Content of mercury in the forest soils exposed to traffic pollution

The increased content of trace elements in the environment is one of the major factors determining hazard for humans, animals and plants. The aim of the paper was to evaluate the total content of mercury forms in the surface horizons of the forest soils exposed to the effect of road traffic pollution in a close vicinity of provincial road #223 between Bydgoszcz and Biale Blota (N Poland). The study involved 12 measurement points 25 meters away from the road, in the afforested land. The research material was sampled from two soil horizons: 5-20 cm and 20-50 cm in depth. The total mercury content was assayed using the AMA-254 analyser. The soil samples showed light grain size composition, with loamy sand dominating. There was a small range of variation in the content of clay fraction from 0.75 to 1.96% as well as silt fraction from 9.35 to 22.11%. The soil reaction was acid and it ranged from 3.9 to 5.2 pH in H2O as well as from 3.6 to 4.6 pH in 1 M KCl. The organic carbon content ranged from 0.6 to 17.2 g/kg. The results showed that there was no mercury contamination. The determined concentrations of mercury were close to the geochemical background level. The total content of the mercury in the soil samples from the humus horizons (5-20 cm) ranged from 55.01 to 117,52 mu g/kg, while from the eluvial horizons (20-50 cm) from 21.61 to 102.17 mu g/kg. We found a decrease in the total mercury content with soil depth. The soil samples analysed can be considered unpolluted with that metal. The close vicinity of the road transport route does not have a considerable effect on the content of the element. The clay fraction and the content of organic carbon does not play a significant role in binding mercury in the analysed soils.