Characterizing land use effect on shallow groundwater contamination by using self-organizing map and buffer zone
Chung‐Mo Lee, Hanna Choi, Yongcheol Kim, Moon-Su Kim, Hyun-Koo Kim, Se‐Yeong Hamm
Abstract
Nitrate–nitrogen (NO 3 –N) contamination in groundwater is a major problem of drinking and domestic waters in rural areas. This study revealed the influence of land use type on shallow alluvial groundwaters in a typical rural area in South Korea by applying a self-organizing map (SOM), principal component analysis (PCA), and hierarchical cluster analysis (HCA). The uncertainty of spatial information on land use was improved by using a buffer zone of the average influence radius of 32.65 m surrounding wells. Two major land-use types, forests (44.9%) and rice fields (28.8%), occupied a total of 73.7% of the rural area. The higher concentrations of NO 3 –N in public facilities and livestock areas were demonstrated to directly recharge groundwater pollutants. NO 3 –N contamination in rice paddies , which also contained chlorine (Cl) and sulfate (SO 4 ), was assessed according to the nutrients and residual salt in the soil. In addition, different NO 3 –N concentrations for the same land use indicate various biochemical reactions and NO 3 –N recharge types into the groundwater system. The shallow groundwaters in the study area were classified into three clusters according to their chemical constituents and land–use properties, especially NO 3 –N concentration, including pH, Cl, and SO 4 , using a SOM, PCA, and HCA. Unlike existing studies, we applied a buffer zone based on the Cooper–Jacob equation to obtain an improved SOM model prediction accuracy approximately 10% greater than that using the original dataset.