RenéE. Van Grieken

Heavy metal contamination in sediments from the Belgian coast and Scheldt estuary

Abstract Sixty-two samples of total sediments and the separated clay/silt size fractions were analysed by energy-dispersive X-ray fluorescence spectrometry to evaluate the pollution level and the trends in samples collected along the Belgian coast over a period of 6 yr and at four stations located in the Scheldt estuary where two of these were sampled periodically for 4 yr. Three correction methods for grain size effects were applied, either to the bulk sediment samples or to the clay/silt size fractions, and the results were compared. Local variations on the concentrations in some of the elements determined were used to establish whether they result from an anthropogenic or natural origin. The level of pollution was assessed as a function of the location, sampling date, and depth.

Geochemistry of suspended matter from the baltic sea. 1. Results of individual particle characterization by automated electron microprobe

Automated electron probe X-ray microanalysis was used to characterize some 15 000 individual suspension particles from 50 samples of suspended matter collected from different depths at 18 stations throughout the Baltic Sea and the transient area to the North Sea. For each particle, 14 minor and major elements were determined and size information data were obtained. To process this huge amount of results, multivariate analysis techniques were invoked: the particles were classified into specific types and the abundance variations of these groups were studied. It appeared that 80% of all investigated particles contained mostly silicon, and seemed to consist of quartz, and K-rich and Fe-rich aluminosilicates. The abundance of BaSO4 particles averaged 5% throughout the Baltic Sea, but amounted to up to 44% at some stations. The abundance of the Fe-rich particles varied significantly with location and depth, and averaged ∼ 4%. They were often found to be associated with significant amounts of P. Both of these particle types and the Mn-rich particles are thought to be mainly authigenic. Calcium carbonate particles are more abundant towards the North Sea (which seems to act as a source). Principal component analysis of the data revealed that most of the compositional variability can be explained by differences between deep and surface waters and by the influences of inflowing North Sea waters. Additional information about the types and sources of the suspended matter in the Baltic Sea was gained from the comparison and correlation of the single particle results with different fractions of the bulk concentrations of elements such as Al, Ca, Mn, Fe, Zn and Ba.

Iron, copper, zinc and lead in hair from Sudanese populations of different age groups

Energy-dispersive X-ray fluorescence was used for the analysis of hair samples from three different age groups of the Sudanese population. Hair samples were digested in a mixture of nitric and perchloric acids and the metals were then precipitated with ammonium pyrrolidine dithiocarbamate. The variations of the Fe, Cu, Zn and Pb content of hair with age were investigated. The averages of the elemental concentrations in each age group were compared with the other age groups and with literature values. The correlation of each pair of elements in the hair samples was also investigated.

Electron microprobe characterization of individual aerosol particles collected by aircraft above the southern bight of the North Sea

Abstract About 50,000 individual aerosol particles from a total of 108 samples collected at six different altitudes above the Southern Bight of the North Sea, have been analysed using electron probe X-ray microanalysis. The results of hierarchical cluster analysis on each sample revealed that, for continental air masses, most of the aerosol particulate matter is characterized by high amounts of aluminosilicates, CaSO4 and Fe-rich particles. For western and marine air masses there was no change in the composition of the most abundant particle type with height. This is in connection with the rather mixed nature of the atmosphere. Non-hierarchical cluster analysis showed that the most abundant particle types in this airshed are: aluminosilicates from coal combustion releases, Fe-rich, sea salts enriched with Pb, and organic material associated with residual oil combustion tracers, accounting for 21, 16, 15 and 12% of the total analysed particles, respectively. Almost 60% of the analysed particles is related to combustion or energy-generation processes. Principal factor analysis on an elemental frequency matrix led to comparable results with principal factor analysis used in combination with cluster analysis. This shows that the method described here is useful for the identification of aerosol sources.

Detection Limits of Grazing-Exit EPMA for Particle Analysis

Abstract. In conventional electron probe microanalysis (EPMA), the electron-induced X-rays are measured at large take-off angles of about 45°. In the grazing exit EPMA (GE-EPMA) method, they are measured at small angles (< 1°). X-rays emitted from deep positions can not be detected at grazing exit angles due to refraction effects at sample-vacuum interface; therefore, it is possible to measure X-rays emitted only from near the surface with a low background. GE-EPMA is especially suitable for the analysis of particles deposited on a flat sample carrier. The detection limits of GE-EPMA were investigated for artificial particles (Al2O3, Fe2O3 and PbO2 , particle sizes: 1 ∼ 18 μm) deposited on flat sample carriers of Au thin films–Si wafers. The detection limits improved with decreasing exit angle. The detection limits for characteristic X-rays at an exit angle of approximately 1.1° were 2–4 times lower than at 45°. A minimum detection limit of ca. 0.1% was obtained for Al in small particles.

Comparison of three dry deposition models applied to field measurements in the Southern Bight of the North Sea

Abstract Dry deposition velocities have been calculated using three different approaches. Turbulent wind profile theory has been used to predict the drag coefficient, wind speed and friction velocity at 10 m height when the wind speed is measured at a higher altitude. The resulting parameters were introduced in a two-layer deposition model. The second approach was the well-known model of Slinn and Slinn (1980, Atmospheric Environment14, 1013–1016), whereas the third corresponded to the model published by Williams (1982, Atmospheric Environment16, 1933–1938). Results point to clear differences. However, in a field experiment carried out at the Southern Bight of the North Sea, all three approaches show relatively comparable results. The role played by the size distribution of atmospheric particulate matter is essential. In our case any of the three models could have given satisfactory outcomes taking into account the wide spread of the experimental results cited in the literature for the same airshed.

Composition and sources of atmospheric particulate matter at Kayseri, central Turkey

A total of 166 atmospheric particulate matter samples were co!!~ted from three different !ocatiens in the city of Kayseri, Central Anatolia, Turkey, during the period from January 1986 to October, 1988. The aerosol samples were analyzed for AI, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb by energy-dispersive X-ray fluorescence. The results indicated that the aerosol elemental composition at Kayseri is mainly dominated by secondary sulfates, reaching an average concentration of up to 34 t~g m -3. It was observed a much higher elemental concentration of those species associated with anthropogenic activities, compared with those from another urban a~rshed with similar characteristics. Enrichment factor calculations showed that the anomalously enriched elements were S, Cr, Ni, Cu, Zn and Pb. The seasonal variability of the elemental concentrations was studied using Si and S. The former was thought to be representative of a natural aerosol, while the latter was associated with anthropogenicaily generated elements. Multivariate analysis of the data base containing the element0t concentrations allowed the identification of five different aerosol sources, namely: secondary sulfates, residual oil combustion, industrial emissions, car exhausts and soil dust.

Effects of titanium dioxide industry waste dumping on sea water chemistry

Abstract An investigation was made to determine the influence of the dumping of a 1000 ton day −1 , on the average, of acid-iron waste from the titanium dioxide industry into the shallow but turbulent Southern Bight of the North Sea. This waste contains some 20% sulfuric acid and 2% iron. After the passage of the barge that discharges 10 ton of waste min −1 into its wake, the vertical and horizontal distributions of the pH, iron-concentration and turbidity were measured as a function of time. It appeared that a few seconds after the discharge and for a very brief period, the pH was down to approx. 4 and the Fe-concentration was 13 mg l −1 . More than 1 min after the discharge a pH below 6 and an iron-level above 3 mg l −1 could not be detected anywhere. The measured factor for waste dilution by sea water, based on the observed acid and iron concentration in the waste and in the discharge track, were around 5000 after 5 min, 9000 after 10 min and 80,000 after 20 min. Before and long after the dumping, the total iron-concentration in this Southern Bight area was around 100 μg l −1 , but this high level might be due to natural causes.

Size-differentiated composition of aerosol in Khartoum, Sudan

Abstract Aerosol samples were collected in Khartoum, Sudan, using a 5-stage cascade impactor. The samples were analyzed for up to 29 elements by particle-induced X-ray emission (PIXE). The size distributions and enrichment factors indicated that most of the elements in the Khartoum aerosol originate from a soil dispersion source and that the anthropogenic contribution is important only for S, Cl, Br, and Pb and to a lesser extent for Cu and Zn. Comparison of the enrichment factors for the elements in the Khartoum aerosol with literature values indicated the lowest enrichment factors reported for these elements so far. Multivariate analysis of the data showed that the anthropogenic contribution was important in the small particle size range (0.25–0.5 μm) and that for the larger particles soil dispersion prevailed.

Air-pollution-induced weathering of slates

Abstract The air-pollution-induced weathering of slates has been studied. Thin sections perpendicular to the weathering zone were made and examined by petrography and electron probe X-ray micro-analysis. Quantitative analysis of weathered and unweathered parts of the slates showed that calcite or aragonite in the slates is transformed into gypsum upon interaction with atmospheric SO2 or H2SO4, which causes a fan-shaped splitting of the slates, because of the larger molar volume.