Aerosols play an
important role in climate and air quality; however,
the mechanisms behind aerosol particle formation in the atmosphere
are poorly understood. Studies have identified sulfuric acid, water,
oxidized organics, and ammonia/amines as key precursors for forming
aerosol particles in the atmosphere. Theoretical and experimental
investigations have indicated that other species, such as organic
acids, may be involved in atmospheric nucleation and growth of freshly
formed aerosol particles. Organic acids, such as dicarboxylic acids,
which are abundant in the atmosphere, have been measured in ultrafine
aerosol particles. These observations suggest that organic acids may
contribute to new particle formation in the atmosphere but their role
remains ambiguous. This study examines how malonic acid interacts
with sulfuric acid and dimethylamine to form new particles at warm
boundary layer conditions using experimental observations from a laminar
flow reactor and quantum chemical calculations coupled with cluster
dynamics simulations. Observations reveal that malonic acid does not
contribute to the initial steps (formation of <1 nm diameter particle)
of nucleation with sulfuric acid-dimethylamine. In addition, malonic
acid was found to not participate in the subsequent growth of the
freshly nucleated 1 nm particles from sulfuric acid-dimethylamine
reactions to diameters of 2 nm.