Moon-Su Kim

Predicting long-term change of groundwater level with regional climate model in South Korea

Global climate change causes a high variability in precipitation and surface temperature increase in the world. Global climate models (GCMs) are effectively used to predict climate change at a global scale. In contrast, regional climate models (RCMs) can more efficiently predict climate change scenarios for a small territory such as South Korea. We estimated the groundwater level change in four drainage basins (the Han River, Nakdong River, Geum River, and Yeongsan-Sumjin River basins) in South Korea over the period 2000–2012, and then predicted the groundwater level change from 2000 to 2100 using a water budget model, considering RCMs with RCP 4.5 and RCP 8.5 scenarios. A distinct trend in the groundwater levels of each drainage basin was detected via the inversely close relationship with precipitation patterns of the drainage basin, showing a decrease in the groundwater level in relation to the increasing precipitation trend of the RCM scenarios. It is also proposed that the precipitation amount during the dry season more dominantly affects groundwater recharge than during the wet season.

Natural Reduction Characteristics of Radon in Drinking Groundwater

To investigate the natural reduction characteristics of radon with a short half-life (3.82 day) in drinking Qgroundwater, we analyzed the changes of radon concentrations of groundwater, waters in storage tanks, and tap waters from the small-scale groundwater-supply systems (N

Hydrogeochemical Characteristics and Natural Radionuclides in Groundwater for Drinking-water Supply in Korea

A total of 247 samples were collected from groundwater being used for drinking-water supply, and hydrogeochemistry and radionuclide analysis were performed. In-situ analysis of groundwaters resulted in ranges of for temperature, 5.9~8.5 for pH, 33~591 mV for Eh, for EC, and 0.2~9.4 mg/L for DO. Major cation and anion concentrations of groundwaters were in ranges of 0.5~227.6 for Na, 1.0~279.3 for Ca, 0.0~9.3 for K, 0.1~100.1 for Mg, 0.0~3.3 for F, 0.9~779.1 for Cl, 0.3~120.4 for , 0.0~27.4 for -N, and 6~372 mg/L for . Uranium-238 and radon-222 concentrations were detected in ranges of N.D- and 18-15,953 pCi/L, respectively. In case of some groundwaters exceeding USEPA MCL level () for uranium concentration, their pH ranged from 6.8 to 8.0 and Eh showed a relatively low value(86~199 mV) compared to other areas. Most groundwaters belonged to Ca-(Na)- type, and groundwaters of metamorphic rock exhibited the highest concentration of Na, Mg, Ca, Cl, -N, U, and those of plutonic rock showed the highest concentration of , and Rn. Uranium and fluoride from granite areas did not show any correlation. However, uranium and bicarbonate displayed a positive relation of some areas in plutonic rocks(

Analysis of Groundwater Discharge into the Geumjeong Tunnel and Baseflow Using Groundwater Modeling and Long-term Monitoring

When constructing tunnels, it is important to understand structural, geological and hydrogeological conditions. Geumgeong tunnel that has been constructed in Mt. Geumjeong for the Gyeongbu express railway induced rapid drawdown of groundwater in the tunnel construction area and surroundings. This study aimed to analyze groundwater flow system and baseflow using long-term monitoring and groundwater flow modeling around Geumgeong tunnel. Field hydraulic tests were carried out in order to estimate hydraulic conductivity, transmissivity, and storativity in the study area. Following the formula of Turc and groundwater flow modeling, the annual evapotranspiration and recharge rate including baseflow were estimated as 48% and 23% compared to annual precipitation, respectively. According to the transient modeling for 12 years after tunnel excavation, baseflow was estimated as with a decreasing tendency.

Evaluation of Natural Attenuation by Addition of Fumarate as Carbon Source and Gene Analysis in Groundwater Sample

In the results of monitoring nitrate concentration in more than 8,000 groundwater wells around agro-livestock, the average and maximum nitrate concentration was 9.4 mg/L and 101.2 mg/L, respectively. Since about 31% of the monitoring wells was exceed the quality standard for drinking water, nitrate control such as remediation or source regulation is required to conserve safe-groundwater in South Korea. Typical nitrate-treatment technologies include ion exchange, reverse osmosis, and biological denitrification. Among the treatment methods, biological denitrification by indigenous microorganism has environmental and economic advantages for the complete elimination of nitrate because of lower operating costs compared to other methods. Major mechanism of the process is microbial reduction of nitrate to nitrite and nitrogen gas. Three functional genes (nosZ, nirK, nirS) that encode for the enzyme involved in the pathway. In this work, we tried to develop simple process to determine possibility of natural denitrification reaction by monitoring the functional gene. For the work, the functional genes in nitrate-contaminated groundwater were monitored by using PCR with specific target primers. In the result, functional genes (nosZ and nirK) encoding denitrification enzymes were detected in the groundwater samples. This method can help to determine the possibility of natural-nitrate degradation in target groundwater wells without multiplex experimental process. In addition, for field-remediation application we selected nitrate-contaminated site where 200~600 mg/L of nitrate is continuously detected. To determine the possibility of nitrate-degradation by stimulated-natural attenuation, groundwater was sampled in two different wells of the site and nitrate concentration of the samples was 300 mg/L and 616 mg/L, respectively. Fumarate for different C/N ratio was added into microcosm bottles containing the groundwater to examine denitrification rate depending on carbon concentration. In the result, once 1.5 times more than amount of fumarate stoichiometry required was added, the 616 mg/L of nitrate and 300 mg/L of nitrate were completely degraded in 8 days and 30 days. The nitrite, byproduct of denitrification process, was also completely degraded during the experimental period.

Evaluation on Four Volatile Organic Compounds (VOCs) Contents in the Groundwater and Their Human Risk Level

Received: June 23, 2017 Revised: August 24, 2017 Accepted: August 30, 2017 In this study, we monitored 4 volatile organic compounds (VOCs) such as chloroform, dichloromethane, 1,2-dichloroethane, and tetrachloromethane in groundwater samples to determine the detection frequency and their concentrations and evaluated the health risk level considering ingestion, inhalation, and skin contact. 75 groundwater wells were selected. 24 wells were from monitoring background groundwater quality level and 51 wells were from monitoring groundwater quality level in industrial or contamination source area. In the results, the detection frequency for chloroform, dichloromethane, 1,2-dichloroethane, and tetrachloromethane was 42.3%, 8.1%, 6.0%, and 3.4%, respectively. The average concentrations of VOCs were high in the order of chloroform (1.7 μg L-1), dichloromethane (0.08 μg L-1), tetrachloromethane (0.05 μg L-1), and 1,2-dichloroethane (0.05 μg L-1). Chloroform had the highest detection frequency and average detection concentration. In the contaminated groundwater, the detection frequency of VOCs was high in the order of chloroform, dichloromethane, 1,2-dchloroethane, and tetrachloromethane. The average concentrations for chloroform, dichloromethane, 1,2-dichloroethane, and tetrachloromethane were 2.23 μg L-1, 0.08 μg L-1, 0.07 μg L-1, and 0.06 μg L-1, respectively. All the 4 compounds were detected at industrial complex and storage tank area. The maximum concentration of chloroform, dichloromethane, and 1,2-dichloroethane was detected at industrial complex area. Especially, the maximum concentration of chloroform and dichloromethane was detected at a chemical factory area. In the uncontaminated groundwater, the detection frequency of VOCs was high in the order of chloroform, dichloromethane, and 1,2-dchloroethane and tetrachloromethane was not detected. The average concentrations for chloroform, dichloromethane, and 1,2-dichloroethane were 0.57 μg L-1, 0.07 μg L-1, and 0.03 μg L-1, respectively. Although chloroform in the uncontaminated groundwater was detected the most, the concentration of chloroform was not exceeding water quality standards. By land use, the maximum detection frequency of 1,2-dichloroethane was found near a traffic area. For human risk assessment, the cancer risk for the 4 VOCs was 10-6~10-9, while the non-cancer risk (HQ value) for the 4 VOCs is 10-2~10-3.

Geological Distribution and Background Level of Copper and Zinc in Non-drinking Groundwater, South Korea

To add new groundwater standard, 7 candidate materials (copper, zinc, selenium, manganese, iron, chromium, aluminum) were calculated by CROWN (Chemical Ranking Of groundwater pollutaNts). Copper and zinc were selected as groundwater candidates through the process and monitored total 430 samples for 2 years with 113 groundwater sampling sites. In this study, geological distribution characteristics (igneous rock, metamorphic rock, sedimentary rock) of copper and zinc were evaluated and the geological background levels obtained by a cumulative probability distribution and pre-selection methods were compared. In the results, the highest average concentrations of the copper and zinc were observed both in the igneous rock. The detection concentration ranges of copper and zinc in 430 groundwater samples were 0.002∼0.931 ㎎ L -1 , and 0.002∼32.293 ㎎ L -1 , respectively. In addition, detection concentration ranges of copper and zinc were 0.002∼0.931 ㎎ L -1 , 0.002∼32.293 ㎎ L -1 in the igneous rock, 0.002∼0.134 ㎎ L -1 , 0.004∼7.038 ㎎ L -1 in the metamorphic rock and 0.002∼0.008 ㎎ L -1 , 0.003∼3.948 ㎎ L -1 in the sedimentary rock, respectively. As a result of the background concentrations with two methods, zinc concentrations with the pre-selected method are comparatively higher than that of the others with the cumulative distribution.

Evaluation of Denitrification Efficiency and Functional Gene Change According to Carbon(Fumarate) Concentration and Addition of Nitrate Contaminated-soil in Batch System

Nitrate is on the most seriou pollutant encountered in shallow groundwater aquifer in agricultural area. There are various remediation technologies such as ion exchange, reverse osmosis, and biological denitrification to recover from nitrate contamination. Biological denitrification by indigenous microorganism of the technologies has been reviewed and applied on nitrate contaminated groundwater. In this work, we selected the site where the annual nitrate (NO3−) concentration is over 105 mg/L and evaluated denitrification process with sampled soil and groundwater from 3 monitoring wells (MW4, 5, 6). In the results, the nitrate degradation rate in each well (MW 4, 5, and 6) was 25 NO3− mg/L/day, 6 NO3− mg/L/day, and 3.4 NO3− mg/L/day, respectively. Nitrate degradation rate was higher in batch system treated with 2 times higher fumarate as carbon source than control batch system (0.42M fumrate/1M NO3−), comparing with batch system with soil sample. This result indicates that increase of carbon source is more efficient to enhance denitrification rate than addition of soil sample to increase microbial dynamics. In this work, we also confirmed that monitoring method of functional genes (nirK and nosZ) involved in denitrification process can be applied to evaluated denitrifcation process possibility before application of field process such as in-situ denitrification by push-pull test.

Survey on Geochemical Characteristics of Groundwater Around Carcass Burial Area and Agricultural Area with Livestock Facilities

In this study, chemical characteristics of groundwater around carcass burial areas and those in agricultural and livestock-farming complex areas in South Korea were monitored. Groundwater samples were collected from 166 wells around carcass burial sites and 466 wells around the agricultural areas where carcass burial sites are absent. The chemical parameters (pH, electrical conductivity, dissolved oxygen, oxidation reduction potential, NO 3- N, NH 4- N, and Cl - ) in carcass burial areas and agricultural areas were similar. The NO 3- N concentrations exhibited minimal seasonal fluctuations below 30 mg L -1 in most of the wells, even in the wells located close to the carcass burial sites; and Cl - concentrations also showed similar patterns. The chemical characteristics of groundwater monitored in this study indicated that groundwater was widely contaminated by agricultural activities and livestock farming, but probably not by leachates derived from nearby carcass burial sites.