Econ. Environ. Geol. 2003; 36(6): 441-455

Published online December 31, 2003

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

The Hydrochemical and Stable Isotope Characteristics of Shallow Groundwater Near the Gwangju Stream

Uk Yun1*, Se-Jung Chi1 and Chil-Sup So2

1Korea Institute of Geoscience and Mineral Resources, Daejon 305-350, Korea
2Department of Earth and Environmental Sciences, Korea University, Seoul 136-701, Korea

Correspondence to :

Uk Yun

yunuk@kigam.re.kr

Received: October 1, 2003; Accepted: October 22, 2003

Abstract

The most common water types are found to be Ca-HCO3, Ca-Na-HCO3 and Ca-Na-HCO3-Cl in Gwangju groundwater. Groundwater near the Gwangju stream are characterized Ca-Cl water type, with over 50 mg/L of Cland 400 μS/cm of EC. The systematic variation of Cl?, HCO3?, EC and δ18O values in groundwater with distance away from drainages is caused by streamwater infiltration. Stable isotope data indicate that δD and δ18O values of groundwaters near drainages were enriched by evaporation effect, showing a equation of δD=7.1×δ18O-1. δ18O values over -6 ‰ are anomalous in the unconfined groundwater zones, which are influenced by the local surface water enriched in 18O composition. Groundwater in highland shows remarkably light δ18O values below -8‰. The infiltration
of streamwater is dominant in unconfined alluvium aquifer near drainages. δ13CDIC values (-17.6~-15.2‰) of groundwaters near drainages revealed that dissolved inorganic carbon (DIC) is predominantly originated from natural soil-derived CO2. δ15N and δ18O values of nitrate are 0~17.0‰ and 6.6~17.4‰, respectively. Relationship between δ15N and δ18O shows a systematic isotopic fractionation caused by denitrification of 40~60%, suggesting that the major source of groundwater nitrate originated from nitrate of soils, and mixing nitrate of soil and sewage or manure.

Keywords Gwangju, groundwater, hydrochemistry, stable isotope, denitrification

Article

Econ. Environ. Geol. 2003; 36(6): 441-455

Published online December 31, 2003

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

The Hydrochemical and Stable Isotope Characteristics of Shallow Groundwater Near the Gwangju Stream

Uk Yun1*, Se-Jung Chi1 and Chil-Sup So2

1Korea Institute of Geoscience and Mineral Resources, Daejon 305-350, Korea
2Department of Earth and Environmental Sciences, Korea University, Seoul 136-701, Korea

Correspondence to:

Uk Yun

yunuk@kigam.re.kr

Received: October 1, 2003; Accepted: October 22, 2003

Abstract

The most common water types are found to be Ca-HCO3, Ca-Na-HCO3 and Ca-Na-HCO3-Cl in Gwangju groundwater. Groundwater near the Gwangju stream are characterized Ca-Cl water type, with over 50 mg/L of Cland 400 μS/cm of EC. The systematic variation of Cl?, HCO3?, EC and δ18O values in groundwater with distance away from drainages is caused by streamwater infiltration. Stable isotope data indicate that δD and δ18O values of groundwaters near drainages were enriched by evaporation effect, showing a equation of δD=7.1×δ18O-1. δ18O values over -6 ‰ are anomalous in the unconfined groundwater zones, which are influenced by the local surface water enriched in 18O composition. Groundwater in highland shows remarkably light δ18O values below -8‰. The infiltration
of streamwater is dominant in unconfined alluvium aquifer near drainages. δ13CDIC values (-17.6~-15.2‰) of groundwaters near drainages revealed that dissolved inorganic carbon (DIC) is predominantly originated from natural soil-derived CO2. δ15N and δ18O values of nitrate are 0~17.0‰ and 6.6~17.4‰, respectively. Relationship between δ15N and δ18O shows a systematic isotopic fractionation caused by denitrification of 40~60%, suggesting that the major source of groundwater nitrate originated from nitrate of soils, and mixing nitrate of soil and sewage or manure.

Keywords Gwangju, groundwater, hydrochemistry, stable isotope, denitrification

    KSEEG
    Apr 30, 2024 Vol.57 No.2, pp. 107~280

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