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Environmental fate & pathways

Adsorption / desorption

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Administrative data

Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From Nov.27, 2010 to Aug.31, 2011.
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: OECD guideline test with GLP compliance, but without GLP certificate. In addition, there are some deviations to the guideline.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2011
Report Date:
2011

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
yes
Remarks:
Only 1 domestic soil was tested in the study. Since the standard European soil are not available.
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
yes
Remarks:
Since solubility of BDP in water is quite low and its adsorption to organic carbon is quite strong, therefore BDP is absorbed instantly when contacted with soil; almost 98% of BDP is found in soil, therefore its amount in aqueous phase could be ignored;
GLP compliance:
yes
Type of method:
batch equilibrium method
Media:
soil

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
other: liquid
Details on test material:
Same with the substance notified in the section 1 of this dossier
Radiolabelling:
no

Study design

Test temperature:
about 20 ºC

Batch equilibrium or other method

Analytical monitoring:
yes
Details on sampling:
Both the concentration of BDP in aqueous solution and its amount in soil is quite low, therefore, in order to analyze its concentration precisely; BDP in soil and water was extracted with acetone and ethyl acetate respectively, and then concentrated for analysis.

Extraction of BDP from soil samples:
a. The soil/water mixture was centrifuged ; The water solution was poured with caution to get the soil sediment.
b. The soil was extacted with 20.0 ml of acetone under sonication for 20 min.
c. The extraction was repeated twice and combined the acetone solvents.
d. Concentrate the acetone extraction to dryness by a rotary evaporator.
e. Dissolve the residue with acetonitrile, transfer it into a 2.0 ml volumetric flask and add acetonitrile to the mark.
f. Filter the solution through a 0.45 µm nylon filter for HPLC analysis.

Extraction of BDP from aqueous solution:
a. Centrifuge the soil/water mixture, pour out the water solution with caution and extract with 50.0 ml of ethyl acetate by a separatory funnel.
b. Repeat the extraction two times and combine the extract solution.
c. Concentrate the ethyl acetate extraction to dryness by a rotary evaporator.
d. Dissolve the residue with acetonitrile, transfer into a 2.0 ml volumetric flask and add acetonitrile to the mark.
e. Filter the solution through a 0.45 µm nylon filter for HPLC analysis.
Details on matrix:
COLLECTION AND STORAGE
- Geographic location: 39°01′59″ N, 106°20′53. 9″E; Hill side in suburb of Shizuishan city
- Sampling depth (cm): A horizon up to a depth of 20 cm was collected.
- Storage conditions: Stored at ambient temperature and air-dried.

PROPERTIES
- Soil texture
- % clay: 14
- Soil taxonomic classification: Sandy loam
- pH: 7.07 (in 0.01 M CaCl2)
- Organic carbon (%): 1.60
Details on test conditions:
Preliminary study:
Two soil water ratio of 1/25 (2.0 g soil and 50.0 ml aqueous solution of BDP) and 1/1 (50.0 g soil and 50.0 ml aqueous solution of BDP) are chosen for the test.
A blank with only soil but no BDP, was subjected to the same test procedure as the main test. This serves as a background control during the analysis to detect interfering compounds or contaminated soils. The control sample with only BDP but no soil in 0.01 M CaCl2 solution was omitted in the test, because it has proved that little BDP can be adsorbed on the surfaces of the test vessels. All experiments, including blanks, were performed in duplicates.
The air-dried soil samples were equilibrated by shaking with proper volume 50 ml of 0.01 M CaCl2 overnight (12 h) before the day of the experiment. 50 μl of the stock solution of 1750.00 mg/L BDP was added to the system. The mixtures were shaken for 2h, 4h, 8h and 24h. BDP in soil and water supernatant were analyzed respectively.

Main test:
Base on the preliminary test , soil/water ratio was set at 1/25, in which 2.0 g soil and 50.0 ml aqueous solution of the test substance were added. The sampling time was adjusted to 20min、5h and 8h.The initial concentration of BDP was 0.83 mg/L. In every soil type one blank is run and subjected to the same test procedure.
Duration of adsorption equilibration
Sample No.:
#1
Duration:
10 min
Initial conc. measured:
0 mg/kg soil d.w.
pH:
7.07
Computational methods:
- Adsorption and desorption coefficients (Kd):
Kd=[Aeq/(100-Aeq)] X (V0/msoil)
Aeq = percentage of adsorption at adsorption equiblibruium, %
V0 = initial volume of the aqueous phase in contact with the soil, cm^-3
Msoil = quantity of the soil phase, expressed in dry mass of soil, g



- Freundlich adsorption and desorption coefficients: Not determined for impossible to calculate.
- Slope of Freundlich adsorption/desorption isotherms: Not determined for impossible to calculate.
- Adsorption coefficient per organic carbon (Koc): Koc= Kd X 100/%OC (cm^3/g)

Results and discussion

Adsorption coefficientopen allclose all
Type:
Kd
Value:
>= 1 225
Temp.:
20 °C
% Org. carbon:
1.6
Type:
log Koc
Value:
>= 6.87
Temp.:
20 °C
% Org. carbon:
1.6

Results: Batch equilibrium or other method

Adsorption and desorption constants:
Not determined because the adsorption equilibrium was reach within 10 min, it is impossible to perform the adsorption kinetics, adsorption isotherm, desorption kinetics and desorption isotherm experiment.
Recovery of test material:
The concentration of BDP in water was very little and which can be ignored, and the recovery of BDP in soil were 96.0%, 97.99% and 97.69% corresponding to 20min, 5h and 8h, which show that BDP was adsorbed in soil and achieved to equilibrium quickly.
Concentration of test substance at end of adsorption equilibration period:
water phase: < LOQ;
Soil phase: 20.48 mg/kg ww
Concentration of test substance at end of desorption equilibration period:
Not determined because the adsorption equilibrium was reach within 10 min, it is impossible to perform the adsorption kinetics, adsorption isotherm, desorption kinetics and desorption isotherm experiment.
Mass balance (%) at end of adsorption phase
Sample no.:
#1
Duration:
10 min
% Adsorption:
ca. 100
Transformation products:
not measured
Details on results (Batch equilibrium method):
Then the Koc is 7.5×10^6 cm^3/g calculated by equations above and log Koc is 6.87.
Statistics:
no data

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
Guideline test with GLP compliance
Conclusions:
The log of the adsorption coefficient (Koc) of BDP was determined to be higher than 6.87 using batch equilibrium method, which indicated that BDP will be strongly adsorbed by organic carbon in soil.