Representativeness of an air quality monitoring station for PM2.5and sourceapportionment over a small urban domain

Özet

In this study, PM2.5concentrations together with the water-soluble ionic compounds and total elements weresimultaneously measured at 16 sites in the city of Varese located in Northern Italy within a domain of 2 × 2 km2.The center point of this domain consisted of an existing urban air quality monitoring station. The representa-tiveness of the monitoring station for PM2.5mass and chemical composition was estimated using a methodologyrelying on statistical/geostatistical analyses. Source apportionment by means of the Chemical Mass Balance(CMB) receptor model was also performed to evaluate the spatial distribution of source contribution throughoutthe domain. Very high soluble fraction was found for Cd, Sb, K and V, indicating the anthropogenic origin ofthose elements. The geostatistical analysis/mapping showed that the monitoring station captured the spatialvariation of PM2.5and most of the anthropogenic originated elements, e.g., As, Cd and V, whereas it did notcaptured the spatial patterns of the ones originated from both natural and anthropogenic sources, e.g., Na, Ni,Pb, K, Zn, Fe, Cr, and Ti. The CMB source contribution estimations in the monitoring station were at least 25%different from many sites of the domain for PM2.5. The significant spatial variation in concentrations and sourcecontribution estimates showed that the monitoring station could not be considered representative for the airquality monitoring studies with exposure assessment and source apportionment purposes in Varese.