Field measurements of the impact of the reactive uptake of reduced nitrogen on the hygroscopicity and light absorption of ambient secondary organic aerosol

Description

The neutralization of condensed-phase organic acids via reaction with gas-phase ammonia or alkylamines to form ammonium salts has been shown previously in laboratory studies to change the light absorption and hygroscopicity of slightly soluble model compounds containing carboxylic acid functionalities. At present it is not clear how laboratory studies translate to ambient conditions, particularly for secondary organic aerosol (SOA) derived from biogenic oxidation products. Data presented will focus on the measurement of ambient aerosol CCN activity during the SOAS campaign at Look Rock, TN, as well as changes in CCN activity due to heterogeneous perturbation experiments of ambient aerosol with gas-phase methylamine, dimethylamine, and ammonia. Ambient CCN measurements are compared with literature values from laboratory studies focusing on SOA formed via isoprene oxidation. Implications for the effect of these heterogeneous reactions on the light absorption and cloud formation properties of ambient aerosols and the comparison of field measurements with laboratory-based studies of model compounds will be discussed.