2025FICUS10266

FICUS: Chemical Characterization of SOA

1 October 2024 - 30 September 2026

Lead Scientist: Jason Surratt

Observatory: AMF

We hypothesize that secondary organic aerosol (SOA) composition resulting from acid-driven multiphase chemistry of isoprenederived epoxydiols (IEPOX) varies with altitude, revealing the need to consider the effects of aerosol acidity, phase state, morphology, and aging processes in atmospheric chemistry models. To address this, we propose two aims: (1) collect aerosol during spring and summer 2025 at the BNF site using EMSL’s Time Resolved Bulk Aerosol Collector (TBAC) and Size and Time-resolved Aerosol Collector (STAC) onboard ARM’s Tethered Balloon System (TBS); and (2) characterize aerosol composition and physicochemical properties of TBS-collected aerosol samples using EMSL’s microscopy and mass spectrometry (MS) tools. This work is directly related to EMSL’s and ARM’s mission of investigating aerosol processes that vary with altitude resulting from “land-atmosphere processes over rural and urban areas.” The ARM BNF site offers the ability to collect aerosol samples that likely formed from the atmospheric chemical interactions of biogenic volatile organic compounds (BVOCs) with anthropogenic pollutants, as well as from long-range transport of wildfire emissions. Chemical characterization of IEPOX-derived SOA at the molecular level with varying altitude is major measurement gap in this region. Thus, our work will help to improve mechanistic representations of IEPOX-derived SOA within Earth system models. We request that ARM collects 10 days of samples in spring 2025 as well as 10 days in summer 2025 (20 days total in 2025) using EMSL’s STAC and TBAC systems onboard ARM’s TBS. We propose 3 sets of both STAC and TBAC samples are collected per day, including one at the ground, another at 500 m, and then at the highest possible altitude (maximum 1.5 km). This will provide a total of 60 collected samples per season (30 STAC/30 TBAC samples). We also propose to deploy EMSL’s TRAVIS platform for VOC analysis in order to measure isoprene and its related oxidation products by EMSL’s TDQTOF-GCMS. PI Surratt will provide authentic compounds of IEPOX-derived SOA (2-methyltetrols, methyltetrol sulfates, and C5H10O3 isomerization products) for offline quantitative chemical analysis conducted at EMSL for TBAC samples using the LCOrbitrap MS system. PI Surratt will share his hydrophilic interaction liquid chromatography (HILIC) method with EMSL colleagues, which resolves IEPOX-derived SOA constituents at the molecular level to improve quantitative MS work. For STAC samples, we propose EMSL conducts chemical and morphological analyses on these samples by using nanospray desorption electrospray ionization (nano-DESI)-HR-MS and computer-controlled scanning electron microscopy (CCSEM), respectively. PI Surratt will send a graduate student to assist with analyses. Finally, since IEPOX-derived SOA contributes significantly to the fine particulate organosulfate mass balance, aerosol samples will also be analyzed for total S and inorganic S using EMSL’s inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography (IC) systems, respectively. This will allow us to determine how much of the total S particulate mass balance is from IEPOX-derived organosulfates and how much organosulfate mass is missing. This will help assess if parameterizations used in Earth system models accurately represent organosulfate contributions to the total particulate S mass balance, which affects estimated aerosol physicochemical properties.