Determining diurnal fossil fuel CO 2 and biological CO 2 by Δ 14 CO 2 observation on certain summer and winter days at Chinese background sites

Diurnal atmospheric Δ CO was measured on two consecutive days in summer and winter, 2016 at Shangdianzi, Lin'an and Luhuitou regional background sites, and at Waliguan global background site in China. The objectives of this study were to determine diurnal fossil fuel CO (CO ) and biological CO (CO ) concentrations and to ascertain the factors influencing them. Evident CO inputs (0-33.0 ± 1.4 ppm) were found, with some small morning and afternoon rush hour signals. Particularly, the long-range transport of air masses influenced the seasonal differences and rapid diurnal variations in CO . Diurnal CO showed violent variations (-20.9-113.3 ppm), with high values at night and low or negative values during the daytime. Diurnal CO variations resulted from the tradeoffs between photosynthetic CO uptake and biological respiration CO emission as well as atmospheric boundary layer heights variations. These results might help to understand the roles of fossil fuel sources and biological sources on atmospheric CO diurnal variations at Chinese background sites.