On heavy metals in soil; rationalization of extractions by dilute salt solutions, comparison of the extracted concentrations with uptake by ryegrass and lettuce, and the possible influence of pyrophosphate on plant uptake

Assessing Bioavailability of Soil Trace Elements

“…Despite reports of good correlations between elements extracted by chelating agents (for example DPTA and EDTA) and their uptake by plants, there is a general acceptance that milder chemical extractants, particularly unbuffered neutral salt solutions can provide a more realistic estimation of potential bioavailability of TEs in contaminated soils [39,[64][65][66][67][68]. Examples of such aqueous chemical solutions used for bioavailability assessment purposes include CaCl 2 , NH 4 NO 3 , Ca(NO 3 ) 2 , NaNO 3 , KNO 3 , MgCl 2 [11,51,66,[68][69][70][71][72].…”

“…Examples of such aqueous chemical solutions used for bioavailability assessment purposes include CaCl 2 , NH 4 NO 3 , Ca(NO 3 ) 2 , NaNO 3 , KNO 3 , MgCl 2 [11,51,66,[68][69][70][71][72]. Lebourg et al [73], while studying the speciation of Cd, Cu, Pb and Zn in different neutral salt extracts observed similarities between the composition of these extracts and the soil solution.…”

Quantifying the influence of soil properties on the solubility of metals by predictive modelling of secondary data

“…However, a wide range of soil extractants have been assessed for their suitability in predicting metal uptake by plants. In recent years many authors have observed that complexing agents such as EDTA and DTPA (which may extract metals bound strongly to organic matter) are less suitable than weak neutral salt solutions such as CaCl 2 (ranging in molarity from 0.002 M to 0.1 M) and NaNO 3 (Jackson and Alloway, 1991;Gupta and Aten, 1993;Davis et al, 1995;Andrewes et al, 1996;Aten and Gupta, 1996;Houba et al, 1996). These latter extractants are thought reasonably to imitate the soil solution and exchangeable metal concentrations and thus provide a measure of metals likely to be available to plants and microbiota at the time of sampling .…”

Extraction of arsenate and arsenite species from soils and sediments

“…This analytical procedure involves sequential chemical extractions separating trace metals into five fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter, and residual. Simplified sequential extraction methods have also been developed for practical applications (Aten and Gupta, 1996;Cai et al, 2002;Gomez-Ariza et al, 2000;Gupta et al, 1996;Pantsar-Kallio and Manninen, 1997). For example, the three-level evaluation system, which separates metals into mobile, mobilizable, and pseudo total metal fractions, seems to be attractive because of its simplicity and potential application in risk assessment and risk management .…”