Comparison of Levels and Sources of Lead in Modern and Ancient Soils in Low Volga Steppes

摘要

Concentrations and isotopic compositions of lead in the total and mobile (acid-soluble and carbonate- bound) forms were determined in remote and roadside Chestnut soils in the dry steppe region of Low Volga, Russia. As a reference to evaluate the level of modern soil contamination with lead, we used ancient soil buried under a Bronze Age kurgan about 4500 years ago. In comparison with buried soil, the roadside modern soils showed clear signs of anthropogenic influence such as elevated total and mobile Pb concentrations and fractions of the mobile forms in the total pool of Pb, higher ratios of Pb/Ti and Pb/Sc, and a shift of Pb isotopic compositions towards the less radiogenic signatures found in modern Russian aerosols and gasoline. In the remote modern soils, however, these signs of anthropogenic influence were much less pronounced and could be observed only in the mobile fractions of Pb, but were practically undetectable in terms of concentrations and isotopic compositions of total lead.Key words: Heavy metals / Pb isotopes / speciation of Pb / historically buried soils / pre-industrial pollution / environmental reconstruction / soil contamination