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Geothermal wells with depths of 4.3 and 4.1 km were drilled into an enhanced geothermal system (EGS) in Pohang, Republic of Korea. After five times of hydraulic fracturing, the groundwater level of the geothermal wells decreased after a Mw 5.5 earthquake in Pohang. The objective of this study was to monitor the groundwater level and temperature and determine the hydrogeological and hydrochemistry of two geothermal wells (PX-1 and PX-2) and one monitoring well (EXP-1) at the EGS site. The hydrochemical data of the EGS wells was also compared with the groundwater characteristics of eight wells at the National Groundwater Monitoring Station (NGMS). First, groundwater samples were collected from a depth of approximately 700 m, and an automatic water level recorder was used to monitor changes in the groundwater level and temperature for two years at the EGS site. Second, groundwater level and temperature data in the NGMS wells were collected from the National Groundwater Information Center's website and annual report on groundwater monitoring for comparisons with the EGS site. The results showed that the rate of groundwater increase was in the order PX-2, PX-1, and EXP-1, and the temperature decrease was the fastest in PX-1 and similar between PX-2 and EXP-1. The eight wells in the NGMS showed only temporary changes. The groundwater in the EGS is the Na-Cl type, but that in the NGMS is a mixture of the Ca-HCO3 and Na-HCO3 type. The EGS site has not yet recovered from the earthquake. [ABSTRACT FROM AUTHOR]

This study analyzed the hydrochemical characteristics and microbial communities of karst water in Samcheok, Korea, and compared water quality results to identify the seasonal characteristics and hydrogeological connectivity of the study areas of Hamaengbang-ri, Gyogok-ri, Yeosam-ri, and the downtown area of Samcheok. Field survey and water quality analysis were performed in July 2019, February 2020, and April 2020. Hydrochemical analysis of karst water (groundwater and surface water) showed that most samples were comprised of Ca-HCO3 and that water–rock interactions were a dominant factor compared to precipitation and evaporation (crystallization). For seasonal characteristics, water–rock interactions appeared more active in the dry season than in the rainy season. Calcite weathering was dominant in the dry season, whereas dolomite weathering dominated the rainy season. Moreover, the saturation indexes for the dry and rainy seasons were less than and greater than 0, respectively, corresponding to an unsaturation (oversaturation) state; thus, white precipitate distributed in the study areas was deposited in the rainy season. Finally, as a result of analyzing the hydraulic characteristics between regions, hydrogeological similarities were identified between Hamaengbang-ri and Yeosam-ri, and between Gyogok-ri and downtown Samcheok, which suggested hydrogeological connectivity between each of the pairs. [ABSTRACT FROM AUTHOR]

The objective of this study is to examine groundwater responses before and after the November 15, 2017 Pohang earthquake (Mw=5.4) in a coastal area of Korea. The earthquake caused devastating damages to many buildings in the city. For this study, groundwater monitoring data (water level, electrical conductivity, water temperature) were obtained for January 2016 to February 2018 from the national groundwater monitoring stations, the rural groundwater monitoring wells, and the seawater intrusion monitoring wells and they are located within 25 km from the epicenter. There are eight national groundwater monitoring stations (PSG, PYI-D, PYI-S, PGB-D, PGB-S, PJH, PDH, PGR), five rural groundwater monitoring wells (PH1, PH2, PH3, PH4, PH5) and four seawater intrusion monitoring wells (GG1, GG2, YI1, YI2). Six of the monitored wells showed groundwater level decreases of 9–81 cm and two of them exhibited a recovery to the previous level within three days while the remaining wells did not. And six monitoring wells showed EC changes to the earthquake with -1,274–161 μS/cm. In addition, three wells showed discernible groundwater temperature fluctuations of -0.2–0.3oC. Here, we found the magnitude of groundwater level change is decreasing with distance of the monitoring wells from the epicenter. Some detailed analyses on the relationship between the responses and a variety of hydrogeological parameters deserve a further study. This work was supported by the Energy Efficiency & Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Trade, Industry and Energy (No. 20183010111860) and by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2015R1A4A1041105). [ABSTRACT FROM AUTHOR]

Seasonal fluctuation in groundwater level (below the ground surface) and water quality variables are mainly attributed to climatic conditions, soil characteristic, drainage method, and management practices. Groundwater degradations and high nitrate values have taken considerable attention in the Republic of Korea. Water management practices needs to be based on results of monitoring of groundwater level and water quality variables. We studied spatial variations based on temporal fluctuations of groundwater level (GWL), and water quality parameters including pH, electrical conductivity (EC), and nitrate (NO3). These contents were monitored from year 2011 to 2014 in 70 groundwater wells of an agricultural region in Korea. The monitoring of contents was done in field and collected data after laboratory analysis, was analyzed by using geostatistical modeling and mapping techniques. Seasonal variations in GWL during the period of four years of monitoring were ranged 2.91–5.17 m and 2.80–4.08 m in wet and dry seasons, respectively. The variations in pH value for the same period ranged 6.55–7.50 and 6.69–7.82 in wet and dry seasons, respectively. The fluctuations in EC values ranged 125–604 μg/cm and 80–272 μg/cm in wet and dry seasons, respectively. The values for NO3 in groundwater ranged 12.87–34.40 mg/L and 9.46–38.80 mg/L during the wet and dry seasons. The GWL shows strong spatial dependence, while pH and EC show strong to weak spatial dependence. The groundwater NO3 shows partial spatial dependence with decreased values in 2014 compared to the values in 2011. This finding is attributed to improved agricultural practices and change in land use pattern from white radish and cabbage to orchards and ginseng fields. This work was supported by the National Research Foundation of Korea (NRF) grant, funded by the Korean government (MSIT) (NRF-2015R1A4A1041105) and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1D1A1B07047200). [ABSTRACT FROM AUTHOR]

Microplastic (MPs) contamination in groundwater has received massive attention since plastic waste has been released directly into the environment. This study investigates MPs contamination in groundwater on the Jeju volcanic Island, Korea. To the best of our knowledge, this is the first study to identify MPs in groundwater from volcanic islands. A total of 21 sites were sampled for groundwater wells and springs in July and September (2021). Sampling was performed without cross-contamination through quality assurance and quality control. The results showed that MPs abundance ranged from 0.006 to 0.192 particles/L in groundwater samples. Additionally, MPs were detected in deep groundwater wells where the groundwater level was 143 m below ground surface. Eight MPs polymer types, including polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride, polystyrene, polyamide, acrylonitrile butadiene styrene, and polyurethane, were detected using Micro-Fourier Transform Infrared Spectroscopy (μ-FT-IR). Most of the detected MPs size ranged from 20 to 100 μm, accounting for 95% of the total. Fragments and fiber shaped MPs were detected, with the majority of them being fragmented in groundwater samples. The concentrations of MPs and major ions in groundwater showed a positive correlation. A negative correlation was observed between MPs concentration and topographic elevation (r = −0.59, p = 0.01). The source of MPs contamination is most likely attributed to agricultural activities, such as plastic mulching and greenhouses, which account for most of the land use in the study area. In this study, MPs entered the aquifer through the soil at the surface and seeped through cracks in fractured rock on basalt with sealed groundwater wells. This study takes 500 L of samples to prevent sample bias, reveal plastic contamination in groundwater, and indicating the characteristics and sources of contaminated plastics. [Display omitted] • Most MPs detected in groundwater were smaller than 50 μm. • Eight polymers were identified, with PP and PE being dominant types in groundwater. • Predominant shapes of MPs in groundwater were fragments. • MPs abundance and groundwater levels have a negative correlation. [ABSTRACT FROM AUTHOR]

The international lack of water is publicly known. Over time, interest in groundwater and surface waters has increased for domestic use as drinking water and agricultural water. Due to the impacts of climate change, floods, landslides, droughts and other disasters related to water are becoming more and more important, and the need for water resources planning and management is emphasized. This study was aimed to assess the trend of groundwater quality in Korea. We also investigated the main drivers behind the trend and are attributed to rock-type and land use. Data was collected for 10 years from groundwater quality monitoring in Korea. Twelve water quality parameters were analyzed year by year. The collected data was statistically analyzed using a nonparametric method (Mann-Kendall trend test, M-K trend test). In addition, normality was analyzed by histogram (K-S test / Kolmogorov-Smirnov test or S-W test / Shapiro-Wilk test) and box plot. The Mann-Kendall trend test used the data for more than 5 years to identify the trends. The results were displayed on the map of the whole country, showing trends by regions. All of the water quality parameters were not statistically normal as a result of verifying the normality of the whole data through P-value in the histogram. Also, it was not normally distributed as a result of verifying the normality of yearly collected data through box plot. As a result of testing the normality of the M-K trend test using P-value, the T and HCO3- increased nationwide, and the pH, Eh and NO3- decreased nationwide. While, Cl-, Mg2+ and SO42- increased in the central area and decreased in the south. Potassium decreased markedly in the south, and EC and Ca2+ showed no regional trends. The reason for the regional difference was thought to be the influence of the rock type of the area where the irrigation had been installed, and it was affected by the land use. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2015R1A4A1041105). [ABSTRACT FROM AUTHOR]