Jasna Injuk

Elemental composition of mineral aerosol generated from Sudan Sahara sand

Eighteen soil samples from central Sudan were fractionated by dry sieving ina size fraction from <45 μm to >300 μm while aerosols generatedfrom these soils were fractionated in the particle size range from 0.25 μmto >16 μm. The elemental concentrations of soil samples were determinedby energy-dispersive X-ray fluorescence, while the elemental concentrationsof generated aerosols were analysed by particle-induced X-ray emission. Theelements Al, K and Rb show a slight positive fractionation with decreasingparticle size throughout the particle size range studied. The concentrationsof Ca, Mn, Fe, Sr and Y are maximum in the small soil size fraction (<45μm) and decrease for the coarse soil size fractions, while in the mineralaerosol particle sizes (0.25– > 16 μm) the concentrations remainmore or less constant. The size distributions for Cr, Ti and Zr show a maximumin the particle size range 45–100 μm and the concentrations of theseelements decrease sharply in the aerosol fraction down to 16 μm to remainconstant in the smaller aerosol fractions.Enrichment factors for the elements were calculated relative to five referencematerials: average crustal rock, average soil, the investigated Sahara bulksoil, the finest fraction of this soil and the aerosol generated from thissoil, and using four reference elements: Al, Si, Ti and Fe. The enrichmentfactors were found to vary significantly depending on the choice of thereference material or the reference element. The enrichment factors for theSudan mineral aerosol were almost identical to those for Khartoum atmosphericaerosol but different from those for Namib mineral aerosol and Israelatmospheric aerosol following dust storms. Multivariate display methods(cluster analysis, principal component analysis and linear discriminantanalysis) were applied to the element ratios in the mineral aerosol from theSahara and Namib and this showed that these mineral aerosol can bedifferentiated into different groups. An attempt was also made to relate themineral aerosol to its parent soil through the use of these multivariatetechniques and the elemental ratios in both the mineral aerosols and the bulksoils (Namib and Sahara). It was also possible using the elemental ratios andthe multivariate display methods to associate the crustal component to themineral aerosol generated from the Sahara.

Dry and wet deposition fluxes of Cd, Cu, Pb, and Zn into the Southern Bight of the North Sea

Abstract During the period from September 1988 to October 1989, 23 sampling flights were carried out over the Southern Bight of the North Sea. In this campaign, both bulk and size-segregated airborne particulate matter samples were collected. Dry deposition velocities for Cd, Cu, Pb and Zn have been estimated using a modified version of the two-layer of Slinn and Slinn and the particle size distribution obtained from size-fractionated samples. Results pointed out that the main difference between our results and those reported in the literature lies in the aerosol size distribution. Dry deposition rates calculated using these deposition velocities as a function of wind sector showed that continental air masses, particularly those associated with the wind sector west/southwest, are predominant in the deposition process. Wet flux estimates were carried out using Slinns approach. Results were also classified taking into account different wind sectors. Here, the wet flux of Pb and Zn is mainly related to wind sectors east/northeast, south/southeast and local, the latter represents air masses with variable origin; whereas those of Cd and Cu correspond to wind sectors west/southwest and south/southeast. Results showed that wet deposition is responsible for almost 70% of the total deposition into the Southern Bight of the North Sea. However, some topics, like heavy metal content in large aerosol particles, temporal distribution of precipitation events, variation of precipitation intensity aloft, need better knowledge before accurate assessments can be made.

Optimisation of total-reflection X-ray fluorescence for aerosol analysis

Abstract The capabilities of total-reflection X-ray fluorescence (TXRF) analysis were investigated to develop an efficient, simple, rapid and low cost analytical method for aerosols. The technique involves direct impaction of airborne particulate matter on the quartz sample-reflector discs for TXRF. Special attention was paid to bounce-off effects, and hence the aerosol size distributions for the impactor stages; influence of siliconizing the quartz discs on the adhesion of particles; choice of the internal standard; local distribution of the material deposited on the quartz disc; and alternative materials for aerosol collection. Moreover, the proposed method could be used in combination with a one-stage impactor for total aerosol mass collection and analysis.

Atmospheric concentrations and deposition of heavy metals over the North Sea: a literature review

A literature review of the atmospheric concentration rates and dry and wet deposition fluxes of particulate Cd, Cr, Cu, Pb and Zn to the North Sea and adjacent areas is given. The results of direct measurements of dry and wet deposition fluxes are compared to indirect estimates and to modelling values. This work points out the large uncertainties in results of different studies on atmospheric input of trace elements into the North Sea. The current knowledge about the dependence of the deposition velocity upon the particle size and about the processes controlling wet deposition fluxes, and the quality and completeness of the emission data are still inadequate for describing the environmental cycle and impact of heavy metals in the North Sea.

Atmospheric concentrations and size distributions of aircraft-sampled Cd, Cu, Pb and Zn over the southern bight of the North Sea

Abstract In an effort to assess the atmospheric input of heavy metals to the Southern Bight of the North Sea, aircraft-based aerosol samplings in the lower troposphere were performed between September 1988 and October 1989. Total atmospheric particulate and size-differentiated concentrations of Cd, Cu, Pb and Zn were determined as a function of altitude, wind direction, air-mass history and season. The obtained data are compared with results of ship-based measurements carried out previously and with literature values of Cu, Pb and Zn, for the marine troposphere of the southern North Sea. The results point out the high variability of the concentrations with the meterological conditions, as well as with time and location. The experimentally found particle size distribution are bimodal with a significant difference in fractions of small and large particles. These large aerosol particles have a direct and essential impact on the air-to-sea transfer of anthropogenic trace metals, in spite of their low numerical abundance and relatively low heavy metal content.

Trace element concentration variations in tree rings

Abstract Both XRF and PIXE were used to measure variations in relative and absolute trace element concentration levels in tree rings. Samples of a 32 years old pine tree from the vicinity of a coal burning power plant were used in the study. Different sample preparation procedures were compared. Trace element concentration fluctuations were discussed in terms of environmental impact of the coal burning power plant.

Variations of trace element contents within single tree rings

Abstract X-ray fluorescence was used to measure variations in relative and absolute trace-element concentrations within single tree rings taken from a 32-year-old pine tree near a coalburning power plant. The Zn/Cu ratio was found to have a constant value, both along individual rings and between different rings. The Fe, Ca and 8 concentrations varied in a single tree ring and depended on the age of the tree. The results indicate that the variations in concentrations of elements along a single ring are caused by heterogeneous tree tissue structure.

Performance and characteristics of two total-reflection X-ray fluorescence and a particle induced X-ray emission setup for aerosol analysis

Abstract Two X-ray emission techniques, total-reflection X-ray fluorescence (TXRF) and proton induced X-ray emission (PIXE), were applied to atmospheric trace element determinations and compared with respect to detection properties, speed of analysis, precision and sampling strategy. The advantage of the commercial TXRF system over all the other techniques evaluated was clearly demonstrated. The lowest detection limits were found to be at a level of 0.01 ng m −3 . The use of an economical TXRF module exhibited reasonably satisfactory results in this atmospheric research study; the detection limits were about one order of magnitude less favourable than those of the commercial unit. For TXRF, aerosols were collected directly on quartz glass or Plexiglas® carriers in a single-orifice impactor during 3–5 h; the measuring time was some minutes. For PIXE, aerosols were deposited on Nuclepore® filters during 48 h. PIXE was performed under less than optimal conditions using 1.4 MeV protons, and therefore the PIXE detection limits were also recalculated for an optimised setup using 2.5 MeV protons.

Elemental concentrations in atmospheric particulate matter sampled on the North Sea and the English Channel

Abstract Air sampling on a series of 10 cruises, spanning the whole area of the North Sea, yielded detailed spatial distributions of atmospheric concentrations of Al, Si, S, Cl, P, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb determined by EDXRF. A strong influence of the air mass history on the heavy metal concentrations was demonstrated for the whole sampling period of 5 years. Factor analysis performed on all samples collected with a stack filter unit resulted in the identification of three factors for the coarse particle fraction (sulphate particles with trace metals, sea salt particles and soil dust or metallurgic particles containing Fe) and four factors for the fine particle fraction (sea salt, sulphate with Pb and Zn), trace metal particles with Cu, Ni, Zn and fly-ash particles. The same statistics performed on all samples collected above the Southern Bight of the North Sea yielded three factors, namely: sea salt particles, particles enriched in Ni and V, originating from natural oil combustion and particles containing a variety of elements such as S, K, Ca, Fe, Pb, Cu and Zn. Compared with relevant measurements of trace elements in this area, a relatively good agreement can be found.

Performance of a nuclear microprobe to study giant marine aerosol particles

The scanning nuclear microprobe analytical facility of the IRMM was used to determine with PIXE major, minor and trace elements in individual giant marine aerosol particles, collected above the North Sea (particle size > 5 μm Ø). The instrumentation is briefly described, and the experimental parameters chosen for these analyses are discussed. Elements with atomic numbers Z > 15 could be determined. Detection limits observed under the prevailing experimental conditions reached down to 50 fg in the case of Ti, V or Cr, corresponding to a mass content of 10 μg/g in particles of 15 μm size. Quantitative evaluation of the acquired spectra revealed basically three aerosol types in these samples: sea salt particles, sea salt combined with high contents of S, K and Ca, and particles rich in heavier elements (Ti, Cr, Fe, Ni). The agglomeration of several large particles forming a giant one could be visualised directly through the heterogeneity found in the elemental maps of such a particle.