Characterisation of aerosol particulate matter from urban and industrial environments: examples from Cardiff and Port Talbot, South Wales, UK

A high-volume cascade impact collector (1100 l/min air flow) was used to collect air samples in an industrial (Port Talbot) and an urban (Cardiff) site with the purpose of characterising both coarse (PM 10–2.5) and fine (PM 2.5) fractions comprising the total sample. PM 10–2.5 and PM 2.5 samples were collected by cascading air through two polyurethane foams on which particles impact and become deposited. Air sample collection rates are to some extent dependent on weather conditions, notably rainfall, humidity, and especially, wind direction, but samples show a very different and distinctive air particle composition between the two collection sites. Thus, although both Cardiff and Port Talbot are coastal sites and therefore have high contents in chlorides, Port Talbot is extremely rich in tiny Fe spherules (>30%, in both coarse and fine fractions) from a nearby steel plant. Mineralogical characterisation using SEM-EDX shows a clear fractionation between the particle composition in the PM fractions, with the coarse fraction being dominated by chlorides, sulphates (gypsum), and silicates, and the fine fraction having high proportions of ammonium sulphates and elemental and organic carbon compounds, most of the latter being linked to traffic pollution.