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Permeability changes induced by earthquakes have been widely studied. The question remains of how multiple large earthquakes influence permeability at different depths in the far-field and permeability changes could possibly be employed for hydraulic characterization of the aquifers has not yet been investigated. We study the change in permeability in fractured aquifers of the North China Paraplatform based on 11 years of groundwater hydrographs of 7 wells and 62 earthquakes. From 2008 to 2018, the permeability changes varied from well to well, all aquifers showed a consistent and distinct magnitude of change in permeability (decrease, increase and no change) following each earthquake. From the perspective of a single well to multiple shocks, the permeability variation of the JN well is the most sensitive to seismic events. From the perspective of multiple wells to one single earthquake, there were no cases of simultaneous permeability changes in all 7 wells induced by a single earthquake. Permeabilities varying within a wide range at a given depth implies that it could be considered as a dynamically self-regulating value, while permeability changes indicate great differences at varying depths. We found that the correlations between permeability changes and seismic energy density or depth are weak, however, the azimuths of seismic waves could greatly impact the changes in permeability, i.e., from 25° to 295°, and the most significant span is 250° to 295°, and fault distribution around the monitoring wells may also contribute to this result. Employing a seismic waves-pressure amplitude model, the mobilization of colloids driven by the oscillation of pressure head as a possible mechanism of permeability change. Distant, large magnitude earthquakes can alter the permeability, also can accelerate or slow down the rate of permeability change of the aquifer material.
Hongbiao Gu; Yirong Xu; Mingyuan Wang; Zhandong Su; Shuangshuang Lan; Nam Chil Woo; Martin Sauter. Spatial permeability variations of aquifers in North China Plain derived from large magnitude earthquake signals. 2021, 1 .
AMA StyleHongbiao Gu, Yirong Xu, Mingyuan Wang, Zhandong Su, Shuangshuang Lan, Nam Chil Woo, Martin Sauter. Spatial permeability variations of aquifers in North China Plain derived from large magnitude earthquake signals. . 2021; ():1.
Chicago/Turabian StyleHongbiao Gu; Yirong Xu; Mingyuan Wang; Zhandong Su; Shuangshuang Lan; Nam Chil Woo; Martin Sauter. 2021. "Spatial permeability variations of aquifers in North China Plain derived from large magnitude earthquake signals." , no. : 1.
Groundwater is the sole water supply source on Jeju volcanic island in Korea and increasing levels of nitrate contamination have raised serious public concerns. This study was objected to understand the nitrate contamination mechanisms of the coastal groundwater overlain by a low-permeability layer in the western part of the island. The 2-yrs of quarterly groundwater monitoring from Sep. 2016 to Oct. 2018 revealed that NO3-N concentrations of 60.7% of sampled wells exceeded 10 mg/L, and those of 17.8% in the range of 3–10 mg/L, indicating those wells are already contaminated or under influence of potential sources. The spatio-temporal variation of groundwater chemistry and stable isotopic signatures suggested that nitrate originated mainly from chemical fertilizers due to agricultural activities and in part from liquefied manure affected by local livestock industries. Two transport processes appeared to be responsible for the nitrate in the confined coastal aquifer: 1) the direct penetration from the land surface through the wellbore leakage at incompletely grouted wells, and 2) the addition of nitrate-contaminated groundwater from upgradient areas where the confining layer is pinched out. Presently the potential nitrate sources are distributed up to 600 m above mean sea level(amsl), and the isotopic signatures implies that the provenance of coastal groundwater could be upland areas of up to 1280 m amsl. Subsequently, nitrate sources at upland areas could be picked up and carried down to the coastal groundwater under the confined condition of the basaltic aquifer that the regional groundwater recharge occurs. Consequently, groundwater contamination in the coastal aquifer should be considered in the big picture of groundwater system accommodating both regional and local flows.
Eunhye Kwon; Jonghoon Park; Won-Bae Park; Bong-Rae Kang; Nam C. Woo. Nitrate contamination of coastal groundwater: Sources and transport mechanisms along a volcanic aquifer. Science of The Total Environment 2021, 768, 145204 .
AMA StyleEunhye Kwon, Jonghoon Park, Won-Bae Park, Bong-Rae Kang, Nam C. Woo. Nitrate contamination of coastal groundwater: Sources and transport mechanisms along a volcanic aquifer. Science of The Total Environment. 2021; 768 ():145204.
Chicago/Turabian StyleEunhye Kwon; Jonghoon Park; Won-Bae Park; Bong-Rae Kang; Nam C. Woo. 2021. "Nitrate contamination of coastal groundwater: Sources and transport mechanisms along a volcanic aquifer." Science of The Total Environment 768, no. : 145204.
Significant variation in the precipitation events caused by global climate change has made it difficult to manage water resources due to the increased frequency of unexpected droughts and floods. Under these conditions, groundwater is needed to ensure a sustainable water supply; thus, estimates of precipitation recharge are essential. In this study, we derived an apparent recharge coefficient (ARC) from a modified water table fluctuation equation to predict groundwater storage changes due to precipitation events. The ARC is calculated as the ratio of the recharge rate over the specific yield (R/Sy); therefore, it implicitly expresses variation in Sy. The ARC varies spatially and temporally, corresponding to the precipitation events and hydrogeological characteristics of unsaturated materials. ARCs for five monitoring wells from two basins in Korea in different seasons were calculated using a 10-year groundwater level and weather dataset for 2005–2014. Then, the reliability of the ARCs was tested by the comparison of the predicted groundwater level changes for 2015 and 2016 with observed data. The root mean square error ranged from 0.03 to 0.09 m, indicating that the predictions were acceptable, except for one well, which had thick clay layers atop the soil layer; the low permeability of the clay slowed the precipitation recharge, interfering with groundwater level responses. We performed a back-calculation of R from the Sy values of the study areas; the results were similar to those obtained via other methods, confirming the practical applicability of the ARC. In conclusion, the ARC is a viable method for predicting groundwater storage changes for regions where long-term monitoring data are available, and subsequently will facilitate advanced decision making for allocating and developing water resources for residents, industry, and groundwater-dependent ecosystems.
Jae Min Lee; Sunjoo Cho; Hyun A Lee; Nam C. Woo. Development of an Apparent Recharge Coefficient (ARC) for Estimating Groundwater Storage Changes Due to Precipitation Events Using Time Series Monitoring Data. Water 2020, 12, 1675 .
AMA StyleJae Min Lee, Sunjoo Cho, Hyun A Lee, Nam C. Woo. Development of an Apparent Recharge Coefficient (ARC) for Estimating Groundwater Storage Changes Due to Precipitation Events Using Time Series Monitoring Data. Water. 2020; 12 (6):1675.
Chicago/Turabian StyleJae Min Lee; Sunjoo Cho; Hyun A Lee; Nam C. Woo. 2020. "Development of an Apparent Recharge Coefficient (ARC) for Estimating Groundwater Storage Changes Due to Precipitation Events Using Time Series Monitoring Data." Water 12, no. 6: 1675.
This study was objected to assess active changes in hydrochemistry of coastal groundwater through the construction of underground low- and intermediate-level radioactive waste (LILRW) disposal facility. Groundwater monitoring data from the construction stage of the facility beginning in 2010 to the operation stage in 2017 revealed seawater intrusion (SWI) into the inland area with significant spatiotemporal variation and subsequent changes in hydrochemical reactions. Groundwater was divided into three groups based on the temporal changes in the seawater mixing ratio. Group 1 showed an increasing trend with some delayed responses to SWI and an ion-exchange dominant process. Group 2 represented dynamic changes of hydrochemical reactions in time toward to a new equilibrium condition along SWI and refreshing. In this group, simultaneous increases in SO4 and Ca, depletion of δ34SSO4, and a slight decline in the SI of gypsum suggest that precipitation and re-dissolution of gypsum occurred during the transition of SWI. These changes are probably attributable to the balance change between seawater and fresh groundwater inflows, and subsequently to preferential flow paths developed in the fractured aquifer. Group 3 groundwater demonstrated a rapid and direct connection with seawater since the beginning of construction of the LILRW facility. In summary, SWI process and subsequent hydrogeochemical reactions in the coastal groundwater varies significantly in time and in space, thus continuous monitoring of groundwater chemistry is warranted for safety management of the underground LILRW facility.
Eunhye Kwon; Jonghoon Park; Jae Min Lee; Youn-Tae Kim; Nam C. Woo. Spatiotemporal changes in hydrogeochemistry of coastal groundwater through the construction of underground disposal facility for low and intermediate level radioactive wastes in Korea. Journal of Hydrology 2020, 584, 124750 .
AMA StyleEunhye Kwon, Jonghoon Park, Jae Min Lee, Youn-Tae Kim, Nam C. Woo. Spatiotemporal changes in hydrogeochemistry of coastal groundwater through the construction of underground disposal facility for low and intermediate level radioactive wastes in Korea. Journal of Hydrology. 2020; 584 ():124750.
Chicago/Turabian StyleEunhye Kwon; Jonghoon Park; Jae Min Lee; Youn-Tae Kim; Nam C. Woo. 2020. "Spatiotemporal changes in hydrogeochemistry of coastal groundwater through the construction of underground disposal facility for low and intermediate level radioactive wastes in Korea." Journal of Hydrology 584, no. : 124750.
In this paper, we studied one of the largest coal mines in Mongolia, the Baganuur Coal Mine, in terms of environmental sustainability related to mining practices, with a focus on discharged water and waste sediments. The present quality and potential for future pollution were assessed. Based on World Health Organization and Mongolian guidelines, groundwater pumped from the mining operations could be used for drinking and domestic purposes. In addition, based on the Na absorption ratio, groundwater samples from GW-2 and GW-3 could be used as agriculture water supplies with salinity reduction, or used to grow halophytes as a measure for desertification control and pasture production. All waste soil samples appeared to have a desertification potential. Dust particles smaller than 150 μm comprised more than 80% of soil samples, which had arsenic levels higher than the Mongolian soil pollution standards. In addition, soil collected between coal seams (S-5) showed high sulphur content based on X-ray fluorescence (XRF) and scanning electron microscopy–energy dispersive X-ray (SEM-EDX) spectroscopy analyses, strong potential for producing acid mine drainage in the analysis of pH of net acid generation and net acid production potential, and potential for leaching of metals, such as Co. Therefore, the Baganuur Coal Mine requires soil pollution control measures to mitigate the risks of dust and desertification. In this perspective, mine groundwater could be used to reduce environmental stresses by supporting pasture crops such as halophytes on waste disposal sites, thereby preventing dust issues and desertification. Continuous efforts, including monitoring and enacting environmental management measures, are needed from both the mining company and the government to ensure sustainable mine development.
Jonghoon Park; Eunhye Kwon; Euijin Chung; Ha Kim; Batbold Battogtokh; Nam C. Woo. Environmental Sustainability of Open-Pit Coal Mining Practices at Baganuur, Mongolia. Sustainability 2019, 12, 248 .
AMA StyleJonghoon Park, Eunhye Kwon, Euijin Chung, Ha Kim, Batbold Battogtokh, Nam C. Woo. Environmental Sustainability of Open-Pit Coal Mining Practices at Baganuur, Mongolia. Sustainability. 2019; 12 (1):248.
Chicago/Turabian StyleJonghoon Park; Eunhye Kwon; Euijin Chung; Ha Kim; Batbold Battogtokh; Nam C. Woo. 2019. "Environmental Sustainability of Open-Pit Coal Mining Practices at Baganuur, Mongolia." Sustainability 12, no. 1: 248.
Hydrograph analysis provides very important information to make decisions for achieving a sustainable urban watershed, especially for urban streams sustained by stream flow augmentation activities. However, it can be complicated by human activities to control flood. The purpose of this study was to understand the hydrological features of an urban stream from its hydrograph using public data and to suggest points that should be considered during its analysis. Public hydrograph data of the Yangjae stream flowing through the Seoul, Korea were studied using the web-based hydrograph analysis tool (WHAT) system with Eckhardt filter. The normal stream discharge at the outlet of watershed with area of 62.2 km2 is 0.42 m3/s, owing to stream flow augmentation activities. The Yangjae stream periodically fluctuates with tides and is significantly affected by precipitation. The lag time for our study period (Jan 2016–Oct 2018) was 2.9 ± 1.4 h at the outlet and direct runoff comprised over 60% in total stream discharge: the Base Flow Index (BFI) value of 0.388 with the optimized BFImax value of 0.5083. Because of flood control activities, the stream discharge showed anomalous peak flows during extreme events (July 2016, July and August 2017, and May 2018) which caused overestimation of base flow in hydrograph analysis using long-time data. Further, the user should be careful in the use of the filtering method when analyzing data with resolution finer than the hourly one. Our results can contribute an increase in feasibility of hydrograph analysis using public data in urban watersheds.
Euijin Chung; Youn-Tae Kim; Nam C. Woo. Hydrographical characteristics of an urban stream flowing through the Seoul metropolitan, Korea. Environmental Earth Sciences 2019, 78, 1 -9.
AMA StyleEuijin Chung, Youn-Tae Kim, Nam C. Woo. Hydrographical characteristics of an urban stream flowing through the Seoul metropolitan, Korea. Environmental Earth Sciences. 2019; 78 (16):1-9.
Chicago/Turabian StyleEuijin Chung; Youn-Tae Kim; Nam C. Woo. 2019. "Hydrographical characteristics of an urban stream flowing through the Seoul metropolitan, Korea." Environmental Earth Sciences 78, no. 16: 1-9.
The sustainability of rural areas depends on the availability of water resources. The Mangyeong River Basin (MRB) in Korea faces a water supply shortage for agriculture and industry. Based on 11-year (2005–2015) precipitation and groundwater monitoring data, groundwater sustainability was evaluated in terms of natural and man-made factors and their spatio-temporal variations. A precipitation time-series revealed a declining trend, but there were different seasonal trends between wet and dry periods, with declining and rising trends, respectively. Groundwater hydrographs from five national groundwater monitoring wells showed temporal variations. Groundwater wells located in downstream areas showed both recharge from upgradient areas and local man-made impacts (e.g. from pumping), resulting in an ambiguous relationship between precipitation and water levels. However, other monitoring wells in the upstream areas displayed water level responses to precipitation events, with a declining trend. Using the standardized precipitation index at a time scale of 12 months (SPI-12) and the standardized groundwater level anomaly, meteorological and groundwater drought conditions were compared to infer the relationship between precipitation deficit and groundwater shortage in the aquifer. The SPI results indicated severely dry to extremely dry conditions during 2008–2009 and 2015. However, the standardized groundwater level anomaly showed various drought conditions for groundwater, which were dependent on the site-specific hydrogeological characteristics. Finally, groundwater sustainability was assessed using water budget modelling and water quality data. Presently, if groundwater is used above 39.2% of the recharge value in the MRB, groundwater drought conditions occur throughout the basin. Considering water quality issues, with nitrate being elevated above the natural background, this critical abstraction value becomes 28.4%. Consequently, in the MRB, sustainable groundwater management should embrace both natural and human-induced factors to regulate over-exploitation and prevent contamination.
Jae Min Lee; Eunhye Kwon; Nam C. Woo. Natural and Human-Induced Drivers of Groundwater Sustainability: A Case Study of the Mangyeong River Basin in Korea. Sustainability 2019, 11, 1486 .
AMA StyleJae Min Lee, Eunhye Kwon, Nam C. Woo. Natural and Human-Induced Drivers of Groundwater Sustainability: A Case Study of the Mangyeong River Basin in Korea. Sustainability. 2019; 11 (5):1486.
Chicago/Turabian StyleJae Min Lee; Eunhye Kwon; Nam C. Woo. 2019. "Natural and Human-Induced Drivers of Groundwater Sustainability: A Case Study of the Mangyeong River Basin in Korea." Sustainability 11, no. 5: 1486.
A geological repository for low and intermediate radioactive waste (bottom at -130 m a.s.l.) was constructed from 2008 to 2014 in the southeastern coastal area in Korea. This research aimed to evaluate the hydrogeochemistry in this area during the construction period and to determine the characteristics that should be monitored during the operational period. During construction, the groundwater level decreased up to 136 m and the upper groundwater flow in the southeastern area reversed. After the groundwater level dropped below the sea level, the electrical conductivity (EC) in several wells along the coastal line started to increase; 23.2% of the measured water was classified as brackish water and the highest EC observed in groundwater was 18.9 mS/cm, nearly 38% of EC in seawater. The response time of the groundwater chemistry differs depending on the depth, even in wells, because of fracture networks. Among locations that showed drastic changes in EC, only the shallow depth of GM-4 showed a peak pattern in EC, but other locations showed increasing EC patterns or patterns with initial increase and sustained high till the end of the construction period. Based on the Cl/Br ratio, the source of the groundwater salinity was seawater intrusion, and ion exchange played an important role. Compared to Cl concentration, sodium was depleted and calcium was in excess in brackish water; however, the SO4/Cl ratio remained constant at a level similar to seawater. Ca and Fe concentrations showed distinguishable characteristics depending on the location, suggesting differences in geological media. During the operational period, periodical evaluation of the groundwater chemistry in the mixing zone and continuous monitoring of EC patterns and seawater fractions are required.
Youn-Tae Kim; Seung Gyu Hyun; Jae-Yeol Cheong; Nam Woo; Sangdeok Lee. Hydrogeochemistry in the coastal area during construction of geological repository. Journal of Hydrology 2018, 562, 40 -49.
AMA StyleYoun-Tae Kim, Seung Gyu Hyun, Jae-Yeol Cheong, Nam Woo, Sangdeok Lee. Hydrogeochemistry in the coastal area during construction of geological repository. Journal of Hydrology. 2018; 562 ():40-49.
Chicago/Turabian StyleYoun-Tae Kim; Seung Gyu Hyun; Jae-Yeol Cheong; Nam Woo; Sangdeok Lee. 2018. "Hydrogeochemistry in the coastal area during construction of geological repository." Journal of Hydrology 562, no. : 40-49.
Hanna Choi; Nam Chil Woo. Natural analogue monitoring to estimate the hydrochemical change of groundwater by the carbonating process from the introduction of CO2. Journal of Hydrology 2018, 562, 318 -334.
AMA StyleHanna Choi, Nam Chil Woo. Natural analogue monitoring to estimate the hydrochemical change of groundwater by the carbonating process from the introduction of CO2. Journal of Hydrology. 2018; 562 ():318-334.
Chicago/Turabian StyleHanna Choi; Nam Chil Woo. 2018. "Natural analogue monitoring to estimate the hydrochemical change of groundwater by the carbonating process from the introduction of CO2." Journal of Hydrology 562, no. : 318-334.
Ulaanbaatar (UB), the capital of Mongolia, is one of the fastest-growing cities in the developing world. Due to increasing demand driven by rapid population and industrial growth, sustainable water resource management is required. Therefore, we investigated sustainability in UB from the perspective of water quality. During five sampling campaigns, we collected 135 water samples (58 from bedrock wells, 44 from shallow wells tapped into the alluvial aquifer, 24 from rivers, and 9 from springs). The hydrochemistry of the water samples was controlled by two major processes: NO3 contamination, and silicate and carbonate mineral weathering. The groundwater samples could be classified into three groups based on their NO3 levels and spatial distribution. Group 1 had natural background NO3 levels (median: 1.7 mg/L) and silicate weathering–dominant water–rock interactions and was distributed in the alluvial aquifer along the floodplain. Group 2 was dominated by carbonate weathering processes, had a maximum NO3 concentration of 47.4 mg/L, and was distributed between the riverbank and upslope area; overall, it reflected ongoing contamination. Group 3 was distributed in the upslope Ger districts and showed significant NO3 contamination (range: 64.0–305.4 mg/L) due to dense and poor living conditions. The stable isotope signatures indicated that the city’s major water supply from riverbank filtration (i.e., Group 1 wells) mixed dynamically with the river; therefore, it showed no sign of NO3 contamination. However, the isotope values and bedrock groundwater quality of wells in Groups 2 and 3 implied that they were closely connected, with the same water source, and showed a strong potential for expanding NO3 contamination toward Group 1 wells. To support sustainable development in UB, the implementation of appropriate institutional measures to protect and preserve water resources, with systematic spatio-temporal monitoring and a focus on Ger districts, is crucial.
Naranchimeg Batsaikhan; Jae Min Lee; Buyankhishig Nemer; Nam C. Woo. Water Resources Sustainability of Ulaanbaatar City, Mongolia. Water 2018, 10, 750 .
AMA StyleNaranchimeg Batsaikhan, Jae Min Lee, Buyankhishig Nemer, Nam C. Woo. Water Resources Sustainability of Ulaanbaatar City, Mongolia. Water. 2018; 10 (6):750.
Chicago/Turabian StyleNaranchimeg Batsaikhan; Jae Min Lee; Buyankhishig Nemer; Nam C. Woo. 2018. "Water Resources Sustainability of Ulaanbaatar City, Mongolia." Water 10, no. 6: 750.
When groundwater drought occurs, baseflow discharges to surface-water bodies will be reduced and then domestic and agricultural water usage becomes at risk of insufficient supply. Thus, in this study, several methods for groundwater drought assessment were tested with long-term monitoring water-level data in the study area to preserve groundwater sustainability from drought, principally caused by reduced precipitation and propagated through agricultural drought and groundwater drought. Because of the Monsoon climate on the Korean Peninsula, the groundwater storage (or water-level) is secured until the end of summer, then falls by natural discharge during the dry seasons of autumn, winter and the following spring. Thus, the rainfall in the wet season seems to mainly influence groundwater storage until the spring of the following year. As the groundwater level (GWL) declines due to natural drainage and the use of agricultural water increases by the end of the dry season (October–May), the GWL will become lowered below the critical level. Below this level, sufficient water supply is not secured. Using the Standardized Precipitation Index (SPI), threshold method and 95% probability occurrence method, drought detection and the frequency of drought are compared. Groundwater drought using the threshold method results in more frequent occurrence than using the SPI method. The 95% occurrence method responds to severe drought but it also has weakness in missing the man-induced GWL decline in every spring season. For groundwater drought assessment, an appropriate drought index should be utilized according to climatic conditions and catchment characteristics. In the study area, variations of the both natural and anthropogenic effects are mixed and the threshold method is more suitable as a measure for preventing water resources shortage.
Jae Min Lee; Jong Hoon Park; Euijin Chung; Nam C. Woo. Assessment of Groundwater Drought in the Mangyeong River Basin, Korea. Sustainability 2018, 10, 831 .
AMA StyleJae Min Lee, Jong Hoon Park, Euijin Chung, Nam C. Woo. Assessment of Groundwater Drought in the Mangyeong River Basin, Korea. Sustainability. 2018; 10 (3):831.
Chicago/Turabian StyleJae Min Lee; Jong Hoon Park; Euijin Chung; Nam C. Woo. 2018. "Assessment of Groundwater Drought in the Mangyeong River Basin, Korea." Sustainability 10, no. 3: 831.
This study focused on characterising aquifer systems based on water-level changes observed systematically at 159 paired groundwater monitoring wells throughout Korea. Using spectral analysis, principal component analysis (PCA), and cross-correlation analysis with linear regression, aquifer conditions were identified from the comparison of water-level changes in shallow alluvial and deep bedrock monitoring wells. The spectral analysis could identify the aquifer conditions (i.e., unconfined, semi-confined and confined) of 58.5% of bedrock wells and 42.8% of alluvial wells: 93 and 68 wells out of 159 wells, respectively. Even among the bedrock wells, 50 wells (53.7%) exhibited characteristics of the unconfined condition, implying significant vulnerability of the aquifer to contaminants from the land surface and shallow depths. It appears to be better approach for deep bedrock aquifers than shallow alluvial aquifers. However, significant portions of the water-level changes remained unclear for categorising aquifer conditions due to disturbances in data continuity. For different aquifer conditions, PCA could show typical pattern and factor scores of principal components. Principal component 1 due to wet-and-dry seasonal changes and water-level response time was dominant covering about 55% of total variances of each aquifer conditions, implying the usefulness of supplementary method of aquifer characterisation. Cross-correlation and time-lag analysis in the water-level responses to precipitations clearly show how the water levels in shallow and deep wells correspond in time scale. No significant differences in time-lags was found between shallow and deep wells. However, clear time-lags were found to be increasing from unconfined to confined conditions: from 1.47 to 2.75 days and from 1.78 to 2.75 days for both shallow alluvial and deep bedrock wells, respectively. In combination of various statistical methods, three types of water-level fluctuation patterns were identified from the water-level pairs: Type I of identical aquifer systems (77.8%), Type II of the different aquifer systems with different recharge flow paths (9.5%), and Type III of unmatched aquifer system pairs and correlations (12.7%). Type I and II could be used as verification of aquifer condition in the paired monitoring system. However, Type III shows the complexity of water-level fluctuation in different aquifer conditions. This study showed that confined or not-confined conditions are not directly related to the depth of wells in the aquifer. Therefore, the utilisation of groundwater as a water-supply source should be carefully designed, tested for its hydrogeologic conditions, and managed to ensure sustainable quantity and quality.
Jae Min Lee; Nam C. Woo; Chan-Jin Lee; Keunje Yoo. Characterising Bedrock Aquifer Systems in Korea Using Paired Water-Level Monitoring Data. Water 2017, 9, 420 .
AMA StyleJae Min Lee, Nam C. Woo, Chan-Jin Lee, Keunje Yoo. Characterising Bedrock Aquifer Systems in Korea Using Paired Water-Level Monitoring Data. Water. 2017; 9 (6):420.
Chicago/Turabian StyleJae Min Lee; Nam C. Woo; Chan-Jin Lee; Keunje Yoo. 2017. "Characterising Bedrock Aquifer Systems in Korea Using Paired Water-Level Monitoring Data." Water 9, no. 6: 420.
The seismicity in the Korean Peninsula has increased since the 2011 Mw9.0 Tohoku-Oki megathrust earthquake. Two strike-slip earthquakes with magnitudes of ML5.1 and 5.8 occurred in the southeastern Korean Peninsula on 12 September 2016. The two events occurred within 48 min. The ML5.8 earthquake was the largest event in the Korean Peninsula since 1978 when national seismic monitoring began. Both events produced strong high-frequency ground motions. More than 500 aftershocks with local magnitudes greater than or equal to 1.5 followed the events for 2 months. An unreported subsurface strike-slip fault with a dip of 65° to the east and a strike of N27°E was responsible for the earthquakes. The fault ruptured at depths of 11–16 km, resulting in a rupture plane of ∼26 km2. The aftershock distribution displayed horizontal streaks at a depth of ∼14 km, which was consistent with the focal mechanism solutions from long-period waveform inversion. The number of aftershocks decreased exponentially with time. The two ML5.1 and 5.8 earthquakes produced regional Coulomb stress changes of −4.9 to 2.5 bar. The spatial distribution of the aftershocks correlated with the Coulomb stress changes. The peak dynamic stress induced by strong ground motions reached 14.2 bar. The groundwater levels changed coseismically in some regions of decreased static stresses. The earthquakes on previously unidentified faults raised attention for the potential seismic hazards by earthquakes with long recurrence intervals.
Tae-Kyung Hong; Junhyung Lee; Woohan Kim; In-Kyeong Hahm; Nam Chil Woo; Seongjun Park. The 12 September 2016 M L 5.8 midcrustal earthquake in the Korean Peninsula and its seismic implications. Geophysical Research Letters 2017, 44, 3131 -3138.
AMA StyleTae-Kyung Hong, Junhyung Lee, Woohan Kim, In-Kyeong Hahm, Nam Chil Woo, Seongjun Park. The 12 September 2016 M L 5.8 midcrustal earthquake in the Korean Peninsula and its seismic implications. Geophysical Research Letters. 2017; 44 (7):3131-3138.
Chicago/Turabian StyleTae-Kyung Hong; Junhyung Lee; Woohan Kim; In-Kyeong Hahm; Nam Chil Woo; Seongjun Park. 2017. "The 12 September 2016 M L 5.8 midcrustal earthquake in the Korean Peninsula and its seismic implications." Geophysical Research Letters 44, no. 7: 3131-3138.
Chronic exposure even to extremely low specific radioactivity of natural uranium in groundwater results in kidney problems and potential toxicity in bones. This study was conducted to assess the potential health risk via intake of the groundwater containing uranium, based on the determination of the uranium occurrence in groundwater. The groundwater was investigated from a total of 4140 wells in Korea. Most of the groundwater samples showed neutral pH and (sub-)oxic condition that was influenced by the mixing with shallow groundwater due to long-screened (open) wells. High uranium contents exceeding the WHO guideline level of 30 μg L(-1) were observed in the 160 wells located mainly in the plutonic bedrock regions. The statistical analysis suggested that the uranium component was present in groundwater by desorption and re-dissolution processes. Predominant uranium phases were estimated to uranyl carbonates under the Korean groundwater circumstances. These mobile forms of uranium and oxic condition facilitate the increase of potential health risk downgradient. In particular, long-term intake of groundwater containing >200 μg U L(-1) may induce internal exposure to radiation as well as the effects of chemical toxicity. These high uranium concentrations were found in twenty four sampling wells of rural areas in this study, and they were mainly used for drinking. Therefore, the high-level uranium wells and neighboring areas must be properly managed and monitored to reduce the exposure risk for the residents by drinking groundwater.
Woosik Shin; Jungsun Oh; Sungwook Choung; Byong-Wook Cho; Kwang-Sik Lee; Uk Yun; Nam-Chil Woo; Hyun Koo Kim. Distribution and potential health risk of groundwater uranium in Korea. Chemosphere 2016, 163, 108 -115.
AMA StyleWoosik Shin, Jungsun Oh, Sungwook Choung, Byong-Wook Cho, Kwang-Sik Lee, Uk Yun, Nam-Chil Woo, Hyun Koo Kim. Distribution and potential health risk of groundwater uranium in Korea. Chemosphere. 2016; 163 ():108-115.
Chicago/Turabian StyleWoosik Shin; Jungsun Oh; Sungwook Choung; Byong-Wook Cho; Kwang-Sik Lee; Uk Yun; Nam-Chil Woo; Hyun Koo Kim. 2016. "Distribution and potential health risk of groundwater uranium in Korea." Chemosphere 163, no. : 108-115.
Dimethylmonothioarsinic acid (DMMTAV) is a highly toxic, thiolated analogue of dimethylarsinic acid (DMAV). In comparison, a further thiolated analogue, dimethyldithioarsinic acid (DMDTAV), and DMAV both exhibit lower toxicity. To understand the environmental conditions responsible for forming DMMTAV, the kinetics of DMAV thiolation are examined. The thiolation of DMAV is pH-dependent and consists of two consecutive first-order reactions under excess sulfide conditions. The first thiolation of DMAV to form DMMTAV is faster than the second one to DMDTAV. DMMTAV is therefore an intermediate. The first reaction is first-order in H2S at pH 6.0 and 20 °C; therefore, the overall reaction is second-order and the rate coefficient in this condition is 0.0780 M–1 s–1. The rate coefficient significantly decreases at pH 8.0, indicating that H2S(aq) triggers the thiolation of DMAV. The second reaction rate is significantly decreased at pH 2.5; therefore, reaction under strongly acidic conditions leads to accumulation of highly toxic DMMTAV in the early stages of thiolation. The transformation of DMDTAV to DMMTAV is catalyzed in the presence of ferric iron. Formation of DMMTAV should be considered when assessing risk posed by arsenic under sulfidic or sulfate reducing conditions.
Youn-Tae Kim; Hosub Lee; Hye-On Yoon; Nam C. Woo. Kinetics of Dimethylated Thioarsenicals and the Formation of Highly Toxic Dimethylmonothioarsinic Acid in Environment. Environmental Science & Technology 2016, 50, 11637 -11645.
AMA StyleYoun-Tae Kim, Hosub Lee, Hye-On Yoon, Nam C. Woo. Kinetics of Dimethylated Thioarsenicals and the Formation of Highly Toxic Dimethylmonothioarsinic Acid in Environment. Environmental Science & Technology. 2016; 50 (21):11637-11645.
Chicago/Turabian StyleYoun-Tae Kim; Hosub Lee; Hye-On Yoon; Nam C. Woo. 2016. "Kinetics of Dimethylated Thioarsenicals and the Formation of Highly Toxic Dimethylmonothioarsinic Acid in Environment." Environmental Science & Technology 50, no. 21: 11637-11645.
A baseline hydrochemistry of the above zone aquifer was examined for the potential of CO early detection monitoring. Among the major ionic components and stable isotope ratios of oxygen, hydrogen, and carbon, components with a relative standard deviation (RSD) of <10 % for the seasonal variation were selected as relatively stable. These components were tested for sensitivity to the introduction of 0.1 mol/L CO (g) using the PHREEQC simulation results. If the relatively stable components were sensitive to the introduction of CO, then they could be used as indicators of CO leakage into the above zone. As an analog to the zone above CO storage formation, we sampled deep groundwater, including geothermal groundwater from well depths of 400–700 m below the ground surface (bgs) and carbonated springs with a high CO content in Korea. Under the natural conditions of inland geothermal groundwater, pH, electrical conductivity (EC), bicarbonate (HCO), δO, δH, and δC were relatively stable as well as sensitive to the introduction of CO (g), thus showing good potential as monitoring parameters for early detection of CO leakage. In carbonated springs, the parameters identified were pH, δO, and δH. Baseline hydrochemistry monitoring could provide information on parameters useful for detecting anomalies caused by CO leakage as measures for early warning.
Hanna Choi; Jize Piao; Nam C. Woo; Heuynam Cho. Hydrochemical variations in selected geothermal groundwater and carbonated springs in Korea: a baseline study for early detection of CO2 leakage. Environmental Geochemistry and Health 2016, 39, 109 -123.
AMA StyleHanna Choi, Jize Piao, Nam C. Woo, Heuynam Cho. Hydrochemical variations in selected geothermal groundwater and carbonated springs in Korea: a baseline study for early detection of CO2 leakage. Environmental Geochemistry and Health. 2016; 39 (1):109-123.
Chicago/Turabian StyleHanna Choi; Jize Piao; Nam C. Woo; Heuynam Cho. 2016. "Hydrochemical variations in selected geothermal groundwater and carbonated springs in Korea: a baseline study for early detection of CO2 leakage." Environmental Geochemistry and Health 39, no. 1: 109-123.
Sulfuric acid, a highly corrosive substance with a high risk of accidental spills, is important worldwide as a raw material in chemical production. This research aims to develop the best analytical method to determine sulfur contents from the accidental spill sites of sulfuric acid. Wavelength dispersive X-ray fluorescence (WDXRF) spectrometry was selected because of its suitability for mass solid samples and calibration standards were prepared to fit the spill conditions. When the calibration standards were prepared by a solution spiking method, the sulfur concentration showed large differences, especially at the 5.0 wt.% as sulfur standard, for which a concentration of only 4.40 wt.% was detected using inductively coupled plasma-atomic emission spectrometry (ICP-AES) analysis. Therefore, the method of reagent addition to the base material was selected in this study. Natural soil and purchased cellulose powder were used as the base material and calcium sulfate as the reagent. The instrument conditions, such as tube current, generator voltage, and measuring time, were tested with two instruments from different manufacturers and were subsequently optimized. The detectable concentration range of sulfur in this research was 0.001–23.6 wt.% in soil media and 0.002–4.0 wt.% in plant media. When six samples from the spilled site were analyzed, the results of WDXRF spectrometry showed 80–117% recovery compared with those from ICP-AES after microwave-assisted acid digestion as reference values.
Youn-Tae Kim; Junseok Lee; Hye-On Yoon; Nam-Chil Woo. Determination of sulfur in soil and plant media using wavelength dispersive X-ray fluorescence spectrometry as a tool for assessment of chemical spills. Microchemical Journal 2016, 124, 594 -599.
AMA StyleYoun-Tae Kim, Junseok Lee, Hye-On Yoon, Nam-Chil Woo. Determination of sulfur in soil and plant media using wavelength dispersive X-ray fluorescence spectrometry as a tool for assessment of chemical spills. Microchemical Journal. 2016; 124 ():594-599.
Chicago/Turabian StyleYoun-Tae Kim; Junseok Lee; Hye-On Yoon; Nam-Chil Woo. 2016. "Determination of sulfur in soil and plant media using wavelength dispersive X-ray fluorescence spectrometry as a tool for assessment of chemical spills." Microchemical Journal 124, no. : 594-599.
Nam C. Woo; Jize Piao; Jae-Min Lee; Chan-Jin Lee; In-Oak Kang; Doo-Houng Choi. Abnormal Changes in Groundwater Monitoring Data Due to Small-Magnitude Earthquakes. The Journal of Engineering Geology 2015, 25, 21 -33.
AMA StyleNam C. Woo, Jize Piao, Jae-Min Lee, Chan-Jin Lee, In-Oak Kang, Doo-Houng Choi. Abnormal Changes in Groundwater Monitoring Data Due to Small-Magnitude Earthquakes. The Journal of Engineering Geology. 2015; 25 (1):21-33.
Chicago/Turabian StyleNam C. Woo; Jize Piao; Jae-Min Lee; Chan-Jin Lee; In-Oak Kang; Doo-Houng Choi. 2015. "Abnormal Changes in Groundwater Monitoring Data Due to Small-Magnitude Earthquakes." The Journal of Engineering Geology 25, no. 1: 21-33.
Groundwater is important for domestic, industrial, and agricultural uses in Ho Chi Minh City, Vietnam. As the city has developed in a coastal environment, the issue of the fresh water supply must be solved for continuous development. The aim of this study was to quantitatively estimate the risk of groundwater salinization in the Ho Chi Minh area due to saline water intrusion into the main coastal aquifer (the Upper Pliocene aquifer) based on field monitoring data, and to evaluate the sustainability of the city with respect to groundwater resources. From the national monitoring database, water level data were obtained for the last 10 years (2000 to 2009), and a total of 33 hydrogeochemical and isotope data sets were obtained from the aquifer. The sustainability of Ho Chi Minh City with respect to the groundwater supply was quantitatively evaluated at an aquifer scale using groundwater sustainability indicators (GWSIs) suggested by the UNESCO/IAEA/IAH Working Group. The results indicated that groundwater in the southern region, part of the western region, and the area along the Saigon riverside was of poor quality, with very high total dissolved solids (>1,000 mg/L) and high concentrations of Cl and Fe, exceeding the World Health Organization’s drinking water guidelines. The Br:Cl ratios and the δ2H and δ18O values of the samples indicated that the salinization of groundwater resulted mainly from mixing with seawater over a long period. During 2004–2009, the saline boundary moved inland, with the farthest distance reaching ∼3.2 km. The long-term abstraction of groundwater, which has been much greater than its recharge capability, is probably causing the decline in water level (in 39% of the aquifer area), the degradation of groundwater quality (in 62% of the area), and the continuously expanding saline water intrusion (by 7.4% in 5 years). Thus, for the sustainable development of Ho Chi Minh City, in addition to passive measures to regulate over-pumping and pollution controls, active measures should be considered to prevent further seawater intrusion and to increase groundwater recharge through artificial recharge or better management of aquifer recharge (MAR).
Minh Thien Ngo; Jae Min Lee; Hyun A. Lee; Nam Chil Woo. The sustainability risk of Ho Chi Minh City, Vietnam, due to saltwater intrusion. Geosciences Journal 2014, 19, 547 -560.
AMA StyleMinh Thien Ngo, Jae Min Lee, Hyun A. Lee, Nam Chil Woo. The sustainability risk of Ho Chi Minh City, Vietnam, due to saltwater intrusion. Geosciences Journal. 2014; 19 (3):547-560.
Chicago/Turabian StyleMinh Thien Ngo; Jae Min Lee; Hyun A. Lee; Nam Chil Woo. 2014. "The sustainability risk of Ho Chi Minh City, Vietnam, due to saltwater intrusion." Geosciences Journal 19, no. 3: 547-560.
Hanna Choi; Nam C. Woo; Min Jang; Fred S. Cannon; Shane A. Snyder. Magnesium oxide impregnated polyurethane to remove high levels of manganese cations from water. Separation and Purification Technology 2014, 136, 184 -189.
AMA StyleHanna Choi, Nam C. Woo, Min Jang, Fred S. Cannon, Shane A. Snyder. Magnesium oxide impregnated polyurethane to remove high levels of manganese cations from water. Separation and Purification Technology. 2014; 136 ():184-189.
Chicago/Turabian StyleHanna Choi; Nam C. Woo; Min Jang; Fred S. Cannon; Shane A. Snyder. 2014. "Magnesium oxide impregnated polyurethane to remove high levels of manganese cations from water." Separation and Purification Technology 136, no. : 184-189.