형산강의 수리지화학 특성 = Hydrogeochemistry in the Hyeongsan River basin, South Korea

다국어 초록 (Multilingual Abstract)

The geochemical characteristics of river are primarily influenced by the weathering of bedrock, but the impacts of industrialization and urbanization as well as seawater intrusion due to rising sea levels are gradually increasing. In this study, we aimed to evaluate the relative contributions of these factors using major elements, trace elements, and strontium isotope ratios (86Sr/87Sr) in river water samples collected at the Hyeongsan River basin. Based on molar concentrations, the relative proportions of major elements in all samples decreased in the order of Na+ (85.4%) > Mg2+ (9.6%) > K+ (2.5%) > Ca2+ (2.4%). The 87Sr/86Sr ratio was 0.708725 ± 0.000470 (1σ, n = 14), in which downstream samples had 87Sr/86Sr ratios consistent with seawater, indicating that the effect of seawater intrusion increased to up to 90% after 49.5 km distance from the upstream. The forward model indicated that major ion chemistry is mainly affected by chemical weathering (82%) with a minor of anthropogenic input (11%) and rainfall (7%). Calculated total chemical weathering rates, silicate weathering rates, and carbonate chemical weathering rates were 6.8 t/km2/yr, 4.4 t/km2/yr, and 2.4 t/km2/yr, respectively. Furthermore, the associated CO2 consumption rates were 203 × 103 mol/km2/yr and 37 × 103 mol/km2/yr, respectively.
In particular, the effect of anthropogenic inputs on the tributaries increased to up to 19%, in which trace element concentrations increased to up to 36 times. This study suggests that continuous geochemical monitoring in the Hyeongsan River basin is necessary in order to prepare in advance for the risk by industrialization and climate change.