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Toxicity to soil microorganisms

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Description of key information

28 -d NOEC = 3.2 mg V/kg soil dw (ISO 14238, nitrification)

Corrected for the molecular weight of divanadyl pyrophosphate (CAS no. 65232 -89 -5): 28-d NOEC = 9.7 mg/kg soil dw

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
9.7 mg/kg soil dw

Additional information

Data on the toxicity of vanadylhydrogenphosphate-hemihydrate (CAS no. 93280-40-1) to soil microorganisms are not available; therefore, a read-across approach to structurally similar pentavalent vanadium substances was performed.

Baken et al. (2011) investigated the effects of V (CAS 13718-26-8) in natural soil on the nitrification as well as the carbon transformation after fresh application as well as after aging of the soils. The study was performed according to ISO 14238 to study the effects on nitrification as well as according to OECD 217 for effects on carbon transformation. The latter test was performed with a deviation of the exposure duration, which was only 1 day instead of 28 d. The study was performed using five different natural soils. The toxicity data derived in freshly spiked soils (15 observations) vary between 3.2 mg added V/kg dw (for nitrification in a natural sandy soil from Belgium) to 670 mg added V/kg dw (for nitrification in a natural soil from Sweden). Reliable EC10 or NOEC values derived from soils where V has been equilibrated for more than 5 months (8 observations) range between 3.2 and 960 mg V/kg soil. The effect values (1-d NOEC/EC10) for carbon transformation ranged from 3.2 to >= 1650 mg V/kg dw. All data are based on measured added V concentrations in soil.

Wilke (1989) studied the effects of vanadium (CAS 13718-26-8) on nitrogen transformation in a sandy cambisol. The soil was aged for about 9 years. No guideline was followed. The soil was incubated for 21 (nitrification) to 28 d (N-mineralization). Both nitrification and N mineralization were not significantly inhibited at the largest total concentration tested of 122 mg V/kg soil (NOEC >= 122 mg V/kg soil dw).

Xiao et al. (2012) investigated the effect of vanadium (CAS 7803-55-6) on the soil microbial biomass carbon, which was analyzed using a chloroform fumigation incubation assay (no guideline followed). The total exposure duration was 60 days. The NOEC was determined as 80 mg V/kg soil dw.

For the assessment of the toxicity of divanadyl pyrophosphate (CAS no. 65232 -89 -5), the effect value based on the vanadium concentration must be corrected for the molecular weight of divanadyl pyrophosphate (33.1 % V). The corrected effect values are given above (see “Description of key information”).