Light induced multiphase chemistry of gas-phase ozone on aqueous pyruvic and oxalic acids

Abstract

In this study for the first time it has been shown that pyruvic acid can affect the atmospheric multiphase reactions of ozone with oxalic acid due to its properties as a photosensitizer. To this end, the photochemical batch multiphase reactions of a mixture of pyruvic acid/oxalic acid (PA/OA) and gas-phase ozone under simulated sunlight were studied as a function of time using high pressure liquid chromatography equipped with a UV detector (HPLC-UV) and electrospray ionization mass spectrometry (ESI-MS) to investigate product formation. Following the simultaneous ozone and light irradiation the first peak for pyruvic and oxalic acids (retention time = 3.68 min) decreased to 67% of the initial intensity after a 12 h reaction while a broad and not well defined peak appeared at longer retention times. After prolonged exposure times this broad peak shifted to shorter retention times: from 14 min at 2 h reaction to 8 min at 12 h. The HPLC-UV analysis of the reaction mixture simultaneously exposed to ozone and irradiated by simulated sunlight for 6-12 h revealed the presence of high weight molecular mass products and formation at longer times of highly non-polar products. The results obtained from ESI-MS have clearly demonstrated that the distribution of high molecular weight products is consistent with an oligomer system. No evidence of oligomer formation was found after the sample (PA/OA) was exposed only to either ozone or irradiated with UV/Vis light using the same instrumental conditions.

Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies

“…Products in that study included C 6 and C 7 carboxylic acids which could act as precursors for smaller acids. Solutions of both oxalic and pyruvic acid also showed the formation of HMWC with oligomeric structures in the presence of ozone and UV light (Grgic et al, 2010). In those experiments, it was suggested that pyruvic acid acts as a photosensitizer that accelerates the oxidation of oxalic acid leading to oligomer formation, i.e.…”

“…Some multiphase experiments that investigate the uptake and further processing of aqSOA precursors into aqueous aerosols, have shown evidence that aqSOA formation could also occur at the gas/particle interface (Ervens and Volkamer, 2010;Grgic et al, 2010;D. Huang et al, 2011).…”

Enhancement effect of relative humidity on the formation and regional respiratory deposition of secondary organic aerosol

“…Another explanation for the enhancement effect of humidity on mass and number of SOA is relevant to the atmospheric processes involving SOA formation through aqueous chemistry in clouds and wet aerosols [25][26][27][28]. In this process, small aldehydes, ketones and alcohols generated from the ozonolysis of d-limonene in the gas phase can partition into the wet surface of the hygroscopic SOA at high RH.…”

“…The regional deposition of aerosol particles in the respiratory tract depends on particle sizes, breathing pattern and respiratory condition (asthma, etc.). The particle sizes of SOA are affected significantly by the relative humidity (RH) owing to the hygroscopicity of SOA [23,24], the aqueous chemistry occurring on the surface of SOA [25][26][27][28], and the gas-phase reactions involving water [29]. In this study, we investigated the effects of RH on the formation, kinetic parameters and respiratory deposition of SOA generated from the ozonolysis of d-limonene.…”

Photolysis and Heterogeneous Reaction of Coniferyl Aldehyde Adsorbed on Silica Particles with Ozone

“…Oxalic acid is known as the smallest dicarboxylic acid deposited in atmospheric condensed particles. [55][56][57] On the other hand, CI 2 leads to vanillic acid which is further oxidized to 3,4-dihydroxybenzoic acid. To the best of our knowledge, there is no previous information available in the literature concerning the mechanism and reaction products of the ozonolysis of coniferyl aldehyde adsorbed on silica particles.…”