생태융합환경공학연구실

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.

Food waste compost (FWC) is a sustainable recycling approach employed in soil media, offering extensive advantages to urban areas by promoting resource circulation and effectively managing water pollution. To improve value, Bacillus subtilis (B. subtilis)-induced FWC-based biomedia (BIBMFWCs) was produced via a secondary treatment involving selective meso-thermophilic stages. During the production of BIBMFWCs, physicochemical properties were found to have favorable characteristics for the efficient removal of metal ions. The produced organic-carbonate complex structure demonstrated the synergistic effect involving simultaneous sorption/precipitation mechanisms for the removal of Pb(II) and Cr(III). Also, the dose of B. subtilis has an impact on the pseudo-second-order (PSO) and intraparticle diffusion (IPD) reaction, leading to distinct removal capacities for Pb(II) and Cr(III) [24.26–24.74 mg g− 1 in Pb(II) and 12.7–23.93 mg g− 1 in Cr(III)]. Furthermore, B. subtilis, an inducing mediator for microbial metabolites, exhibits the potential to facilitate the removal of Pb(II) and Cr(III) through biological modification of raw materials, which are transformed, facilitating the presence of hydroxyl groups, immobilizing metal ions, and enabling ion exchange via biogenic carbonate formation processes. Finally, the developed BIBMFWCs could be used as a naturebased solution (NBS) material without in-situ pH control.

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.

ABSTRACT

This study assessed the optimal injection dosage of calcium polysulfide (CPS) for the remediation of groundwater contaminated with cadmium (Cd) and zinc (Zn) at varying concentrations. CPS, a powerful reducing agent, was applied to groundwater samples from two contaminated sites with high and low heavy metal levels. Increasing CPS dosage resulted in higher pH and lower oxidation-reduction potential (ORP). In the high-concentration sample, a CPS dosage of 0.3% achieved over 99% removal of Cd and Zn, with CPS/heavy metal mass ratios of 2.29 for Cd and 3.13 for Zn. In the low-concentration sample, CPS dosages between 0.03% and 0.06% also achieved 99% removal but required higher mass ratios (15.88 for Cd and 5.33 for Zn). Surface analysis using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energydispersive X-ray spectroscopy (SEM-EDS) confirmed the formation of metal sulfides such as CdS and ZnS. The findings suggest that lower metal concentrations necessitate higher CPS-to-metal ratios for effective remediation, underscoring the importance of site-specific optimization of CPS injection for stabilizing heavy metals in groundwater.

Key words : Calcium polysulfide (CPS, CaSx), Complex heavy metals, Groundwater, Precipitation, Metal suilfides

해수에 의해 염분의 영향을 받는 기수호(brackish lake)인 송지호의 퇴적물(sediment), 대수층 충진재(aquifer materials), 지표수, 지하수를 채수 및 채취하여 분석하고, 해당 시료를 이용하여 염분의 영향을 받는 혼합대(hyporheic zone)를 모사하는pilot scale 컬럼 실험을 진행하였다. 지하수의 상향류 실험 결과, 소량의 염분을 포함한 지하수가 대수층 및 퇴적물로 용승하며낮은 용존산소 농도를 유지하였다. 또한 대수층에서 염분과 낮은 용존산소로 인해 부분 탈질(partial denitrification)이 발생해 NO2 -의 축적이 확인되었다. 퇴적물에서는 긴 체류시간에 의해 질소계 화합물이 흡착되거나 미생물 매개의 산화/환원 반응으로인해 질소계 화합물 농도가 저감되었다. 지표수의 하향류 실험 결과, 높은 농도의 용존산소와 염분을 포함한 기수호의 지표수가퇴적물과 대수층으로 침투하며 높은 용존산소 농도를 공급하였다. 이로인해 퇴적물과 대수층에서 생물학적 질산화(nitrification)가발생하였고, 지표수의 높은 염분 농도에도 불구하고 질소계 오염물질이 저감되었다. 이를 통해, 염분의 영향을 받는 상향류의혼합대의 경우 낮은 용존산소 농도로 부분 탈질이 발생하며 염분에 의해 NO2 -가 축적되고, 하향류의 혼합대의 경우 높은 용존산소농도에 의해 질산화가 발생하며 염분의 영향을 크게 받지 않는다. 이를 통해 기수호 내 염분이 혼합대의 질소 거동에 일부 영향을미치나 DO, pH, 기질 농도, 유기물질 농도 등의 요인이 복합적으로 영향을 미치는 것을 확인하였다.