PROGRESS IN GEOGRAPHY ›› 2015, Vol. 34 ›› Issue (6): 726-738.doi: 10.18306/dlkxjz.2015.06.008

• Ecology and Environment • Previous Articles     Next Articles

A review of urbanization impact on nitrogen cycle

Qun GAO1, Cheng YU1,2   

  1. 1. Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, CAS, Nanjing 210008, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2014-10-01 Revised:2015-05-01 Online:2015-06-15 Published:2015-06-15

Abstract:

Nitrogen (N) cycle has been poorly characterized in urban ecosystems. In China, urbanization is an important process that alters urban ecosystem and urban nitrogen biogeochemical cycle. Human activities have more than doubled the nitrogen inputs to urbanized areas, and the sources, magnitude, spatiotemporal patterns, and drivers of N fluxes have been mediated by human activities. The imbalance of nitrogen cycle has far exceeded the safe limits of urban sustainable development in some urban areas in China. The urbanized areas are facing a series of environmental problems induced by excessive emission and deposition of reactive nitrogen. Urban smog is becoming very serious in a large number of Chinese cities. However, owing to the limited knowledge on the role of humans in the N biogeochemical cycle and the complexity and uncertainty of urban ecosystems, ecological research of nitrogen emission, deposition, transformation, removal, and retention in urban areas is relatively weak. Thus, comprehensively quantifying changes of nitrogen cycle in urbanized areas and understanding the effects of human activities, such as urbanization and economic development, on the variations of reactive nitrogen fluxes, have been a crucial topic in urban ecological research. This article reviews the state-of-the-art research in this field on the basis of comparison and analysis of Chinese and international studies. The problems exist in current research were summarized and future areas of research aiming at a much improved understanding of the scope of the anthropogenic N problem are discussed. With serious nitrogen pollution and environmental effects in urban areas, it is essential to carry out a long-term study of nitrogen flux and nitrogen budget to investigate the problem of nitrogen imbalance. It is necessary to think beyond the control of pollutant emissions and approach the issue and solution from an urban planning perspective and conduct comprehensive studies to understand the variation of nitrogen input and output trends and driving mechanisms.

Key words: urban smog, nitrogen cycle, nitrogen budget, urban ecosystem, urbanization