Modelling of Benzo(a)pyrene Concentrations in North Sea Coastal Areas: Contribution of Ship Emissions

The effect of benzo(a)pyrene (BaP) ship emissions in the greater North Sea region is investigated in this study. The carcinogenic BaP which belongs to the group of polycyclic aromatic hydrocarbons (PAHs) occurs mainly particle bound at temperatures prevailing in the mid-latitudes. The BaP concentration and deposition distribution is investigated by means of the Community Multiscale Air Quality modelling system (CMAQ). CMAQ is a chemistry transport model developed by the US EPA that is here set up on a 54x54 km grid for Europe. Two different model runs, one excluding and one including ship emissions were performed for January and July 2000. For a sensitivity study three additional model runs considering also ship emissions of NOx, SO2, and PM10 were performed for January 2000. It is shown that the contribution of BaP ship emissions to the total BaP emissions is generally small but shows a noticeable seasonal variation. Furthermore, the sensitivity study shows indirect effects of other ship emissions on BaP concentration and deposition over land that are larger than those by the added BaP ship emissions alone.