Spatial distribution of levoglucosan and alternative biomass burning tracers in atmospheric aerosols, in an urban and industrial hot-spot of Central Italy

Domestic biomass heating and wildfires strongly affect particulate matter (PM) concentration in the atmosphere. The individuation of alternative chemical tracers may provide a valuable tool to apportion different possible contributions to biomass burning. In this study, we used a new experimental procedure, based on high spatial resolution analyses of PM10, to assess the spatial distribution of levoglucosan (LVG) and evaluate the possible use of alternative biomass burning tracers in the Terni basin, a wide urban and industrial hot-spot of Central Italy, which includes several spatially disaggregated sources. Spatially-resolved chemical characterization of PM10 was obtained through the use of innovative samplers working in parallel in a dense monitoring network (20 sampling sites, about 1 km between each other), during wintertime. PM10 samples were analyzed for LVG, water-soluble organic carbon (WSOC) and water-soluble and insoluble fraction of 33 elements. Principal component analysis (PCA) on the obtained spatially-resolved data allowed us to identify biomass burning tracers across the polluted study area. Analyses of size-segregated PM samples showed the presence of LVG, and water-soluble Cd, Cs, K, Rb and Tl in particles with size fraction smaller than 1 μm, confirming them as tracers of combustion processes (mainly related to biomass burning). Pearson correlation coefficients demonstrated that concentrations of WSOC and water-soluble Cd, Cs, K, Rb and Tl were well correlated with the spatial variability of LVG concentration. The combined use of spatially and dimensionally resolved data was found to be particularly advantageous for the identification of alternative source tracers, which were used to reliably trace the main local biomass burning sources in the study area.