Spatiotemporal variability of the near-surface CO2 concentration across an industrial-urban-rural transect, Nanjing, China

Yunqiu Gao; Xuhui Lee; Shoudong Liu; Ning Hu; Xiao Wei; Cheng Hu; Cheng Liu; Zhen Zhang; Yichen Yang

doi:10.1016/j.scitotenv.2018.03.126

Spatiotemporal variability of the near-surface CO₂ concentration across an industrial-urban-rural transect, Nanjing, China

Sci Total Environ. 2018 Aug 1:631-632:1192-1200. doi: 10.1016/j.scitotenv.2018.03.126. Epub 2018 Mar 16.

Authors

Yunqiu Gao¹, Xuhui Lee², Shoudong Liu³, Ning Hu¹, Xiao Wei¹, Cheng Hu⁴, Cheng Liu¹, Zhen Zhang¹, Yichen Yang¹

Affiliations

¹ Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change (ILCEC), Nanjing University of Information Science & Technology, Nanjing 210044, China; Key Laboratory of Meteorological Disaster, Ministry of Education (KLME), Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science & Technology, Nanjing 210044, China.
² Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change (ILCEC), Nanjing University of Information Science & Technology, Nanjing 210044, China; School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA. Electronic address: xuhui.lee@yale.edu.
³ Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change (ILCEC), Nanjing University of Information Science & Technology, Nanjing 210044, China; Key Laboratory of Meteorological Disaster, Ministry of Education (KLME), Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD), Nanjing University of Information Science & Technology, Nanjing 210044, China. Electronic address: lsd@nuist.edu.cn.
⁴ Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change (ILCEC), Nanjing University of Information Science & Technology, Nanjing 210044, China; Department of Soil, Water, and Climate, University of Minnesota-Twin Cities, Saint Paul, MN, USA.

PMID: 29727944
DOI: 10.1016/j.scitotenv.2018.03.126

Abstract

Urban lands are CO₂ emission hotspots. In this paper, we report the CO₂ concentration observations along an industrial-urban-rural transect and in a network of sites in the urban center, in Nanjing, China. The mean CO₂ concentration was highest at the industrial site, not at the densely populated urban center (urban: 429.2±8.7ppm, rural: 421.2±10.0ppm, industrial: 443.88±18.3ppm), based on four sampling periods in four different seasons in 2014 and 2015. At the urban sites, a reversed weekend effect was observed, whereby the weekend CO₂ concentration was higher than the weekday concentration by a mean of 0.9ppm over the four measurement periods and by 8.1ppm in the spring, suggesting higher traffic volume on weekends than on weekdays. The vertical CO₂ gradient was weak above the urban canopy layer, with a mean difference of only 1.1ppm between the 60-m and 110-m measurement heights, reflecting efficient mixing in both daytime and nighttime periods. The average along-wind concentration gradient was 0.25±0.87ppmkm^-1 at the height of 110m according to the observations made at five urban sites. Based on a simple box model, we estimated an anthropogenic surface flux of about 0.4mgCO₂m^-2s^-1 for the urban center.

Keywords: CO(2) concentration; Horizontal gradient; Vertical gradient; Weekend effect.