Abstract
Factors controlling the spatial distribution and temporal trend of groundwater quality at a national scale are important to investigate for sustaining livelihood and ecological balance. This study evaluated groundwater quality data for 12 parameters (n = 6405 for each parameter), collected from 97 groundwater monitoring stations (=289 monitoring wells) for ten years. Spatial distribution of groundwater quality parameters varied through the regional scale. Six parameters: T, EC, Ca2+, Mg2+, HCO3−, and Cl− were having dominant increasing trend, remaining pH, Eh, Na+, K+, SO42−, and NO3− showed a dominant decreasing trend over time. Among land use types, the upland fields had the highest mean of groundwater NO3− (22.2 mg/L), confirming plenty of application of fertilizers (5–10 kg/a more than standard) to upland fields. Means of groundwater Cl− and Na+ (705.3 and 298.4 mg/L, respectively) in the residential areas are greater than those in other land use types by 408–685.9, 154.3–274.2 mg/L, respectively. Agricultural activities were the main controlling factor of groundwater NO3− contamination in rural areas, domestic activities were responsible for groundwater Cl− and Na+ in urban areas, and seawater intrusion was controlling groundwater Cl− in coastal areas (within 10 km from sea). Groundwater hydrochemistry was controlled by the mechanism of geogenic rock and evaporation dominance. The rock dominance mechanism indicated that groundwater was interacting with rocks and resulted in groundwater chemistry. The findings of this study showed that groundwater was mainly contaminated by anthropogenic factors in some rural and residential areas. Effective measures by government authorities are needed to improve the groundwater quality.
Highlights
The quality of groundwater, influenced by several anthropogenic and natural factors, is one of the most profound issues worldwide [1]
The government operates several monitoring networks, including the Groundwater Quality Monitoring Network (GQMN) operated by Korea Environment Corporation (KECO), which is affiliated with the Ministry of Environment (ME), and the National Groundwater Monitoring Network (NGMN) operated by K-water, which is affiliated with the ME [9]
Median values are more appropriate to find the dominant pattern of ions in water when the parameters data is large or is showing not normal distribution [14]
Summary
The quality of groundwater, influenced by several anthropogenic and natural factors, is one of the most profound issues worldwide [1]. To manage and preserve groundwater, it is necessary to evaluate the status and variability of groundwater quality. In this regard, the Korean government regularly monitors groundwater quality to develop basic guidelines for groundwater policy [9]. The government operates several monitoring networks, including the Groundwater Quality Monitoring Network (GQMN) operated by Korea Environment Corporation (KECO), which is affiliated with the Ministry of Environment (ME), and the National Groundwater Monitoring Network (NGMN) operated by K-water, which is affiliated with the ME [9]. The GQMN monitors groundwater quality on a national scale every quarter with several parameters, including field measured parameters and major ions. The regions under GQMN are divided into uncontaminated (background) regions and already contaminated (or suspected contamination) regions [10]
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