Hydrogeochemical interpretation of South Korean groundwater monitoring data using Self-Organizing Maps

Byoung Young Choi, Seong Taek Yun, Kyoung Ho Kim, Ji Wook Kim, Hyang Mi Kim, Yong Kwon Koh

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)

Abstract

The National Groundwater Monitoring Network (NGMN) of South Korea provides data since 1995 to monitor the water level and quality of groundwater on a national scale. Major ions such as Ca, Mg, Na, K, HCO3, Cl, SO4 and NO3 have been monitored since 2008 to assess groundwater quality. Hydrochemical data of bedrock groundwater samples collected from 299 monitoring stations in 2009 were examined using the Self-Organizing Map (SOM) approach. Based on hydrochemical characteristics, bedrock groundwater is clustered into two groups and six subgroups. Group I containing 70.2% of groundwater samples (and monitoring stations) is characterized by lower TDS values and NO3 concentrations than Group II, indicating that Group I waters are less affected by contamination. Subgroup I-1 (39.1%) represents Ca-HCO3-type groundwater with relatively low pH, TDS and concentrations of most ions compared with groundwater of Subgroups I-2-1 (26.1%) and I-2-2 (5.0%). Subgroup I-2-2 represents a moderately alkaline, F-rich, Na-HCO3-type groundwater. Group II records either anthropogenic or natural processes. Subgroup II-1 (16.1%) contains groundwater with low values of TDS, HCO3 and pH, and moderately high NO3 concentrations due to nitrification, while groundwater of Subgroups II-2-1 and II-2-2 is characteristically high in Ca and Mg. Subgroup II-2-1 is also very high in SO4 and HCO3 but very low in NO3, while Subgroup II-2-2 is substantially enriched in Cl and NO3. The hydrochemistry of groundwater of Subgroup II-2-1 likely results from dissolution of carbonates and gypsum in clastic sedimentary rocks and is affected by dissolution of pyrite and/or S-bearing fertilizers in crystalline rocks. The enrichment of NO3, Cl, Ca and Mg in groundwater of Subgroup II-2-2 is the result of substantial contamination from agrochemicals and manure. Thus, about 20.5% (Subgroups II-1 and II-2-2) of bedrock groundwater in South Korea records anthropogenic contamination. This study shows that the SOM approach can be successfully used to classify and characterize the groundwater in terms of hydrochemistry and quality on a regional scale.

Original languageEnglish
Pages (from-to)73-84
Number of pages12
JournalJournal of Geochemical Exploration
Volume137
DOIs
Publication statusPublished - 2014 Feb

Bibliographical note

Funding Information:
This work was supported by the National Research Foundation of Korea Grant (2012, University-Institute Cooperation Program) funded by the Korean Government ( Ministry of Science, ICT & Future Planning ). Additional supports were provided by the 2010 Eco-Technopia 21 Project from the KEITI (project title: Studies of geological and geochemical factors related to the behavior and leakage of carbon dioxide in geologic carbon storage: Suggestion of optimal methods for environmental impact assessment of carbon storage), the Radioactive Waste Management Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea Government Ministry of Knowledge Economy (No. 201017102002D ), and the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources (KIGAM) . Prof. Rodney Grapes helped improve early version of this manuscript. Constructive comments from two anonymous reviewers and Dr. HE Gäbler (Associate Editor) helped clarify and improve the manuscript.

Keywords

  • Bedrock groundwater
  • Classification and characterization
  • Hydrochemistry
  • National Groundwater Monitoring Network
  • Self-Organizing Map (SOM) approach
  • South Korea

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Economic Geology

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