The production and hydrolysis of organic nitrates from OH radical oxidation of <i>β</i>-ocimene

Abstract. Biogenic volatile organic compounds (BVOCs) emitted by plants represent the largest source of non-methane hydrocarbon emissions on Earth. Photochemical oxidation BVOCs represents a significant pathway in production secondary aerosol (SOA), affecting Earth's radiative balance. Organic nitrates (RONO2), formed from presence NOx, important precursors and affect oxidative capacity atmosphere, part sequestering NOx. In phase, RONO2 hydrolyze to form nitric acid numerous water-soluble products, thus contributing an increase mass. However, only small number studies have investigated OH terpenes, among those, few studied their hydrolysis. Here, we report laboratory study OH-initiated β-ocimene, acyclic, tri-olefinic monoterpene released during daytime vegetation, including forests, agricultural landscapes, grasslands. We conducted β-ocimene NOx using 5.5 m3 all-Teflon photochemical reaction chamber, which quantified total (gas- particle-phase) yield SOA yields. sampled produced measured hydrolysis rate constants across range atmospherically relevant pH. The nitrate was determined be 38(±9) %, consistent with available literature regarding dependence (from RO2 + NO) carbon number. found highly pH dependent, lifetime 51(±13) min at = 4 24(±3) 2.5, typical for deliquesced aerosols. also employed high-resolution mass spectrometry preliminary product identification. results indicate that ocimene (< 1 %) under loadings atmosphere is significantly lower than reported yields cyclic such as α-pinene, likely due alkoxy radical decomposition formation smaller, higher-volatility products. This observed particle-phase – i.e., 1.5(±0.5) % dry conditions. expected hydroxy chemical ionization (CIMS) some dihydroxy dinitrates, first-generation nitrates. Lower were high relative humidity (RH) conditions, indicating importance aerosol-phase ambient RH. provides insight into fate nitrates, yields, cycling forested environments monoterpenes not currently included atmospheric models.