Urban Nitrogen Metabolism in Xiamen City, China

Wei Huang1, Shenghui Cui1, Yang Yu1, Bing Gao1, Xuemei Bai2

1 Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, 1799 Jimi Road, Xiamen, China, 361021, whuang@iue.ac.cn
2 Fenner School of Environment and Society, College of Medicine, Biology and Environment, Australian National University, Canberra, Australia, 0200, xuemei.bai@anu.edu.au


Urban settlements, as highly concentrated areas for human production and consumption activities, have become important components in the alteration of regional and even global nitrogen (N) cycle. This study, by using substance flow analysis (SFA), establishes an urban N metabolism model and quantifies a detailed N mass balance for Xiamen, a rapidly urbanizing city in China, in 2008. The results show that the total N input into Xiamen was 103.2 kt in 2008, including 64% through products and 36% from the environment. The total N output was 99.6 kt, with 12% as products exported to other regions and 88% released to the environment. Fossil fuels ranked first of the N inputs, contributing 78% of N to the atmosphere. About 50% of N inputs were retained within the urban ecosystem. N use efficiency in the food chain was only 11%. Several interventions are suggested to improve N efficiency and reduce N environmental impacts, including municipal solid waste composting, reduced fossil fuel consumption, fuel N removal and integrated watershed management.