Aerosols generated from the controlled combustion of various solid fuels (coal, peat and wood) were sampled from the flue of a chimney and compared with those collected in residential areas of three rural towns with known air quality problems. Chemical analysis performed using Ultra High Resolution Mass Spectrometry (UHRMS) showed that each of these samples contained thousands of individual organic compounds. The highly complex nature of these samples was broken down with the use of advanced data analytical tools to elucidate the following:
• Typically, around 45% of compounds contained only Carbon, Hydrogen and Oxygen (CHO family), while 55% contained Sulfur and/or Nitrogen (CHON, CHOS, CHONS families).
• A high proportion (55-95%) of all species were aromatic compounds.
• Wood combustion produced the most oxidized compounds, followed by coal and peat.
• Although there are a large number of common species in the various fuel types, some of molecular formulae can be used to distinguish between coal, peat and wood combustion.
Further off-line chemical analysis was performed using advanced chromatographic techniques for the identification and quantification of a range of target compounds. Large amounts of established combustion marker compounds such as nitroaromatics, phenolic compounds, lignin-type compounds, PAHs and anhydrosugars (i.e. levoglucosan) were detected in all samples. Good progress was also made in identifying candidate marker compounds for each fuel type, although, further work is needed in this area.
A series of simulation chamber experiments was also conducted on two key compounds (2,5-dimethylfuran and -valerolactone) emitted by combustion of biomass and other solid fuels. A state-of-the-art online analytical technique (FIGAERO-CIMS) was used to identify the oxidation products and chemical mechanisms for their formation have been proposed. These simulation chamber experiments have generated novel information on the reaction pathways for anthropogenic SOA formation that can be incorporated into atmospheric models dealing with both air quality and climate.
In order to elucidate further details of the species and processes leading to anthropogenic SOA formation, a field measurement campaign was conducted during winter in Cork city. Results obtained during one night-time pollution event indicated the presence of a large number of oxidised and nitrated aromatic species such as phenols, nitrophenols, nitroaromatics, nitro-PAHs etc. The results thus indicate that aromatic hydrocarbons and PAHs are key sources of anthropogenic SOA in locations strongly affected by biomass or solid fuel burning.
Overall, the unique information obtained from this combined field and laboratory study is expected to contribute to a greatly improved understanding of the composition, sources and processes leading to organic aerosol formation in the atmosphere, and in turn, the impact of SOA on human health and climate.
The results have been presented at three international conferences and form the basis of four research publications. Communication of the project results to the general public has been achieved through the project website, social media and a short film.
