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Table 1 Chemical composition (concentrations in mM) of the artificial pore-water (APW) used to saturate the intervals [target composition derived from Pearson (1999) and Pearson et al. (2003)] and of the interval solutions after saturation of the borehole and equilibration of the surrounding clay for ~8 months

From: Impact of the electron donor on in situ microbial nitrate reduction in Opalinus Clay: results from the Mont Terri rock laboratory (Switzerland)

Component APW Interval 1 Interval 2 Interval 3
Na+ 162 174.0 174.0 174.0
K+ 1.05 1.2 1.2 1.2
Ca2+ 12.6 11.7 11.0 10.7
Mg2+ 8.6 9.7 9.5 9.1
Sr2+ 0.4 0.4 0.4 0.4
Total dissolved Fe n.a. n.a. <0.0004
Cl 181 203.1 205.9 203.1
\({\text{SO}}_{4}^{2 - }\) 12.28 11.03 11.66 11.66
\({\text{NO}}_{3}^{ - }\) <0.01 <0.01 <0.01
\({\text{NO}}_{2}^{ - }\) <0.1 <0.1 <0.1
\({\text{NH}}_{4}^{ + }\) n.a. n.a. 0.083
CHOO <0.0056 <0.0056 <0.0056
CH3COO <0.009 <0.009 <0.009
\({\text{C}}_{2} {\text{O}}_{4}^{2 - }\) <0.006 <0.006 <0.006
TIC 2.8 5.2 2.8 2.8
TOC 0.7 0.92 0.8
pH (−) 7.8 7.1 7.2 7.4
  1. The errors on the concentrations are 4% ([\({\text{SO}}_{4}^{2 - }\)]), 5.5% ([\({\text{NO}}_{3}^{ - }\)]), 6% ([Cl]), 10% ([Na+], [K+], [Ca2+], [Mg2+], [Sr2+], [\({\text{NH}}_{4}^{ + }\)], [CHOO], [CH3COO-], [\({\text{C}}_{2} {\text{O}}_{4}^{2 - }\)] and TIC), 15% ([\({\text{NO}}_{2}^{ - }\)], [total dissolved Fe]) and 30% (TOC) (95% confidence), while the uncertainty on the pH is estimated to be 0.1 pH unit (95% confidence)
  2. n.a. not analyzed