Since the mid-twentieth century, geology has gradually evolved as an interdisciplinary context in South Korea. The journal of Economic and Environmental Geology (EEG) has a long history of over 52 years and published interdisciplinary articles based on geology. In this study, we performed a literature review using topic modeling based on Latent Dirichlet Allocation (LDA), an unsupervised machine learning model, to identify geological topics, historical trends (classic topics and emerging topics), and association by analyzing titles, keywords, and abstracts of 2,571 publications in EEG during 1968-2020. The results showed that 8 topics ('petrology and geochemistry', 'hydrology and hydrogeology', 'economic geology', 'volcanology', 'soil contaminant and remediation', 'general and structural geology', 'geophysics and geophysical exploration', and 'clay mineral') were identified in the EEG. Before 1994, classic topics ('economic geology', 'volcanology', and 'general and structure geology') were dominant research trends. After 1994, emerging topics ('hydrology and hydrogeology', 'soil contaminant and remediation', 'clay mineral') have arisen, and its portion has gradually increased. The result of association analysis showed that EEG tends to be more comprehensive based on 'economic geology'. Our results provide understanding of how geological research topics branch out and merge with other fields using a useful literature review tool for geological research in South Korea.
<p>Due to urbanization, land use and cover change (LUCC) are considered one of the concerns in groundwater recharge by precipitation because urban development increases impermeable surfaces. The main objective of this study is to investigate the effects of LUCC on groundwater recharge by precipitation in South Korea. Ten monitoring wells were selected based on a significant difference in LUCC using Arc-GIS software. Then lag-time between precipitation and groundwater level response was estimated based on correlation coefficients computed from cross-correlation function (CCF) and moving average (MA) for 3 years before and after LUCC. As a result of the estimated lag-time, monitoring wells were classified into two groups: group &#8544; (n = 3) with more than 30% increase in the impermeable surface and group &#8545; (n = 7) with less than 30% increase in the impermeable surface. Group I showed a significant increase in lag-time computed from MA (28 to 127 days) and CCF (6 to 19 days), while group II showed no significant difference in lag-time. The results of this study indicate that groundwater recharge is regulated by the occurrence of the impermeable surface, interrupting direct groundwater recharge from rainwater infiltration.</p>
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