Contents of Potentially Toxic Elements in Forest Soils of the Jizera Mountains Region

Abstract

In central Europe, the region termed ‘the Black Triangle’ corresponds to an area of concentrated burning of fossil fuels during the period between early 1950s up to the mid 1980s. Although major polluting activities have ceased, effects of atmospheric deposition are still evident. The aims of this study were to determine potentially toxic element (PTE) concentrations in organic and mineral horizons of forest soils in the Jizera Mountains region and to assess the relationship between their distributions and stand factors (altitude, grass cover, forest type). One hundred thirty-eight samples were taken from 98 positions, comprising O, A, E and B horizon samples. Target elements (Cu, Cd, Pb, Zn, Mn) were extracted using 2 M HNO3 and then analysed by FAAS. Basic statistical parameters were determined, and correlation, t test and ANOVA were used to assess the relationship to stand factors. Maps were created using ArcMap 9.1. Two map creation techniques were used—kriging and inverse distance weighting. Highest mean metal contents (except for Mn) were found in organic horizons, with Cu and Pb being particularly concentrated in the upper layers. Strong positive correlation exists between Cd content and altitude, while negative correlation exists for Mn. Cadmium concentration was also significantly higher in areas of grass cover and under spruce canopy as opposed to beech. Surface maps indicated a similar source of pollution with highest concentrations corresponding also to relief and the prevailing wind direction. Overall, mean PTE contents were not excessive. Top enrichment factors proved the anthropogenic origin of Cd, Cu, Pb and Zn, whereas Mn is probably of geologic origin. Analysis of stand factors showed a statistically significant influence of altitude, grass cover and forest type on cadmium concentration in forest soils. Spatial distribution of metals showed a similar pattern for Cd, Cu, Pb and Zn in O horizon soil, which points toward a single source of pollution.