Chemical Characterization of Secondary Organic Aerosol at a Rural Site in the Southeastern U.S.: Insights from Simultaneous HR-ToF-AMS and FIGAERO-CIMS Measurements

Abstract

Abstract. The formation and evolution of secondary organic aerosol (SOA) was investigated at Yorkville, GA, in late summer (mid-August ~ mid-October, 2016). Organic aerosol (OA) composition was measured using two on-line mass spectrometry instruments, the high-resolution time-of-flight aerosol mass spectrometer (AMS) and the Filter Inlet for Gases and AEROsols coupled to a high-resolution time-of-flight iodide-adduct chemical ionization mass spectrometer (FIGAERO-CIMS). Through analysis of speciated organics data from FIGAERO-CIMS and factorization analysis of data obtained from both instruments, we observed notable SOA formation from isoprene and monoterpenes during both day and night. Specifically, in addition to isoprene epoxydiols (IEPOX) uptake, we identified isoprene SOA formation via hydroxyl hydroperoxide oxidation (ISOPOOH oxidation via non-IEPOX pathways) and isoprene organic nitrate formation via photooxidation in the presence of NOx and nitrate radical oxidation. Monoterpenes were found to be the most important SOA precursors at night. We observed significant contributions from highly-oxidized acid-like compounds to the aged OA factor from FIGAERO-CIMS. Taken together, our results showed that FIGAERO-CIMS measurements are highly complementary to the extensively used AMS factorization analysis, and together they provide more comprehensive insights into OA sources and composition.

A Coupled Volatility and Molecular Composition Based Source Apportionment of Atmospheric Organic Aerosol

“…This multipeak behavior has been observed for one of the top 3 components, C 3 H 4 O 5 , in other FIGAERO HRToF-CIMS experiments where the first local maximum is thought to correspond to a dicarboxylic acid and the T max was interpreted as a product of thermal decomposition of lower volatility components. 12 However, the top two components of the factor have compositions of C 5 H 8 O 5 and C 4 H 6 O 5 , both likely connected to isoprene chemistry. 23,24 C 4 H 6 O 5 has been observed in laboratory studies of SOA formation via ozonolysis of isoprene.…”

“…In a study by Chen et al, PMF was applied to integrated particle signals measured by the FIGAERO, where five factors were attributed to various sources using general oxidation states of factors along with diurnal trends. 12 Buchholz et al recently applied PMF to FIGAERO-CIMS thermograms from laboratory chamber generated SOA particles. 13 Herein, we examine the hypothesis that conducting NNMF with the simultaneously resolved time and composition thermograms enhances the separation and identification of OA sources in an ambient environment.…”

Evaluating Organic Aerosol Sources and Evolution with a Combined Molecular Composition and Volatility Framework Using the Filter Inlet for Gases and Aerosols (FIGAERO)

“…Deployment of the FIGAERO-CIMS in field settings has documented the dynamic nature of SOA molecular composition due to changes in emissions, partitioning, and chemistry. ,,,− ,, An example is the abundance and speciation of organic nitrates (C x H y N 1 O z ). Nighttime oxidation pathways involving the nitrate radical reacting with isoprene and monoterpenes produce chemically distinct species compared to daytime photochemical reactions between organic peroxy radicals and NO, while the relative importance of isoprene and monoterpenes changes over the course of a day due to the light dependence of isoprene emissions. ,,, By enabling observations of hourly changes in molecular composition, inferences into the lifetimes of OA components and thus the turnover of OA mass from specific sources can be derived. Such estimates for OA in the Southeast U.S. implied a short residence time of biogenic organic nitrates, on the time scale of hours, implying turnover of particulate organic carbon mass on the same order as OA mass concentrations …”

Multi-Oxygenated Organic Compounds in Fine Particulate Matter Collected in the Western Mediterranean Area

“…Other systems were an analogous collection of a thermal desorption inlet to a proton transfer reaction mass spectrometer (PTR-MS) to detect organic and inorganic compounds. Recently, the Filter Inlet for Gases and AEROsol (FIGAERO) instrument was developed, which allows both the separation of components in a volatility space via a temperature-programmed thermal desorption and the determination of the corresponding molecular composition on an hourly timescale [22,23]. Ion mobility spectrometry-mass spectrometry (IMS-MS) with the simultaneous characterization of the elemental composition and molecular structures of organic species in the gas and particulate phases [24] and high-resolution time-of-flight mass spectrometer have also been adapted to the AMS (HR-ToF-AMS) to distinguish the elemental composition of ions having the same nominal mass [25] and to improve the chemical aerosol characterization.…”