Mixing ratio and carbon isotopic composition investigation of atmospheric CO2 in Beijing, China

• Published in: The Science of the total environment 2016-01, Vol.539, p.322-330
• Main Authors: Pang, Jiaping, Wen, Xuefa, Sun, Xiaomin
• Format: Article
• Language: English
• Subjects: Air Pollutants - analysis; Atmosphere - chemistry; Atmospheric CO2 source; Atmospherics; Beijing; Carbon; Carbon dioxide; Carbon Dioxide - analysis; Carbon Isotopes - analysis; Coal; Combustion; Environmental Monitoring; Heating; Isotope ratio infrared spectroscopy (IRIS); Keeling plot; Mixing ratios; Seasons; δ13C
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2015.08.130

The stable isotope composition of atmospheric CO2 can be used as a tracer in the study of urban carbon cycles, which are affected by anthropogenic and biogenic CO2 components. Continuous measurements of the mixing ratio and δ13C of atmospheric CO2 were conducted in Beijing from Nov. 15, 2012 to Mar. 8, 2014 including two heating seasons and a vegetative season. Both δ13C and the isotopic composition of source CO2 (δ13CS) were depleted in the heating seasons and enriched in the vegetative season. The diurnal variations in the CO2 mixing ratio and δ13C contained two peaks in the heating season, which are due to the effects of morning rush hour traffic. Seasonal and diurnal patterns of the CO2 mixing ratio and δ13C were affected by anthropogenic emissions and biogenic activity. Assuming that the primary CO2 sources at night (22:00–04:00) were coal and natural gas combustion during heating seasons I and II, an isotopic mass balance analysis indicated that coal combustion had average contributions of 83.83±14.11% and 86.84±12.27% and that natural gas had average contributions of 16.17±14.11% and 13.16±12.27%, respectively. The δ13C of background CO2 in air was the main error source in the isotopic mass balance model. Both the mixing ratio and δ13C of atmospheric CO2 had significant linear relationships with the air quality index (AQI) and can be used to indicate local air pollution conditions. Energy structure optimization, for example, reducing coal consumption, will improve the local air conditions in Beijing. [Display omitted] •Continuous measurement of atmospheric CO2 and δ13C in Beijing.•δ13C depleted in heating season and enriched in vegetative season.•Diurnal variation of δ13C showed two peaks in heating season.•Coal combustion was the main local CO2 source.•δ13C showed significant liner relationship with air quality index (AQI).