Biogenic oxidized organic functional groups in aerosol particles from a mountain forest site and their similarities to laboratory chamber products

Abstract

Abstract. Submicron particles collected at Whistler, British Columbia, at 1020 m a.s.l. during May and June 2008 on Teflon filters were analyzed by Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) techniques for organic functional groups (OFG) and elemental composition. Organic mass (OM) concentrations ranged from less than 0.5 to 3.1 µg m −3 , with a project mean and standard deviation of 1.3±1.0 µg m −3 and 0.21±0.16 µg m −3 for OM and sulfate, respectively. On average, organic hydroxyl, alkane, and carboxylic acid groups represented 34%, 33%, and 23% of OM, respectively. Ketone, amine and organosulfate groups constituted 6%, 5%, and <1% of the average organic aerosol composition, respectively. Measurements of volatile organic compounds (VOC), including isoprene and monoterpenes from biogenic VOC (BVOC) emissions and their oxidation products (methyl-vinylketone/methacrolein, MVK/MACR), were made using co-located proton transfer reaction mass spectrometry (PTR-MS). We present chemically-specific evidence of OFG associated with BVOC emissions. Positive matrix factorization (PMF) analysis attributed 65% of the campaign OM to biogenic sources, based on the correlations of one factor to monoterpenes and MVK/MACR. The remaining fraction was attributed to anthropogenic sources based on a correlation to sulfate. The functional group composition of the biogenic factor (consisting of 32% alkane, 25% carboxylic acid, 21% organic hydroxyl, 16% ketone, and 6% amine groups) was similar to that of secondary orCorrespondence to: L. M. Russell (lmrussell@ucsd.edu) ganic aerosol (SOA) reported from the oxidation of BVOCs in laboratory chamber studies, providing evidence that the magnitude and chemical composition of biogenic SOA simulated in the laboratory is similar to that found in actual atmospheric conditions. The biogenic factor OM is also correlated to dust elements, indicating that dust may act as a nonacidic SOA sink. This role is supported by the organic functional group composition and morphology of single particles, which were analyzed by scanning transmission X-ray microscopy near edge X-ray absorption fine structure (STXM-NEXAFS).

Identifying organic aerosol sources by comparing functional group composition in chamber and atmospheric particles

“…The largest carboxylic acid group concentrations were identified with fuel combustion emissions for measurements in Houston and Mexico City, in which urban combustion sources are known to account for much of the fine particle mass. Two locations had substantial amounts of carbonyl groups: at a midmountain forested site in Whistler, British Columbia, Canada, and on the research vessel (R/V) Ronald Brown in the Gulf of Maine, suggesting an association between forest emissions and carbonyl groups that is consistent with the reported correlations of carbonyl-containing factors with biogenic VOCs in these projects (12,20). The highest hydroxyl fractions were found over the Atlantic and Arctic Oceans [International Chemistry Experiment in the Arctic LOwer Troposphere (ICEALOT)] and in the more remote regions of the Southeastern Pacific Ocean [VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx)], suggesting that these highly oxygenated organic components are associated with marine sources.…”

Determination of the biogenic secondary organic aerosol fraction in the boreal forest by NMR spectroscopy

“…The mass spectra of these two OOA components, with the ions at m/z 44 (CO + 2 ) dominating the OOA type 1 and m/z 43 (mostly C 2 H 3 O + ) dominating the OOA type 2, closely match those most commonly isolated in previous studies Lanz et al, 2007). Overall, they strongly resemble those found at Hyytiälä in spring 2005 (Raatikainen et al, 2010) and in other works performed in mid-latitude forests (Slowik et al, 2010;Allan et al, 2006) where the OOA1 represented the more oxidized, aged organic fraction, and the OOA2 represented the less oxidized, fresher secondary organics.…”

Organic functional groups in aerosol particles from burning and non-burning forest emissions at a high-elevation mountain site

“…In addition to the functional group analysis discussed above, the composition and contribution of multiple components in submicron FTIR spectra were inferred by application of Positive Matrix Factorization (PMF; Paatero and Tapper, 1994), and regression analysis to the spectra matrix consisting of samples and wavenumbers in the two dimensions. PMF has been applied to FTIR spectra to identify and separate varying components Hawkins and Russell, 2010;Schwartz et al, 2010). Solutions using rotation parameter FPEAK of −1.2 to 1.2 by increments of 0.6, seed values of 1, 10, and 100, and number of factors between two to six were examined.…”