Detail Abstract

Novel Method to Identify the Source of Groundwater Nitrate Pollution in Intensive Agricultural and Livestock Areas in Japan

Abstract

Groundwater pollution by nitrate is a common problem in many parts of the world. The agriculturally important Shimabara area in Nagasaki, Japan, is experiencing this problem. The general source of drinking water in the study area is groundwater and consequently, nitrate pollution is a significant problem.</br>   Investigating contaminant sources is indispensable to developing effective countermeasures against nitrate pollution in groundwater. Major nitrogen sources are chemical fertilizer, livestock waste, and domestic wastewater. The scatter diagram of δ¹⁸O and δ¹⁵N of NO₃⁻ (Kendall, 1998) has been used to identify pollution sources. However, it can be difficult to distinguish sources because of the overlapping δ¹⁸O and δ¹⁵N ranges of chemical fertilizer and livestock waste sources. In this study, we propose the use of coprostanol as a method to identify the source of the pollution. Coprostanol has been used as a fecal contamination indicator because it is one of the major fecal sterols formed by the conversion of cholesterol by intestinal bacteria in the gut of higher animals. The proposed method was applied to a case of nitrate contamination in Shimabara City, Nagasaki Prefecture, and its applicability was discussed.