A Comparative Study of Polycyclic Aromatic Hydrocarbon Sources in Mosses in Aberdeen and Glasgow Cities

Abstract The concentration of PAHs on mosses differs between Aberdeen and Glasgow. In both cities, PAHs are dominated by 4- and 5-ring PAHs, which are primarily associated with traffic. In Aberdeen, mosses had a mean PAH concentration of 2,000 µg/kg; in Glasgow, the concentration was 10,008 µg/kg per dry mass of moss. The concentration of HMW PAHs on pleurocarpous mosses was highest, notably in mosses from residential car parks. In Glasgow, the mean concentrations of highly carcinogenic PAHs, such as BaP, were 70 µg/kg and 424 µg/kg. The use of MP-P MDR indicated that Glasgow PAHs were likely from diesel and petrol vehicle emissions. Particulate-phase PAHs such as Benzo[a]anthracene and Chrysenes characterised mosses in Glasgow. Fl and Py were the most abundant PAHs on mosses from both cities, with concentrations in Glasgow of 1,503 µg/kg and 1,044 µg/kg of moss, while mosses from Aberdeen had lower concentrations of 309 µg/kg and 301 µg/kg. Aberdeen may have had lower concentrations due to fewer vehicles and traffic, the influx of clean coastal air, and measures such as hydrogen-powered bus fleets. Aberdeen has much lower levels of HMW and MMW PAH, which are mostly derived from petrol-powered vehicles. As a coastal city, Aberdeen benefited from the dilution of its urban air with marine air, which cleans PAHs by causing them to deposit in marine water. Glasgow, with a larger population and more vehicles, is not coastal. Due to socio-economic differences, it may have older vehicles and a higher proportion of diesel cars, making its vehicles more polluting.