Under changing climate, increasing groundwater use has risen the concern for groundwater quality variations over recent years, to maintain a healthy ecosystem. The objectives were to identify trend of temporal variations in groundwater quality and its suitability for different uses in Republic of Korea. Water quality data were collected from 198 monitoring stations of Groundwater Quality Monitoring Network (GQMN), annually for the period of ten years (2008–2017). Non-parametric trend analysis of a Mann–Kendall test and Theil–Sen’s slope was done on groundwater physico-chemical data of ten years. Groundwater suitability evaluation was done for use in main sectors including domestic (drinking) and agriculture (irrigation). For drinking suitability analysis, results were compared with World Health Organization (WHO) and Korean Ministry of Environment (KME) established guidelines. For irrigation suitability evaluation, electrical conductivity (EC), Sodium Adsorption Ratio (SAR), percent of Na⁺, Residual Sodium Carbonate (RSC), US Salinity Laboratory (USSL), and Wilcox diagram were used. Most significantly, water type belongs to Ca-HCO₃ and Ca-SO₄ types, but a small proportion belongs to Na-CO₃ and Na-Cl types. Approximately, 96% and 93% of groundwater samples are suitable for drinking, based on WHO and KME guidelines, respectively. Around 98% and 83% of groundwater samples are in suitable range for irrigation use, based on USSL and Wilcox diagrams, respectively.

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.

이 연구는 강원도 양구군 해안분지 외곽에서 586일 동안 10분 간격으로 수집한 토양수분 및 기상관측 자료를 이용하여 잠재 지하수 함양량을 모의 분석하였다. 토양수분 함량은 일반적으로 깊이가 깊을수록, 경사가 완만할수록 높았으며 강우량에 비례했다. 현장에서 측정한 토양수분 함량과 모의분석한 토양수분 함량의 상관계수는 0.9-0.93으로 높은 상관성을 보였다. 잠재 지하수 함양량은 토양수분 변동 범위가 넓은 우기의 자료와 HYDRUS-1D를 이용하여 추정하였다. 잠재 지하수 함양량은 YHS2에서 2017년에 555 mm, 2018년에 332mm, YHS3에서 2017년에 418 mm, 2018년에 408 mm로 2017년에 지하수가 더 많이 함양되었다.

본 연구에서는 남극 바톤반도 해안에서 내륙으로 1.5 ㎞ 이격한 경사각(18, 15, 8°)이 다른 3개 관측지점에서 토양수분 및 지온을 측정하였다. 이들의 시계열적 특성을 파악하기 위하여 자기상관분석, 스펙트럼분석 및 교차상관분석을 하였다. 또한 활동층의 열적 특성을 해석하기 위해 열확산계수를 산정하고 두께를 추산하였다. 토양수분 및 지온 센서는 5, 10, 15, 20 ㎝ 깊이에 설치하였고 2019년 12월 19일부터 2020년 1월 4일까지 17일간 5분 간격으로 측정하였다. 토양수분 함량이 모든 지점의 20 ㎝ 깊이에서 가장 많았다. 0.5 ㎜/day 이하의 강우는 토양수분 함량에 영향을 미치지 못했다. 토양온도는 최대 13.2℃, 최소 -0.6℃였으며 중앙값은 깊어질수록 낮았고 12월 20일 1~5시를 제외하고는 24시간 동안 0℃ 이상이었다. 자기상관분석 결과 경사각이 완만할수록 토양수분에 대한 지연시간이, 얕을수록 토양온도에 대한 지연시간이 짧았다. 토양수분의 주기는 2.5-4.7일, 토양온도의 주기는 1.0-1.1일이었다. 기온(입력)과 토양온도(출력)에 대한 교차상관분석 결과, 입력값을 태양복사로 했을 때보다 지연시간이 더 짧고 상관계수가 더 컸다. 열확산계수는 0.01-121.94 ㎟/sec의 범위(중앙값=0.34-0.59 ㎟/sec)였다. 이 중앙값은 동일 방법을 이용한 기존 연구의 값(0.4-3.3 ㎟/sec)의 최솟값에 가까웠다. 활동층의 두께는 23.6-38.6 ㎝이며 이는 기존에 연구된 바톤반도 해안 근처(0.2 ㎞ 이내)의 활동층 두께(41-77 ㎝)보다 얇다. 이렇게 열확산계수가 작고 활동층 두께가 얇은 이유는 이번 연구지역이 기존 연구보다 해안으로부터 멀리 떨어져 있기 때문으로 사료된다.

The effects of the unpredictability of the flow system in a karst area, with respect to bacterial communities in the aquatic environment, were evaluated. Bacterial communities from two different types of flow conditions (spring and sinkhole) were characterized and compared in the karst area. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the major phyla present in the sampled spring and sinkhole waters. The water samples from the spring points were heavily loaded with Actinobacteria, especially Firmicutes, which accounted for 4.3% of the bacterial content. Furthermore, Actinobacteria were prevalent in some water samples, serving as indicators of the effects of seawater inundation. The richness and diversity of bacterial species were evaluated at the spring and sinkhole water points. The spring waters showed a higher bacterial richness and diversity compared to the sinkhole waters. Our results provide valuable information for the evaluation and investigation of microbial compositions in karst areas, which are characterized by heterogeneous hydrological conditions. The microbial species in karst areas are already exposed to changing hydrogeological conditions, and are likely to be confronted with future changes; thus, their spatiotemporal variations reflect the shifting baselines of physicochemical and ecosystem processes.