Evaporation Rates and Vapor Pressures of Individual Aerosol Species Formed in the Atmospheric Oxidation of α- and β-Pinene

Abstract

The semivolatile oxidation products (trans-norpinic acid, pinic acid, cis-pinonic acid, etc.) of the biogenic monoterpenes (α-pinene, β-pinene, etc.) contribute to the atmospheric burden of particulate matter. Using the tandem differential mobility analysis (TDMA) technique evaporation rates of glutaric acid, trans-norpinic acid, and pinic acid particles were measured in a laminar flow reactor. The vapor pressure of glutaric acid was found to be log(p⁰_glutaric/Pa) = − 3510 K/T + 8.647 over the temperature range 290−300 K in good agreement with the values previously reported by Tao and McMurry (1989). The measured vapor pressure of trans-norpinic acid over the temperature range 290−312 K is log(p⁰_norpinic/Pa) = − 2196.9 K/T + 3.522, and the vapor pressure of pinic acid is log(p⁰_pinic/Pa) = − 5691.7 K/T + 14.73 over the temperature range 290−323 K. The uncertainty on the reported vapor pressures is estimated to be approximately ± 50%. The vapor pressure of cis-pinonic acid is estimated to be of the order of 7 × 10^-5 Pa at 296 K.