Highly Oxidized Molecules (HOMs) with low and extremely-low volatility are crucial in new particle formation and their subsequent growth in a pristine atmosphere. To investigate the chemical composition and potential sources of neutral and naturally-charged HOMs, a field campaign was conducted from July to September, 2016 in Linzhi station (29°45'56"N, 94°44'18"E), Tibet Plateau. A nitrate-based chemical ionization -atmospheric pressure interface – time-of-flight mass spectrometer (CI-APi-TOF), an atmospheric pressure interface – time-of-flight mass spectrometer (APi-TOF), a proton transfer reaction - mass spectrometer (PTR-MS), and an aerosol chemical speciation monitor (ACSM) were deployed to detect HOMs, their potential volatile organic compound (VOC) precursors, and chemical composition of submicron particles, respectively. Our results show that the formation of HOMs was favored with high O3 concentration, low relative humidity and intense radiation. Dimer and trimer of HOMs were higher in day time than that in night time. This diurnal trend is opposite to that in a low altitude pristine atmosphere. During our campaign, high concentrations of O3, OH radical and VOCs with low concentrations of NOx that can terminate the autoxidation processes of RO2 radicals were conducive to the generation of dimers and trimers of HOMs in the daytime. Nonetheless, at nighttime, low concentrations of O3 along with high relative humidity suppressed the formation of dimers and trimmers of HOMs. Meanwhile, organic compounds were dominant in submicron particles, illustrating that organic compounds (most likely HOMs) play crucial roles in particle growth.

Chemical characterization of highly oxidized molecules (HOMs) in Linzhi, Tibet

255th National Meeting (2018)

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