Kyung-Seok Ko

Hydrogeochemical characteristics of groundwater in a mid-western coastal aquifer system, Korea

Hydrogeochemical characteristics of shallow groundwater in a mid-western coastal aquifer system, Korea have been investigated to identify the salinization process. The spatial distributions of the groundwater components are well consistent with the groundwater flow pattern that follows topography in the study area. The groundwater at many locations in the study area is not suitable for drinking water because of its high salinity, which is mainly caused by seawater intrusion. The chemical composition of the groundwater is characterized by high chloride concentration and high variations in cation concentrations due to the cation exchange reaction between aquifer minerals and seawater components. The similar distributions of chemical components between rainy and dry seasons suggest that the groundwater flow system is almost in a steady state condition. The groundwater is classified into Ca(HCO3)2, CaCl2, and NaCl types based on its hydrogeochemical characteristics. The groundwater from the alluvial aquifer shows higher salinity in the rainy season than the dry season while the groundwater in the bedrock aquifer shows lower salinity year-round. Isotope data and factor analysis also indicate that the hydrogeochemical characteristics of groundwater are not only influenced by seawater intrusion but also by agricultural activities.

Groundwater flow system inferred from hydraulic stresses and heads at an underground LPG storage cavern site

Underground Liquefied Petroleum Gas (LPG) storage caverns were constructed below the groundwater table to contain pressurized gas by groundwater pressure. Continuous and regular groundwater monitoring data were used to analyze whether the gas containment condition was satisfied or not. The monitoring data included time series analysis of hydraulic heads, gas and groundwater pressures, and groundwater chemistry. Through cross-correlation analyses of the time series data, the major factors causing hydraulic head fluctuation were found to be groundwater recharge from precipitation and cavern gas pressures. Hydraulic head and hydrochemical data indicate that a fault zone acts as the groundwater recharge zone and water curtain tunnels reduce head fluctuations.

Effect of mining and geology on the chemistry of stream water and sediment in a small watershed

Chemical characteristics of the stream water and sediment in the small watershed with two distinctive mineralization zones (Cu and Pb−Zn), 7 abandoned mines and an active quarry were investigated to examine the effects of mining activity and regional geology on the chemistry. The stream water affected by the abandoned mines had Ca−SO4 type but the other had Ca−HCO3 type. The mine affected stream water and sediment showed relatively high concentrations of metals (Cu, Pb, Zn, Cd, Co, Ni, Mn, Al and Fe). The concentrations of Al, Mn, Fe and Cu of the stream water collected near an abandoned mine (Guryong) exceeded the EPA surface water quality standards (Al: 5.52 mg L−1, Mn: 1.58 mg L−1, Fe: 1.49 mg L−1, Cu: 0.63 mg L−1). The effect of mining activity on the stream water chemistry was attenuated in a relatively short distance from the source (<200 m) along the watercourse but the signature in the sediment showed a longer lasting effect (about 2 km) than that in the stream water: The residual and reducible forms were the dominant fractions of the heavy metals in the stream sediment. The particulate trnnsportation was the major cause of the dispersion of heavy metals in the watershed. There was a contrasting spatial distribution of background metal concentration in the stream sediment: a relatively higher concentration of Cu in the Cu mineralization zone and a relatively higher concentration of Pb, Zn and Mn in the Pb−Zn mineralization zone.

Applications of Isotope Ratio Infrared Spectroscopy (IRIS) to Analysis of Stable Isotopic Compositions of Liquid Water

Recently, stable isotopes (δ 18 O and δD) of water are increasingly analyzed using laser-based technologies. These methods have advantages over Isotope Ratio Mass Spectrometry (IRMS) in that they can be used for in-situ measurements and require much less maintenance and preparation work. Two types of laser-based methods are currently available, which have different analytical principles; OA-ICOS (off-axis integrated cavity output spectroscopy) and WS-CRDS (wavelength-scanned cavity ring-down spectroscopy). In the WS-CRDS instrument, water is vaporized at controlled environment and transferred to an optical cavity by nitrogen carrier gas, and stable isotopic compositions of water vapor are measured using the degree of absorbance of specific wavelengths and the ratios of attenuation time of the laser intensity with the sensitivity of ppb to tens of ppt level. In this study, we introduce the principle of the WS-CRDS technology and the performance results including stability and comparisons with Isotope Ratio Mass Spectrometry (IRMS) and suggest possible applications of various topics in isotope hydrology.

An Energy Budget Algorithm for a Snowpack-Snowmelt Calculation

Understanding snowmelt movement to the watershed is crucial for both climate change and hydrological studies because the snowmelt is a significant component of groundwater and surface runoff in temperature area. In this work, a new energy balance budget algorithm has been developed for melting snow from a snowpack at the Central Sierra Snow Laboratory (CSSL) in California, US. Using two sets of experiments, artificial rain-on-snow experiments and observations of diel variations, carried out in the winter of 2002 and 2003, we investigate how to calculate the amount of snowmelt from the snowpack using radiation energy and air temperature. To address the effect of air temperature, we calculate the integrated daily solar radiation energy input, and the integrated discharge of snowmelt under the snowpack and the energy required to generate such an amount of meltwater. The difference between the two is the excess (or deficit) energy input and we compare this energy to the average daily temperature. The resulting empirical relationship is used to calculate the instantaneous snowmelt rate in the model used by Lee et al. (2008a; 2010), in addition to the net-short radiation. If for a given 10 minute interval, the energy obtained by the melt calculation is negative, then no melt is generated. The input energy from the sun is considered to be used to increase the temperature of the snowpack. Positive energy is used for melting snow for the 10-minute interval. Using this energy budget algorithm, we optimize the intrinsic permeability of the snowpack for the two sets of experiments using one-dimensional water percolation model, which are 52.5 × 10 �10 m 2 and 75 × 10 �10 m 2 for the artificial rain-on-snow experiments and observations of diel variation, respectively.

Groundwater response analysis to multiple earthquakes on Jeju volcanic island

Earthquakes have been known to induce a groundwater response. This study statistically analyzed the relationship between the changes in groundwater level (oscillation) and seismic waves, as well as the relationship between the changes in groundwater level and earthquakes of various magnitudes and epicenters more than 1,000 km distance from Jeju Island. The analysis showed that the groundwater level in Jeju Island is changed mostly by earthquakes larger than M = 7.0 within a 3,000 km from the epicenter. A positive relationship appeared between the earthquake magnitude and groundwater level change. A similar positive trend was observed between the maximum groundwater level and the seismic amplitude of the earthquakes. Geologically and spatially, the northern area of the island showed the highest response to earthquakes, the southern area showed an intermediate response, and the western and eastern areas showed the lowest response. The highest groundwater response in the northern area might be linked to its permeable structures and geological layers.