The reduction in C 2 H 6 from 2015 to 2020 over Hefei, eastern China, points to air quality improvement in China

摘要

Ethane ( C 2 H 6 ) is an important greenhouse gas and plays a significant role in tropospheric chemistry and climate change. This study first presents and then quantifies the variability, sources, and transport of C 2 H 6 over densely populated and highly industrialized eastern China using ground-based high-resolution Fourier transform infrared (FTIR) remote sensing along with atmospheric modeling techniques. We obtained a retrieval error of 6.21? ± ?1.2 (1 σ )% and degrees of freedom (DOFS) of 1.47? ± ?0.2 (1 σ ) in the retrieval of C 2 H 6 tropospheric column-averaged dry-air mole fraction (troDMF) over Hefei, eastern China (32 ° ?N, 117 ° ?E; 30? m a . s . l . ). The observed C 2 H 6 troDMF reached a minimum monthly mean value of 0.36? ± ?0.26? ppbv in July and a maximum monthly mean value of 1.76? ± ?0.35? ppbv in December, and showed a negative change rate of ? 2.60? ± ?1.34? %?yr ?1 from 2015 to 2020. The dependencies of C 2 H 6 troDMF on meteorological and emission factors were analyzed using generalized additive models (GAMs). Generally, both meteorological and emission factors have positive influences on C 2 H 6 troDMF in the cold season (December–January–February/March–April–May, DJF/MAM) and negative influences on C 2 H 6 troDMF in the warm season (June–July–August/September–October–November, JJA/SON). GEOS-Chem chemical model simulation captured the observed C 2 H 6 troDMF variability and was, thus, used for source attribution. GEOS-Chem model sensitivity simulations concluded that the anthropogenic emissions (fossil fuel plus biofuel emissions) and the natural emissions (biomass burning plus biogenic emissions) accounted for 48.1?% and 39.7?% of C 2 H 6 troDMF variability over Hefei, respectively. The observed C 2 H 6 troDMF variability mainly results from the emissions within China (74.1?%), where central, eastern, and northern China dominated the contribution (57.6?%). Seasonal variability in C 2 H 6 transport inflow and outflow over the observation site is largely related to the midlatitude westerlies and the Asian monsoon system. Reduction in C 2 H 6 abundance from 2015 to 2020 mainly results from the decrease in local and transported C 2 H 6 emissions, which points to air quality improvement in China in recent years.