Vanadium dioxide

Adsorption / desorption

Description of key information

Reliable (Klimisch 2) information for Kp values in soil is based on laboratory studies of the partitioning of vanadium - added in form of soluble pentavalent V substances (NH4VO3, Na3VO4 or NaVO3) - between the solid and solution phase. Information available for sediment and suspended matter is based on paired monitoring data of elemental V concentrations in sediment or suspended matter and water.

Regarding partitioning of vanadium in soil, a study on Kp values for 464 European agricultural soils with varying properties collected within the framework of the GEMAS project (Geochemical Mapping of Agricultural and Grazing Land Soil, pH: 3.3-8.0; organic carbon: 0.5-49%; clay: 0.1-70%) is selected as key study and used for Kd derivation due to the representativeness of the available dataset (Janik et al., 2010). Log Kp values for added vanadate range from 1.09 to 4.13 L/kg, with a median of 2.79 L/kg. The median was selected for the chemical safety assessment. In addition, 44 reliable Kp values from several supporting studies are available for soils with varying properties (pH: 3.9-8.5; organic matter: 0-20%; clay: 0.1-54.7%). Log Kp values range from 1.14 to 3.96 L/kg. The 5th, 50th and 95th percentiles of the log Kp values according to the best-fitting distribution (log logistic) are 1.85, 2.66 and 3.47 L/kg, respectively. An additional, smaller dataset incorporating 26 partition coefficients derived from 26 spiked soils produced a median log Kp of 3.46 in a supporting study by Larsson et al. (2016). Field data available from lysimeter experiments performed on vanadium-contaminated sites further point to a low mobility of vanadium in pore water, i.e. mean pore water concentrations of 0.89-1.55 µg V/L with measured total vanadium concentrations of 90.4 mg/kg in soils (Shaheen et al., 2014).

Two reliable Kp values of non-European sediments are available, i.e. a log Kp value of 5.2 L/kg for sediments from Hanoi river, Vietnam and a mean log Kp of 4.57 L/kg for freshwater sediments from South Africa. However, given the wealth of representative and reliable data provided by the FOREGS Geochemical Baseline Mapping Programme that aimed to provide high quality geochemical baseline data for Europe, the assessment of sediment partitioning of vanadium is based on Kp values derived from a subset of the FOREGS dataset. Accordingly, a total of 757 paired stream water and sediment samples covering a wide range of pH, hardness and organic carbon concentrations of stream water (filtered to < 0.45 µm) and sediment (wet sieved in the field to <0.15 mm) were processed to derive a median logKpsolids-water in sediment of 5.06.

Reliable data for Kp of suspended matter are available for 6 water systems, with log Kp values ranging from 3.24 to 4.83 L/Kg (median 4.60) for freshwater and a log Kp value of 4.77 for marine water. Because Log Kp values for freshwater and marine water seem to be similar, all data are grouped together and the 5th, 50th and 95th percentiles of the log Kp values according to the best-fitting distribution (log logistic) are determined with 3.82, 4.50 and 5.17 L/kg, respectively. The 50th percentile was selected for the chemical safety assessment.

Key value for chemical safety assessment

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

2.66

Other adsorption coefficients

Type:

log Kp (solids-water in sediment)

Value in L/kg:

5.06

Other adsorption coefficients

Type:

log Kp (solids-water in suspended matter)

Value in L/kg:

4.5