Solid−Solution Speciation and Phytoavailability of Copper and Zinc in Soils

Abstract

The soil solution speciation and solid-phase fractionation of copper (Cu) and zinc (Zn) in 11 typical uncontaminated soils of South Australia were assessed in relation to heavy metal phytoavailability. The soils were analyzed for pH (4.9-8.4), soil organic matter content (3.5 to 23.8 g of C kg(-1)), total soil solution metal concentrations, Cu8 (49-358 microg kg(-1)) and Zn8 (121-582 microg kg(-1)), and dissolved organic matter (DOM) (69-827 mg of C L(-1)). The solid-liquid partition coefficient (Kd) ranged from between 13.9 and 152.4 L kg(-1) for Cu and 22.6 to 266.3 L kg(-1) for Zn. The phytoavailability of Cu and Zn could be predicted significantly using an empirical model with the solid-phase fractions of Cu and Zn, as obtained from selective sequential extraction scheme, as components. Phytoavailable Cu and Zn were found to significantly correlate with fulvic complex Cu (r= 0.944, P < 0.0001) and exchangeable Zn (r = 0.832, P = 0.002), respectively. The fulvic complex Cu was found to explain 89.2% of the variation in phytoavailable Cu, where as, the exchangeable Zn together with fulvic complex Zn could explain 78.9% of the variation in phytoavailable Zn. The data presented demonstrate the role of solid-phase metal fractions in understanding the heavy metal phytoavailability. The assessment of the role of solid-phase fractions in heavy metal phytoavailability is a neglected area of study and deserves close attention.

Liming and Ionic speciation of an Oxisol under no-till system

“…A detailed study of the soil solution thorough chemical speciation contributes to a better understanding of the mobility and availability of nutrients or phytotoxic metals (Krishnamurtiand & Naidu, 2002), despite the variability in the methods of obtaining and the dependence on edafoclimatic conditions (Wolt, 1994). In the soil solution, most of the ions are present either as free ions or interacting with other ions or molecules, forming soluble complexes (Sposito, 1994).…”

Influence of Dissolved Organic Matter on Cd Speciation in Rhizosphere Soil Solution and Phytoextraction by Sedum alfredii and Sedum sarmentosum

“…Cornu et al reported that Cd was dominated by free Cd 2+ in soil solution. While other studies showed that the dominant Cd speciation in most soil solution was Cd-organic complex [4,6]. Schmidt [28] demonstrated that the increase in DOC induced Cu mobility, which was more pronounced at high than low pH.…”

“…Following this, metal-complexes dissociate to replenish the pool of free metal ions. Nevertheless, some authors [4] observed that low molecular-weight organic acids, which comprise DOM, can be taken up by plant roots along with the metals that they have bound. Hernandez-Soriano and Jimenez-Lopez [34] described how, although the metal aqueous complexes might be less available species, they may constitute a pool of readily available metal for plant uptake, and a significant increase on Pb and Zn uptake occurred concomitantly with an enhancement of the percentage of metal-organic complex in solution.…”

“…However, Krishnamurti and Naidu [4] reported that heavy metal speciation and solubility in soil solutions are two important factors that control the efficacy of phytoextraction and the metal-accumulating capacity of plants. A previous study demonstrated that different metal species in soil solutions, such as free hydrated metals and metal-ligand complexes, can be taken up by plant roots to varying extents [5].…”

Solid-phase speciation and phytoavailability of copper in representative soils of Italy

“…The bioavailability of trace metals, their biological uptake, and their eco-toxicological effects on the soil biota can be better understood in terms of their chemical speciation. The mobility and bioavailability and hence potential toxicity of metal in the soil depend on its concentration in soil solution, the nature of its association with other soluble species, and the soil's ability to release the metal from the solid phase to replenish that removed from soil solution by the plants (Krishnamurti and Naidu, 2002).…”