Long-range transport clusters and positive matrix factorization source apportionment for investigating transboundary...

Source apportionment studies of particulate matter are common and have been performed either as source region analyses using air mass back trajectories or by source type using source apportionment techniques. By combining the two approaches, it is possible to estimate the relative importance of emitters in different regions. PM_2.5 samples were collected in Gothenburg between September 2008 and September 2009. The mean daily PM_2.5 level was 6.1 μg m^-3 (range 0.79-30.91 μg m^-3). Elemental analyses were done using Energy dispersive X-ray fluorescence (EDXRF) spectroscopy. Source apportionment was carried out using the US EPA PMF 5.0 software. The sources long-range transport (LRT), LRT-Pb (lead-containing LRT), ship emissions, combustion, marine, and resuspension were identified. Air mass trajectories were estimated using HYSPLIT model (version 4.9). Six transport clusters were identified: South Scandinavia 21%, North Scandinavia 11%, Baltic Sea 8%, Eastern Europe 6%, UK/North Sea/Denmark 25%, and North Atlantic Ocean 30%. LRT was the major contributor to PM_2.5 levels across all six transport clusters (48%) followed by ship emissions (20%) and combustion (19%). The transport cluster associated with the highest PM_2.5 levels was Eastern Europe followed by South Scandinavia, UK/North Sea/Denmark, and Baltic Sea. After considering the frequency of the transport clusters, the transport clusters associated with the highest PM_2.5 levels were UK-NorthS-DK, S-Scandic, and N-Atlantic, while Eastern Europe only contributed 9% towards PM_2.5 levels. Abatement strategies aimed at reductions of ship emissions, industry emissions, and road traffic emissions on an European level and local combustion sources on a city-scale level would be the two most effective directions for reducing ambient PM_2.5 in Gothenburg.