Differences in Organic Functional Groups between Aged Biomass Burning and Mixed Diesel and Residual Oil Combustion Aerosol

LELIA N. HAWKINS (1), Lynn M. Russell (1)

(1) Scripps Institution of Oceanography, UCSD

     Abstract Number: 375
     Last modified: November 9, 2009

Abstract
Separating, identifying, and characterizing organic aerosol sources in urban atmospheres can be challenging when multiple sources exist. This challenge is increased when those sources are sufficiently removed from the sampling location to allow for aging of the organic aerosol, blurring composition differences and reducing the usefulness of tracer molecules and molecular fragments. To address this, organic functional group concentrations in submicron aerosol particles collected from 27 June to 17 September at the Scripps Pier in La Jolla, California as part of AeroSCOPE 2008 were quantified using Fourier Transform Infrared (FTIR) spectroscopy. Organic and inorganic non-refractory components in the same air masses were quantified using a Quadrupole Aerosol Mass Spectrometer (Q-AMS). Previous measurements at the Scripps pier indicate that a large fraction of submicron particle mass originates in Los Angeles and the port of Long Beach. These sources also emit sulfur, vanadium, and nickel. Additional particle sources to the region include local urban emissions and periodic biomass burning during large wildfires. Three distinct types of organic aerosol components were identified from organic composition and elemental tracers, including biomass burning, fossil fuel combustion, and polluted marine components. Fossil fuel combustion organic aerosol was dominated by unsaturated alkane and was correlated with sulfur, vanadium, and nickel supporting ships and large trucks in and around the port region as the dominant source. Biomass burning organic aerosol comprised a smaller unsaturated alkane fraction and larger fractions of non-acid carbonyl, amine, and carboxylic acid and was correlated with potassium and bromine. Polluted marine organic aerosol was dominated by organic hydroxyl and unsaturated alkane and was not correlated with any elemental tracers but did show a moderate correlation with m/z 79 (a methane sulfonic acid fragment) for samples with little combustion aerosol influence. Mass spectra of the organic aerosol support the aerosol sources determined by organic functional groups and elemental tracers and contain fragments commonly attributed to oxygenated organic aerosol (OOA), hydrocarbon-like organic aerosol (HOA), and biomass burning organic aerosol (BBOA). Comparisons of the PMF-derived Q-AMS source spectra with FTIR source spectra and functional group composition provide additional information on the relationship between commonly reported organic aerosol factors and organic functional groups in specific organic aerosol sources rather than mixtures of multiple sources.