Moss bag (Sphagnum papillosum) magnetic and elemental properties for characterising seasonal and spatial variation in urban pollution

Abstract

This study investigates the seasonal and spatial variation of traffic-induced particle matter in order to evaluate the pollutant distribution and the representativeness of the single air quality monitoring station in the city centre of Turku, southwest Finland. Study focused on parks, kindergarten and school yards as well as heavily trafficked sites. Sampling was done using active magnetic biomonitoring, which is highly applicable in polluted areas lacking native species. Sphagnum papillosum moss bags were exposed separately in road dust period, which is experienced after snow melt and the resuspension of sanding material in spring, and summer season for about 60 days in 2013. Moss bags are magnetically and elementally (e.g. Al, Cr, Fe, Na, Ni, Pb) more enriched in road dust period and near heavily trafficked sites than in summer season and in the courtyard or park sites. Magnetic properties indicate that particle matter is composed of fine-grained pseudo-single-domain magnetite towards superparamagnetic–single-domain grain sizes. Intensive road dust period overrides the variation of prevailing conditions as indicated by three paired samples showing finer grain sizes and higher element levels in courtyard/park sites than in traffic sites in summer. The results emphasise the effectiveness of active magnetic biomonitoring for the assessment of spatially representative air quality monitoring stations and related modelling approaches.