Molecular Characterization of Organosulfate-Dominated Aerosols over Agricultural Fields from the Southern Great Plains by High-Resolution Mass Spectrometry

Abstract

The molecular composition of organic aerosols, especially for day/nighttime variations of organosulfates above agricultural fields, is not well understood despite profound impacts on regional climate, crop production, air quality, and human health. Here, nanospray desorption electrospray ionization with high-resolution mass spectrometry (nano-DESI-HRMS) is used to interrogate the molecular composition of organic aerosols collected at the Southern Great Plains, located in an agricultural region of Oklahoma. Identified molecular formulae featured carbon, hydrogen, oxygen (CHO), nitrogen (CHNO), and/or sulfur (CHOS, CHNOS), with higher organosulfate proportions during daytime (41%) compared to nighttime (30%). Nighttime aerosols featured increases in CHO, CHNO, and extremely low volatility organic carbon (ELVOC) species. However, due to high relative humidity, the nighttime aerosols phase state was found to be more liquid-like than daytime aerosols using parametrized glass transition temperatures. Aerosol molecular composition from an anthropogenically influenced plume (southerly winds) showed significant increases in CHOS and ELVOC species. By comparison with chamber studies, CHOS species are suspected to be of mixed biogenic and anthropogenic origin, whereas CHNOS species (not identified in the southerly winds) are suggested to predominately be of biogenic origin. Overall, this study provides key insight into organosulfates above agricultural fields, demonstrating dependence upon day/night cycles and episodic anthropogenic emissions.

Chemical identification of new particle formation and growth precursors through positive matrix factorization of ambient ion measurements

“…The increasing abundance of sulfuric acid with back trajectories from the south is consistent with the results of Hodshire et al (2016) who demonstrated that sulfuric acid contributes significantly to SGP particle growth when air masses originate from the south. It is also broadly consistent with the recent work of Vandergrift et al (2022) which showed that many organosulfates in SOA were unique to air masses originating from the south. The increase in the low m/z nitrates factor in the southeast cluster could result from increased biogenic emissions to the east of the site.…”

“…Glycolic acid sulfate has been previously observed in the gas-phase (Ehn et al, 2010;Le Breton et al, 2018). In addition to gas-phase measurements, glycolic acid sulfate has been detected in SOA derived from isoprene and its oxidation products in both ambient samples (Surratt et al, 2008;Safi Shalamzari et al, 2013;Wach et al, 2019;Vandergrift et al, 2022) and chamber experiments (Surratt et al, 2008;Galloway et al, 2009;Wach et al, 2019).…”

“…The Department of Energy Atmospheric Radiation Measurement Southern Great Plains (SGP) research station, located in an agriculturally intensive region, hosts an extensive array of instruments for atmospheric measurements. Previous measurements at the site have investigated aerosol chemical composition (Parworth et al, 2015;Chen et al, 2018;Liu et al, 2021;Vandergrift et al, 2022) and growth pathways (Hodshire et al, 2016), and have suggested that diamines may contribute to NPF at this location (Jen et al, 2016). Gas-phase measurements of compounds thought to be important for NPF and growth such as extremely low volatility organic compounds and a broad array of reduced nitrogen species are lacking and thus these species remain poorly constrained.…”

Case study evaluation of size-resolved molecular composition and phase state of carbonaceous particles in wildfire influenced smoke from the Pacific Northwest

“…Similar strategies to those used here for data analysis, including blank subtraction and data filtering, have been previously described. 46 Molecular formulae assignment was conducted using MFAssignR, 47 an open source software tool. Assigned molecular formula were limited to C, H, N (maximum of 2 per individual formula) and O elemental constituents of deprotonated, singly-charged ion types.…”

Nonequilibrium Behavior in Isoprene Secondary Organic Aerosol

“…C, H, and S (maximum of 1) atoms were allowed in both ion modes. A detailed description of the nano-DESI-HRMS methodology used herein has been previously described 71 and is provided in the Supporting Information Section S2.…”