PM2.5 monitoring in urban site (Modena, Italy) by TEOM

A Tapered Element Oscillating Microbalance (TEOM, Rupprecht & Patashnick Co.) has been installed at the Department of Mechanical and Civil Engineering at the University of Modena and Reggio-Emilia. The instrument allows automated and continuous measurement of weight concentration of airborne particulate matter; the inlet is provided with an EPA-standard PM10 head impactor and a PM2.5 sharp cut cyclone. The weighting microbalance is kept at 50°C in order to measure particulate matter in conditions of constant and low humidity and to avoid sampling artefacts from particle-bound water. Underestimation of PM concentration from TEOM measurements have been documented in the literature, due to particulate volatilisation caused by sensor heating. The instrumental equipment has been set up at a height of 9 m above the ground in the Faculty of Engineering building, with the inlet stretched 1 m outside the window and connected to the sensor unit by a 5 cm long conductive Tygon tube. From June 2007 continuous monitoring of PM2.5 has been ran, and since December 2007 the TEOM has been enhanced with a FDMS (Filter Dynamic Measurement System) device to correct PM underestimation of conventional TEOM. The University site can be considered representative of air quality of the residential background for the municipality of Modena: summer and autumn PM2.5 average hourly concentration resulted in 15.0 μg/m3 and 20.7 μg/m3 respectively. From recent FDMS measurements, underestimation of autumn PM can be roughly assessed in 33%.