Application
of chlorine bleach solution (major component sodium
hypochlorite, NaOCl) in indoor environments leads to the emission
of gaseous hypochlorous acid (HOCl) and chlorine (Cl2),
both of which are strong oxidants. In contrast to the outdoor atmosphere,
where mixing ratios of HOCl and Cl2 tend to be low (10s–100s
of ppt), indoor HOCl and Cl2 can reach high levels during
cleaning activities (100s of ppb or higher). HOCl and Cl2 may react with unsaturated organic compounds on indoor surfaces
and in indoor air. In this study, we studied the reaction of limonene,
one of the most common indoor volatile organic compounds (VOCs) arising
from use of cleaning products, fragrance, and air fresheners, with
HOCl and Cl2 in an environmental chamber. A dark reaction
was observed between limonene and HOCl/Cl2 leading to gas-phase
reaction products that were investigated using proton transfer reaction
mass spectrometry (PTR-MS). With subsequent exposure to indoor fluorescent
lights or diffuse sunlight through a nearby window, a substantial
mass loading of secondary particles were formed with an averaged mass
yield of 40% relative to the amount of limonene consumed. Aerosol
mass spectrometry (AMS) measurements indicate a large contribution
of particulate chlorine species. Electrospray ionization mass spectrometry
(ESI-MS) analysis of filter-collected particles indicates the formation
of high molecular weight products. This is the first study of the
oxidation of limonene with HOCl and Cl2, and it illustrates
the potential for particle formation to occur with indoor lighting
during the use of common cleaning products.