Hydrogeochemistry of seepage water collected within the Youngcheon diversion tunnel, Korea: Source and evolution of SO4-rich groundwater in sedimentary terrian

Gi Tak Chae, Seong Taek Yun, Sang Ryul Kim, Chan Hahn

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

In the Youngcheon Diversion Tunnel area, South Korea, 46 samples of tunnel seepage water (TSW) and borehole groundwater were collected from areas with sedimentary rocks (mainly sandstone and shale) and were examined for hydrogeochemical characteristics. The measured SO4 concentrations range widely from 7.7 to 942.0 mg/l, and exceed the Korean Drinking Water Standard (200 mg/l) in about half the samples. The TDS (total dissolved solid) content generally is high (171-1461 mg/l) from more shale-rich formations and also reflects varying degrees of water-rock interaction. The water is classified into three groups: Ca-SO4 type (61 % of the samples collected). Ca-SO4-HCO3 type (15%) and Ca-HCO3 type (24%). The Ca-HCO3 type water (mean concentrations = 369 mg/l Ca, 148 mg/l HCO3 and 23 mg/l SO4) reflected the simple reaction between CO2-recharged water and calcite, whereas the more SO4-rich nature of Ca-SO4 type water (mean concentrations = 153 mg/l Ca, 66 mg/l HCO3 and 416 mg/l SO4) reflected the oxidation of pyrite in sedimentary rocks and fracture zones. Pyrite oxidation resulted in precipitation of amorphous iron hydroxide locally within the tunnel as well as in high concentrations of Ca (mean 153 mg/l) and Na (mean 49 mg/l) for TSW, and is associated with calcite dissolution resulting in pH buffering. The pyrite oxidation required for the formation of Ca-SO4 type water was enhanced by the diffusion of oxygenated air through the fractures related to the tunnel's construction. The subsequent outgassing of CO2 into the tunnel resulted in precipitation of iron-bearing carbonate.

Original languageEnglish
Pages (from-to)1565-1583
Number of pages19
JournalHydrological Processes
Volume15
Issue number9
DOIs
Publication statusPublished - 2001 Jun 30

Fingerprint

hydrogeochemistry
tunnel
groundwater
pyrite
oxidation
sedimentary rock
shale
calcite
water
iron hydroxide
water-rock interaction
buffering
fracture zone
seepage water
borehole
drinking water
dissolution
sandstone
carbonate
iron

Keywords

  • Hydrogeochemistry
  • Sedimentary terrain
  • Sulphate
  • Tunnel seepage water

ASJC Scopus subject areas

  • Water Science and Technology

Cite this

Hydrogeochemistry of seepage water collected within the Youngcheon diversion tunnel, Korea : Source and evolution of SO4-rich groundwater in sedimentary terrian. / Chae, Gi Tak; Yun, Seong Taek; Kim, Sang Ryul; Hahn, Chan.

In: Hydrological Processes, Vol. 15, No. 9, 30.06.2001, p. 1565-1583.

Research output: Contribution to journalArticle

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abstract = "In the Youngcheon Diversion Tunnel area, South Korea, 46 samples of tunnel seepage water (TSW) and borehole groundwater were collected from areas with sedimentary rocks (mainly sandstone and shale) and were examined for hydrogeochemical characteristics. The measured SO4 concentrations range widely from 7.7 to 942.0 mg/l, and exceed the Korean Drinking Water Standard (200 mg/l) in about half the samples. The TDS (total dissolved solid) content generally is high (171-1461 mg/l) from more shale-rich formations and also reflects varying degrees of water-rock interaction. The water is classified into three groups: Ca-SO4 type (61 {\%} of the samples collected). Ca-SO4-HCO3 type (15{\%}) and Ca-HCO3 type (24{\%}). The Ca-HCO3 type water (mean concentrations = 369 mg/l Ca, 148 mg/l HCO3 and 23 mg/l SO4) reflected the simple reaction between CO2-recharged water and calcite, whereas the more SO4-rich nature of Ca-SO4 type water (mean concentrations = 153 mg/l Ca, 66 mg/l HCO3 and 416 mg/l SO4) reflected the oxidation of pyrite in sedimentary rocks and fracture zones. Pyrite oxidation resulted in precipitation of amorphous iron hydroxide locally within the tunnel as well as in high concentrations of Ca (mean 153 mg/l) and Na (mean 49 mg/l) for TSW, and is associated with calcite dissolution resulting in pH buffering. The pyrite oxidation required for the formation of Ca-SO4 type water was enhanced by the diffusion of oxygenated air through the fractures related to the tunnel's construction. The subsequent outgassing of CO2 into the tunnel resulted in precipitation of iron-bearing carbonate.",
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AB - In the Youngcheon Diversion Tunnel area, South Korea, 46 samples of tunnel seepage water (TSW) and borehole groundwater were collected from areas with sedimentary rocks (mainly sandstone and shale) and were examined for hydrogeochemical characteristics. The measured SO4 concentrations range widely from 7.7 to 942.0 mg/l, and exceed the Korean Drinking Water Standard (200 mg/l) in about half the samples. The TDS (total dissolved solid) content generally is high (171-1461 mg/l) from more shale-rich formations and also reflects varying degrees of water-rock interaction. The water is classified into three groups: Ca-SO4 type (61 % of the samples collected). Ca-SO4-HCO3 type (15%) and Ca-HCO3 type (24%). The Ca-HCO3 type water (mean concentrations = 369 mg/l Ca, 148 mg/l HCO3 and 23 mg/l SO4) reflected the simple reaction between CO2-recharged water and calcite, whereas the more SO4-rich nature of Ca-SO4 type water (mean concentrations = 153 mg/l Ca, 66 mg/l HCO3 and 416 mg/l SO4) reflected the oxidation of pyrite in sedimentary rocks and fracture zones. Pyrite oxidation resulted in precipitation of amorphous iron hydroxide locally within the tunnel as well as in high concentrations of Ca (mean 153 mg/l) and Na (mean 49 mg/l) for TSW, and is associated with calcite dissolution resulting in pH buffering. The pyrite oxidation required for the formation of Ca-SO4 type water was enhanced by the diffusion of oxygenated air through the fractures related to the tunnel's construction. The subsequent outgassing of CO2 into the tunnel resulted in precipitation of iron-bearing carbonate.

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