Particulate matter samples were collected with two co–
located Gent samplers, one employed a stacked filter unit (SFU)
with coarse (PM10–2.5) Nuclepore polycarbonate membrane filters
(Whatman; 4 μm pore diameter) and fine (PM2.5) quartz fiber filters
and the second employed a SFU with coarse Nuclepore
polycarbonate membrane filters and fine Teflon filters (Maenhaut
et al., 1993). Polycarbonate and Teflon filters were pre–weighed
and used as received. Quartz fiber filters were pre–fired at 900 °C
in a muffle furnace for 6 hours and were wrapped in aluminum foil
prior to use. Co–located samplers were utilized in an effort to more
accurately determine fine particle mass, since quartz fiber filters
are well–known to display both positive and negative sampling
artifacts, making the measurement of an accurate gravimetric
mass difficult (Turpin et al., 2000; Mader et al., 2001; Viana et al.,
2007). The monitoring program ran from May–June 2010 and a
total of 35 PM2.5 and PM10–2.5 filters were collected from midday–
midday on days with little or no rain over the sampling period.
Once samples had been collected the loaded filters were stored in
a freezer (–30 °C) until analysis.