H. Van Malderen

Individual aerosol particle composition variations in air masses crossing the north sea.

Single-particle analysis on North Sea aerosol and rainwater samples was performed by electron-probe X-ray microanalysis (EPXMA). The analysis was mainly focused on the determination of the inorganic composition of giant particles with diameters above 1 pm. Multivariate techniques were used for the reduction of the data set and for source apportion. Based on the relative abundances found by hierarchical cluster analysis according to the Ward error sum method, three to eight different aerosol types were distinguished. Crossing the North Sea, the changes in air mass composition appeared as a decrease in the abundance for the aluminosilicate particles and a relative increase for NaCl and seawater crystallization products. Principal factor analysis revealed four different aerosol sources: aluminosilicates and NaC1, seawater crystallization products as a marine source, and two industrial sources. Relations between the particle composition, origin, and shape were studied by manual EPXMA, and for most of the particle types, a characterization based on their shape was obtained.

Hierarchical cluster analysis with stopping rules built on Akaike's information criterion for aerosol particle classification based on electron probe X-ray microanalysis

Abstract The interpretation of the results of hierarchical cluster analysis depends very much on the correct choice of the number of clusters. An approach based on the application of the Akaike information criterion is proposed. Examples of the classification of Lake Baikal aerosol particles based on the clustering of electron probe X-ray microanalysis data are given. Bondarenko, I., Van Malderen, H, Treiger, B., Van Espen, P. and Van Gricken, R., 1994. Hierarchical cluster analysis with stopping rules built on Akaikes information criterion for aerosol particle classification based on electron probe X-ray microanalysis. Chemometrics and Intelligent Laboratory Systems , 22: 87–95.

Composition of individual aerosol particles above Lake Baikal, Siberia

More than 20,000 individual aerosol particles, taken from research vessels over the total area of Lake Baikal (Siberia) during June 1992 and September 1993, were analysed by automated electron probe X-ray microanalysis. The obtained data set was reduced by a combination of multivariate techniques. Hierarchical cluster analysis indicated 11 major particle types, among which soil dust, Fe-rich, Ca-rich, organic, biogenic, S-rich particles and gypsum were the most abundant. Abundance variations as a function of sampling position were investigated by means of nonhierarchical clustering techniques. Significant differences were found between the pristine northern and middle basin, and the anthropogenically influenced southern basin. Emissions from industrial complexes near Irkutsk and in the valley of the Angara and Selenga river seem to have an impact on the atmosphere over the lake. Samples taken in the proximity of the Baikalsk paper plant revealed a huge influence by the factory on the natural aerosol. Principal factor analysis showed four possible sources of the Baikal aerosol.

Elucidating the composition of atmospheric aerosols through the combined hierarchical, non-hierarchical and fuzzy clustering of large electron probe microanalysis data sets

Abstract Combined utilization of hierarchical, non-hierarchical and fuzzy clustering is introduced to find the intrinsic Structure of large analytical data sets. Modified algorithms for nonhierarchical and fuzzy clustering are used. The interpretation of the results of clustering is based on the extensive use of different types of graphs. New approaches to the graphical representation of the results of fuzzy clustering are proposed. The method is applied to data of electron probe X-ray microanalysis of individual aerosol particles. The advantages of the method are shown.

Studying aerosol samples by non-linear mapping of electron probe microanalysis data

Abstract One of the graphical multivariate data analysis, namely non-linear mapping, is applied to the processing of the results of electron probe x-ray microanalysis of individual aerosol particles. A method of representation of the results of non-linear mapping in the form of triplot is proposed. It is shown that it can be used for the fast evaluation of the data structure. The results for aerosol samples from the Lake Baikal are discussed.

Fluxes and Sources of Heavy Metal Inputs into the Southern Bight of the North Sea

Chemicals, both natural and man-made, reach the North Sea through a number of different routes. For many years, research on pollution of the marine environment has focused on the most obvious inputs: those borne by rivers and direct discharges of waste. However, a number of studies conducted at the end of the 1970’s and at the beginning of the 1980’s revealed that a substantial fraction of the contamination entering the ocean, the North Sea and Baltic Sea, derives from sources located on land via atmospheric input. Gradually more importance has been given to the atmospheric route relative to the other pathways. The aim of this study was to estimate from field measurements the atmospheric input of some heavy metals into the Southern Bight of the North Sea, namely between the Dutch and English coast, for comparison with the input by other pathways, and to serve as a calibration reference for model calculations.

Study of Individual Particle Types and Heavy Metal Deposition for North Sea Aerosols using Micro and Trace Analysis Techniques

In the period under review (1991-1994), our group has participated in three sampling programs that have been organised in the framework of the EUROTRAC ASE project: the “Mace Head Intercomparison Experiment” (8th-20th April 1991), the “North Sea Experiment” (15th-27th September 1991) and the ASE experiment on the research platform “Nordsee” (lst-22nd September 1992). Also, an extensive aerosol sampling program was accomplished during several research cruises on the North Sea with the R.V. Belgica (1991, 1992, 1993, 1994) and at a fixed station at the Belgian coast (1992-1994). Our research was intended to estimate the amount of atmospheric pollutant fluxes to the North Sea and to identify the nature of the particles responsible for this flux. In such a complex study, the combined use of different analytical techniques namely: energy dispersive X-ray fluorescence (EDXRF), total reflection X-ray fluorescence (TXRF), micro-proton induced X-ray emission (micro-PIXE) and electron probe X-ray micro-analysis (EPXMA) was effectively implemented.

Gypsum and other calcium-rich particles above the North Sea

Ca-containing particles, especially CaSO4 particles, have been encountered in several atmospheric aerosol studies. An overview is given of the different sources of airborne Ca-containing particles. The North Sea atmosphere is studied to identify the different Ca-containing particle types and to find the correlation between their occurrence and the source regions of the corresponding air masses. About 50 000 individual aerosol samples were collected above the Southern Bight of the North Sea for several wind directions and analyzed for their composition using electron probe X-ray microanalysis. Nonhierarchical cluster analysis is performed on the data to reveal the different particle types, their relative abundances and their sources. CaSO4 in most cases constitutes the largest fraction of the Ca-containing particles. Extremely high numbers of CaSO4 particles are found for northeastern winds, coming from the central part of Germany, suggesting that a great fraction is derived from anthropogenic sources loca...