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The geochemical evolution of very dilute CO 2 ‐rich water in Chungcheong Province, Korea: processes and pathways

2007; Hindawi Publishing Corporation; Volume: 8; Issue: 1 Linguagem: Inglês

10.1111/j.1468-8123.2007.00200.x

1468-8123

Kangjoo Kim, Do-Hwan Jeong, Yonghwi Kim, Yong Kwon Koh, Sung‐Han Kim, E. PARK,

Methane Hydrates and Related Phenomena

Abstract A geochemical study was carried out on the CO 2 ‐rich water occurring in granite areas of Chungcheong Province, Korea. In this area, very dilute and acidic CO 2 ‐rich waters [62–242 mg l −1 in total dissolved solid (TDS), 4.0–5.3 in pH; group I) occur together with normal CO 2 ‐rich waters (317–988 mg l −1 in TDS, 5.5–6.0 in pH; group II). The concentration levels and ages of group I water are similar to those of recently recharged and low‐mineralized groundwater (group III). Calculation of reaction pathways suggests that group I waters are produced by direct influx of CO 2 gas into group III type waters. When the groundwater is injected with CO 2 , it develops the capacity to accept dissolved solids and it can evolve into water with very high solute concentrations. Whether the water is open or closed to the CO 2 gases becomes less important in controlling the reaction pathway of the CO 2 ‐rich groundwater when the initial p co 2 is high. Our data show that most of the solutes are dissolved in the CO 2 ‐rich groundwater at pH > 5 where the weathering rates of silicates are very slow or independent of pH. Thus, groundwater age is likely more important in developing high solute concentrations in the CO 2 ‐rich groundwaters than accelerated weathering kinetics because of acidic pH caused by high p co 2 .