As the most economically developed region in China, the Yangtze River Delta (YRD) region contributed 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.

The Yangtze River Delta (YRD) is the most developed region in China. Influenced by intensive and complex anthropogenic activities, atmospheric pollution in this region is highly variable, and reports are sparse. In this study, a seven-year history of the atmospheric O₃ and NO_x mixing ratios over a typical city, Hangzhou, was presented to enrich the studies on air pollution in the YRD region. Our results revealed that the diurnal variation in NO_x corresponded to traffic rush hours, while O₃ was mainly impacted by photochemical reactions in the daytime. The weekend effect was significant for NO_x, but inapparent for O₃. Two O₃ peaks in May and September were caused by seasonal atmospheric stability and climatic conditions. The lower NO_x and higher O₃ levels observed suggested direct effects from traffic restrictions and large-scale industrial shutdowns during the COVID-19 lockdown in 2020 compared with those in the periods before and after lockdown. The model simulation results showed that O₃ mixing ratios were not only related to regional anthropogenic emissions but were impacted by air mass transportation from surrounding provinces and the China shelf seas. The NO_x mixing ratios showed a decreasing trend, while the O₃ mixing ratios showed the opposite trend from 2015 to 2021, which is indicative of the implementation of the Air Pollution Prevention and Control Acton Plan issued by the Chinese government in 2013.