Gadoliniumsulfite trihydrate

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Gadoliniumsulfite trihydrate

EC Number:

456-900-2

EC Name:

Gadoliniumsulfite trihydrate

Cas Number:

51285-81-5

Molecular formula:

Gd2(SO3)3*3H2O

IUPAC Name:

digadolinium(3+) trihydrate trisulfite

Test material form:

solid: particulate/powder

Details on test material:

Off white, crystalline powder
Batch number FSG 3896 or 02-FW-095

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Details on test solutions:

Due to the low solubility of the test item in test water, adequate amounts of the test item were directly weighed into each test flask. 3,5-Dichlorophenol was used as a reference item (positive
control): 0.5 g of 3,5-Dichlorophenol was dissolved according to the OECD Guideline No. 209 in 10 mL 1 mol/L NaOH and diluted to about 30 mL with deionised water. Excess of NaOH was neutralized with 0.5 mol/L H2SO4 to the point of incipient precipitation. Thereafter, the mixture was made up to one litre with deionised water. The final pH was measured to be 7.9 and the final concentration amounted to 500 mg/L.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The sludge was washed by centrifugation and the supematant liquid phase was decanted. The solid material was resuspended in tap water and again centrifuged. The latter procedure was repeated twice. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (g) to its dry weight (g) determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3 g dry material per litre, were made up with tap water. The pH of the activated sludge was determined tobe pH 7.4.

Study design

Limit test:

yes

Total exposure duration:

3 h

Test conditions

Test temperature:

19 - 21 °C

pH:

7.1 (start) - 8.3 (end)

Nominal and measured concentrations:

nominal: 10, 32, 100, 320 and 1000 mg/L Gadolinium sulfite trihydrate

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol (3.2, 10 and 32 mg/L)

Results and discussion

Effect concentrations

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Results with reference substance (positive control):

The following nominal concentrations of the positive control 3,5-Dichlorophenol were tested on the same activated sludge and under identical conditions as the test item: 32, 10 and 3.2 mg/L. In comparison to the controls the respiration rate of the activated sludge was inhibited by 26.8 % at the lowest nominal concentration of 3.2 mg/L. At the nominal concentrations of 10 and 32 mg test item/L, the respiration rate was inhibited by 69.9 % and 86.3 %, respectively. The 3-hour EC 50 of 3,5-Dichlorophenol was calculated to be 7.5 mg/L, 95 % confidence limits could not be calculated.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Based on measured inhibition rates, the 3-hour EC 20 and EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 20 % inhibition was noted after three hours incubation. Nevertheless, the 3-hour EC 20 and EC 50 are clearly higher than 1000 mg/L nominal under the present test conditions.

Executive summary:

The influence of the Gadolinium sulfite trihydrate) on the activity of activated sludge was evaluated by measuring the respiration rate under defined conditions. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test item after an incubation period of 3 hours. In comparison to the inoculum controls the respiration rate of the activated sludge was not or only slightly inhibited by between -9.6 % and 1.4 % up to the highest nominal test concentration of 1000 mg/L. Test item concentrations exceeding 1000 mg/L were not tested. Based on measured inhibition rates, the 3-hour EC 20 and EC 50 could not be quantified because up to the highest nominal test concentration of 1 000 mg/L less than 20 % inhibition was noted after three hours incubation. Nevertheless, the 3-hour EC 20 and EC 50 are clearly higher than 1000 mg/L nominal under the present test conditions. The 3-hour EC 50 for the positive control 3,5-Dichlorophenol, which was tested in the same way as the test item, was found to be 7.5 mg/L and is within the range of 5 - 30 mg/L recommended by the test guidelines; thus, confirming suitability of the activated sludge.