2023 Fiscal Year Final Research Report

International comparative study on nitrogen flows and environmental pollutions among rapidly-growing Asian countries

Research Project

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Project/Area Number	20H02285
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 22060:Environmental systems for civil engineering-related
Research Institution	University of Yamanashi
Principal Investigator	Nishida Kei 山梨大学, 大学院総合研究部, 教授 (70293438)
Co-Investigator(Kenkyū-buntansha)	遠山忠山梨大学, 大学院総合研究部, 教授 (60431392) 中村高志山梨大学, 大学院総合研究部, 准教授 (60538057) 亀井樹山梨大学, 大学院総合研究部, 助教 (80792168) 齋木真琴総合地球環境学研究所, 研究部, 研究員 (60967058)
Project Period (FY)	2020-04-01 – 2024-03-31
Keywords	Nitrogen cycle / Development level / Urban / Agriculture / Groundwater
Outline of Final Research Achievements	The title of this study is “International comparative study on nitrogen flows and environmental pollutions in rapidly growing Asian countries”. The research questions is “how the level of economic development and social impacts affect nitrogen issues”. In Nepal, with the lowest Nominal GDP per capita (NGDP/c) and the highest population growth rate, the shallow groundwaters of Kathmandu area were severely polluted with nitrogen originated from wastewaters. In Cambodia, with double NGDP/c of Nepalese and the lowest population density among the four countries, the nitrogen level of the surface waters and groundwaters of rural areas were relatively low. In Japan, with one order-larger size of NGDP/c than that of other three countries, no temporal variations in nitrate concentrations of groundwaters were significantly observed in the last ten years, and the high concentrations were noticeably seen in urbanisation and agriculture prevailing areas.
Free Research Field	Environmentology
Academic Significance and Societal Importance of the Research Achievements	例えば、ネパール・カトマンズにおいては深層地下水に地質由来のアンモニア性窒素が多く含まれていること、地中でそれらが一旦酸化された後に微生物代謝によって除去されることが明らかとなった。これは、経済発展段階や人口密度・増加率といった社会要因と地理や気候に影響された自然要因の相互作用が窒素循環を形成していることを示すものである。また、浅層地下水の窒素汚染に対しては自律分散小型の用排水処理の導入、深層地下水のそれには分散処理に加えて、自然要因に駆動される長期的な変動の予測も視野に入れた水用途または水源の変更を実装可能な対策として提案した。