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Table 1 Chemical composition by IC and pH of the groundwater in Taya Caves, the water of the nearby pond, and rainwater, averaged over the 2019 and 2020 samplings

From: Taya Caves, a Buddhist marvel hidden in underground Japan: stone properties, deterioration, and environmental setting

  Caves' interior Caves' exterior
Turtle hall Asahina's Benzaiten Pond Rain
Na+ 11.0 (± 1.4) 6.9 (± 0.7) 9.6 1.3
Mg2+ 7.7 (± 1.4) 4.4 (± 0.9) 8.5 0.2
K+ 2.0 (± 0.4) 1.4 (± 0.2) 2.8 1.1
Ca2+ 32.9 (± 12.2) 12.8 (± 3.8) 31.6 0.7
  Caves' interior Caves' exterior
Turtle hall Asahina's Benzaiten Pond Rain
NO3 0.4 (± 0.2) 0.4 (± 0.1) 0.6 0.1
SO42– 26.5 (± 5.0) 19.8 (± 3.3) 47.9 2.6
Cl 22.6 (± 2.3) 8.6 (± 1.1) 20.0 2.4
  Caves' interior Caves' exterior
Turtle hall Asahina's Benzaiten Pond Rain
pH 7.5 (± 0.2) 7.2 (± 0.2) 7.4 6.3
  1. Ion concentrations are in ppm, pH is dimensionless
  2. The values in parentheses are standard deviations