Groundwater nitrate contamination in small agriculture area: assessing the source and process using isotopes and ions

Abstract

Source identification of nitrate contamination in groundwater is an important first step for groundwater management and quality prediction. Therefore, a small scale field research was conducted in an agriculture-dominated alluvial fan in Kofu, Japan, where nitrate contamination was found in the groundwater. Methods used in this study were combining isotopes, ions (biochemical process) and precipitation data (physical process) to understand the nitrate source and process leading to the groundwater nitrate contamination. Our investigations suggest that the nitrate from manure source gave significantly larger contribution than fertilizer. In winter period, there was no strong evidence that anthropogenic nitrate exist in the groundwater. It also found that denitrification process might occur during the recharge process, hence reducing the nitrate concentration. As a preliminary step to describe groundwater dynamics, isotopes and ions provide effective tools to trace sources of contamination and to study processes affecting nitrate.