Evaluation of the daytime tropospheric loss of 2-methylbutanal

Abstract

Abstract. Saturated aldehydes, e.g. 2-methylbutanal (2 MB, CH3CH2CH(CH3)C(O)H), are emitted into the atmosphere by several biogenic sources. The first step in the daytime atmospheric degradation of 2 MB involves gas-phase reactions initiated by hydroxyl (OH) radicals, chlorine (Cl) atoms, and/or sunlight. In this work, we report the rate coefficients for the gas-phase reaction of 2 MB with OH (kOH) and Cl (kCl), together with the photolysis rate coefficient (J), in the ultraviolet solar actinic region in Valencia (Spain) at different times of the day. The temperature dependence of kOH was described in the 263–353 K range by the following Arrhenius expression: kOH(T)=(8.88±0.41)×10-12 exp[(331±14)/T] cm3 molec.−1 s−1. At 298 K, the reported kOH and kCl are (2.68±0.07)×10-11 and (2.16±0.32)×10-10 cm3 molec.−1 s−1, respectively. Identification and quantification of the gaseous products of the Cl reaction and those from the photodissociation of 2 MB were carried out in a smog chamber by different techniques (Fourier transform infrared spectroscopy, proton transfer time-of-flight mass spectrometry, and gas chromatography coupled to mass spectrometry). The formation and size distribution of secondary organic aerosols formed in the Cl reaction were monitored by a fast mobility particle sizer spectrometer. A discussion on the relative importance of the first step in the daytime atmospheric degradation of 2 MB is presented together with the impact of the degradation products in marine atmospheres.

Atmospheric chemistry of CF3CHFCF2OCH3 (HFE-356mec3) and CHF2CHFOCF3 (HFE-236ea1) initiated by OH and Cl and their contribution to global warming

“…elsewhere (Antiñolo et al, 2020;Asensio et al, 2023Asensio et al, , 2022Ballesteros et al, 2017;Ceacero-Vega et al, 2012). In the kinetic study of reaction R3, methane (CH4) and 1,2,2trichloroethane (CH2ClCHCl2) were used as reference compounds, while for R4 due to the difficulty of finding a suitable reference compound, only 1,1,1-trichloroethane (CH3CCl3) was used.…”

“…for HFE-356mec3, 150min for HFE-236ea1 and 90min for CH2ClCHCl2. kloss and kRef,loss (Table S4) were measured prior to each experiment and include heterogeneous losses, photolysis and/or reaction with Cl2, as described in previous works (Antiñolo et al, 2020;Asensio et al, 2022).…”

“…The UV absorption spectroscopy system has been described in detail elsewhere (Asensio et al, 2022;Blázquez et al, 2020). It consists of a deuterium lamp (StellarNet, SL4 DT-200) placed at the entrance of a jacketed Pyrex® cell (optical path length, ℓ=(107.0±0.5)cm), connected by an optical fiber to a f/2 spectrograph (StellarNet, BLK-C) that possesses a concave holographic grating (590 grooves/mm) and a slit of 100µm…”

Atmospheric impact of 2-methylpentanal emissions: Kinetics, photochemistry, and formation of secondary pollutants

“…UFPs and other secondary pollutants are formed in the gas-phase reactions of volatile organic compounds (VOCs), such as aldehydes, with oxidants such as hydroxyl (OH) radicals or chlorine (Cl) atoms. In the 30 atmosphere, OH radicals are ubiquitous, while Cl is mainly present in marine or coastal atmospheres since it is formed from reactions of sea-salt aerosols (Atkinson et al, 1995;Wennberg et al, 2018;Rodríguez et al, 2012;Atkinson and Arey, 2003;Antiñolo et al, 2019;Antiñolo et al, 2020). Ceramic industries can also emit Cl2 inlands (Galán et al, 2002).…”

“…natural gas from power stations, landfill gas, 35 flaring from offshore, and transport (Calvert et al, 2011). But they can also be formed in situ in the atmosphere as secondary pollutants from reactions of alkenes and alcohols with oxidants (Atkinson et al, 1995;Wennberg et al, 2018;Rodríguez et al, 2012;Atkinson and Arey, 2003).…”