Yeongkyoo Kim

Yeongkyoo Kim. Econ. Environ. Geol. 2026;59:631-40. https://doi.org/10.9719/EEG.2026.59.4.631

The transformation of iron(III) minerals and the associated solid-phase partitioning of trace metal(oid)s are crucial for controlling the fate and transport of hazardous metal(oid)s in acid mine drainage (AMD) environments. This study investigated the mineralogical changes and the redistribution of trace metal(oid)s (As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) during the in situ transformation of ferrihydrite to goethite in sediment cores from a coal mine acid mine drainage (AMD) wetland. X-ray diffraction (XRD) and scanning electron microscopy (SEM), supported by specific surface area measurements, confirmed the gradual transformation of ferrihydrite to goethite with increasing core depth, accompanied by a reduction in surface area. Total concentration data and Fe-normalized ratios showed As, Co, and Zn decreased relative to Fe with depth, indicating potential release as ferrihydrite transforms into more crystalline phases with lower surface areas. Conversely, Cr exhibited an opposite trend, suggesting an apparent preferential association with goethite-rich layers, which maintain a higher positive charge at the near-neutral pH of the drainage. Sequential extraction revealed that while As, Pb, and Zn became more strongly bound (primarily in the crystalline fraction) during the transformation, Cr and Cd remained predominantly in the exchangeable fraction, indicating high sensitivity to environmental changes. These results provide field-based insights into how ferrihydrite-to-goethite transformation under natural AMD conditions influences solid-phase partitioning of trace metal(oid)s, which may affect their long-term stability and remobilization risk in AMD-affected areas.

Jin Woo Yeo, Seongyeop Kim, Yeongkyoo Kim. Econ. Environ. Geol. 2026;59:305-15. https://doi.org/10.9719/EEG.2026.59.2.305

Cobalt is often released into the natural environment through industrial waste from alloying industries and acid mine drainage. Additionally, it exists as a radionuclide (60Co) contributing to high-level radioactive waste. Smectite is a mineral that can be useful for adsorption and isolation of this element. In this investigation, Cheto-type montmorillonite (Cheto-MM), a source clay mineral of The Clay Mineral Society's (CMS) with well-established characteristics, was used as the primary material. The study aimed to assess how cobalt adsorption is affected by the adsorption site in the presence of interlayer water and after subsequent dehydration through heating. Adsorption kinetics and adsorption isotherm models were employed to explore the cobalt adsorption mechanism on Cheto-MM.Results demonstrated notable variations in adsorption characteristics post-dehydration and subsequent shrinkage. Approximately 38% of cobalt was found to adsorb at the edge of Cheto-MM, while about 62% was adsorbed at the interlayer site, indicating the significant influence of the interlayer on cobalt adsorption in Cheto-MM. Adsorption kinetic models showed that the cobalt adsorption kinetics on Cheto-MM can be explained by a pseudo-second-order model. Moreover, isotherm experimental result was best represented by the Langmuir isotherm adsorption model. This study provides fundamental insights into cobalt adsorption characteristics on montmorillonite, emphasizing distinct adsorption sites. Such findings are instrumental in predicting smectite's adsorption behavior in high-level radioactive waste disposal sites in the future.

Duk-Hee Jo, Yeongkyoo Kim. Econ. Environ. Geol. 2024;57:811-21. https://doi.org/10.9719/EEG.2024.57.6.811

Gyure Kim, Yeongkyoo Kim. Econ. Environ. Geol. 2023;56:301-10. https://doi.org/10.9719/EEG.2023.56.3.301

Various iron minerals that precipitate in acid mine drainage have a great influence on the concentration change and mobility of trace elements in the drainage during phase transition to other minerals as well as the precipitation process. This study investigated the change of mineral properties and the behaviors of trace elements influenced by pH and time for the precipitates collected from the acid mine drainage treatment system of the Dalsung mine, where schwertmannite is mainly precipitated. However, the main mineral precipitated in the drainage was goethite, suggesting schwetmannite has already undergone a phase transition to goethite to some extent, and it was observed that at higher pH, the peak width at half maximum of XRD peak was narrower. This can be interpreted as the transformation of small amount of amorphous schwctmannite to goethite or an increase in the crystallinity of goethite, and it showed that the higher the pH, the greater this change was. The concentration of Fe was also greatly affected by the pH values, and as the pH increased, the concentration of Fe in the drainage decreased. With increasing time, the Fe concentration increased and then decreased, which can he interpreted to indicate the dissolution of schwertmannite and precipitation of goethite. This mineral change probably resulted in the rapid increase of the concentration of S at initial stage, but its concentration was stabilized later. The concentration of S is also related to the stability of schwctmannite, showing a high concentration at a low pH at which schwertmannite is stable and a low concentration at a high pH at which goethite is stable. The trace elements present as cations in the drainage also showed a close relationship with the pH, generally the lower the pH, the higher the concentration, due to the solubility changes by the pH, and the precipitation and the changes in mineral surface charge at high pH. On the other hand, in the case of As, existing as an anion, although it showed a high concentration at low pH, its concentration increased with time at all pH values, which is probably related to the concentration of Fe which can be coprecipitated in the drainage, and the increase of As concentration with time is also considered to be related to the decrease in schwertmannite rather than the mineral surface charge.

The Nakdong River is the longest river in South Korea, and flows through various geological terrains with different land use characteristics; therefore, the geochemistry of its water is expected to be influenced by many factors. In this work, the geochemical characteristics of the Nakdong River were examined, and its chemical compositions, δD, δ¹⁸O, and δ¹³C_DIC values, and ⁸⁷Sr/⁸⁶Sr ratios were determined to investigate the geological and anthropogenic effects on the geochemistry of the Nakdong River water. The obtained concentrations of major ions were strongly affected by both the anthropogenic activity and weathering of the rocks. With increasing the flow distance, the ion concentrations slightly increased; and after the inflow of the Kumho River, which was the largest tributary running through Daegu (the fourth largest city in South Korea), the concentrations of Na and SO₄ ions abruptly increased and decreased again, suggesting the existence of strong anthropogenic effects caused by sewage treatment plants and dyeing industrial complex. Other activities such as agricultural ones also increased the NO₃ concentration. In July, the high precipitation level from tropical cyclones and downpours decreased the ion concentrations as well as the δD and δ¹⁸O values. The δ¹³C_DIC magnitudes showed that the dissolved inorganic carbon mainly originated from mineral weathering upstream, while the oxidation of soil organic materials influenced by agricultural activity became more important downstream. The ⁸⁷Sr/⁸⁶Sr ratios revealed that in the upstream regions, the weathering of granite and gneiss complex was dominant, while in the downstream regions, the weathering of sedimentary rocks became more important. The weathering and anthropogenic effects on the river water chemistry were also demonstrated using statistical analysis, which revealed that the water geochemistry was mostly influenced by the anthropogenic sources, including industrial complex, represented by Na, Cl, and SO₄. The obtained results show that, as compared to the geochemistry of the Han River (which is also a major river in Korea), the geochemistry of the Nakdong River is more influenced by anthropogenic activities (including agriculture and the industrial complex) due to the different land use.