Evolution of Atmospheric Carbon Dioxide and Methane Mole Fractions in the Yangtze River Delta, China

As the most economically developed region in China, the Yangtze River Delta (YRD) region contributed to similar to 17% of the total anthropogenic CO2 emissions from China. However, the studies of atmospheric CO2 and CH4 in this area are relatively sparse and unsystematic. Here, we analyze the changing characters of those gases in different development periods of China, based on the 11-year atmospheric CO2 and CH4 records (from 2010 to 2020) at one of the four Chinese sites participating in the World Meteorological Organization/Global Atmospheric Watch (WMO/GAW) program (Lin'an regional background station), located in the center of YRD region, China. The annual average atmospheric CO2 and CH4 mole fractions at LAN have been increasing continuously, with growth rates of 2.57 +/- 0.14 ppm yr(-1) and 10.3 +/- 1.3 ppb yr(-1), respectively. Due to the complex influence of regional sources and sinks, the characteristics of atmospheric CO2 and CH4 varied in different periods: (i) The diurnal and seasonal variations of both CO2 and CH4 in different periods were overall similar, but the amplitudes were different. (ii) The elevated mole fractions in all wind sectors tended to be uniform. (iii) The potential source regions of both gases expanded over time. (iv) The growth rate in recent years (2016-2020) changed significantly less than that in the earlier period (2010-2015). Our results indicated that the CO2 and CH4 mole fractions were mainly correlated to the regional economic development, despite the influence of special events such as the G20 Summit and COVID-19 lockdown.