Evaluating radionuclide mobility in groundwater recharge areas of fractured natural barrier systems using multiple isotopes and microbial indicators.

The distribution of uranium (U) concentrations, which reached up to 322 µg/L, was found to correlate with the pattern of fractures within the natural barrier system (NBS). Analysis of the vertical distribution of dissolved oxygen (DO), dissolved organic carbon (DOC), tritium (H), microbial communities, and HO and SO isotopes revealed insights into oxic water infiltration within the heterogeneous fractured system. Their distribution showed that the average infiltration depth at the KURT site is 200 m, while in external areas with a high frequency of fractures, oxic conditions extended down to 495 m.

Thoron, radon and microbial community as supportive indicators of seismic activity in groundwater.

Earthquakes have a significant impact on groundwater environments as well as human life. However, identifying active and affected zones from seismic events using isotopic and microbial diversity indicators remains a challenging frontier. To validate the applicability of this coupled method for real-time analysis, we analyzed thoron (Rn), radon (Rn), microbial community compositions, and hydrochemistry in groundwater samples during the 2017 Pohang earthquake for the first time.

Evaluation of intensive remediation using simulation-optimization modeling based on long-term monitoring at a DNAPL contaminated site.

Simulation-optimization modeling is extensively used to identify optimal remediation designs. However, verifying these optimal solutions often remains unclear. In this study, we determine optimal groundwater remediation strategies using simulation-optimization modeling and assess the effectiveness of previous remediation efforts by validating optimized results through 14 years of long-term monitoring of trichloroethylene (TCE) contamination.

Improving monitoring network design to detect leaks at hazardous facilities: Lessons from a CO storage site.

Exploring the challenges posed by uncertainties in numerical modeling for hazardous material storage, this study introduces methodologies to improve monitoring networks for detecting subsurface leakages. The proposed approaches were applied to the Korea CO Storage Environmental Management (K-COSEM) test site, undergoing calibration, validation and uncertainty analysis through hydraulic and controlled-CO release tests. The calibration phase involved inter-well tracer and multi-well pumping tests, leveraging the Parameter ESTimation (PEST) model to determine the aquifer flow and solute transport properties of the K-COSEM site.

Coupling of radon and microbial analysis for dense non-aqueous-phase liquid tracing and health risk assessment in groundwater under seasonal variations.

Dense non-aqueous-phase liquids (DNAPLs) represent one of the most hazardous contaminants of groundwater, posing health risks to humans. Radon is generally used to trace DNAPLs; however, external factors, such as rainfall or stream water, can influence its efficacy. To overcome these limitations, this study pioneered the integration of radon and microbial community structures to explore DNAPL tracing and natural attenuation in the context of seasonal variations for human health risk assessments.

Experimental study for visualizing CO-dissolved water plume migration under hydraulic gradient conditions and implication for field monitoring data.

Investigating the possible direction of a CO-dissolved water plume migration near the potential CO leakage area is a significant task because it helps estimate the spatial and temporal monitoring scale to detect the signal of released CO from the storage. Accordingly, the Korea CO Storage Environmental Management (K-COSEM) research center tried to develop an intensive monitoring system and applied it to the artificial CO release test in the actual field. Monitoring data from the field tests depicted the horizontal movement of the CO-dissolved water plume along the direction of the groundwater flow.

The effects of heavy rain on the fate of urban and agricultural pollutants in the riverside area around weirs using multi-isotope, microbial data and numerical simulation.

The increase in extreme heavy rain due to climate change is a critical factor in the fate of urban and agricultural pollutants in aquatic system. Nutrients, including NO and PO, are transported with surface and seepage waters into rivers, lakes and aquifers and can eventually lead to algal blooms. δN-NO, δO-NO, and δB combined with hydrogeochemical and microbial data for groundwater and surface water samples were interpreted to evaluate the fate of nutrients in a riverside area around weirs in Daegu, South Korea.

Identifying the origin and fate of dissolved U in the Boeun aquifer based on microbial signatures and C, O, Fe, S, and U isotopes.

The uranium inventory in the Boeun aquifer is situated near an artificial reservoir (40-70 m apart) intended to supply water to nearby cities. However, toxic radionuclides can enter the reservoir. To determine the U mobility in the system, we analyzed groundwater and fracture-filling materials (FFMs) for environmental tracers, including microbial signatures, redox-sensitive elements and isotopes.

Seasonal effects on hydrochemistry, microbial diversity, and human health risks in radon-contaminated groundwater areas.

Groundwater is an important human resource. Daejeon in South Korea faces severe water quality issues, including radon, uranium, and fluoride pollution, all of which pose health risks to humans. With climate change, threats to potable water, such as heavy rain and typhoons, have become common.

Nitrate sources, timing, and pathways of a permeable volcanic aquifer system with mixed land use in Jeju Island, South Korea.

The occurrence of various N-related human activities increases the difficulty in distinguishing the major sources of NO contamination in groundwater, especially in areas with mixed land uses. In addition, the estimation of the timing and pathways of NO is necessary to better understand the processes of NO contamination in the subsurface aquifer system. This study applied environmental tracers, such as stable isotopes and age tracers (δN and δO of NO, δB, chlorofluorocarbons, and H), to elucidate the sources, timing, and pathways of NO contamination in the groundwaters of the Hanrim area, which has suffered from illegal disposal of livestock wastes since the 1980s, and also characterizes them based on mixed N-contaminant sources such as chemical fertilizers and sewage.

A modified and rapid method for the single-well push-pull (SWPP) test using SF, Kr, and uranine tracers.

In the present study, a single-well push-pull (SWPP) test was conducted with multi-component tracers, including inert gas (SF and Kr) and uranine (conservative), to understand the volatile/semi-volatile component transport characteristics in the groundwater system. In an SWPP test, it is essential to obtain an initial breakthrough curve (BTC) of the inert gas concentration at the beginning of the pulling stage to analyze the hydraulic properties of the groundwater system. As a result of the SWPP test using a proposed method in this study, physicochemical parameters of the groundwater and BTC of gas tracers and uranine were acquired simultaneously and successfully.

Estimation of nutrient sources and fate in groundwater near a large weir-regulated river using multiple isotopes and microbial signatures.

The excessive input of nutrients into groundwater can accelerate eutrophication in associated surface water systems. This study combined hydrogeochemistry, multi isotope tracers, and microbiological data to estimate nutrient sources and the effects of groundwater-surface water interactions on the spatiotemporal variation of nutrients in groundwater connected to a large weir-regulated river in South Korea. δB and δN-NO values, in combination with a Bayesian mixing model, revealed that manure and sewage contributed 40 % and 25 % respectively to groundwater nitrate, and 42 % and 27 % to nitrate in surface water during the wet season.

Integrated application of a Bayesian mixing model, numerical model, and environmental tracers to characterize groundwater recharge sources in a mountainous area.

In this study, the combined use of a Bayesian mixing model (BMM), numerical model (random walk particle tracking-RWPT), and environmental tracers (δO-δD, H, and CFC) was applied to elucidate the probabilistic contribution of the recharge sources, flow path, and residence time of groundwater across the mountainous area of Jeju Island, South Korea. Especially, the BMM ability to estimate the variable recharge contributions to the aquifer by different elevations and seasons was investigated. The δO-δD isotopes showed that groundwater in the study area was primarily fed by precipitation during the wet season, and the BMM estimated that wet season recharge contributed to approximately 64% of the total.

Constraining the effectiveness of inherent tracers of captured CO for tracing CO leakage: Demonstration in a controlled release site.

Geological storage of carbon dioxide (CO) is an integral component of cost-effective greenhouse gas emissions reduction scenarios. However, a robust monitoring regime is necessary for public and regulatory assurance that any leakage from a storage site can be detected. Here, we present the results from a controlled CO release experiment undertaken at the K-COSEM test site (South Korea) with the aim of demonstrating the effectiveness of the inherent tracer fingerprints (noble gases, δC) in monitoring CO leakage.

Abnormal groundwater levels and microbial communities in the Pohang Enhanced Geothermal System site wells pre- and post-M 5.5 earthquake in Korea.

In this study, two geothermal wells (PX-1 and PX-2) exhibiting abnormal groundwater levels and microbial communities were examined at the Enhanced Geothermal System site before and after the Pohang earthquake (November 2017). Furthermore, the EXP-1 well level, water temperature, microbial communities and their association with earthquakes, as well as the possibility of future earthquakes were explored. The primary objectives of this research were to: (1) perform correlation and cluster analyses of hydrophysical parameters for earthquakes using next-generation sequencing; (2) analyze pre-, co-, and post-seismic changes in groundwater levels, temperatures, and microbial communities; and (3) further assess the analyzed results of the post-earthquake changes in the groundwater levels and temperatures to interpret their implications.

Physicochemical and isotopic properties of ambient aerosols and precipitation particles during winter in Seoul, South Korea.

The aim of this study was to characterize the physicochemical properties and microbial communities of particulate matter (PM) in Seoul, Korea. We collected long-term (2017-2019) precipitation samples and PM and PM monitoring data to determine the impact of soluble and insoluble chemical species on the soil surface. Ambient PM concentrations were higher than PM concentrations during the monitoring period, but both decreased during rainfall due to the washing effect of precipitation.

Earthquakes and very deep groundwater perturbation mutually induced.

We report unique observations from drilling and hydraulic stimulation at a depth of approximately 4.3 km in two Enhanced Geothermal System (EGS) wells at the Pohang EGS site, South Korea. We surveyed drilling logs and hydraulic stimulation data, simulated pore pressure diffusion around the fault delineated by seismic and drilling log analyses, conducted acoustic image logging through the EGS wells, observed significant water level drops (740 m) in one of the two EGS wells, and obtained hydrochemical and isotopic variation data in conjunction with the microbial community characteristics of the two EGS wells.

Delineation of groundwater quality locations suitable for target end-use purposes through deep neural network models.

Groundwater is the main source of water for beverages, and its quality varies depending on extraction location; this is particularly the case in regions with complex geology, topography, and multiple forms of land use. Thus, it is important to determine a suitable groundwater extraction location based on intended water use and the related water quality standards. In this study, deep neural network (DNN) models and GIS data relating to groundwater quality were applied to estimate potential maps of Gangwon Province in South Korea, where groundwater is frequently extracted for drinking purposes.

Differentiation of natural and anthropogenic contaminant sources using isotopic and microbial signatures in a heavily cultivated coastal area.

Hydrogeochemical and multiple isotope data for groundwater samples were obtained and interpreted to discriminate anthropogenic and natural contaminant sources in a coastal aquifer underlying a heavily cultivated watershed in Hwaseong, South Korea. The local aquifers are vulnerable to contamination, due to high anthropogenic N inputs and the location close to the ocean facilitating seawater intrusion. Thus, to effectively control the groundwater quality in the study area, it is necessary to differentiate between anthropogenic and natural contaminant sources.

Characterization of a NAPL-contaminated site using the partitioning behavior of noble gases.

Noble gases have been used for oil field exploration due to their partitioning behavior in oil-water systems. However, their application to study sites contaminated with non-aqueous phase liquids (NAPL) has been limited, except for Rn, which has been traditionally used as a partitioning tracer for contaminated sites. This study applied natural noble gas components such as Rn, He, Ne, Ar, Kr, and Xe to the characterization of a field site contaminated with trichloroethylene (TCE) located in Wonju, Korea.

Complexity of groundwater age mixing near a seawater intrusion zone based on multiple tracers and Bayesian inference.

Aquifer flow systems near seawater interfaces can be complicated by density-driven flows and the formation of stagnation zones, which inevitably introduces uncertainty into groundwater age-dating. While age-dating has proved effective to understand the seawater intrusion and aquifer salinization process in coastal aquifers, further efforts are needed to propagate model and data uncertainty to the uncertainty associated with the inferred age distributions. This study was performed in a coastal aquifer located close to the Yellow Sea, South Korea, where there is a decreasing trend of groundwater levels due to recent heavy exploitation, raising a warning of induced seawater intrusion.

Application of geographically weighted regression models to predict spatial characteristics of nitrate contamination: Implications for an effective groundwater management strategy.

Groundwater nitrate contamination has been the main water quality problem threatening the sustainable utilization of water resources in Jeju Island, South Korea. The spatially varying distribution of nitrate levels associated with complex environmental and anthropogenic factors has been a major challenge restricting improved groundwater management. In this study, we applied ordinary least squares (OLS) regression and geographically weighted regression (GWR) models to determine the relationships between the NO-N concentration and various parameters (topography, hydrology and land use) across the island.

Reproducing natural variations in CO concentration in vadose zone wells with observed atmospheric pressure and groundwater data.

Continuous CO gas monitoring was performed to understand the natural variations of the gas concentration in the vadose zone wells. The monitoring results demonstrated sudden rise and fall signals, which posed a possibility of error in interpreting the CO leaking signal from the sequestrating reservoir or evaluating the quantity of removed VOCs at a contaminated site. Based on the monitoring data, conceptual models were established and three cases were numerically simulated to determine whether or not reproducing the natural variations of gas concentration is possible.

Nationwide groundwater monitoring around infectious-disease-caused livestock mortality burials in Korea: Superimposed influence of animal leachate on pre-existing anthropogenic pollution.

A foot-and-mouth disease (FMD) outbreak during 2010 affected the entire country of South Korea and approximately 3.4 million swine and bovine mortalities were disposed of at approximately 4800 on-farm burial sites for a few months following the first outbreak. Furthermore, outbreaks of avian influenza (AI) have struck Korea consistently since 2014.