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Geologic controls on the chemical behaviour of nitrate in riverside alluvial aquifers, Korea
Author(s) -
Min JoongHyuk,
Yun SeongTaek,
Kim Kangjoo,
Kim HyoungSoo,
Kim DongJu
Publication year - 2003
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.1189
Subject(s) - nitrate , groundwater , aquifer , hydrology (agriculture) , water table , environmental science , alluvium , fertilizer , irrigation , water quality , manure , surface water , environmental chemistry , geology , environmental engineering , ecology , chemistry , geotechnical engineering , geomorphology , biology
To investigate the origin and behaviour of nitrate in alluvial aquifers adjacent to Nakdong River, Korea, we chose two representative sites (Wolha and Yongdang) having similar land‐use characteristics but different geology. A total of 96 shallow groundwater samples were collected from irrigation and domestic wells tapping alluvial aquifers. About 63% of the samples analysed had nitrate concentrations that exceeded the Korean drinking water limit (44·3 mg l −1 NO 3 − ), and about 35% of the samples had nitrate concentrations that exceeded the Korean groundwater quality standard for agricultural use (88·6 mg l −1 NO 3 − ). Based on nitrogen isotope analysis, two major nitrate sources were identified: synthetic fertilizer (about 4‰ δ 15 N) applied to farmland, and animal manure and sewage (15–20‰ δ 15 N) originating from upstream residential areas. Shallow groundwater in the farmland generally had higher nitrate concentrations than those in residential areas, due to the influence of synthetic fertilizer. Nitrate concentrations at both study sites were highest near the water table and then progressively decreased with depth. Nitrate concentrations are also closely related to the geologic characteristics of the aquifer. In Yongdang, denitrification is important in regulating nitrate chemistry because of the availability of organic carbon from a silt layer (about 20 m thick) below a thin, sandy surface aquifer. In Wolha, however, conservative mixing between farmland‐recharged water and water coming from a village is suggested as the dominant process. Mixing ratios estimated based on the nitrate concentrations and the δ 15 N values indicate that water originating from the village affects the nitrate chemistry of the shallow groundwater underneath the farmland to a large extent. Copyright © 2003 John Wiley & Sons, Ltd.