Registration Dossier

Administrative data

Endpoint:
bioaccumulation: terrestrial
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well performed study of which the results of the experiment with the insoluble Zr(OH)4 are the most relevant for ZrO2.
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Phytoavailability of zirconium in relation to its initial added form and soil charachteristics.
Author:
Ferrand, E., Dumat, C., Leclerc-Cessac, E., Benedetti, M.F.
Year:
2006
Bibliographic source:
Plant Soil 287, 313-325

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
In this study, transfer of Zr from soil to tomato and pea plants was studied during a 7-day exposure period in two soils amended with either a soluble or an insoluble Zr compound.
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
Zirconium dichloride oxide
Cas Number:
7699-43-6
Molecular formula:
ZrOCl2
IUPAC Name:
Zirconium dichloride oxide
Constituent 2
Reference substance name:
zirconium oxychloride
IUPAC Name:
zirconium oxychloride
Constituent 3
Chemical structure
Reference substance name:
Zirconium acetate
EC Number:
231-492-7
EC Name:
Zirconium acetate
Cas Number:
7585-20-8
Molecular formula:
C2H4O2.xZr
IUPAC Name:
zirconium(2+) diacetate
Constituent 4
Reference substance name:
Zirconium tetrahydroxide
EC Number:
238-472-7
EC Name:
Zirconium tetrahydroxide
Cas Number:
14475-63-9
IUPAC Name:
zirconium tetrahydroxide
Radiolabelling:
no

Sampling and analysis

Details on sampling:
- Spiked soils were not sampled for analysis.
- Background Zr was determined in soil samples from both soils prior to testing.
- After 7 days of exposure, roots and aerial parts were separated for measuring weights and analyzing for Zr content.

Test substrate

Vehicle:
no
Details on preparation and application of test substrate:
- Method of mixing into soil (if used): soils were spiked with solutions of ZrOCl2 or Zr acetate (soluble) to increase the total soil Zr concentration by 100 mg Zr/kg dry soil - in a third experiment soils were spiked with Zr(OH)4 (insoluble) to increase the total soil Zr concentration by 286 mg Zr/kg dry soil
- Controls: in each experiment, five control replicates were used (unspiked cultivated soils)
- Background Zr concentrations in soil A and B were 417.4 and 164 mg Zr/kg dry soil. According to Kabata-Pendias and Pendias (1992) the main minerals of Zr present in soil are the low soluble zircon (ZrSiO4) and baddeleyite (ZrO2).
- In the experiments with the soluble Zr compounds total Zr concentrations were hence 517.4 and 264 mg Zr/kg dw in soil A and B, respectively.
- In the experiment with the insoluble Zr compound total Zr concentrations were hence 703.4 and 450 mg Zr/kg dw in soil A and B, respectively.

Test organisms

Test organisms (species):
other: Lycopersicon esculentum and Pisum sativum
Details on test organisms:
Pisum sativum
- Common name: pea
- Plant family: Fabaceae
- Variety: cv. "Express"
- Prior seed treatment/sterilization: disinfected in a bath of 6% H2O2 and rinsed with deionized water

Lycopersicon esculentum
- Common name: tomato
- Plant family: Solanaceae
- Variety: cv. St. Pierre
- Prior seed treatment/sterilization: disinfected in a bath of 6% H2O2 and rinsed with deionized water

Study design

Total exposure / uptake duration:
7 d

Test conditions

Test temperature:
Ambient temperature (15-32°C), greenhouse conditions
pH:
Soil A: 5.45
Soil B: 8.3
Nutrient solution: 5.5
TOC:
Soil A: 31.8% OC
Soil B: 33.6% OC
Moisture:
Air humidity = 80%
Soil water content = 38-39% (pF = 1.5)
Details on test conditions:
TEST SYSTEM
- Testing facility: greenhouse
- Test container (type, material, size): plastic pots containing 175 g of soil
- Amount of soil: 175 g
- Method of seeding: Seeds were placed in a preculture device composed of PVC cylinders, to which a base of a 500 µm grid had been glued. The seeds were germinated in a 5L aerated nutrient solution and were protected from excess light for the first 7 days. Germinated plants were placed in contact with 5L aerated nutrient solution in the soil experiments for another 14 days prior to exposure.
- No. of seeds per container: not reported
- No. of plants (retained after thinning): not reported
- No. of replicates per treatment group: 5
- No. of replicates per control: 5

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
COLLECTION AND STORAGE
- Geographic location: two agricultural soils were sampled close to the underground research laboratory (Meuse/Haute Marne, France) of the National Agency for management of radioactive wastes (Andra)
- Sampling depth (cm): top soils 0-20 cm
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): air-dry soils were crushed and sieved under 2 mm
PROPERTIES
Soil A (acidic sandy clayey loamy)
- % sand: 31.9
- % silt: 48.7
- % clay: 19.4
- pH: 5.45
- Organic carbon (%): 31.8
- CEC (meq/100 g): 9.0 cmol/kg
- Background Zr content: 417.4 mg/kg dw
Soil B (clayey calcareous soil)
- % sand: 10.7
- % silt: 50.7
- % clay: 38.6
- pH: 8.3
- Organic carbon (%): 33.6
- CEC (meq/100 g): 10.02 cmol/kg- Geographic location:
- Background Zr content: 164 mg/kg dw

NUTRIENT MEDIUM (if used)
- Description: only used during preculturing (see materials and methods section for composition)

GROWTH CONDITIONS
- Photoperiod: ambient (greenhouse experiment)
- Light source: natural sunlight
- Day/night temperatures: 15-32°C temperature range
- Relative humidity (%): 80
- Watering regime and schedules: initial water content 38-39%, afterwards deionised water was added when required
- Water source/type: initially nutrient solution, afterwards deionised water
Nominal and measured concentrations:
- In the experiments with the soluble Zr compounds total Zr concentrations were 517.4 and 264 mg Zr/kg dw in soil A and B, respectively (i.e., 100 mg/kg added).
- In the experiment with the insoluble Zr compound total Zr concentrations were 703.4 and 450 mg Zr/kg dw in soil A and B, respectively (i.e., 286 mg/kg added).

Results and discussion

Bioconcentration factoropen allclose all
Type:
BSAF
Value:
<= 0.005 dimensionless
Basis:
organ d.w.
Calculation basis:
other: concentrations in soil and plants after 7 days of exposure
Remarks on result:
other: aerial parts (highest value of 0.005 for pea in soil B amended with Zr acetate)
Type:
BSAF
Value:
<= 0.1 dimensionless
Basis:
organ d.w.
Calculation basis:
other: concentrations in soil and plants after 7 days of exposure
Remarks on result:
other: roots (highest value of 0.1 for tomato in soil A amended with Zr acetate
Kinetic parameters:
no data
Metabolites:
not relevant
Details on results:
Zr is mainly accumulated in the roots of both plants.
Generally a higher Zr root concentration was oberved in the acidic soil.
Translocation of Zr from roots to aerial parts was limited.
The amount of Zr bound to root cell walls was signifcantly much smaller than the amount of Zr absorbed by the roots.
The BSAF for Zr decreases according to the following sequence: Zr-acetate > ZrOCl2 > Zr(OH)4 = natural Zr forms.
Zr soluble salts were more readily available than the hydroxide.
Reported statistics:
ANOVA + mean comparison using the LSD Fisher test

Applicant's summary and conclusion

Conclusions:
In this study, transfer of Zr from soil to tomato and pea plants was studied during a 7-day exposure period in two soils (an acidic and a calcareous soil) amended with either a soluble (ZrOCl2 or Zr acetate) or an insoluble Zr compound (Zr(OH)4). Zr accumulated mainly in the roots, with Zr adsorption to the root surface being of minor relevance. Translocation to aerial parts was limited. BSAF values for roots were the highest for Zr acetate and the lowest for Zr(OH)4. They were all <= 0.1. BSAF values for aerial parts were all <= 0.005 and were also generally the highest for Zr acetate and the lowest for Zr(OH)4.