Secondary organic aerosol formation from camphene oxidation: measurements and modeling

Abstract. While camphene is one of the dominant monoterpenes measured in biogenic and pyrogenic emission samples, oxidation has not been well-studied environmental chambers very little known about its potential to form secondary organic aerosol (SOA). The lack chamber-derived SOA data for may lead significant uncertainties predictions from using existing parameterizations when a contributor total monoterpenes. Therefore, advance understanding formation improve representation air quality models, series experiments was performed University California Riverside chamber explore mass yields properties across range chemical conditions at atmospherically relevant OH concentrations. experimental results were compared with modeling simulations obtained two chemically detailed box models: Statewide Air Pollution Research Center (SAPRC) Generator Explicit Chemistry Kinetics Organics Atmosphere (GECKO-A). derived both two-product volatility basis set (VBS) approaches. Experiments added nitrogen oxides (NOx) resulted higher (up 64 %) than without NOx 28 %). In addition, increased (Mo) lower loadings, but threshold reached loadings which no longer Mo. SAPRC studies suggested that initial levels primarily due production peroxy radicals (RO2) generation highly oxygenated molecules (HOMs) formed through unimolecular RO2 reactions. predicted presence NOx, reacts NO resultant undergoes hydrogen (H)-shift isomerization reactions; as documented previously, such reactions rapidly add oxygen products low (i.e., HOMs). end have significantly volatilities, O : C ratios, those by reacting hydroperoxyl (HO2) or other RO2. Further analysis reveals existence an extreme regime, wherein yield can be suppressed again high / HO2 ratios. Moreover, particle densities found decrease 1.47 1.30 g cm−3 [HC]0 [NOx]0 decreased. observed differences largely explained gas-phase chemistry competition between RO2+ HO2, NO, RO2, autoxidation