Japan Geoscience Union Meeting 2016

Presentation information


Symbol A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW19] Water Environment and Geology in Urban Areas

Wed. May 25, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Takeshi Hayashi(Faculty of Education and Human Studies, Akita University), Hiroaki SUZUKI(Strategic Technology Development Dept. Research & Development Center, Nippon Koei Co., Ltd.), Kei Nishida(Interdisciplinary Centre for River Basin Environment, Interdisciplinary Graduate School, University of Yamanashi), Motoyuki Asada(Shimizu Corporation), Satoshi Takizawa(Department of Urban Engineering, Graduate School of Engineering, the University of Tokyo), Masaya Yasuhara(Rissho Univ.)

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

*Yuki Yamamoto1, Takashi Nakamura1, Kei Nishida1 (1.University of Yamanashi,Interdisciplinary Centre for River Basin Environment)

Keywords:Nitrogen isotope in ammmonia, Groundwater, Kathmandu Valley

The objectives of this study are to improve analysis methods of ammonia isotope and to apply for pollution source analysis of the environmental water sample. The target analysis is the groundwater of Nepal Kathmandu Valley. In this area, the dependence rate on groundwater is more than half of the total water demand, and there are many spots of exceed the ammonia standard value.
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.