Tracing the Transport and Behavior of Anthropogenic Pb in Soils Using Isotopic Ratios

Yigal Erel, Nadya Teutch, Simon Emmanuel (Institute of Earth Sciences, The Hebrew University, Jerusalem 91904, Israel), Ludwik Halicz (Division of Geochemistry, The Geological Survey of Israel, Jerusalem 95501, Israel)

The concentrations and isotopic composition of Pb in the soil are used to determine the extent of Pb pollution in the soil, to quantify the distribution of natural versus anthropogenic Pb in different soil fractions, to determine the mechanisms and rates of anthropogenic Pb infiltration into the soil, and to estimate the effects of climate and soil type on the distribution of anthropogenic Pb between the soil components.

Samples were collected from contaminated and pristine soil profiles in Israel and in the Czech Republic. All samples were digested completely to obtain the whole soil composition. In addition, a selective sequential dissolution procedure (SSD) was used in order to determine the content of Pb in the following soil fractions: (1) soil carbonate (carb), (2) organic matter (org), (3) Fe oxides and hydrous oxides (Fe-ox), and (4) aluminosilicates (Al-Si). Lead isotopic ratios were measured in order to distinguish between natural versus anthropogenic Pb in different soil components.

In both countries uncontaminated soil contains approximately 20 ppm Pb, whereas Pb concentrations in polluted soils range between 100 to 800 ppm. Anthropogenic Pb accumulates mainly in the upper few cm of the soil profile and its concentration decreases exponentially with depth. Natural Pb was detected mostly in the deep pristine soils and was associated with aluminosilicates (~60%) and Fe-oxides (30%). In contrast, anthropogenic Pb was accumulated in the more labile components such as carbonates and organic matter and only 15% of the Pb was found in aluminosilicates. It was found that Pb in the labile fractions of relatively uncontaminated soils has anthropogenic signature, and in the heavily contaminated soils even Pb in aluminosilicates has anthropogenic signature.