AIRUSE-LIFE+: A harmonized PM speciation and source apportionment in five southern European cities

The AIRUSE-LIFE+ project aims at character- izing similarities and heterogeneities in particulate matter (PM) sources and contributions in urban areas from south- ern Europe. Once the main PMx sources are identified, AIRUSE aims at developing and testing the efficiency of spe- cific and non-specific measures to improve urban air qual- ity. This article reports the results of the source apportion- ment of PM10 and PM2.5 conducted at three urban back- ground sites (Barcelona, Florence and Milan, BCN-UB, FI- UB and MLN-UB), one suburban background site (Athens, ATH-SUB) and one traffic site (Porto, POR-TR). After col- lecting 1047 PM10 and 1116 PM2.5 24h samples during 12 months (from January 2013 on) simultaneously at the five cities, these were analysed for the contents of OC, EC, anions, cations, major and trace elements and levoglucosan. The USEPA PMF5 receptor model was applied to these data sets in a harmonized way for each city. The sum of vehicle exhaust (VEX) and non-exhaust (NEX) contributes between 3.9 and 10.8μg m−3 (16–32 %) to PM10 and 2.3 and 9.4 μg m−3 (15–36 %) to PM2.5, although a fraction of secondary nitrate is also traffic-related but could not be estimated. Important contributions arise from sec- ondary particles (nitrate, sulfate and organics) in PM2.5 (37– 82 %) but also in PM10 (40–71 %), mostly at background sites, revealing the importance of abating gaseous precursors in designing air quality plans. Biomass burning (BB) contributions vary widely, from 14–24 % of PM10 in POR-TR, MLN-UB and FI-UB, 7 % in ATH-SUB, to < 2 % in BCN-UB. In PM2.5 , BB is the second most important source in MLN-UB (21%) and in POR-TR (18 %), the third one in FI-UB (21 %) and ATH- SUB (11 %), but is again negligible (< 2 %) in BCN-UB. This large variability among cities is mostly due to the de- gree of penetration of biomass for residential heating. In Barcelona natural gas is very well supplied across the city and is used as fuel in 96 % of homes, while in other cities, PM levels increase on an annual basis by 1–9 μg m−3 due to biomass burning influence. Other significant sources are the following.