Lead isotopic composition in soils of the Cherepovets steel mill impact zone

Abstract

The total content of lead, the content of its acid-soluble and mobile forms of compounds in sod-carbonate soils of the impact zone of the Cherepovets Steel Mill (Vologda region) were studied. The isotopic composition of lead of its specified forms of compounds has been determined. It is shown that lead, being a part of the gas and dust emissions of the enterprise, is detected in increased quantities up to 6–10 km in the north direction studied by us from the source of pollution. The penetration of technogenic lead compounds down the soil profile up to horizon B is observed. The isotopic ratios of lead ²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁷Pb studied by us reveal clear dependencies on the lead content in soils. For all isotopic ratios in the series «total lead < acid-soluble lead < mobile lead», the contribution of technogenic lead compounds to its isotopic composition increases, since in the same series there is an increase in the proportion of technogenic lead compounds from its total amount. Extrapolation of the dependence of the ratio ²⁰⁶Pb/²⁰⁷Pb on the lead content in the low content area gives the value of this ratio in the range of 1,19–1,25, which corresponds to the isotopic composition of the total lead of the background soils of the European part of Russia. In high polluted soils near Steel Mill, this ratio decreases to 1.10, which corresponds to numerous literature data. The choice of isotope ratio is crucial for obtaining more detailed information about the nature and sources of technogenic lead contamination of soils. Thus, in soils with a low lead content, according to the values of the isotope ratio ²⁰⁸Pb/²⁰⁷Pb, lead is released associated with another source of pollution, presumably from a city thermal power plant operating on coal.