Zirconium bis(hydrogen phosphate)

Bioaccumulation: terrestrial

Administrative data

Endpoint:

bioaccumulation: terrestrial

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: well performed study, however no guideline followed

Data source

Reference

Reference Type:

publication

Title:

Phytoavailability of zirconium in relation to its initial added form and soil characteristics

Author:

E. Ferrand, C. Dumat, E. Leclerc-Cessac, M. F. Benedetti

Year:

2006

Bibliographic source:

Plant Soil (2006) 287:313–325

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

The uptake of stable Zr by roots of young pea and tomato plants in contact with two contrasting soils and the subsequent transfer to aerial parts was measured in this study. Zr was added as oxychloride, acetate and hydroxide. Accordingly, the Zr adsorption / bioavailability and bioaccumulation has been tested in a 7-day exposure period.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

zirconium oxychloride

IUPAC Name:

zirconium oxychloride

Constituent 2

Reference substance name:

Zirconium acetate

EC Number:

231-492-7

EC Name:

Zirconium acetate

Cas Number:

7585-20-8

IUPAC Name:

zirconium(2+) diacetate

Constituent 3

Reference substance name:

zirconium(IV)hydroxide

IUPAC Name:

zirconium(IV)hydroxide

Details on test material:

Test substance 1:
- zirconium oxychloride
- Molecular formula (if other than submission substance): ZrOCl2
- Analytical purity: 98%
- Supplier: Sigma-Aldrich

Test substance 2:
- zirconium acetate
- Molecular formula (if other than submission substance): C2H4O2Zr
- Analytical purity: not reported (high purity)
- Supplier: Sigma-Aldrich

Test substance 3:
- zirconium(IV)hydroxide
- Zr(OH)4
- Analytical purity: 97%
- Supplier: Aldrich

Radiolabelling:

no

Sampling and analysis

Details on sampling:

After the contact period (i.e. 7 days), roots and soils were separated. The roots were thoroughly rinsed with milliQ water to remove any trace of
soil particle. The shoots and roots of plants were separated and their fresh weight measured.
Zr sorbed on fresh roots was recovered with a 0.01 M HCl extraction (Chaignon and Hinsinger 2003). The concentration of metal remaining in the roots after the HCl washing was assumed to result from cross-membrane uptake. Roots and aerial parts were then dried at 60°C and reweighed. After the HNO3/HClO4 digestion of dried material in a closed Teflon vessel, the total Zr concentrations were measured

Test substrate

Vehicle:

no

Details on preparation and application of test substrate:

The two soils were spiked with different Zr rich solutions. A set of unspiked cultivated soils was used as control samples. In order to investigate
the influence of the Zr added form on its plant availability, soils were spiked with solutions containing different forms of Zr and a solid form of Zr:
(i) addition of ZrOCl2 (Sigma–Aldrich, 98%) or Zr acetate solution (Sigma–Aldrich) to increase the total soil Zr concentration by 100 mg Zr/kg dry soil;
(ii) mixing the soil with solid Zr(OH)4(s) (Aldrich, 97%) to increase the concentration by 286 mg Zr/kg dry soil. The organic form was used to test the influence of organic ligands, such as root exudates. For both soils, the added Zr quantities were lower or had the same order than the naturally occurring Zr levels. Such high Zr additions were chosen in relation to the analytical limit of the measured concentrations in plants. Indeed, even with an initial spike of 100 mg Zr/kg dry soil, very low concentrations are measured in roots. The quantity of available Zr in solution for the plant
being much less important with a solid form, the chosen concentration for Zr(OH)4(s) was higher than for the other forms

Test organisms

Test organisms (species):

other: tomato (Lycopersicon esculentum L. cv. St. Pierre) and pea (Pisum sativum L. cv. ‘‘Express’’)

Details on test organisms:

1. TEST ORGANISM
- Common name: tomato (Solanaceae family)
- Seeds were disinfected in a bath of 6% H2O2 and then rinsed with deionised water.

2. TEST ORGANISM
- Common name pea (Fabaceae family)
- Seeds were disinfected in a bath of 6% H2O2 and then rinsed with deionised water.

Study design

Total exposure / uptake duration:

7 d

Test conditions

Test temperature:

15–32 °C, greenhouse conditions

pH:

Soil A = 5.45
Soil B = 8.3
nutrient solution: fixed to 5.5

TOC:

Soil A: 31.8% OC
Soil B: 33.6% OC

Moisture:

humidity = 80%; water contents of the soils around 39% and 38% for soil A and B

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:

The two soils were spiked with different Zr rich solutions. A set of unspiked cultivated soils was used as control samples. In order to investigate the influence of the Zr added form on its plant availability, soils were spiked with solutions containing different forms of Zr and a solid form of Zr: (i) addition of ZrOCl2 (Sigma–Aldrich, 98%) or Zr acetate solution (Sigma–Aldrich) to increase the total soil Zr concentration by 100 mg Zr/kg dry soil; (ii) mixing the soil with solid Zr(OH)4(s) (Aldrich, 97%) to increase the concentration by 286 mg Zr/kg dry soil.

Results and discussion

Bioconcentration factor

Bioconcentration factor 1

Type:

BSAF

Value:

<= 0.005

Basis:

organ d.w.

Calculation basis:

other: concentrations in soil and plants after 7 days of exposure

Remarks on result:

other: The transfer value (TF) has been measured. This is the maximum value for the transfer factors for the aerial parts (peas cultivated on the soil B). It is a worst-case consideration.

Bioconcentration factor 2

Type:

BSAF

Value:

<= 0.1

Basis:

organ d.w.

Calculation basis:

other: concentrations in soil and plants after 7 days of exposure

Remarks on result:

other: The transfer value (TF) has been measured. This is the maximum value for the transfer factors for the roots (tomatoes cultivated on the soil A). It is a worst-case consideration.

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 Transfer Factors (TF =BSAF) for Zr decreases according to the following sequence: Zr-acetate > ZrOCl2 > Zr(OH)4 = natural Zr forms.
Transfer factors (TF) for aerial parts obtained for the two soils are within the range: 10^–5 < TF < 10^–3
Zr soluble salts were more readily available than the hydroxide.

Zr concentrations (mg Zr/kg dry matter; means ±SD for 5 replicates) after cultivation in soil with 100 mg/kg ZrOCl2:
Tomato - aerial parts - soil A: 0.9±0.1 (control 0.56±0.05)
Tomato - aerial parts - soil B: 0.45±0.05 (control 0.42±0.09)
Tomato - roots - soil A: 19.8±1.3 (control 7.96±1.51)
Tomato - roots - soil B: 14.55±1.96 (control 2.6±0.3)
Pea - aerial parts - soil A: 0.64±0.02 (control 0.26±0.04)
Pea - aerial parts - soil B: 0.37±0.08 (control 0.33±0.03)
Pea - roots - soil A: 15±2 (control 1.2±0.1)
Pea - roots - soil B: 8.4±1.2 (control 1.1±0.1)

Reported statistics:

Anova factorial statistical analysis and Fisher test with P < 0.05

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

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) spiked with either a soluble (ZrOCl2 or Zr acetate) or an insoluble Zr compound (Zr(OH)4). Zr adsorbed and accumulated mainly in the roots, with Zr adsorption to the root surface being of minor relevance. Translocation to aerial parts was limited. TF (translocation factor) values for roots were the highest for Zr acetate and the lowest for Zr(OH)4. They were all <= 0.1. TF (translocation factor) values for aerial parts were all <= 0.005 and were also generally the highest for Zr acetate and the lowest for Zr(OH)4.