Comparison of original and modified BCR sequential extraction procedures for the fractionation of copper, iron, lead, manganese and zinc in soils and sediments

This article describes a detailed comparison between the original BCR sequential extraction procedure, step 2 of which involves treatment with 0.1 mol l(-1) hydroxylammonium chloride at pH 2, and the revised BCR procedure (step 2: 0.5 mol l(-1) hydroxylammonium chloride at pH 1.5). An intermediate protocol was also evaluated in which 0.5 mol l(-1) hydroxylammonium chloride at pH 2 was used. The procedures were applied to five soil and sediment substrates: a sewage sludge-amended soil, two different industrially contaminated soils, a river sediment and an inter-tidal sediment. Extractable iron and manganese concentrations were measured to assess the effects of the procedural modifications on dissolution of the reducible matrix components. Trace elements copper, lead and zinc were also determined. Statistical analysis (two-tailed t-tests at 95% confidence interval) indicated that recovery of iron in step 2 was not markedly enhanced when the intermediate protocol was used. However, significantly greater amounts were isolated with the revised BCR scheme than with the original procedure. Copper behaved similarly to iron. Lead recoveries were increased by use of both modified protocols, with the greatest effect occurring for the revised BCR extraction. In contrast, manganese and zinc extraction did not vary markedly between procedures. The work indicates that the revised BCR sequential extraction provides better attack on the iron-based components of the reducible matrix for a wide range of soils and sediments. (C) 2002 Elsevier Science B.V. All rights reserved

Effect of EDTA on the fractionation and uptake by Taraxacum officinale of potentially toxic elements in soil from former chemical manufacturing sites

The revised Community Bureau of Reference (BCR) sequential extraction procedure has been applied to investigate the effectiveness of two soil remediation strategies to reduce the amounts of potentially toxic elements in three contrasting contaminated soils (soils A, B and C) from derelict chemical manufacturing sites in the UK. Soil A was from the 35-45 cm deep layer of a site used for the manufacture of sulfuric acid. Soils B and C were topsoils from a site used for the manufacture of explosives, nitric acid and nylon The remediation strategies were flushing with EDTA in a column experiment (applied to soils A, B and C) and EDTA enhanced phytoremediation with Taraxacum officinale in pots (applied to soil B). Soil B, which contained the least amounts of aqua regia extractable metals, except for lead, but higher proportions of analytes in non-residual (i.e. acid exchangeable, reducible and oxidisable) forms was found to release greater amounts of analytes when flushed with EDTA. Comparison of the BCR sequential extraction fractionation patterns obtained before and after flushing of soil B, suggested that EDTA removed calcium mainly from the acid exchangeable pool, manganese mainly from the reducible pool, zinc from both acid exchangeable and reducible pools, and copper and lead from acid exchangeable, reducible and oxidisable pools. The chelate enhanced phytoremediation pot experiment conducted using soil B showed that EDTA treatment was significantly positively, correlated (p < 0.05) with an increase in the proportion of analytes recovered from the soil in step 1 of the BCR extraction scheme, for all analytes, and also enhanced metal uptake by plants. The sum of the amounts of analyte released in the first three steps of the sequential extraction, commonly regarded as the maximum amount of elements potentially available for plant uptake, was not positively correlated with plant-uptake