Evaluating specificity of sequential extraction for chemical forms of lead in artificially-contaminated and field-contaminated soils

Abstract

In the present study, we evaluate a commonly employed a modified Bureau Communautaire de Référence (BCR test) 3-step sequential extraction procedure for its ability to distinguish forms of solid-phase Pb in soils with different sources and histories of contamination. When the modified BCR test was applied to mineral soils spiked with three forms of Pb (pyromorphite, hydrocerussite and nitrate salt), the added Pb was highly susceptible to dissolution in the operationally-defined “reducible” or “oxide” fraction regardless of form. When three different materials (mineral soil, organic soil and goethite) were spiked with soluble Pb nitrate, the BCR sequential extraction profiles revealed that soil organic matter is capable of retaining Pb in more stable and acid-resistant forms than silicate clay minerals or goethite). However, the BCR sequential extraction for field-collected soils with known and different sources of Pb contamination was not sufficiently discriminatory in the dissolution of soil Pb phases to allow soil Pb forms to be “fingerprinted” by this method. It is concluded that standard sequential extraction procedures are probably not very useful in predicting lability and bioavailability of Pb in contaminated soils.

Concentrations of lead, cadmium and barium in urban garden-grown vegetables: The impact of soil variables

“…Highly variable spatial distribution of Pb in soils of urban environments, from the scale of several hundred meters (Säumel et al, 2012; Shinn et al, 2000) to the minute scale of the root zone, soil aggregates and microscopic particles (Tai et al, 2013; Wharton et al, 2012). …”

Bioaccessibility of As and Pb in orchard and urban soils amended with phosphate, Fe oxide and organic matter

“…Previous investigations using the electron microprobe have revealed a strong tendency for Pb in anthropogenically contaminated soils to be spatially distributed in a highly heterogeneous manner (Cotter-Howells, 1996;Fleming et al, 2013;Tai et al, 2013;McBride, 2016). This characteristic was observed in the soils of the present study, with the EDS X-ray spectra of selected Pb-rich regions within the (Albany) urban soil and orchard soil in Figure 3 showing a clearer indication of a Pb phosphate phase in the former soil, as the Pb "peak" has greater intensity than the P "peak", consistent with the measured X-ray spectrum of pyromorphite (not shown here).…”

“…We used a density separation procedure to concentrate Pb-rich particles in the high-Pb urban and orchard soils, as previous investigation of contaminated orchard and urban soils had indicated that Pb tends to be concentrated in discrete particles (Tai et al, 2013).…”

Removal of Lead and Zinc From Contaminated Soil by a Novel Chelating Surfactant

“…The sequential extraction procedure, as shown in Tab. , was chosen for the optimized BCR scheme . Sequential extraction was performed for both fractions of contaminated soil: The fraction extracted by LED3A and the fraction without extraction.…”

“…At present, sequential extraction techniques are commonly used to study heavy metal behavior in soils. The BCR (formerly the Community Bureau of Reference) sequential extraction procedure is recommended by the Standards, Measurements and Testing Program of the European Commission .…”