Contributions of Amines and Highly Oxidized Organics to New Particle Formation in the Atmosphere: Global Simulations and Implications

Particle number concentration is an important factor in the health and climate impacts of atmospheric aerosols. Secondary particles formed via new particle formation (NPF) or nucleation dominate the global total particle number abundance, contributing as high as 80-95% to total particle (larger than ~3 nm) and 50-80% to cloud condensation nuclei (CCN) number concentrations in most parts of the troposphere. Recent laboratory measurements indicate important roles for amines and highly oxidized low volatility secondary organic gases (LVSOG) in NPF in experimental chambers but the actual role of these species in NPF in the real atmospheric remains unclear. Here, we investigate the possible contributions of amines and LVSOG to atmospheric NPF, using a state-of-the-art global chemical transport model (GEOS-Chem) with an advanced particle microphysics (APM) model incorporated. Schemes to calculate the concentrations of amines and LVSOG as well as nucleation rates involving these species have been implemented into GEOS-Chem/APM. For particle growth, the model considers kinetic condensation of H2SO4 and LVSOG, equilibrium uptake of nitrate and ammonium, partitioning uptake of relatively high volatility secondary organic gases, and particle self-coagulation. The particle number concentrations predicted based on LVSOG-H2SO4 and amines-H2SO4-H2O nucleation parameterizations are compared to those based on the binary ion-mediated nucleation (IMN) of H2SO4-H2O as well as to relevant field measurements. We show that both LVSOG-H2SO4 and IMN schemes capture the observed high frequency of NPF in spring, but the LVSOG-H2SO4 scheme significantly over-predicts while the IMN scheme slightly under-predicts NPF and particle number concentrations in summer. Amines-H2SO4-H2O nucleation is significant in the boundary layer in Asia, central Europe, and some parts of America but is small above boundary layer and over oceans. Key parameters controlling nucleation rates based on different schemes, uncertainties, implications, and future research needs will be discussed.