Woo-Hyun Jeon

A multi-method approach revealing the groundwater-stream water interaction in the Inbuk stream, Korea

We examined groundwater and stream water interaction in the Inbuk stream, Korea, using various approaches including hydrologic, thermal, hydrochemical, and isotopic methods. For this purpose, we installed four piezometers (IYHW1–4) in the streambed at 10 m interval across the stream and at depths of 0.90 to 1.54 m. We monitored water levels and water temperatures every hour using automatic transducers at the piezometers and in the stream (IYSW1) from September 2013 to April 2014. We also analyzed chemical and isotopic compositions for the hyporheic waters, stream water, and nearby groundwater in early September and late November in 2013. The water levels and hydraulic gradients revealed that three (IYHW1, 2, and 4) of the piezometers were in upwelling conditions for most of the monitoring period, except for the earliest short period (considered to be the wet season), whereas one piezometer (IYHW3) showed a reverse behavior, indicating that the gaining was dominant in the dry period. The mean calculated influx to the stream was 3.04 × 10−4 cm/sec. Observed temperatures of stream water, hyporheic waters, and groundwater also revealed that stream water was downwelling in the early monitoring period (wet season), whereas the groundwater was generally upwelling in most of the resting period, which is consistent with the water level interpretation. Chemical composition analysis indicated that most of the waters were Ca-HCO3 type for both seasons. However, no distinctive difference between chemical compositions of water without substantial seasonal variation negated any inference on the flow conditions. The mixing ratios computed from oxygen and hydrogen isotopic compositions indicated that losing conditions were dominant in the wet season, whereas gaining conditions prevailed in the dry season. The interpretations of stream water and groundwater interactions based on these different methods are relatively consistent for this study area, indicating that such combined methods will be very useful in enhancing understanding of groundwater and stream water interaction.

Evaluation of Contaminant Concentrations in Wet and Dry Seasons during Pump-and-Treat Pilot Tests

This study was performed to examine use of the pump-and-treat method for remediation of TCE, CF and CT in groundwater contaminated by DNAPL. The Woosan industrial complex is located in Wonju, about 120 km east of Seoul, Korea. Two pumping wells (KDPW7 and KDPW8) and five monitoring wells (KDMW7, KDMW8, KDMW9, KDMW10, and SKW2) were installed for the test. An asphalt laboratory is a main source of the extensive subsurface contamination at this site. To evaluate change in the concentrations of TCE, CF, and CT in groundwater in the study area, three rounds of pump-and-treat pilot tests were performed (6 July to 6 August, 22 August to 6 September, and 19 September to 2 December in 2011). The groundwater levels and the concentrations of TCE, CF, and CT exhibited negative correlations in the wet season but positive correlations in the dry season, which suggests that the TCE concentrations were mainly controlled by dilution through rainfall during the wet season and by residual TCE, CF, and CT in the unsaturated zone during the dry season. These possibilities should be considered in the full-scale remediation plan.

Status of Community Drinking Water in Korea and Implications for Appropriate Management

ABSTRACT Community drinking water (CDW), mostly naturally flowing groundwater, plays important roles in supplying drinkingwater for urban and rural residents in Korea. Over 1,600 CDW facilities are distributed throughout the country, many ofthem situated in the outskirts of metropolitan cities. A large proportion of Korean people have become dependent onCDW for drinking due to a distrust of piped water’s quality and a strong belief in the special medicinal effects of someCDWs. However, administrative and official management and the control of CDW facilities have been inadequate whencompared with the strict examination and control of commercial bottled water, which is physically treated groundwaterfrom deep bedrock aquifers. In this study, even though signs of anthropogenic contamination were not generally found, thetested chemical compositions of selected CDWs featured high enrichment of some constituents including Ca, Mg, Na, andHCO 3 with natural origins such as water-rock interactions. Careless consumption of particular CDWs, which has noscientific basis, will not guarantee health improvement. Consequently, more intensive management of CDW facilities anda long-term interdisciplinary examination of the health effects of CDWs are needed to effectively protect people’s health.Key words :Community drinking water, Yaksu (medical water), Carbonate, Iron, Anthropogenic contamination

Relationship between Water Levels and TCE Concentrations during Pump-and-Treat Tests for a TCE-Contaminated Aquifer

Pilot tests of a pump and treat system were performed three times in the wet season and two times in the dry season over 139 days in a trichloroethylene (TCE) contaminated aquifer. Both groundwater levels and TCE concentrations were measured at two pumping and five monitoring wells. The measured data were used to examine the relationships between groundwater levels, TCE concentrations, and pumping rates. In the wet season, the groundwater levels and TCE concentrations showed negative correlations at both pumping wells and some of the monitoring wells due to heavy rainfall by dilution. At the other monitoring wells, they showed positive correlations because of influence of a residual TCE around the wells. In the dry season, they had positive correlations at most wells. TCE concentrations were also influenced by the pumping rates in a zone including residual TCE. However, TCE concentrations did not show any correlation with the pumping rates out of the zone.

Unexpected nationwide nitrate declines in groundwater of Korea

Elevated levels of nitrate in groundwater are an important concern for health and the environment. The overapplication of nitrogen (N) fertilizer to croplands is one of the major sources of high nitrate content in groundwater. In this study, we analyse the nitrate concentrations in Korean groundwater based on data from groundwater quality monitoring wells (n=1,022–2,072), which were sampled twice annually over a recent 13-year analysis period (2001–2013). We report that groundwater nitrate levels are decreasing, despite steadily increasing groundwater use. The maximum nitrate concentration decreased from 168.91 to 48.11 mg/L, while the mean values also show a gradual decreasing trend. Nonparametric Mann-Kendall tests on nitrate concentrations also confirm the decreasing trend. The nitrate decrease is more clearly evident in agricultural groundwater as compared to domestic and drinking groundwaters. This decrease of nitrate in groundwater coincides with a large decline in N fertilizer application due to reduced cropland areas, more sustainable agricultural practices, and progressive improvement of sewage disposal services. This study proposes that the long-term adoption of best practices in agriculture has had a positive impact on groundwater nitrate control.

Groundwater Environment in Seoul, Republic of Korea

Abstract The Republic of Korea (hereafter referred to as Korea) is located in Northeast Asia, on the southern half of the Korean Peninsula, jutting out from the far east of the Asian landmass. Seoul, the capital city of Korea, is located at 37°25′–37°41′N and 126 o 45′–127 o 11′E in the midwest of the Korean Peninsula, covering a total area of 605.5xa0km 2 . The Han River flows through the city from east to west, dividing it into north and south. The city consists of 25 districts. The population of the city has grown rapidly since the Korean War to about 10 million – representing around 20% of the total population of Korea. Seoul is well known for its high population density and its metropolitan area is one of the most densely populated cities in Asia. Economic growth and industrialization have stimulated population growth in Seoul, and this growth has been profitable to the city as it has become a center of governance, education, culture, commerce, and production.