CHEMICAL CHARACTERIZATION AND SOURCE APPORTIONMENT OF INDIVIDUAL AEROSOL-PARTICLES OVER THE NORTH-SEA AND THE ENGLISH-CHANNEL USING MULTIVARIATE TECHNIQUES

More than 25 000 individual aerosol particles in 51 particulate matter samples, all taken from a research vessel over the North Sea and the English Channel, in a time range of 4 years, were analyzed by automated electron probe X-ray microanalysis (EPXMA). Multivariate methods were used to reduce the total data set. Single-particle analysis combined with hierarchical cluster analysis yields nine major particle types. The North Sea aerosol is predominantly composed of sea salt, sulfur-rich particles, silicates, and calcium sulfate particles. Their abundance is dependent on meteorological conditions and sample location. Differences between all samples were studied on the basis of the abundance variations by using principal component analysis. Three factors explain 91% of the total covariance between the samples. The first component represents the marine-derived aerosol fraction and is more important as wind speed increases or at more remote sampling locations. The second component differentiates anthropogenically derived CaSO4-rich samples. Their relative abundance is much more pronounced as the sampled air masses spend longer residence times over the south of England. The samples of the third cluster are related to high silicate and sulfur abundances. Source apportionment of this group was obtained by a second principal component analysis. Two different clusters separate mixed marine/continental samples from pure continental-derived silicate and sulfur-rich particulate samples.