Agricultural Fire Impacts on Ozone Photochemistry Over the Yangtze River Delta Region, East China

Agricultural fires could affect tropospheric photochemistry by emitting trace gases, interacting with solar radiation or providing reactive surfaces for heterogeneous reactions. This study examines the effects of a typical agricultural fire event (8-13 June 2012) on ozone photochemistry over the Yangtze River Delta region, East China. The online coupled Weather Research and Forecasting-Chemistry model is used, with the inclusion of a detailed agricultural fire emission inventory and seven heterogeneous reactions on soot surfaces. Comparisons with satellite and ground observational data indicate that the model is capable of reproducing the transport and evolution of this crop fire event. The precursor emissions from agricultural fires play a major role in modifying ozone photochemistry, with a maximal increase in ozone mixing ratio reaching 20ppb (40%) near the fire zones in northern Anhui. The radiation feedback generates a small increase of surface NO2 levels by 2% and a decrease in surface O-3 levels by 1% in the smoke plume. The effects due to heterogeneous uptake on soot are rather small, on average, changing the average O-3, NO2, OH, and HO2 concentrations by +0.8%, -0.5%, -0.7%, and +0.8%, respectively. This study highlights the complicated interactions between agricultural fire emissions and photochemistry.