Determination of the Aerosol Yield of Isoprene in the Presence of an Organic Seed with Carbon Isotope Analysis

Abstract

We examined a new method to determine the aerosol yield of precursors of secondary organic aerosols in the presence of organic seed particles. To distinguish between the oxidation products of the compound in question and the organic seed, the compound was labeled with stable isotopes and aerosol samples were analyzed by isotope ratio mass spectrometry (IRMS). 13C labeled isoprene was obtained from isoprene emitting plants that were exposed to (13)CO2. The aerosol yield of isoprene was determined from the 13C/12C ratio measured in the aerosol. Measurements at organic aerosol mass concentrations as low as 10 microg m(-3) were performed. Three different methods of aerosolsampling procedureswere evaluated: impactor, filter, and electrostatic deposition. The excess-% 13C measured by the three sampling methods agreed well. The aerosol yield of isoprene derived from these measurements showed a strong dependence on further oxidation of first-generation products and is within the range of reported yield values (1-5%) obtained so far from pure isoprene experiments.

Isoprene in poplar emissions: effects on new particle formation and OH concentrations

“…Isoprene is also known to have a small but significant yield of SOA mass formation. Depending on seed aerosol, initial precursor concentration and relative NO x levels, SOA yields in the range of 1-5 % were reported in the literature (Kroll et al, 2005;Dommen et al, 2006;Kroll et al, 2006;Dommen et al, 2009). Including SOA from isoprene in calculations of the global SOA burden increases SOA by factors between 0.5 and 2 depending on scenarios used (Henze and Seinfeld, 2006).…”

Volatility and Aging of Atmospheric Organic Aerosol

“…Unfortunately, there are very few direct measurements of activity coefficients for relevant organic molecules over relevant organic mixtures. It seems reasonable to expect seemingly similar OA, such as SOA derived from different precursors, to interact in a more or less ideal fashion, and indeed isotopic labeling experiments have confirmed this [57,58]. However, mixing of less similar organics, such as relatively non-polar POA and more polar SOA, is less clear.…”

Secondary organic aerosol (SOA) yields from NO<sub>3</sub> radical + isoprene based on nighttime aircraft power plant plume transects

“…Laboratory chamber studies of SOA mass yield at OA loadings of ∼ 10 µg m −3 from isoprene have typically found low yields from O 3 (1 % Kleindienst et al, 2007) and OH (2 % at low NO x to 5 % at high NO x Kroll et al, 2006;Dommen et al, 2009;1.3 % at low NO x and neutral seed aerosol pH but rising to 29 % in the presence of acidic sulfate seed aerosol due to reactive uptake of epoxydiols of isoprene IEPOX Surratt et al, 2010). One recent chamber study on OH-initiated isoprene SOA formation focused on the fate of second-generation RO 2 radical found significantly higher yields, up to 15 % at low NO x , suggesting that omitting later-generation oxidation chemistry could be an important limitation of early chamber determinations of isoprene SOA yields.…”