생태융합환경공학연구실

This study investigated the performance of calcium polysulfide (CPS) for immobilizing mixed heavy metals in
acidic–oxidizing groundwater collected from a smelting-impacted refinery in South Korea. A laboratory column
experiment was conducted using site-specific soil and groundwater to evaluate CPS transport, redox evolution,
metal precipitation, and hydraulic response under realistic geochemical conditions. The injection of CPS rapidly
established reducing and alkaline environments, promoting the precipitation of metal sulfides (MeS(s)), gypsum,
and secondary iron (hydr)oxides while inducing only moderate reductions in hydraulic conductivity. Massbalance
analyses demonstrated nearly complete cadmium sequestration and partial removal of zinc and magnesium,
governed primarily by sulfide affinity and solubility equilibria. Mineralogical and spectroscopic characterization
confirmed the formation of ZnS(s), CdS(s), and CaSO4⋅2H2O(s), whereas microbial community
profiling revealed enrichment of sulfur- and iron-metabolizing taxa within CPS-reactive zones, suggesting potential
microbial contributions to long-term stability. Compared with previous tests employing clean model
sands, the overall removal efficiency in site soil was lower, reflecting the effects of geochemical complexity,
competing ions, and localized precipitation. These findings demonstrate that the efficiency and longevity of CPS
treatment are controlled by the interplay among metal-specific thermodynamics, site mineralogy, and redox
buffering. The results highlight the importance of integrating mass-balance evaluation, mineralogical confirmation,
and microbial characterization to accurately assess in-situ performance and to optimize design parameters
for sustained sulfide-based remediation of mixed-metal contaminated groundwater.

This study demonstrates the feasibility of using calcium polysulfide (CPS) for in-situ redox manipulation (CPS-ISRM) to remediate Zn-contaminated groundwater, focusing on concentrations exceeding 10,000 mg/L at a zinc smelting site in South Korea. Experiments with sand-only and sand-clay columns revealed that subsurface heterogeneity significantly impacts CPS transport, reactivity, and removal efficiency. Homogeneous sand conditions allowed rapid CPS migration and over 99 % Zn removal, albeit within a shorter reactive time frame. In contrast, heterogeneous sand-clay media enabled prolonged localized reactions due to CPS retention, although with less than 50 % Zn removal due to restricted distribution. CPS interactions with groundwater and geochemical constituents varied based on subsurface conditions, influencing permeability and chemical evolution. Precipitation including the formation of ZnS(s) and CaSO4(s) drove localized clogging and changes in hydraulic conductivity, particularly in confined zones of the sand-clay column. These findings highlight the importance of subsurface characterization and tailored CPS injection protocols, considering site-specific factors such as subsurface heterogeneity, groundwater chemistry, and interactions between CPS, groundwater constituents, and the targeted contaminants. Understanding these system dynamics is imperative for optimizing CPS-ISRM technology for field-scale groundwater remediation.

With the accelerating global industrialization, Cadmium (Cd) pollution in rice has become a significant threat to both ecological safety and human health. But the universal factors influencing Cd content across different terrains remain under-investigated. Hence, 300 groups of root system-rice samples were collected from typical rice planting areas in the plains and hills of Southern China to investigate the driving factors of Cd content in rice at a large scale. Moreover, a Cd content prediction model in rice was built. Results showed that although total Cd (T-Cd) and available Cd (DTPA-Cd) contents in rice soils from hilly areas were significantly lower than those in plains, the Cd content in rice was significantly higher (P < 0.05). In a geographical distribution analysis, there was a weak correlation between geographical distance and Cd content in soil (∣R∣<0.30, P < 0.05), although this showed evidence of gradual geographical changes. In addition, this study found that DTPA-Cd (positive correlation, feature importance score of 42.67) and soil pH (negative correlation, 38.91) were the most critical factors that influenced Cd content in rice from different terrains using a network diagram and random forest model computation. In summary, there was evidence of a complicated interaction between terrain and soil pH in rice-Cd pollution at a large regional scale. Soil pH and DTPA-Cd were dominant influencing factors of Cd content in rice when compared to geographical distribution. These results provide an important scientific reference for large-scaled Cd pollution monitoring, control, and risk evaluation.

This study investigated the mineral carbonation and neutralization behavior of red mud (RM) using CO₂ microbubbles (CO₂ MBs) under ambient temperature and pressure conditions, and further assessed the feasibility of utilizing carbonated RM as a cement substitute. Batch experiments were conducted at various solid-to-liquid ratios (S/L = 0.001–1.0), monitoring pH, electrical conductivity (EC), and aqueous carbonic acid (H₂CO₃(_aq)) concentrations. In the RM–CO₂ MBs system, pH initially dropped sharply and then recovered to the buffering zone (pH 7–8.5), while EC exhibited a rapid rise followed by gradual decline, indicating sequential ion release and carbonate precipitation. The H₂CO₃(_aq) concentration decreased over time due to both carbonation consumption and pH-induced speciation shift. In continuous experiments (reactor dimensions: D = 14.6 cm, H = 34 cm, S/L = 0.025), both powdered (RM-P) and sludge-type (RM-S) samples achieved neutralization (pH = 7) within 4 minutes, accompanied by a characteristic EC decrease–rebound pattern. The total inorganic carbon (TIC)-based CO₂ uptake of RM-S reached 8.87 g-CO₂/kg-RM, corresponding to approximately 84% of the theoretical maximum carbonation potential (TMCP). Mortar specimens incorporating carbonated RM as a partial cement replacement (0–15 wt%) exhibited decreasing compressive strength with increasing substitution ratio, yet 5 wt% replacement maintained adequate strength for non-structural construction materials. These results demonstrate that CO₂ MBs enable rapid (≤2 min), high-efficiency carbonation and neutralization of RM under ambient conditions without pressurized systems. The proposed process provides a low-energy, environmentally friendly pathway for simultaneous CO₂ sequestration and red mud valorization, contributing to sustainable carbon-neutral technology.

Uncertainties in climate change and precipitation patterns reduce the predictability of groundwater and surface watermanagement. In the process of constructing groundwater flow models for existing groundwater management, large-scalewatersheds are typically the primary focus. However, in watershed environments with complex boundary conditionswhere coastal lagoons and rivers coexist, it is necessary to establish conditions distinct from those of large-scalewatersheds. This study, targeting the Songji lagoon watershed on the east coast, determined that defining boundaryconditions in small-scale basins can significantly influence the predictive stability of the model and the results ofsensitivity analysis. It quantitatively investigated the impact of boundary condition settings on the calibration andpredictive accuracy of groundwater flow models. To this end, nine scenarios were constructed by stepwise combination ofhydraulic conductivity, river, lake, and drainage conditions. Steady-state simulations using MODFLOW and parametercalibration based on PEST were performed to simulate groundwater flow for each scenario. Analysis results indicated thatthe scenario employing a stepwise calibration method, where river and lake water levels (stage) and conductance were setfirst, yielded the most effective water level prediction accuracy (R2 = 0.998 and RMSE = 0.138). This demonstrates that,in small coastal basins, a boundary-focused calibration strategy is an effective approach that reduces spatial uncertaintyand enhances model reliability compared to traditional parameter calibration.

This study evaluated the applicability and reliability of various baseflow separation methods in the Yeongsan and Seomjin watersheds,  and  investigated  the  relationship  between  watershed  characteristics  and  the  baseflow  index  (BFI).  Both graphical approaches (HYSEP-FIM, SIM, LMM, UKIH-Min, PART) and digital filter methods (Lyne-Hollick 1·2-Pass, Chapman, CM, Eckhardt, EWMA) were applied to estimate BFI, and their performance was assessed using statistical indicators including NSE, KGE, PBIAS, and RSR. Sensitivity analysis revealed that BFI results were highly dependent on parameter settings, particularly for digital filters, with the Eckhardt method demonstrating the most stable and reliable performance, thus identified as the optimal method. Correlation analyses between watershed characteristics (e.g., area, elevation, slope, land use) and BFI showed statistically significant relationships in some main river reaches, while tributary basins exhibited complex interactions requiring multivariate analysis. These findings provide a methodological foundation for future baseflow estimation, and serve as essential baseline data for watershed-scale hydrologic modeling, ecological flow assessment, and integrated water resources planning.