Atmospheric aerosol chemistry From air pollution to climate….ppt

BSOA workshop August 2008 NOx-mediated Chemistry - Climate Interactions via Atmospheric AerosolsJulie Fry, currently unemployed!(was UC Berkeley, starting at Reed College next week) NO3 + VOCs RONO2 aerosol NOx Climate effects? NO + oxyRO2 RONO2(g) Chamber studies of SOA formation AMS organic nitrate standard studies Modeling regional importance of NOx-mediated SOA formation Future: Measuring aerosol chemical composition with Hi-Vol samplers offline GC-MS, FTIR, NMR; regional modeling (WRF-Chem) March 13, 2008 NO3 in Juelich SAPHIR chamber, June 2007 NO3 TD-LIF NO2 TD-LIF inlets o N2O5 +NO3 + β-pinene Δ aerosol DRY 60% RH Y~50% Y~50% aerosol formation Absorptive partitioning model requires Pvap = 4x10-6 Torr estimated Pvap~6x10-4 Torr Modeling nitrate partitioning Modeling NO3 + β-pinene Yield(Alkyl nitrates) = 30% How much aerosol could NO3 + β-pinene make globally? Mass yield of aerosol from NO3 + β-pinene: ~50% Global annual β-pinene emissions: ~ 33 Tg yr-1 Fraction of β-pinene that reacts with NO3, based on relative NO3, O3, and OH lifetimes: ~ 30% → .3 x .5 x 33 Tg yr-1 = 5 Tg yr-1 SOA source estimates: Kanakidou et al, 2005: 12 – 70 Tg year-1 Goldstein Galbally, 2007: 510 – 910 Tg year-1 * So what I’ve been getting into in my post-doc research is following this nitrate into the aerosol. We’re interested in studying chemistry that leads to aerosol formation, which in turn influences Earth climate. I’ll start by discussing the big-picture aerosol-climate interactions that motivate us to think about aerosol, and then move backwards to the specific chemistry we’re looking at, but here’s a quick preview of the big picture. NOx in the atmosphere, emitted by human activities, can undergo daytime photochemistry or nighttime nitrate radical chemistry to form organic nitrates, some of which may be big and sticky enough to partition to the aerosol phase. This addition of organic nitrates to the aerosol affects the composition and therefo