Hygroscopic Coating of Sulfuric Acid Shields Oxidant Attack on the Atmospheric Pollutant Benzo(a)pyrene Bound to Model Soot Particles

Abstract

Substantial impacts on climate have been documented for soot‒sulfuric acid (H2SO4) interactions in terms of optical and hygroscopic properties of soot aerosols. However, the influence of H2SO4 on heterogeneous chemistry on soot remains unexplored. Additionally, oxidation rate coefficients for polycyclic aromatic hydrocarbons intrinsic to the atmospheric particles evaluated in laboratory experiments seem to overestimate their degradation in ambient atmosphere, possibly due to matrix effects which are hitherto not mimicked in laboratory experiments. For the first time, our kinetics study reports significant influence of H2SO4 coating on heterogeneous ozonation of benzo(a)pyrene (BaP) deposited on model soot, representative to atmospheric particles. The approximate specific surface area of model soot (5 m2g−1) was estimated as a measure of the availability of surface molecules to a typical gaseous atmospheric oxidant. Heterogeneous bimolecular reaction kinetics and Raman spectroscopy studies suggested plausible reasons for decreased BaP ozonation rate in presence of H2SO4: 1. decreased partitioning of O3 on soot surface and 2. shielding of BaP molecules to gaseous O3 by acid-BaP reaction or O3 oxidation products.

Transforming Chimney Soot via Stochastic Polymerization for Active Electrode Coating

“…Since carbon is the main constituent in the material, it is not surprising that Raman spectroscopy is a widely used method for the characterization of any type of soot [3,5,6,8,12,13,[34][35][36][37][38][39][40][41][42].…”

“…The incomplete combustion of hydrocarbons associated with both anthropogenic (various combustion systems for energy and heat production, transport, etc.) and natural sources (forest fires) is responsible for the formation and emission of more than 8 Tg of soot annually into the atmosphere [2][3][4][5][6][7]. With a more than 80% contribution, elemental carbon is the main constituent of soot particles regardless of the source [8][9][10].…”

Impacts of Cloud‐Processing on Ice Nucleation of Soot Particles Internally Mixed With Sulfate and Organics

“…(e) Structural compaction and increased porosity for cloud‐processed particles (Mahrt, Alpert, et al., 2020; Mahrt, Kilchhofer, et al., 2020), by which IN via pore condensation and freezing (PCF; Campbell & Christenson, 2018; Christenson, 2013; David et al., 2019; Koehler et al., 2009; Marcolli, 2014; Wagner et al., 2016) can be enhanced. However, transferring empirical conclusions from previous studies to the case of cloud‐processed soot particles of different sources may lead to inconsistent conclusions, considering the heterogeneity of atmospheric soot particles in chemical composition (Cziczo et al., 2004; Gong et al., 2011; Ray et al., 2018), mixing states and morphology (Bhandari et al., 2019; Bond et al., 2013; Liati et al., 2019; Wang et al., 2017). For example, Wagner et al.…”