Preprints
https://doi.org/10.5194/egusphere-2024-1808
https://doi.org/10.5194/egusphere-2024-1808
27 Jun 2024
 | 27 Jun 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Extreme Heat and Wildfire Emissions Enhance Volatile Organic Compounds: Insights on Future Climate

Christian Mark Garcia Salvador, Jeffrey D. Wood, Emma Grace Cochran, Hunter A. Seubert, Bella D. Kamplain, Sam S. Overby, Kevin R. Birdwell, Lianhong Gu, and Melanie A. Mayes

Abstract. Climate extremes are projected to cause unprecedented deviations in the emission and transformation of volatile organic compounds (VOCs), which trigger feedback mechanisms that will impact the atmospheric oxidation and formation of aerosols and clouds. However, the response of VOCs to future conditions such as extreme heat and wildfire events is still uncertain. This study explored the modification of the mixing ratio and distribution of several anthropogenic and biogenic VOCs in a temperate oak–hickory–juniper forest as a response to increased temperature and transported biomass burning plumes. A chemical ionization mass spectrometer was deployed on a tower at a height of 32 m in rural central Missouri, United States, for the continuous and in situ measurement of VOCs from June to August of 2023. The maximum observed temperature in the region was 38 °C, and during multiple episodes the temperature remained above 32 °C for several hours. Biogenic VOCs such as isoprene and monoterpene followed closely the temperature daily profile but at varying rates, whereas anthropogenic VOCs were insensitive to elevated temperature. During the measurement period, wildfire emissions were transported to the site and substantially increased the mixing ratios of acetonitrile and benzene, which are produced from burning of biomass. An in-depth analysis of the mass spectra revealed more than 250 minor compounds, such as formamide and methylglyoxal. The overall volatility, O:C, and H:C ratios of the extended list of VOCs responded to the changes in extreme heat and the presence of combustion plumes. Multivariate analysis also clustered the compounds into five factors, which highlighted the sources of the unaccounted-for VOCs. Overall, results here underscore the imminent effect of extreme heat and wildfire on VOC variability, which is important in understanding future interactions between climate and atmospheric chemistry.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Christian Mark Garcia Salvador, Jeffrey D. Wood, Emma Grace Cochran, Hunter A. Seubert, Bella D. Kamplain, Sam S. Overby, Kevin R. Birdwell, Lianhong Gu, and Melanie A. Mayes

Status: open (until 21 Aug 2024)

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Christian Mark Garcia Salvador, Jeffrey D. Wood, Emma Grace Cochran, Hunter A. Seubert, Bella D. Kamplain, Sam S. Overby, Kevin R. Birdwell, Lianhong Gu, and Melanie A. Mayes
Christian Mark Garcia Salvador, Jeffrey D. Wood, Emma Grace Cochran, Hunter A. Seubert, Bella D. Kamplain, Sam S. Overby, Kevin R. Birdwell, Lianhong Gu, and Melanie A. Mayes

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Short summary
Critical volatile organic compounds were continuously measured in a temperate deciduous and juniper forest in the midwestern US using PTR-ToF-MS. The forest included several sources of biogenic compounds and was influenced by short- and long-range transport of anthropogenic emissions. Extreme heat and wildfire emissions impacted the atmospheric conditions of the forest during the field measurement; such emissions are vital phenomena that provide insights into future climate.