[A-HW25] 都市域の地下水・環境地質

[AHW25-02] ネパール・カトマンズ盆地の地下水中のアンモニアの起源推定

*中村 高志¹、西田 継¹、山本 勇生²、平賀 皓大²、Anoj Khanal³、Suresh Das Shrestha³、風間 ふたば¹ (1.山梨大学・国際流域環境研究センター、2.山梨大学・工学部、3.CDG, Tribhuvan University)

キーワード：カトマンズ, 都市, 地下水, アンモニア性窒素同位体, 硝酸性窒素・酸素同位体

Groundwater quality is a critical problem in the Kathmandu Valley, Nepal. The population of the city increased by 6 times in the last six decades and more than half of water demand depends on groundwater source. Microbial and nitrogen contamination causes loss of water resources, nevertheless, understanding of nitrogen source and dynamics in groundwater system still remains insufficient in the central area of the valley. Objective of this study is to identify source of ammonium contamination on shallow and deep groundwater.
Groundwater samples were collected from 34 shallow wells and 5 deep tube wells in September 2014. Ammonium ion were detected from 12 shallow wells and 2 deep wells. Those ammonium concentrations ranged from 1.3 to 103 ppm. Nitrogen isotope values in ammonium ranged from -0.3 to 9.3 permill; this wide range of the nitrogen isotope values suggested possibility of ammonium contamination from natural and anthropogenic sources.

Acknowledgement
This study are supported by the Science and Technology Research Partnership for Sustainable Development Program (SATREPS, Project Manager: Prof. Narendra Man Shakya and Prof. Futaba Kazama) of Japan Cooperation Agency (JICA)/Japan Science and Technology Agency (JST).