Sensitivity of Nitrate Aerosol Production to Vehicular Emissions in an Urban Street

摘要

This study investigated the sensitivity of nitrate aerosols to vehicular emissions in urban streets using a coupled computational fluid dynamics (CFD)–chemistry model. Nitrate concentrations were highest at the street surface level following NH 3 emissions from vehicles, indicating that ammonium nitrate formation occurs under NH 3 -limited conditions in street canyons. Sensitivity simulations revealed that the nitrate concentration has no clear relationship with the NO x emission rate, showing nitrate changes of only 2% across among 16 time differences in NO x emissions. NO x emissions show a conflicting effect on nitrate production via decreasing O 3 and increasing NO 2 concentrations under a volatile organic compound (VOC)-limited regime for O 3 production. The sensitivity simulations also show that nitrate aerosol is proportional to vehicular VOC and NH 3 emissions in the street canyon. Changes of VOC emissions affect the nitrate aerosol and HNO 3 concentrations through changes in the O 3 concentration under a VOC-limited regime for O 3 production. Nitrate aerosol concentration is influenced by vehicular NH 3 emissions, which produce ammonium nitrate effectively under an NH 3 -limited regime for nitrate production. This research suggests that, when vehicular emissions are dominant in winter, the control of vehicular VOC and NH 3 emissions might be a more effective way to degrade PM 2.5 problems than the control of NO x .