Influence of Candle Emissions on Monoterpene Oxidation Chemistry and Secondary Organic Aerosol

Candle burning is a considerable
contributor to indoor
pollutants,
while secondary organic aerosols (SOA) from monoterpene ozonolysis
represent another type. However, knowledge of the interactions of
different indoor pollutants is limited. We investigated physicochemical
properties of SOA generated from typical indoor chemistry of the O3/α-pinene reaction with and without the presence of
particles and gases from a burning candle. Ozonolysis of α-pinene
in the presence of candle gaseous emissions yielded a considerably
lower particle number, larger particle sizes, and lower particle oxygen-to-carbon
ratio compared with experiments without candle emissions. More nitrogen-containing
organic compounds were observed in the aerosol phase with candle emissions.
Furthermore, concentrations of some typical particle-phase products
from the O3/α-pinene reaction (i.e., terebic acid, cis-pinic acid, and 3-methyl-1,2,3-butanetricarboxylic acid)
were less abundant in the presence of candle emissions. The predicted
volatility of particulate organic compounds was higher in experiments
with candle emissions. The study demonstrates that candle burning
can affect the chemical and physical properties of particles formed
from other sources (e.g., α-pinene ozonolysis) by affecting
gas-phase chemistry and gas-particle partitioning.