Contribution of wood combustion to wintertime atmospheric aerosol in Emilia Romagna region

Currently, numerous studies demonstrate the increasing relevance of biomass combustion emissions as a source of atmospheric particles in urban environments in Europe, especially during winter, when the domestic burning of wood logs, briquettes, chips and pellet represents an important renewable energy source. Biomass burning activities are significant emission sources for particulate matter (PM), contributing for a relevant share to the total PM2.5 and PM10 emitted, which may contain numerous toxic/carcinogenic components with a potentially high impact on human health. Therefore, a quantitative understanding of the contributions from biomass burning (BB) to fine organic aerosol is essential for the planning of efficient PM abatement strategies. This work investigates the contribution of residential wood combustion in urban and rural sites in Emilia Romagna (Northern Italy) during five intensive experimental campaigns held in fall/winter through the 2011-2014 years, as a part of the of the “Supersito” project. A comprehensive study was conducted on daily samples to investigate the concentrations of several individual polar and apolar organic compounds related to emissions from wood combustion. Of these individual compounds, levoglucosan, mannosan and galactosan were found to be the dominant species as the most specific tracers. Other abundant compounds included low-molecular-weight carboxylic acids, polycyclic aromatic hydrocarbons and methoxylated phenols. In addition, elemental and organic carbon (EC/OC) were investigated. The diagnostic ratios between anhydrosugars and methoxylated phenols were computed to characterize the type of wood burnt, in particular to discriminate between hardwood and softwood. The obtained values indicate the concomitant contribution of both the wood type, with an increased contribution of hardwood in some periods. The ambient mono-tracer approach using ambient levoglucosan concentrations was applied to compute the relative contribution of wood burning emissions to the Organic Carbon (OC) and Organic Matter (OM) in atmospheric aerosol. Wood burning is an important contributor to as it accounted on average for 36% of OC and 29% of OM. No substantial spatial variability was found in concentrations of the investigated markers at urban and the rural background sites, which indicate homogeneous impact of wood combustion within the study areas.