5:15 PM - 6:30 PM
[AHW19-P05] Modification of ammonium diffusion method for δ15N analysis and application for contaminated groundwater in Nepal Kathmandu Valley
Keywords:Nitrogen isotope in ammmonia, Groundwater, Kathmandu Valley
Ammonia isotope analysis of this study is a modification of the ammonia diffusion method of Holmes et al (1998). We succeeded in shortening the ammonium diffusion time from 14 days (original method) to 5 days. Ammonium concentrations were detected in the range of 2.0~17.1mg/L (n=9) and 1.8~15.3mg/L (n=6) from shallow dug well and shallow tube well, respectively.δ15N-NH4 was 2.1~23.3‰ (n=9) and 1.2~3.8‰ (n=6) from shallow dug well and shallow tube well, respectively. According to the previous studies, wastewater (human origin) has δ15N-NH4=24~40‰ (Ambio, 2004) and lake sediment (natural origin) has δ15N-NH4=-3.4~+2.1‰ (Vreca&Muri, 2006). These results suggest that the main source of ammonium contamination is soil and mixture of soil and wastewater for shallow tube wells and dug wells, respectively.