Seasonal and vertical variability of saccharides and other organic tracers of PM10 in relation to weather conditions in an urban environment of Upper Silesia, Poland

Abstract

Abstract PM10 samples collected over one year from the city of Sosnowiec, part of the Upper Silesia metropolis were studied. The locale was a gradient meteorological station, 4 m and 100 m above ground. The dominant compounds identified were anhydro-, mono- and disaccharides which were divided into three groups of organic tracers (OT): biomass burning (BB) including low-rank coal burning, pollen grains (PG) and fungal spores (FS). The BB group included: levoglucosan, mannosan and galactosan, complemented with vanillic and dehydroabietic acids. The PG group included: fructose, glucose and sucrose, supplemented with D-pinitol, and the FS tracers included: arabitol, mannitol and trehalose. Levoglucosan reached 1503 ng/m3 in heating season at 4 m and 983 ng/m3 at 100 m. These values are among the highest mean concentrations of levoglucosan reported in Europe, confirming severe pollution of the Upper Silesian urban environment. We also suggest that the significant levoglucosan levels during the non-heating seasons could be from wind advected polluted soil and dust. All FS tracers correlate well with fungal spore counts, while the correlation of pollen numbers with their typical molecular tracers is statistically less significant. Weather conditions significantly influence the concentration of OT in aerosols. Among these, air temperature is a factor that affects the occurrence/existence of OT in the atmosphere, while temperature inversions are the main phenomenon which determines elevated concentrations of pollutants and their vertical variation in ambient air. For example, the concentration of BB tracers can be twice as high at 4 m as at 100 m under moderate to strong temperature inversions associated with low wind speed. Water vapor pressure and sun irradiation are also important factors controlling OT concentrations. This is one of the first studies of vertical differences in organic tracers which presents the variability and complexity of the processes affecting their concentrations in ambient air.