A Coloured Snow Episode on the Swedish West Coast, January 1987 A Quantitative and Qualitative Study of Air Borne Particles

ABSTRACT

The authors have made an analysis of particles brought down by snow on the Swedish west coast in January 1987. The analyses included a quantitative study of the deposition and its organic/inorganic relationship, and a qualitative one including mineralogical composition, quartz grain size distribution and pollen distribution. The quantitative part showed that during this snowfall the Göteborg region received about 2.3 g/m² or 1.5 time its normal monthly deposition of solid particles. Organic matter made up for about 60 per cent of the material. The mineralogical analysis showed that the orgin must be from an area with young and quartz-rich soils. The grain size distribution showed that the material must have been transported a short distance only. The largest quartz particles found were 0.34 mm in size. The pollen composition indicates a vegetation like that of southern Scandinavia, northern Germany or some parts of Holland or England, and it is also obvious that the material has it orgin in an agricultural landscape. The presence of alien pollen grains like those by Ephedra and Helianthemum in our samples would best be explained by contamination from higher atmospheric levels.

Having studied the distribution of the coloured snow, organic and inorganic content, grain size distribution, mineralogical composition and pollen, along with the meteorological trajectory pattern, we have little doubt that the material originated in Denmark.