Lead isotope ratios in Podzol profiles as a tracer of pollution source in the subalpine zone of the Karkonosze National Park, Sudety Mts (south-western Poland)

The Karkonosze National Park (south-western Poland) represent central European medium-elevation mountains. At the end of the twentieth century, an ecological disaster was observed in this nature reserve, resulting in the defoliation of large areas of spruce forest. One of the considered reasons for this phenomenon was contamination with heavy metals. The aim of this study was to determine the origin of lead (lithogenic versus several specific anthropogenic sources) occurring in the soils of the highest located parts of the Karkonosze Mts. Lead concentrations and its isotope ratios were investigated in nine Podzol profiles located in the subalpine zone (1200-1400 m a.s.L.) of the Karkonosze Mts. Concentrations of total lead and its isotopes were measured in particular genetic horizons; then lead isotope ratios were calculated. On the basis of lead isotope signatures known from literature data, different anthropogenic sources of this element have been assessed (emissions from coal combustion, mining, metallurgy, and fuel combustion). The results obtained revealed the highest Pb concentrations (121.0-353.0 mg kg(-1)) in the surface horizons. The podzolization process, differentiating soil profiles into eluvial (Es) and illuvial (Bh and Bs) horizons, has contributed to different concentration of lead through the profile. The concentrations of this element in eluvial, illuvial Bh, and parent material horizons were 15.5-28.4 mg kg(-1), 25.8-55.6 mg kg(-1), and 8.7-29.6 mg kg(-1), respectively. The Pb isotope composition determined in the ectohumus horizons and eluvial horizons showed that about 86-95% of lead existing in these surface horizons originated from emissions resulting from the burning of coal exploited in Poland and the Czech Republic. The Pb isotope signatures of lead present in the illuvial horizon (Bs) and parent material (C) pointed to the lithogenic origin of this element. The results obtained indicated that higher-elevation areas of the Karkonosze National Park have been contaminated with lead from long distance emissions. Pollution with lead has been limited only to ectohumus and eluvial horizons, although the soil-forming process contributed to translocation of lithogenic lead down the soil profile to the illuvial Bh horizon.