Modelling trace metal extractability and solubility in French forest soils by using soil properties

Abstract

Soil/solution partitioning of trace metals (TM: Cd, Co, Cr, Cu, Ni, Sb, Pb and Zn) has been investigated in six French forest sites that have been subjected to TM atmospheric inputs. Soil profiles have been sampled and analysed for major soil properties, and CaCl2‐extractable and total metal content. Metal concentrations (expressed on a molar basis) in soil (total), in CaCl2 extracts and soil solution collected monthly from fresh soil by centrifugation, were in the order: Cr > Zn > Ni > Cu > Pb > Co > Sb > Cd , Zn > Cu > Pb = Ni > Co > Cd > Cr and Zn > Ni > Cu > Pb > Co > Cr > Cd > Sb , respectively. Metal extractability and solubility were predicted by using soil properties. Soil pH was the most significant property in predicting metal partitioning, but TM behaviour differed between acid and non‐acid soils. TM extractability was predicted significantly by soil pH for pH < 6, and by soil pH and Fe content for all soil conditions. Total metal concentration in soil solution was predicted well by soil pH and organic carbon content for Cd, Co, Cr, Ni and Zn, by Fe content for Cu, Cr, Ni, Pb and Sb and total soil metal content for Cu, Cr, Ni, Pb and Sb, with a better prediction for acidic conditions (pH < 6). At more alkaline pH conditions, solute concentrations of Cu, Cr, Sb and Pb were larger than predicted by the pH relationship, as a consequence of association with Fe colloids and complexing with dissolved organic carbon. Metal speciation in soil solutions determined by WHAM‐VI indicated that free metal ion (FMI) concentration was significantly related to soil pH for all pH conditions. The FMI concentrations of Cu and Zn were well predicted by pH alone, Pb by pH and Fe content and Cd, Co and Ni by soil pH and organic carbon content. Differences between soluble total metal and FMI concentrations were particularly large for pH < 6. This should be taken into account for risk and critical load assessment in the case of terrestrial ecosystems.

Assessment of the bioavailability and toxicity of lead polluted soils using a combination of chemical approaches and bioassays with the collembolan Folsomia candida

“…See [17] for soil physicochemical properties and Pb concentrations and value of 6.0 for F. candida [12], which also increased Pb bioavailability for the collembolans. Therefore, the low pH may amplify the ecological risk caused by bioaccumulation of Pb in acid soils [26,29].…”

Evaluation of lichen species resistance to atmospheric metal pollution by coupling diversity and bioaccumulation approaches: A new bioindication scale for French forested areas

“…Metal atmospheric pollution has already been studied for these sites through surface horizons of soils (Gandois et al, 2010a;Hernandez et al, 2003), bulk atmospheric deposition (Gandois et al, 2010b), and lichen bioaccumulation (Agnan et al, 2015). The metal concentrations registered in lichens collected on the trees considered for bioindication are given in Table 2.…”

Lead-induced genotoxicity to Vicia faba L. roots in relation with metal cell uptake and initial speciation

“…Due to lower genotoxicity observed in the case of direct contact with soil, these authors concluded to a potential influence of soil organic matters. As soil solution represents the main available compartment for metals uptake by plants (Degryse et al, 2009;Gandois et al, 2010), one scientific question asked is the relation between aqueous extract of soil used in current genotoxicity to V. faba test and soil solution. Therefore, the objectives of the present study were to identify the correlation between Pb speciation, phytoavailability and genotoxicity to V. faba as a function of organic chelates nature and levels.…”