Hans Lannefors

Background aerosol composition in Southern Sweden—Fourteen micro and macro constituents measured in seven particle size intervals at one site during one year

Abstract The aerosol composition as a function of particle size, has been studied at a rural location in southern Sweden, during a period of one year. The sulphur and heavy metal concentrations have been measured in 113 cascade impactor samples by particle induced X-ray emission (PIXE). Elemental concentrations were orders of magnitude lower than in central Europe but only a factor of two to four higher than the winter concentrations in the Arctic. The size distributions were rather broad except for some of the anthropogenic components. Enrichment factors calculated in both the fine and coarse particle mode gave information on possible anthropogenic contributions in the fine mode for the expected soil derived elements K and Mn. The samples were classified according to calculated air mass trajectories. Air masses having traversed the British Isles or central Europe contained up to an order of magnitude higher concentrations of known anthropogenic components e.g. S, V, Ni, Cu, Zn and Pb than air masses originating in the north Atlantic. The foreign contribution of the elemental concentrations was estimated to 70–80% for S and Pb, 50% for Ni and 30% for V. The anthropogenic components (except sulphur) showed the largest seasonal variations being highest in the winter. Dry deposition estimates indicate that the wet deposition was dominant for the fine particle oriented elements (S, V, Ni, Cu, Zn and Pb), while for the large particle oriented elements Ti and Fe dry and wet deposition were of equal importance. An appendix concludes this paper and presents elemental concentration frequency distributions in the fine and coarse mode.

Aerosol characteristics in a mature coniferous forest—Methodology, composition, sources and spatial concentration variations

A forest site in southern Sweden representative of a wider range of coniferous forest Londscapes has been characterized with respect to aerosol composition (NO−3, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn. Br and Pb). In one series aerosol sampling was carried out simultaneously along a horizontal transect with four stations, one located in open field, one at the forest edge and two within the forest. In another series simultaneous sampling was performed along a vertical transect with four sampling points, one located below but near the canopy top and the others further downwards through the canopy (height c. 25 m). Sampling strategy and analytical methods are presented in detail. Statistical analyses of concentration data suggest that K, Ca, Ti, Mn and Fe in the coarse particle fractions originated from soil, whereas other components (S, V, Cu and Pb) were of mainly anthropogenic origin. Depletion of coarse fraction concentrations within the forest was detected for several elements, whereas spatial variations of fine fraction concentrations showed weak or no systematic trends. This result is interpreted as a net effect of counteracting mechanisms in the forest: losses due to deposition and inputs due to turbulence and gravitationally settling particles.

Nonurban aerosol composition near Beijing, China

Abstract The urban aerosol plume of Beijing has been sampled as a function of particle size and time at a site 110 km NE of the city, 9–16 March 1980, during the season for space heating by coal combustion. A fine particle mode, contained mostly in the 0.5–2 μm aerodynamic diameter range, could be distinguished from a coarse mode of dust having terrestial composition by reference to the size distribution of Ca. Elemental composition determined by PIXE analysis for 17 elements, including S and heavy metals, indicates fine mode concentrations higher than background aerosol but with a similarity to cleaner air with respect to both relative elemental abundances and elemental particle size distributions. The results indicate that elements contained in aged coal combustion aerosol occur mainly in 0.5–2 μMAD particles, not smaller, and the aerosol is not substantially different from background aerosol except in overall concentrations. This result may simplify the prediction of the impact of coal combustion on air quality. The results also hint that the background aerosol in more remote continental areas may also be combustion derived.

Aerosol concentration profiles within a mature coniferous forest—Model versus field results

Aerosol mass concentration profiles along a horizontal and a vertical transect in a forest are modelled from field site information on aerosol particle size distributions, forest structure and aerodynamics. Model outputs are compared with concentration profiles obtained from field measurements at the site. The comparisons suggest that model properties are qualitatively valid. Though field data are insufficient for a systematic quantitative test of model behaviour, the investigation does not indicate any quantitatively fundamental model deficiencies.

Elemental concentrations and particle size distributions in an atmospheric background aerosol

Abstract The concentrations and particle size variations of typically 12–15 elements from sulphur and upwards were measured at the rural site Velen, between lakes Vanern and Vattern in southern Sweden, in 44 impactor-samples taken from December 1975 until May 1976. Analysis was made by particle induced X-ray emission (PIXE). The average concentrations were close to those observed in northern Canada. Air-mass trajectory analysis suggests that the concentrations were strongly dependent on the recent history of the air mass. Very low concentrations in some samples suggests the influx of old atlantic air, in contrast to higher concentrations obtained in air originating from heavily-industrialized parts of Europe.

Long range aerosol transport in Southern Sweden: An example of multtvariate statistical evaluation methodology

The utilization of multivariate statistical techniques is discussed with emphasis on the rather new method SIMCA, when applied to multielemental data. The procedures of scaling and normalizing are described. The data base used is from a project studying long range aerosol transport to southern Sweden. SIMCA reveals low variability in fine mode elemental composition in southerly air masses being clearly different from the elemental compositions found in northerly air masses.