Interpreting the <sup>13</sup>C ∕ <sup>12</sup>C ratio of carbon dioxide in an urban airshed in the Yangtze River Delta, China
Observations of atmospheric CO<sub>2</sub> mole fraction and the <sup>13</sup>C ∕ <sup>12</sup>C ratio (expressed as <i>δ</i><sup>13</sup>C) in urban airsheds provide constraints on the roles of anthropogenic and natural sources and sinks i...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/3385/2017/acp-17-3385-2017.pdf |
| Summary: | Observations of atmospheric CO<sub>2</sub> mole fraction and the
<sup>13</sup>C ∕ <sup>12</sup>C ratio (expressed as <i>δ</i><sup>13</sup>C) 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 CO<sub>2</sub> mole fraction and
<i>δ</i><sup>13</sup>C were (439.7 ± 7.5) µmol mol<sup>−1</sup> and (−8.48 ± 0.56) ‰ over this observational period. The peak monthly mean <i>δ</i><sup>13</sup>C (−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 <sup>13</sup>C-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 <sup>13</sup>C ∕ <sup>12</sup>C ratio of CO<sub>2</sub> 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 CO<sub>2</sub>. |
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| ISSN: | 1680-7316 1680-7324 |