Abstract
Environmental context There is growing concern that lead in the environment may cause adverse health effects in human populations. We investigated the combined use of isotopic abundance and isotopic dilution to show how the origins of soil Pb and soil characteristics affect lability. Soil pH and soil Pb content are the dominant controls on Pb lability; the lability of recent petrol-derived Pb is similar to that of other sources in urban soils but greater than geogenic Pb in rural roadside topsoils. Abstract Lability of lead in soils is influenced by both soil properties and source(s) of contamination. We investigated factors controlling Pb lability in soils from (i) land adjacent to a major rural road, (ii) a sewage processing farm and (iii) an archive of the geochemical survey of London. We measured isotopically exchangeable Pb (E-values; PbE), phase fractionation of Pb by a sequential extraction procedure (SEP) and inferred source apportionment from measured Pb isotopic ratios. Isotopic ratios (206Pb/207Pb and 208Pb/207Pb) of total soil Pb fell on a mixing line between those of petrol and UK coal or Pb ore. The main determinant of the isotopically exchangeable Pb fraction (%E-value) was soil pH: %E-values decreased with increasing pH. In rural roadside topsoils, there was also evidence that petrol-derived Pb remained more labile (35%) than Pb from soil parent material (27%). However, in biosolid-amended and London soils, %E-values were low (~25%), covered a restricted range and showed no clear evidence of source-dependent lability.
Highlights
Industrial pollution, combustion of leaded petrol and mining activities have increased environmental Pb concentrations since the Industrial Revolution
The objective of this study was to broaden the investigation of the effect of soil properties and sources of contamination on Pb lability in soils, as determined by isotopic dilution
Twenty one topsoils (0-20 cm) and twenty one subsoils at a range of depth intervals were collected from four sites along a major road leading to the M1 motorway in a rural area of Nottinghamshire, UK (52°48’N, 1°16’W), where soils were likely to have received petrol-derived Pb from heavy traffic
Summary
Industrial pollution, combustion of leaded petrol and mining activities have increased environmental Pb concentrations since the Industrial Revolution. Human exposure to Pb, via inhalation of particles and ingestion of contaminated soil, can result in physiological damage, to the nervous system. Due to these health concerns, the commercial use of Pb has been considerably reduced over the last three decades and unleaded petrol introduced to reduce aerial Pb deposition (Erel et al, 2002; Flament et al, 1996; Johnson et al, 1995). To fully quantify the risks associated with Pb it is useful to assay the labile pool of Pb in soil, which is more closely linked to bioavailability and solubility than the total concentration in soil (Meers et al, 2007; Sauvé et al, 2000; Tongtavee et al, 2005)
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