Performance evaluation of a very-low-volume sampler for atmospheric particulate matter

A cheap and small device for sampling atmospheric particulate matter (PM) has been recently developed. It works at a very low flow rate (0.5 L min–1) and is able to collect the atmospheric aerosol on filters, allowing subsequent chemical analyses. The samplings have a long duration (1–2 months), and the devices can be used to make cheap networks over a territory. These very-low-volume samplers (VLVS) can be used to trace long-term concentration variations and to draw up concentration maps of PM and its chemical components. The performance of the VLVS was evaluated in terms of measurement repeatability and of agreement with the results obtained when using a 2.3 m3 h–1 reference sampler (REF). The study period was 1 year. The considered PM components were ions, polycyclic aromatic hydrocarbons (PAHs), levoglucosan and elements. The repeatability of the measurements was very good for all the examined PM components: the standard deviation of 3 replicates (co-located samplers) over 9 measurement periods was in the range 2.0–5.5% for ions, 10–17% for PAH, 5.2% for levoglucosan and 5.6–16% for elements. It was 8.2% for the PM mass concentration. This satisfactory performance indicates that the VLVSs can be reliably used to evaluate the spatial variability and to draw concentration maps of PM and PM components. A very good agreement with the reference sampler was obtained for ions, with the only exception of ammonium nitrate and ammonium chloride (VLVS values were up to 10–20% lower than the reference values), levoglucosan and elements. In the case of PAH, instead, the ratio VLVS/REF was in the range 1.2–1.6 for 4-ring congeners and 0.4–0.8 for 5-and 6-ring congeners. For all the congeners, anyway, these typical ratios were kept, with small variations, during the whole study period.