Secondary Organic Aerosol Formation from Cl-Initiated Oxidation of Limonene under Indoor and Outdoor Lighting Conditions

PEARL ABUE, Pawel K. Misztal, Lea Hildebrandt Ruiz, The University of Texas at Austin

     Abstract Number: 329
     Working Group: Indoor Aerosols

Abstract
Limonene is an abundant volatile organic compound (VOC) outdoors and indoors. Oxidation of limonene by the hydroxyl radical (OH), nitrate radical (NO₃), and ozone have been studied. However, the role of chlorine (Cl) radical in the oxidation of limonene in indoor and outdoor environments has not received much attention. High concentrations of limonene and Cl₂ have been observed in indoor environments (10s of ppb of limonene and up to 100 ppb of Cl₂ after terpene and bleach cleaning, respectively). Here, we present results from environmental chamber experiments on Cl-initiated oxidation of limonene under varied lighting, NOx, relative humidity (RH), and temperature conditions. In addition to typical UV blacklights used for radical generation, the impact of LED lights in the visible spectrum typical of indoor lighting conditions was explored. Under UV lighting, organic aerosol mass yields from these experiments are around 1, exceeding recorded yields from OH and NO₃ oxidation of limonene. We observe the formation of oxidation products driven by simulated indoor lighting conditions (LED). We also measure early generation products in the gas phase from hydrogen abstraction like C₁₀H₁₅O₂ and products of chlorine addition like C₁₀H₁₆ClO₂. These experiments provide evidence for indoor oxidative chemistry that may contribute to indoor SOA or subsequent SOA formation following transport outside the home.

We utilize an Aerosol Chemical Speciation Monitor (ACSM), Scanning Electrical Mobility System (SEMS), Proton Transfer Reaction Mass Spectrometer (Vocus-2R-PTRMS), and an iodide mode, filter inlet mounted on a High-Resolution Time of Flight Chemical Ionization Mass Spectrometer (I- FIGAERO-CIMS) to measure gas and particle-phase products and record multiple highly oxygenated molecules in both phases.