Pools of Heavy Metals in Soils with Different Vegetation Cover and Soil Material in Former Zn-Pb Mining Area (Olkusz Region, S Poland)

Summary

Samples of soil generic horizons in former zink and lead mining region around Olkusz, southern Poland, were collected from 9 soil plots at 49 sites. The sampling scheme included all major vegetation types growing directly on waste material from the mining, as well as on abandoned agricultural topsoil and sand deposits. The total amount of Zn, Pb and Cd, were extremely high, especially in the illuvial B horizons, with overall average values way above any permissible norm. Sites with moist or thermophilous grasslands developed directly on waste of gangue and processed ore material contained the most contaminated soils. At these sites the average levels of Zn, Pb, and Cd were 30.5, 21.4 and 0.21 g kg-1, respectively. Generally, the levels of heavy metal followed each other and were related to the Iron (Fe) content of the soil, which could be seen as a proxy for the content of ore material. Higher levels of available and exchangeable Pb were found in more acid soils (in forested sites), while high levels of Cd and Zn were found in soils with high base saturation (BS) and high soil pH (i.e. grasslands). These differences were likely due to that Pb is the least mobile heavy metal in soils. One may therefore argue that available and exchangeable Cd and Zn has been leached out of the more acid forest soils but is still held back in the more alkaline soils of thermophilous grasslands. This research was financed under the project FM EEA PL 0265 (Financial Mechanism of European Economic Area).