Characterizing the availability of metals in contaminated soils. I. The solid phase: sequential extraction and isotopic dilution

Abstract

The two approaches most commonly applied to characterizing the chemical form and 'reactivity' of metals in the soil solid phase are sequential extraction procedures (SEPs) and isotopic dilution (ID). The development and limitations of both approaches are described and their application to contaminated soils discussed. It may be argued that ID offers a better means of discriminating between 'reactive' and 'inert' forms of metal. However, the literature on SEPs is considerably larger, providing greater scope for comparative analysis of new data. Although ID methods are subject to operational constraints, the procedural dependency of SEPs is probably much greater. Thus greater effort has been expended to standardize and verify methodologies for SEPs. However, despite achieving a level of 'political ratification' at the procedural level, the use of SEPs within risk assessments for planning or development purposes is currently almost absent. The future for ID methods in this context may lie in site-specific risk assessments that include improved methods for the prediction of metal solubility and bioavailability.

Predicting availability of mineral elements to plants with the DGT technique: a review of experimental data and interpretation by modelling

“…Moreover, isotopic dilution studies suggest that labile and non-labile pools are reasonably distinguishable, since the isotopically exchanged metal generally changes little with isotope equilibration time, beyond a few days of equilibration. [21,22] Modelling and conceptualising uptake by plants Uptake fluxes and plant concentrations The way in which uptake of elements by plants is quantified depends on the model used or on the experimental approach. Mechanistic models often quantify uptake by expressing the uptake as a root area based flux, i.e.…”

Metal speciation in soil at a contaminated glassworks site in southeastern Sweden

“…To obtain a site-specific estimate of the "potentially mobile" fraction (or"labile" or "geochemically active" fraction), a variety of different single extractions have been proposed [eg. 6,7]. As an alternative that may give additional information on which "sinks" that dominate for metals in the site-specific soil matrix, sequential extractions can be used [eg.…”

Experimental Study of Mobility and Kinetic Characterization of Trace Elements in Contaminated Sediments from a River Basin in Northern Peru

“…In this sense, the use of selective chemical extractions is the usual approach for understanding the interaction of heavy metals with soil and sediment components and to assess their mobility and availability to plants (Sahuquillo et al 2003;Ure 1996). Single-extraction schemes provide a simpler generic approach by dividing the sorbed phases into just two categories: labile and non-labile (Young et al 2005). …”

“…Kinetic extraction by a single reagent can be defined as the proper methodology to determine the distribution of species in natural environments (Fangueiro et al 2002(Fangueiro et al , 2005Gismera et al 2004). The most widely utilized reagents for single-extraction schemes are powerful chelating agents, such as ethylenediamine tetra-acetate (EDTA) and diethylenetriamine penta-acetate (DTPA) (Madrid et al 2007;Young et al 2005).…”