Evaluation of Our Understanding of Organic Carbon Evolution: Insights from Intensive Observations and Explicit Chemical Modelling

Organic compounds are key components to tropospheric reactivity, secondary pollutant formation, and air-climate interactions. Yet their sources and transformation pathways remain incompletely constrained, especially under warm, stagnant conditions such as polluted summers.  In this work, a regional dataset over (Western) Europe combining background, urban, suburban, and forest locations is used to characterize the variability of organic and inorganic species during summer 2022, a hot dry summer which is considered as a proxy of future climate over Western Europe. A large number of datasets from 2 major campaigns Atmospheric ChemistRy Of the Suburban forest (ACROSS) and European Monitoring and Evaluation Programme (EMEP) Intensive Measurement Campaign (EIMP) have been utilized for this work. ACROSS (13 June - 25 July 2022) is a comprehensive, multi-platform field measurement campaign mainly focused on the understanding of the interactions of urban air and biogenic organic compounds (Cantrell and Michoud, 2022). EIMP campaign for VOC was carried out linked to a European heat wave during 12- 19 July 2022 involving 27 European Sites (EMEP sites) (Solberg et al., 2024). A large suite of offline and online sampling methods have been incorporated during these two campaigns, yielding more than 100 different compounds. To interpret these observations, a set of zero-dimensional simulations was created and a highly detailed gas-phase chemical mechanism generated with the GECKO-A tool. A set of primary organic compounds including around 200 anthropogenic and 150 biogenic species have been input into GECKO-A. Then GECKO-A generates the explicit mechanism of about 2.5 millions of secondary organic species from the experimental kinetic laboratory data and structure activity relationships. The generated mechanism and the inorganic mechanism together goes as a input into the box model with the meteorological parameters, boundary conditions and emissions to represent daily mean scenarios of the species during the ACROSS and EIMP campaigns. Thus, the box model framework allows exploration of emission speciation from anthropogenic and biogenic sources and their major oxidation pathways at the molecular scale. Comparisons between explicit simulations and observations are used to identify systematic discrepancies in daily profiles and magnitudes of more than 100 organic and inorganic species concentrations. The results indicate differences between observed and modelled behavior of organic carbon and associated secondary pollutants. These results will be interpreted in order to improve emission representations and chemical schemes.  

 

Keywords: Organic Compounds, ACROSS campaign, EIMP campaign, GECKO-A tool, explicit modeling

 

References:

Cantrell, C., Michoud, V., 2022. An Experiment to Study Atmospheric Oxidation Chemistry and Physics of Mixed Anthropogenic–Biogenic Air Masses in the Greater Paris Area. Bull. Am. Meteorol. Soc. 103, 599–603. https://doi.org/10.1175/BAMS-D-21-0115.1

Sverre Solberg, Anja Claude, Stefan Reimann. EMEP_CCC Report_4_2024_VOC_measurements_2022.pdf. https://emep-ccc.nilu.no/static/reports/EMEP_CCC