Influence of ship emissions on NOx, SO2, O3 and PM concentrations in a North-Sea harbor in France.

The influence of in-port ship emissions on gases and PM10 concentrations has been estimated in the port city of Calais, northern France, one of the busiest harbor in Europe, with numerous rotations of ferries or roll-on/roll-off cargo in average per day. NOx, SO2, O3 and PM10 concentrations were continuously measured over a three-month period, as well as real-time particle size distribution. A rural site located at Cape Gris-Nez, 20km from Calais, was considered to deduce intrinsic contribution of ship emissions at the harbor city. The average concentrations of the studied species as well as the pattern of the conditional bivariate probability function at the two sites evidenced that in-port shipping, especially during the maneuvering operations, has an important influence on the NOx and SO2 concentrations. The impact of shipping in the harbor of Calais on average concentrations was estimated to 51% for SO2, 35% for NO, 15% for NO2 and 2% for PM10 in the studied period. Concentration peaks of SO2 and NOx associated with an O3 depletion appeared synchronized with departures and arrivals of ferries. For winds blowing from the harbor, when compared to the background level, the number of particles appeared 10 times higher, with the highest differences in the 30-67nm and the 109-167nm size ranges. The average impact of in-port ships on PM10 concentrations was estimated to +28.9μg/m3 and concerned mainly the PM1 size fraction (40%). Punctually, PM10 can potentially reach a concentration value close to 100μg/m3.