Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 3385-3399, 2017
http://www.atmos-chem-phys.net/17/3385/2017/
doi:10.5194/acp-17-3385-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
09 Mar 2017
Interpreting the 13C  ∕ 12C ratio of carbon dioxide in an urban airshed in the Yangtze River Delta, China
Jiaping Xu1, Xuhui Lee1,2, Wei Xiao1, Chang Cao1, Shoudong Liu1, Xuefa Wen3, Jingzheng Xu1, Zhen Zhang1, and Jiayu Zhao1 1Yale-NUIST Center on Atmospheric Environment, Nanjing University of Information Science & Technology, Nanjing, China
2School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA
3Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
Abstract. Observations of atmospheric CO2 mole fraction and the 13C ∕ 12C ratio (expressed as δ13C) in urban airsheds provide constraints on the roles of anthropogenic and natural sources and sinks in local and regional carbon cycles. In this study, we report observations of these quantities in Nanjing at hourly intervals from March 2013 to August 2015, using a laser-based optical instrument. Nanjing is the second largest city located in the highly industrialized Yangtze River Delta (YRD), eastern China. The mean CO2 mole fraction and δ13C were (439.7 ± 7.5) µmol mol−1 and (−8.48 ± 0.56) ‰ over this observational period. The peak monthly mean δ13C (−7.44 ‰, July 2013) was 0.74 ‰ higher than that observed at Mount Waliguan, a WMO (World Meteorological Organization) baseline site on the Tibetan Plateau and upwind of the YRD region. The highly 13C-enriched signal was partly attributed to the influence of cement production in the region. By applying the Miller–Tans method to nighttime and daytime observations to represent signals from the city of Nanjing and the YRD, respectively, we showed that the 13C ∕ 12C ratio of CO2 sources in the Nanjing municipality was (0.21 ± 0.53) ‰ lower than that in the YRD. Flux partitioning calculations revealed that natural ecosystems in the YRD were a negligibly small source of atmospheric CO2.

Citation: Xu, J., Lee, X., Xiao, W., Cao, C., Liu, S., Wen, X., Xu, J., Zhang, Z., and Zhao, J.: Interpreting the 13C  ∕ 12C ratio of carbon dioxide in an urban airshed in the Yangtze River Delta, China, Atmos. Chem. Phys., 17, 3385-3399, doi:10.5194/acp-17-3385-2017, 2017.
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Short summary
The Yangtze River Delta is one of the most industrialized regions in China. In situ optical isotopic measurement in Nanjing, a city located in the Delta, showed unusually high atmospheric δ13C signals in the summer (−7.44 ‰, July 2013 mean), which we attributed to the influence of cement production in the region. Flux partitioning calculations revealed that natural ecosystems in the region were a negligibly small source of atmospheric CO2.
The Yangtze River Delta is one of the most industrialized regions in China. In situ optical...
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