Chemical characterisation of particle emissions from burning leaves

Abstract

Particulate matter emissions (PM10) from open-air burning of dry leaves were sampled and analysed for a series of organic and inorganic species, including carbon fractions, anhydrosugars, humic-like substances (HULIS), water-soluble ions, metals and organic trace components. The study was performed to investigate whether open-air burning of leaves in rural areas is a potential source of high amounts of unexplained organic matter (OM) in ambient PM. Results of the carbon analysis indicated that the amount of OM, more than 90% of emitted PM10, is significantly higher in smoke from leaves than from wood burning [Schmidl, C., Marr, I.L., Caseiro, A., Kotianova, P., Berner, A., Bauer, H., Kasper-Giebl, A., Puxbaum, H., 2008. Chemical characterization of fine particle emissions from wood stove combustion of common woods growing in mid-European Alpine regions. Atmospheric Environment 42, 126-141, till now considered as the main combustion source of organic PM used in source apportionment. While the proportion of total carbon (TC), 67% of PM10, is very similar to that in wood smoke, the make-up of the total carbon is different. In wood smoke, levels of elemental carbon (EC) equivalent to soot, of around 20% were found, however in leaf smoke EC was very low, between 0 and 10% depending on the analytical methodology. In addition chemical markers were identified that permit the discrimination of wood smoke from leaf smoke in ambient PM samples. In particular the levels of anhydrosugars, sugar alcohols, PAH and n-alkanes in leaf smoke differ significantly from those in wood smoke. The ratios of levoglucosan to galactosan and benzo[- a]pyrene to tetracosane differ by an order of magnitude between smoke of leaf burning and that of typical mid-European firewood (Schmidl et al., 2008). Furthermore sugar alcohols were found in notable concentrations in leaf burning samples, which were not found in wood smoke. Complete chemical profiles for leaf burning as a particulate matter source are presented here, including organic trace compounds to be used in source apportionment studies either by the chemical mass balance (CMB) or the macrotracer approach.