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.

A new meteorological station (DMS) was established at the Morning Glory summit in Zhejiang Province to provide regional background information on atmospheric composition in the Yangtze River Delta (YRD) region, China. This study investigated the first carbon monoxide (CO) records at DMS from September 2020 to January 2022. The annual average concentration of CO was 233.4 ± 3.8 ppb, which exceeded the measurements recorded at the other Asian background sites. The winter CO concentration remained elevated but peaked in March in the early spring due to the combined effect of regional emissions within the YRD and transportation impacts of North China and Southeast Asia sources. The diurnal cycle had a nocturnal peak and a morning valley but with a distinct afternoon climb, as the metropolis in the YRD contributed to a local concentration enhancement. The back trajectory analysis and the Weighted Potential Sources Contribution Function (WPSCF) maps highlighted emissions from Anhui, Jiangxi, Zhejiang, and Jiangsu provinces as significant sources. Due to well-mixed air conditions and fewer anthropogenic influences, DMS records closely aligned with the CO averages derived from the Copernicus Atmospheric Monitoring Service (CAMS) covering the YRD, confirming its representativeness for regional CO levels. This study underscored DMS as a valuable station for monitoring and understanding CO spatiotemporal characteristics in the YRD region.

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.

To reveal the spatiotemporal distributions of atmospheric CO₂ and CH₄ mixing ratios and regulation mechanisms over the China shelf sea, two field surveys were conducted in the southern Yellow Sea in China in November 2012 and June 2013, respectively. The results observed showed that mean background atmospheric CO₂ and CH₄ mixing ratios were 403.94 (±13.77) ppm and 1924.8 (±27.8) ppb in November 2012 and 395.90 (±3.53) ppm and 1918.0 (±25.7) ppb in June 2013, respectively. An improved data-filtering method was optimised and established to flag atmospheric CO₂ and CH₄ emission from different sources in the survey area. We found that the spatiotemporal distributions of atmospheric CO₂ and CH₄ mixing ratios over the southern Yellow Sea were dominated by land–sea air mass transport, which was mainly driven by seasonal monsoon, while the influence of air–sea exchange was negligible. In addition, atmospheric CO₂ and CH₄ mixing ratios over the southern Yellow Sea could be elevated remarkably at a distance of approximately 20 km offshore by land-to-sea air mass transportation from the Asian continent during the early-winter monsoon.

To reveal the spatiotemporal distributions of atmospheric CO₂ and CH₄ mixing ratios and regulation mechanisms over the China shelf sea, two field surveys were conducted in the south Yellow Sea in China in November 2012 and June 2013, respectively. Observed results showed that mean atmospheric CO₂ and CH₄ mixing ratios were 403.50 ± 13.70 ppm and 1934.1 ± 33.6 ppb in November 2012, and 396.40 ± 12.30 ppm and 1919.2 ± 30.2 ppb in June 2013, respectively. An improved data filtering method were established to flag diverse sources of atmospheric CO₂ and CH₄ in survey area. Fe found that, compared to the influences of air-sea exchange, the spatiotemporal distributions of atmospheric CO₂ and CH₄ mixing ratios over the south Yellow Sea were dominated by land-sea air masses transport, which was driven by seasonal monsoon. In addition, atmospheric CO₂ and CH₄ mixing ratios over the south Yellow Sea could be elevated remarkably in a distance of approximate 20 km offshore by land-to-sea air masses transportation from the Asia Continent during early winter monsoon.

基于2022年9月长江口−杭州湾海洋污染基线试点调查航次，本文开展了溶解甲烷浓度和海−气交换通量及主要调控因子的观测研究。结果显示，观测海域表层海水中溶解甲烷浓度范围为（6.89～43.41）nmol/L，平均值为（18.58 ± 8.88）nmol/L，底层海水中溶解甲烷浓度范围为（8.88～36.15）nmol/L，平均值为（8.25 ± 89.34）nmol/L。溶解甲烷浓度总体呈长江口和杭州湾内较高、离岸外海较低的分布特征，显示陆源河流输入和沉积物释放是观测海域溶解甲烷的主要来源。观测海域表层海水中溶解甲烷平均饱和度达（275.10 ± 6.70）%，海−气甲烷交换通量平均值为（157.40 ± 145.68）μmol/(m²·d)，是大气甲烷的源。初步估算该海域甲烷年释放量约为1.78 ×10⁹ mol，约占全球海洋年释放量的0.16%，可直接导致观测海域海表大气甲烷摩尔分数抬升约3.2 nmol/mol。