An assessment of Aviation's contribution to current and future fine particulate matter in the United States

The impacts of aviation emissions on current and future year fine particulate matter (PM_2.5) were investigated using the Community Multiscale Air Quality model, accounting for aviation emissions from 99 airports and below 3 km during landing and takeoff (LTO) cycles. Results indicated that current year aviation emissions increased annual average PM_2.5 concentrations by 3.2 ng m^-3 (0.05%) in the continental U.S. while projected 2025 aviation emissions increased annual average PM_2.5 by 11.2 ng m^-3 (0.20%). Ammonium nitrate aerosol was the largest contributor to the increase in PM_2.5 concentrations, particularly in the future year. Using an indicator of inorganic PM_2.5 change, we attributed ammonium nitrate aerosol contributions in both years to excess free ammonia (8% higher NH₃ and 35% lower NO_x emissions from non-aviation sources in 2025 than 2005), and higher aircraft emissions of NO_x (which when converted to HNO₃ forms ammonium nitrate aerosol) than SO₂ (a precursor of ammonium sulfate aerosol). Our findings highlight the critical role that non-aviation emissions play in assessing the air quality impacts of aviation emissions in a future year scenario. © 2011 Elsevier Ltd.