Source apportionment of PM2.5 in Milan by PMF receptor model

This case study discusses the application of a multivariate receptor model, the EPA PMF 5.0 to the PM2.5 dataset from Lombardy region in Italy. The aim of the study is to perform source apportionment investigation of the applied dataset and identify different PM2.5 sources that greatly impact the composition of particulate matter in the studied region. PMF model evaluates contribution to diverse source types of measured PM2.5 concentrations by investigating chemical composition of ambient pollution samples. As a type of receptor models, PMF used as an input data, PM concentrations and their relative chemical specification and provides as an outcome the number of sources, their composition and the source contributions. The analysis has been performed to dataset which is comprised of PM2.5 sampling campaign performed in the downtown Milan between 2002 and 2003. The original data set is consisting of 162 daily samples of PM2.5 mass concentration and relative chemical specification of 21 chemical species (carbon components, inorganic ions and trace elements). However, as some samples did not contain measurements for all species, and this represent the main requirement for model to be run, the original dataset had to be reduced. Likewise, reduced dataset consisted of 99 daily samples of PM2.5 mass concentration and 11 chemical species. The analysis of total annual PM2.5 mass concentration revealed presence of 6 sources (secondary sulfate, traffic non-exhaust, biomass combustion/break wear, domestic heating, re-suspended soil dust and secondary nitrate). After the general examination, the dataset was split into two subsets, warn and cold season for the more detailed study. The warm season analyses identified 4 sources (secondary nitrates and organics, biomass combustion/break wear, traffic exhaust and secondary sulfate), while on the other hand the cold season identified 4 sources (secondary nitrates and organics, domestic heating, crustal matter and re-suspended soil dust).