Biogenic emissions and land–atmosphere interactions as drivers of the daytime evolution of secondary organic aerosol in the southeastern US

Abstract

Abstract. The interactions between biogenic volatile organic compounds (BVOCs), like isoprene and monoterpenes, and anthropogenic emissions of nitrogen and sulfur oxides lead to high concentrations of secondary organic aerosol (SOA) in the southeastern United States. To improve our understanding of SOA formation, we study the diurnal evolution of SOA in a land–atmosphere coupling context based on comprehensive surface and upper air observations from a characteristic day during the 2013 Southern Oxidant and Aerosol Study (SOAS) campaign. We use a mixed layer model (MXLCH-SOA) that is updated with new chemical pathways and an interactive land surface scheme that describes both biogeochemical and biogeophysical couplings between the land surface and the atmospheric boundary layer (ABL) to gain insight into the drivers of the daytime evolution of biogenic SOA. MXLCH-SOA reproduces observed BVOC and surface heat fluxes, gas-phase chemistry, and ABL dynamics well, with the exception of isoprene and monoterpene mixing ratios measured close to the land surface. This is likely due to the fact that these species do not have uniform profiles throughout the atmospheric surface layer due to their fast reaction with OH and incomplete mixing near the surface. The flat daytime evolution of the SOA concentration is caused by the dampening of the increase due to locally formed SOA by entrainment of SOA-depleted air from the residual layer. SOA formation from isoprene through the intermediate species isoprene epoxydiols (IEPOXs) and isoprene hydroxyhydroperoxides (ISOPOOHs) is in good agreement with the observations, with a mean isoprene SOA yield of 1.8 %. However, SOA from monoterpenes, oxidised by OH and O3, dominates the locally produced SOA (69 %), with a mean monoterpene SOA yield of 10.7 %. Isoprene SOA is produced primarily through OH oxidation via ISOPOOH and IEPOX (31 %). Entrainment of aged SOA from the residual layer likely contributes to the observed more oxidised oxygenated organic aerosol (MO-OOA) factor. A sensitivity analysis of the coupled land surface–boundary layer–SOA formation system to changing temperatures reveals that SOA concentrations are buffered under increasing temperatures: a rise in BVOC emissions is offset by decreases in OH concentrations and the efficiency with which SVOCs partition into the aerosol phase.

Sulfur Dioxide Modifies Aerosol Particle Formation and Growth by Ozonolysis of Monoterpenes and Isoprene

“…Recently, the influence of anthropogenic emissions on the formation of biogenic SOA (BSOA) has garnered significant attention (Goldstein et al, 2009;Nagori et al, 2019;Ng et al, 2017;Xu et al, 2015;Ye et al, 2018). A number of recent field studies in forests have shown alterations in BSOA formation with increased anthropogenic emissions, underlining the important effects of the interactions between biogenic VOC (BVOC) emissions and pollutant plumes on the regional climate (de Gouw et al, 2005;Goldstein et al, 2009;Massoli et al, 2018;Shilling et al, 2013;Xu et al, 2015).…”

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

“…Elemental ratios, including oxygen-to-carbon ratio (O:C), hydrogen-to-carbon ratio (H:C), and nitrogen-to-carbon ratio (N:C), were obtained using the method outlined by . By comparing AMS with parallel 15 particle-into-liquid sampler (PILS) coupled to ion chromatograph (IC) and filter measurements, a constant CE of 0.9 was applied to AMS measurements (Nah et al, 2018a).…”

“…The most abundant pON species in NGT-ONRich were C 5 H 9 NO 7 and 10 C 10 H 15 NO 8 , accounting for 7.8 and 3.5 % of pON signals in this factor, respectively. C 10 H 15 NO 8 has been characterized in multiple chamber studies as major products of α-/β-pinene/limonene+NO 3 ⋅ and α-/β-pinene photooxidation with the presence of NO x (Nah et al, 2016;Lee et al, 2016;Faxon et al, 2018;Takeuchi and Ng, 2019). At Yorkville, the majority of C 10 H 15 NO 8 was presented in NGT-ONRich, implying that nocturnal chemistry is its most important source.…”

“…For isoprene-derived SOA, isoprene 15 epoxydiols (IEPOX) uptake followed by subsequent condensed-phase reactions (Surratt et al, 2010;Lin et al, 2012;Paulot et al, 2009) is known to be the major pathway in the southeastern U.S., approximately contributing 18 -36 % to total OA in warm seasons (Budisulistiorini et al, 2013;Hu et al, 2015;Xu et al, 2015a;Xu et al, 2015b). Isoprene organic nitrates formed from both photooxidation and nitrate radical oxidation have been characterized in ambient measurements and included in models 20 (Lee et al, 2016;Bates and Jacob, 2019), as well as non-IEPOX SOA formed from hydroxy hydroperoxide (ISOPOOH) oxidation (Krechmer et al, 2015;Nagori et al, 2019). Monoterpene nocturnal reactions have been shown to be an important source of particulate organic nitrates in the southeastern U.S. (Xu et al, 2015a;Xu et al, 2015b;Pye et al, 2015), while more recent studies have demonstrated that monoterpenes are also the prominent source of total OA in the southeastern U.S.…”

“…CIMS Day-MO factor, and these two factors were well correlated (R = 0.71). For AMS MO-OOA, different theories regarding its sources and formation pathways have been proposed (which are not mutually exclusive), including photochemical aging of fresh OA (Jimenez et al, 2009;Ng et al, 2010;Bougiatioti et al, 2014), aqueous processes (Xu et al, 2017), formation of highly oxygenated molecules (HOMs) (Ehn et al, 2014), long-range transport (Hayes et al, 2013), and entrainment of 5 aged SOA from the residual layer (Nagori et al, 2019). In our previous discussion, we tentatively related FIGAERO-CIMS Day-MO, which correlated with AMS MO-OOA, to aqueous processes, but cannot rule out other processes.…”