title: Impact of soil pH and organic matter on the chemical bioavailability of vanadium species: The underlying basis for risk assessment.
abstract: The main objective of this study was to unravel the chemical reactions and processes dictating the potential bioavailability of vanadium (V). In environmental solutions V exists in two stable oxidation states, +IV and +V, of which + V is considered to be more toxic. In this study, the effect of speciation and soil pH on the chemical accessibility of V was investigated with two soils: 1) field soil rather rich in soil organic matter (SOM) and 2) coarse mineral soil low in SOM. Fresh soil samples treated with V(+V) (added as NaVO3) or V(+IV) (added as VOSO4) (pH adjusted to the range 4.0-6.9) were incubated for 3 months at 22 °C. The adsorption tendency of V species was explored by water extraction (Milli-Q water, 1:50 dw/V) and by sequential extraction (0.25 M KCl; 0.1 M KH2/K2HPO4; 0.1 M NaOH; 0.25 M H2SO4, 1:10 dw/V). The potential bioavailability of V was found to be dictated by soil properties. SOM reduced V(+V) to V(+IV) and acted as a sorbent for both species, which lowered the bioaccessibility of V. A high pH, in turn, favored the predominance of the V(+V) species and thus increased the chemical accessibility of V.
authors.affiliation: Soil and Environmental Chemistry, Department of Food and Environmental Sciences, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 27, 00014 Finland. Electronic address: inka.reijonen@helsinki.fi.
authors.forename: Inka
authors.initials: I
authors.lastname: Reijonen
authors.affiliation: Soil and Environmental Chemistry, Department of Food and Environmental Sciences, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 27, 00014 Finland.
authors.forename: Martina
authors.initials: M
authors.lastname: Metzler
authors.affiliation: Soil and Environmental Chemistry, Department of Food and Environmental Sciences, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 27, 00014 Finland.
authors.forename: Helinä
authors.initials: H
authors.lastname: Hartikainen
mesh_terms: D000327:Adsorption; D002412:Cations; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D017968:Vanadium Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D002412:Cations; D012987:Soil; D012989:Soil Pollutants; D017968:Vanadium Compounds; D014867:Water; C034028:vanadyl sulfate
keywords: Bioavailability; Chemistry; Soil; Speciation; Vanadium