Detailed Chemical Characterisation of organic aerosols emitted from Domestic Solid Fuel Burning 

Elena Gómez Alvareza), Niall O’Sullivana), Sarah Steimerb), Stig Hellebusta), Markus Kalbererb) and John Wengera)

a) School of Chemistry & Environmental Research InstituteUniversity College Cork, Cork, Ireland

b) Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, United Kingdom

The burning of solid fuels for home heating causes air quality problems worldwide. Wood or biomass is by far the most prominent type of solid fuel, however in Ireland, a combination of peat, coal and wood is typically used, especially in rural towns. In order to develop effective air pollution control strategies, information on the chemical composition and source strength of each of the solid fuels is required. In this study, we aim to use information on the detailed molecular composition of aerosols to establish a link between chemical speciation and different solid fuel types. Particles produced by burning commercially available coal, peat and wood in a modern stove were collected on quartz fibre filters and analysed, for the first time, using nanoelectrospray ionization ultra-high resolution mass spectrometry. The results from the combustion experiments have been compared with those obtained from analysis of ambient PM2.5 collected in three small towns in Ireland.

Comprehensive mass spectral data evaluation methods, including Kendrick mass defect, Van Krevelen diagrams, carbon oxidation state and aromaticity equivalent were used to identify different compound classes, as well as the mass distributions of the detected species. Ten thousand unique chemical formulae were identified across all eight samples (5 fuel types, 3 ambient samples). The majority of species detected were highly condensed aromatics, nitroaromatic compounds, lignin-type compounds, anhydrosugars (e.g., levoglucosan) and fatty acids. Furthermore, nitrogen- and sulfur-containing organic species were found to contribute at least 40% of the total identified number of formulae. This was not only the case for ambient samples, but also for aerosols sampled directly fat the rooftop chimney during the solid fuel combustion experiments, indicating that nitrogen- and sulfur-containing organic species can also originate from primary emissions as well as from in situ chemical processing in the atmosphere.

Finally, up to 90% of the chemical formulae with the most intense signals in the ambient samples also displayed similarly intense signals in the fuel combustion samples, confirming that domestic solid fuel burning overwhelmingly influences the particle composition in these locations. Further offline analysis using a range of chromatographic methods (HPLC-UHRMS Orbitrap available in Cambridge) and Leipzig is currently underway. It is envisaged that these methods will enable identification and quantification of established biomass burning markers such as nitrocatechols and fatty acids, while also facilitating identification of new and unique markers for each of the solid fuel types.