Acta Geographica Sinica ›› 2012, Vol. 67 ›› Issue (6): 758-770.doi: 10.11821/xb201206004

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Research on Carbon Cycle and Carbon Balance of Nanjing Urban System

ZHAO Rongqin1,2, HUANG Xianjin1, PENG Buzhuo1   

  1. 1. School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China;
    2. College of Resources and Environment, North China University of Water Conservancy and Hydroelectric Power, Zhengzhou 450011, China
  • Received:2011-09-20 Revised:2012-02-09 Online:2012-06-20 Published:2012-06-20
  • Supported by:
    National Social Science Foundation of China, No.10ZD&030; China Clean Development Mechanism Fund; China Postdoctoral Science Foundation Funded Project, No.2012M511243; Startup Project for High-level Talented Person of North China Institute of Water Conservancy and Hydroelectric Power, No.201164

Abstract: Cities are areas where human energy activities and carbon emission concentrated. The study on carbon cycle of urban system is helpful to understand the role of cities in the regional carbon cycle process, and can provide theoretical reference for establishing urban carbon emission estimation standard and low-carbon urban development pattern. Based on the method of IPCC and other researches, systematic urban carbon storage and carbon flux estimation methods was established, carbon cycle of urban system of Nanjing city was studied, and carbon storage, carbon flux and carbon balance of Nanjing city were analyzed. The main conclusions can be drawn as follows. (1) The total carbon storage of Nanjing city presented a slow rising trend. In 2009, the total carbon storage was 6937?104 t, in which natural carbon storage accounted for 88%. Human carbon storage, especially the carbon pool in urban greenbelt and buildings presented a drastically increasing trend. (2) Vertical carbon input flux of Nanjing city mainly included photosynthesis and water carbon absorption. Lateral carbon input flux rapidly increased and reached 3043?104 t, in which carbon input by energy and timber increased and carbon input by food deceased. (3) Vertical carbon output flux rapidly increased and reached 3295?104 t, in which carbon emission by fossil energy use accounted for nearly 80%, but carbon from natural process only accounted for 6%, indicating that human carbon emission constituted the main part of urban vertical carbon flux. Lateral carbon output flux presented a declining trend, which included energy products, aquatic products and organic waste. (4) In the past years, the carbon output was higher than carbon input of Nanjing city, and the balance between them showed an expanding trend. Generally, the percentage of hidden carbon flow and the carbon needed for manufacturing decreased, which indicated that the carbon efficiency was increasing. (5) Carbon compensation rate of Nanjing city obviously decreased, which indicated that the terrestrial carbon sink function of Nanjing city were not enough to compensate the anthropogenic carbon emissions, and the carbon balance of Nanjing city was seriously disturbed, which caused the increase of carbon cycle pressure.

Key words: urban system, carbon cycle, carbon balance, carbon storage, carbon flux, Nanjing city