwater. 159 International Journal of GEOMATE, Oct., 2019 Vol.17, Issue 62, pp. 158 - 166 2- 4. RESULT SO4 concentrations for inland wells (well numbers over 30) were mainly 1 to 10 mg/l and 5 4.1 Shallow groundwater sampled at a private to 50 mg/l respectively and some good house well concentrations were over 10 and 50 mg/l 2+ 2- respectively. Mg and SO4 concentrations for Fig.4 shows the distribution of δ18O and δD coastal wells were higher than those for inland values for shallow groundwater sampled at a wells. Therefore, all soluble substances for coastal private house well more than 10 m in depth. Well, wells were higher than those for inland wells. numbers are shown in Fig.2. δ18O and δD values Coastal areas were thought to be influenced by for coastal wells (well numbers 1 to 30) were sewage wastewater because coastal wells are mainly -8 to -6 ‰ and -54 to -38 ‰ respectively. located near a high population area, namely δ18O and δD values for inland wells (well numbers Wakayama City. δ18O and δD values for coastal over 30) were mainly -8 to -4 ‰ and -54 to -30 ‰ wells were more uniform than those for inland respectively. δ18O and δD values for coastal wells wells. were more uniform than those for inland wells. 60 30 Fig.5 shows the distribution of Na+ and Cl- NO3- 50 25 concentrations for shallow groundwater. Well, K+ + - numbers are shown in Fig.2. Na and Cl 40 20 concentrations for coastal wells (well numbers 1 to (mg/l) (mg/l) - 30 15 + 30) were mainly 10 to 30 mg/l and some good 3 + - K concentrations reached over 100 mg/l. Na and Cl NO concentrations for inland wells (well numbers over 20 10 30) were mainly 10 to 20 mg/l although some good 10 5 concentrations were about 30mg/l. Then, Na+ and - 0 0 Cl concentrations for coastal wells were higher 0 10 20 30 40 50 60 than those for inland wells. well No. Fig.6 shows the distribution of Ca2+ and HCO - 3 Fig.7 Distribution of K+ and NO - concentration concentration for shallow groundwater. Well, 3 2+ - for shallow groundwater. numbers are shown in Fig.2. Ca and HCO3 concentrations for coastal wells (well numbers 1 to 120 30 30) were mainly 10 to 40 mg/l and 40 to 160 mg/l SO42- Mg2+ respectively, some well’s concentrations reached 100 25 2+ - over 50 and 200 mg/l respectively. Ca and HCO3 80 20 concentrations for inland wells (well numbers over (mg/l) (mg/l) 60 15 30) were mainly 5 to 30 mg/l and 20 to 120 mg/l 2+ 2- 4 Mg respectively while some good concentrations were SO over 30 and 120 mg/l respectively.