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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Remarks:
Batch equilibrium ad-/desorption test with samples from 5 different soils
Adequacy of study:
key study
Study period:
Study initiation date June 26, 2017; Experimental starting date June 27, 2017; Experimental completion date August 9, 2017; Study completion date November 13, 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
Adopted 21 January 2000
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: Chemical Registration Center of MEP. The Guidelines for the Testing of Chemicals Physical-Chemical Properties and Physical Hazards, 106 Adsorption-Desorption Using a Batch Equilibrium Method.Second Edition.Beijing: China Environmental Press. 2013:47-85.
Version / remarks:
Method published in 2013
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: China National Technical Committee for Standardization of Dangerous Chemicals Management.GB/T 21851-2008.Chemicals Adsorption - desorption using a batch equilibrium method[S]. Beijing: Standards Press of China, 2008.
Version / remarks:
Method published in 2008
Deviations:
no
GLP compliance:
yes
Type of method:
batch equilibrium method
Media:
soil
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Batch No.: See confidential section of test material information.
- Expiration date of the lot/batch: October 2017
- Purity test date: Information not reported.

RADIOLABELLING INFORMATION (if applicable): Not applicable, compound was not radio-labelled.

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Stored according to requirements as stated on substance label: Keep container tightly closed. Stored in dry and cool place. Avoid contacting with strong oxidizers.
- Stability under test conditions: Stable in container after opening /in water/in light/in soil.
- Solubility and stability of the test substance in the solvent/vehicle: Not applicable, no solvent or vehicle used.
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: Not applicable, no solvent or vehicle used.

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: No treatment of test material prior to testing.
- Preliminary purification step (if any): No purification step required.
- Final dilution of a dissolved solid, stock liquid or gel: For preparation of the test substance solution as used in the Batch study 0.0150 g of test substance was dissolved with 500 mL 0.01 M CaCl2. The obtained stock solution had a test substance concentration of 30.0 mg/L.
- Final preparation of a solid: Not applicable, test compound is liquid.

FORM AS APPLIED IN THE TEST (if different from that of starting material): Applied form of test substance not different from starting material.

OTHER SPECIFICS:
Test compound is fully miscible in water, from 0 to 100%.
Radiolabelling:
no
Test temperature:
25 °C ± 1 °C
Details on study design: HPLC method:
Not applicable. Performed study is a Batch equilibrium test with soil samples.
Analytical monitoring:
yes
Details on sampling:
- Concentrations: In test solutions following range was investigated (depending on selected soil/solution ratio): 0.400, 0.800, 1.60, 2.40, 3.20 mg/L.
- Sampling interval: Sampling was performed after equilibrium periods.
Equilibration times: adsorption: 4 h, 8 h, 24 h or 48 h (soil #1, #2); 4 h, 8 h, 22 h, 30 h or 48 h (soil #3, #4, #5).
Equilibration times: desorption: 4 h, 8 h, 22 h, 30 h or 48 h (all soils).
- Sample storage before analysis: Normal sample storage was below 96 h (according to study plan), in some cases storage time was 168 h (1 week).
Matrix no.:
#1
Matrix type:
other: Red soil (probably Oxisol)
% Org. carbon:
0.407
pH:
4.083
CEC:
10 other: cmol(+) per kg
Matrix no.:
#2
Matrix type:
other: Black soil
% Org. carbon:
1.97
pH:
5.73
CEC:
31 other: cmol(+) per kg
Matrix no.:
#3
Matrix type:
other: Sierozem
% Org. carbon:
1.68
pH:
7.764
CEC:
13.8 other: cmol(+) per kg
Matrix no.:
#4
Matrix type:
other: Paddy soil
% Org. carbon:
1.8
pH:
5.722
CEC:
19 other: cmol(+) per kg
Matrix no.:
#5
Matrix type:
other: Flavo-aquic soil
% Org. carbon:
1.73
pH:
7.602
CEC:
20 other: cmol(+) per kg
Details on matrix:
COLLECTION AND STORAGE
- Geographic location:
Matrix #1: S-1: sampled at Jiangxi, China.
Matrix #2: S-2: sampled at Heilongjiang, China.
Matrix #3: S-3: sampled at Xinjiang, China.
Matrix #4: S-4: sampled at Hubei, China.
Matrix #5: S-5: sampled at Anhui, China.
Samples were purchased from Chinese Academy of Geological Sciences, Institute of Geophysical and Geochemical Exploration.
- Collection procedures: Information not reported. Soil samples were air-dried.
- Sampling depth (cm): Information not reported.
- Storage conditions: Information not reported.
- Storage length: Information not reported.
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): The air-dried soil samples used in test were equilibrated by shaking at 165 r/min and 25°C with defined amount of 0.01 M CaCl2 overnight (16 h) before testing. Further details not available.

PROPERTIES
- Soil texture: Soit texture (percentage content of sand, silt and clay) not reported.
- Horizon: Sampling depth and soil horizon not reported.
- Soil taxonomic classification: Not reported.
- Soil classification system: Information not available.
- Soil series: Information not available.
- Soil order: Information not available.
- pH: The pH values (in 0.01 M CaCl2) detected in the five investigated soil samples were in the range of 4.083 to 7.764. See table of matrix properties for details.
- Organic carbon (%): The organic carbon content detected in the five investigated soil samples was in the range of 0.407 to 1.97%. See table of matrix properties for details.
- CEC (meq/100 g): The CEC detected in the five investigated soil samples was in the range of 10.0 to 31.0 cmol(+)/kg soil. See table of matrix properties for details.
- Carbonate as CaCO3: Information not available.
- Insoluble carbonates (%): Information not available.
- Extractable Cations (Ca, Mg, Na, K, H) (MEQ/100 g): Information not available.
- Special chemical/mineralogical features: Information not available.
- Clay fraction mineralogy: Information not available.
- Moisture at 1/3 atm (%): Following Moisture contents (without further detection conditions) were reported for the 5 investigated soil samples:
Matrix #1: S-1 (Red soil): 1.33%,
Matrix #2: S-2 (Black soil): 1.99%,
Matrix #3: S-3 (Sierozem): 1.51%,
Matrix #4: S-4 (Paddy soil): 1.49%,
Matrix #5: S-5 (Flavo-aquic soil):.1.77%.
- Bulk density (g/cm3): Information not available.
- Biomass (e.g. in mg microbial C/100 mg, CFU or other): Following organic matter contents (without further detection conditions) were reported for the 5 investigated soil samples:
Matrix #1: S-1 (Red soil): 7.3 (+/- 0.5) g/kg soil,
Matrix #2: S-2 (Black soil): 34.5 (+/- 1.3) g/kg soil,
Matrix #3: S-3 (Sierozem): 12.7 (+/- 0.5) g/kg soil,
Matrix #4: S-4 (Paddy soil): 33.3 (+/- 1.0) g/kg soil,
Matrix #5: S-5 (Flavo-aquic soil):.17.0 (+/- 1.0) g/kg soil.
Details on test conditions:
TEST CONDITIONS
- Buffer: 0.01 M CaCl2 was used as solution phase of the Batch study.
- pH: pH was not adjusted, no further details available.
- Suspended solids concentration: Information not available.

TEST SYSTEM
- Type, size and further details on reaction vessel: Details about test containers not available.
- Water filtered (i.e. yes/no; type of size of filter used, if any): All the test stock solutions and test solutions were filtered by 0.45 µm or 0.22 µm membrane and analyzed for concentration.
- Amount of soil/sediment/sludge and water per treatment (if simulation test): The optimal soil/solution ratio was 1/1 for all five soil matrices tested.
This was result of a comparison of different soil/solution ratios (1/1, 1/5 and 1/25, respectively).
- Soil/sediment/sludge-water ratio (if simulation test): Not applicable.
- Number of reaction vessels/concentration: Two vessels for blank samples; 8 vessels (parallels) per test group (concentration). Two parallels were sampled per time with total of four times.
- Measuring equipment: Following instruments were used:
Agilent 1260 RRLC (Manufacturer: American Agilent Technologies Factory),
ST 16R refrigeration centrifuge (Manufacturer: Thermo Electron LED GmbH),
KQ5200DE Numerical control cleaners (Manufacturer: Kun Shan Ultrasonic Instruments Co., Ltd),
BSA223S and CPA225D Electronic lalances (Manufacturer: Sartorius, Germany),
HZ150L Constant temperature shaker (Manufacturer: Wuhan Ruiha Instrument Equipment Co., Ltd).
Further test equipment comprise triangular flask, beaker, volumetric flask, measuring cylinder, vial, centrufuge tube and graduated straw.
- Test performed in closed vessels due to significant volatility of test substance: Test vessels were closed to allow shaking (agitation) during equilibrium periods.
- Test performed in open system: Not applicable for Batch test as performed.
- Method of preparation of test solution: Dilution from stock solution.
- Are the residues from the adsorption phase used for desorption?: No. For detection of desorption kinetics 0.0149 g of the test substance was weighed into a flask and dissolved with 500 mL 0.01 mol/L CaCl2 solution. The solution was shaken to obtain the stock solution with the concentration of 29.8 mg/L. Then the actual concentration of the stock solution was analyzed.

Deviations to the study plan and SOPs
In the study plan, the sample storage time was not more than 96 hours, but the storage time of some samples in the test was 168 hours, which deviated from the project proposal. This deviation is due to the increased pressure of the instrument system, resulting in partial sample retention time drift. Replace the white filter in the purge valve, the pressure returned to normal, and then the concentration of the samples was analyzed again. The stability test of the test substance was showed that the sample could remain stable within 168h (see Annex A). The concentration of samples was analyzed after store 168h, and the results were still accurate and reliable.
Sample No.:
#1
Duration:
8 h
Initial conc. measured:
0.075 other: mL/g (kd value)
Temp.:
25 °C
Remarks:
Adsorption rate: 6.85%
Sample No.:
#2
Duration:
24 h
Initial conc. measured:
0.382 other: mL/g (kd value)
Temp.:
25 °C
Remarks:
Adsorption rate: 27.2%
Sample No.:
#3
Duration:
22 h
Initial conc. measured:
0.173 other: mL/g (kd value)
Temp.:
25 °C
Remarks:
Adsorption rate: 14.5%
Sample No.:
#4
Duration:
22 h
Initial conc. measured:
0.187 other: mL/g (kd value)
Temp.:
25 °C
Remarks:
Adsorption rate: 15.4%
Sample No.:
#5
Duration:
30 h
Initial conc. measured:
0.236 other: mL/g (kd value)
Temp.:
25 °C
Remarks:
Adsorption rate: 18.8%
Sample no.:
#1
Duration:
22 h
Conc. of adsorbed test mat.:
1.76 other: mL/g (kdes value)
Temp.:
25 °C
Remarks:
Desorption rate: 36.6%
Sample no.:
#2
Duration:
8 h
Conc. of adsorbed test mat.:
1.96 other: mL/g (kdes value)
Temp.:
25 °C
Remarks:
Desorption rate: 34.3%
Sample no.:
#3
Duration:
8 h
Conc. of adsorbed test mat.:
1.33 other: mL/g (kdes value)
Temp.:
25 °C
Remarks:
Desorption rate: 43.3%
Sample no.:
#4
Duration:
8 h
Conc. of adsorbed test mat.:
1.66 other: mL/g (kdes value)
Temp.:
25 °C
Remarks:
Desorption rate: 38.0%
Sample no.:
#5
Duration:
8 h
Conc. of adsorbed test mat.:
1.72 other: mL/g (kdes value)
Temp.:
25 °C
Remarks:
Desorption rate: 37.4%
Computational methods:
No details available about specific statistical procedures or software tools used for the calculations.
- Freundlich Adsorption and desorption coefficients (Kd): The Kd and Kdes values (both in mL/g) were calculated according to the Freundlich equation.
- Slope of Freundlich adsorption/desorption isotherms: The calculated slopes of the ad-/desorption isotherms as well as the graphs are available in the test report. The slopers (1/n values) are in a range of 0.7916 and 0.9891 (adorption) and 0.9599 to 1.086 (desorption) for the five soil samples (S-1 to S-5) investigated in this study.
- Adsorption coefficient per organic carbon (Koc): Calculated Koc values are summarised in table "adsorption coefficients".
- Regression coefficient of Freundlich equation: The regression coefficients (r²) of the Freundlich equations were calculated and are available in the test report. The regression coefficients (r²) of the Freundlich equations are in a range of 0.9575 to 0.9978 (adsorption) and 0.9470 to 09918 (desorption) for the five soil samples (S-1 to S-5) investigated in this study.
- Other: Mass balances were alos calculated by comparing total mass of test substance extracted from the soil and walls of test vessels with the initial mass concentration of the test solution in contact with soil (see equation in section 7.7 of test report).
Sample No.:
#1
Type:
Koc
Value:
18.4 L/kg
pH:
4.083
Temp.:
25 °C
Matrix:
Red soil (probably Oxisol)
% Org. carbon:
0.407
Sample No.:
#2
Type:
Koc
Value:
19.4 L/kg
pH:
5.73
Temp.:
25 °C
Matrix:
Black soil
% Org. carbon:
1.97
Sample No.:
#3
Type:
Koc
Value:
10.3 L/kg
pH:
7.764
Temp.:
25 °C
Matrix:
Sierozem
% Org. carbon:
1.68
Key result
Sample No.:
#4
Type:
Koc
Value:
10.4 L/kg
pH:
5.722
Temp.:
25 °C
Matrix:
Paddy soil
% Org. carbon:
1.8
Sample No.:
#5
Type:
Koc
Value:
13.6 L/kg
pH:
7.602
Temp.:
25 °C
Matrix:
Flavo-aquic soil
% Org. carbon:
1.73
Sample No.:
#1
Phase system:
soil-water
Type:
other: Kd
Remarks:
Adsorption constant
Value:
0.075 L/kg
Temp.:
25 °C
pH:
4.083
Matrix:
Red soil (probably Oxisol)
% Org. carbon:
0.407
Sample No.:
#2
Phase system:
soil-water
Type:
other: Kd
Remarks:
Adsorption constant
Value:
0.382 L/kg
Temp.:
25 °C
pH:
5.73
Matrix:
Black soil
% Org. carbon:
1.97
Sample No.:
#3
Phase system:
soil-water
Type:
other: Kd
Remarks:
Adsorption constant
Value:
0.173 L/kg
Temp.:
25 °C
pH:
7.764
Matrix:
Sierozem
% Org. carbon:
1.68
Sample No.:
#4
Phase system:
soil-water
Type:
other: Kd
Remarks:
Adsorption constant
Value:
0.187 L/kg
Temp.:
25 °C
pH:
5.722
Matrix:
Paddy soil
% Org. carbon:
1.8
Sample No.:
#5
Phase system:
soil-water
Type:
other: Kd
Remarks:
Adsorption constant
Value:
0.236 L/kg
Temp.:
25 °C
pH:
7.602
Matrix:
Fluvi-aquic soil
% Org. carbon:
1.73
Details on results (HPLC method):
Not applicable. Performed study is a Batch equilibrium test with soil samples.
Adsorption and desorption constants:
It was shown that the adsorption equilibrium time in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 8h, 24h, 22h, 22h, 30h, respectively. The adsorption rate in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 6.85%, 27.2%, 14.5%, 15.4%, 18.8%, respectively.
The organic carbon adsorption coefficient Koc of test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 18.4 mL/g, 19.4 mL/g, 10.3 mL/g, 10.4 mL/g, 13.6 mL/g, respectively. The lg Koc of test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 1.26, 1.29, 1.01, 1.02, 1.13, respectively.
Recovery of test material:
It was shown that the mass balance rate in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 104%, 104%, 108%, 107%, 104%, respectively.
Concentration of test substance at end of adsorption equilibration period:
Mass balance test revealed a range of 104 to 108% for the five soils investigated.
Concentration of test substance at end of desorption equilibration period:
Desorption part of test demonstrated that the adsorption of the compound was irreversible. D (%) values were in a range between 34.3% to 43.3% for the five soils investigated.
Sample no.:
#1
Duration:
48 h
% Adsorption:
104
Remarks on result:
other: mass balance rate in Jiangxi red soil
Sample no.:
#2
Duration:
48 h
% Adsorption:
104
Remarks on result:
other: mass balance rate in Heilongjiang black soil
Sample no.:
#3
Duration:
48 h
% Adsorption:
108
Remarks on result:
other: mass balance rate in Xinjiang sierozem soil
Sample no.:
#4
Duration:
48 h
% Adsorption:
107
Remarks on result:
other: mass balance rate in Hubei paddy soil
Sample no.:
#5
Duration:
48 h
% Adsorption:
104
Remarks on result:
other: mass balance rate in Anhui fluvo-aquic soil
Sample no.:
#1
Duration:
22 h
% Desorption:
< 75
Remarks on result:
other: Total desorption less than 75% of the amount adsorbed
Remarks:
Adsorption of test compound to the soil is considered as irreversible,
Sample no.:
#2
Duration:
8 h
% Desorption:
< 75
Remarks on result:
other: Total desorption less than 75% of the amount adsorbed
Remarks:
Adsorption of test compound to the soil is considered as irreversible,
Sample no.:
#3
Duration:
8 h
% Desorption:
< 75
Remarks on result:
other: Total desorption less than 75% of the amount adsorbed
Remarks:
Adsorption of test compound to the soil is considered as irreversible,
Sample no.:
#4
Duration:
8 h
% Desorption:
< 75
Remarks on result:
other: Total desorption less than 75% of the amount adsorbed
Remarks:
Adsorption of test compound to the soil is considered as irreversible,
Sample no.:
#5
Duration:
8 h
% Desorption:
< 75
Remarks on result:
other: Total desorption less than 75% of the amount adsorbed
Remarks:
Adsorption of test compound to the soil is considered as irreversible,
Transformation products:
not measured
Remarks:
Transfer or degradation products were not investigated. Such processes are also not to be expected during test duration
Details on results (Batch equilibrium method):
PRELIMINARY TEST
- Sample purity: purity of test substance sample: 99.68%
- Weighed soil: 1 or 2 g of soil were used in each batch.
- Volume of CaCl2 solution: 500 mL 0.01 M CaCl2 was used for stock solution.
In each batch 9, 10, 22.5 or 25 mLCaCl2 were used, depending on chosen soil/solution ratio.
In each batch 0.0, 1.0 or 2.5 mL stock solution were used, depending on chosen soil/solution ratio.
The total volume of the aqueous phase was 10 or 25 mL, depending on the soil/solution ratio.
- Initial test substance concentration: 0.0150 g of test substance was used for stock solution
- Test substance concentration in final solution: 30 mg/L
- Analytical test substance concentration in final solution: Analytical verification was performed

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: Test substance was stable.
- Experimental conditions maintained throughout the study: Yes
- Buffer/test substance interactions affecting sorption: No
- Further chemical interactions: None
- Buffer-catalyzed degradation of test substance: No
- Anomalies or problems encountered (if yes): No
- Other observations: None

TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount: Transformation products not investigated.

RESIDUES
- Total unidentified radioactivity (range) of applied amount: Not applicable
- Extractable residues (% of applied amount at end of study period): Mass balance detections were performed (see table)
- Non-extractable residues (% of applied amount at end of study period): See results of desorption part of study (adsorption was irreversible; D values (%) between 34.3% to 43.3% for the five soils investigated.

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: Not applicable

RESULTS OF SUPPLEMENTARY EXPERIMENT (if any): No further supplementary experiments performed.
Statistics:
No details available about specific statistical procedures or software tools used for the calculations. Adsorption rate (A, %), desorption rate (D, %), distribution coefficients Kd (mL/g), organic carbon normalised adsorption coefficient Koc (mL/g), apparent desorption coefficient Kdes (mL/g) mass balance (MB), Freundlich adsorption & desorption isotherm equations were calculated. Furthermore, graphs of the isotherms were plotted.

Result of stability tests

The stability tests were conducted with the test substance supernatant of Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil, Anhui fluvo-aquic soil and aqueous phase (0.01 mol/L CaCl2). Results were shown in Annex Table A. 1. It was shown that the test substance was stable for 168 h in the aqueous phase and the soil supernatant of Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil, Anhui fluvo-aquic.

Selection of optimal soil/solution ratios and Adsorption kinetics

In general practice it is useful to settle on a few fixed ratios, for which the percentage adsorbed is above 20%, and preferably >50%. Where low adsorption occurs, a 1/1 soil solution ratio is recommended, while care should be taken to keep the test substance concentration in the aqueous phase high enough to be measured accurately. Therefore, the optimal soil/solution ratios of Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 1/1, respectively.

It was shown that the adsorption equilibrium time in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 8 h, 24 h, 22 h, 22 h, 30 h, respectively. The adsorption rate in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 6.85%, 27.2%, 14.5%, 15.4%, 18.8%, respectively. The distribution coefficient Kd of test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem , Hubei paddy soil and Anhui fluvo-aquic soil were 0.0749 mL/g, 0.382 mL/g, 0.173 mL/g, 0.187 mL/g, 0.236 mL/g, respectively. The organic carbon adsorption coefficient Koc of test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 18.4 mL/g, 19.4 mL/g, 10.3 mL/g, 10.4 mL/g, 13.6 mL/g, respectively. The lg Koc of test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 1.26, 1.29, 1.01, 1.02, 1.13, respectively.

Mass balance

It was shown that the mass balance rate in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 104%, 104%, 108%, 107%, 104%, respectively.

Desorption kinetics

It was shown that the desorption equilibrium time in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 22 h, 8 h, 8 h, 8 h, 8 h respectively. The desorption rate in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 36.6%, 34.3%, 43.3%, 38.0%, 37.4%, respectively. The apparent desorption coefficient Kdes of test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were 1.76 mL/g, 1.96 mL/g, 1.33 mL/g, 1.66 mL/g, 1.72 mL/g, respectively. The total desorption is less than 75% of the amount adsorbed, the adsorption is considered to be irreversible, so the test substance was irreversibly adsorbed on five types of soil.

Adsorption isotherm

The Freundlich adsorption equation of the test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were y =0.7916x -0.6790, y =0.9891x -0.3025, y =0.8566x -0.5734, y =0.9330x -0.5063, y =0.9775x -0.5488, respectively. The correlation coefficient r² were 0.9782, 0.9918, 0.9575, 0.9978, 0.9892, respectively. According to the Freundlich equation, Freundlich adsorption coefficient KF(ads) were 0.2094 mL/g, 0.4984 mL/g, 0.2670 mL/g, 0.3117 mL/g, 0.2826 mL/g, respectively. The slope 1/n were 0.7916, 0.9891, 0.8566, 0.9330, 0.9775, respectively.

Desorption isotherm

The Freundlich desorption equation of the test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were y = 1.026x -0.5142, y =1.046x -0.1679, y =0.9715x -0.4167, y =0.9599x -0.4094, y = 1.086x -0.3478, respectively. The correlation coefficient r² were 0.9635, 0.9918, 0.9470, 0.9647, 0.9686, respectively. According to the Freundlich equation, Freundlich desorption coefficient KF(des) were 0.3061 mL/g, 0.6793 mL/g, 0.3831 mL/g, 0.3896 mL/g, 0.4490 mL/g, respectively. The slope 1/n were 1.026, 1.046, 0.9715, 0.9599, 1.086, respectively.

Validity of test

In analytical methods, the recovery of the aqueous phase fell within the criterion of 80%-110%, and the recovery of the soils fell within the criterion of 70%-110%. The validation of the analysis method was referred the test report of "A 17031 -Tl 6064-1R".

Conclusion

Under the test condition, the adsorption/desorption test results of the test substance in Jiangxi red soil, Heilongjiang black soil, Xinjiang sierozem, Hubei paddy soil and Anhui fluvo-aquic soil were shown as follows.

Table 1: Results of adsorption kinetics test

 Soil type  Soil-/Solution ratio Equilibration time (h)

A (%) 

Kd (mL/g) 

 Koc (mL/g)

lg Koc 

 Jiangxi red soil

 1:1

6.85 

 0.0749

 18.4

 1.26

 Heilongjiang black soil

 1:1

24 

27.2 

0.382 

 19.4

 1.29

 Xinjiang sierozem

 1:1

 22

 14.5

 0.173

 10.3

 1.01

 Hubei paddy soil

 1:1

 22

 15.4

 0.187

 10.4

 1.02

 Anhui fluvo-aquic soil

 1:1

 30

 18.8

 0.236

 13.6

 1.13

Table 2: Results of desorption kinetics test

 Soil type  Soil-/Solution ratio Equilibration time (h)

D (%) 

Kdes (mL/g) 

 Desorption process

 Jiangxi red soil

 1:1

22 

36.6 

1.76

 irreversible

 Heilongjiang black soil

 1:1

34.3 

1.96 

irreversible

 Xinjiang sierozem

 1:1

 8

 43.3

1.33

 irreversible

 Hubei paddy soil

 1:1

 8

 38.0

1.66

 irreversible

 Anhui fluvo-aquic soil

 1:1

 8

 37.4

1.72

 irreversible

Table 3: Results of adsorption isotherms test

 Soil type  Soil-/Solution ratio KF (adsorption)

1/n

Freundlich equation 

 

 Jiangxi red soil

 1:1

0.2094 

0.7916 

y = 0.7916x - 0.6790

 0.9782

 Heilongjiang black soil

 1:1

0.4984

0.9891 

y = 0.9891x - 0.3025 

0.9918

 Xinjiang sierozem

 1:1

 0.2670

0.8566

y = 0.8566x - 0.5734

 0.9575

 Hubei paddy soil

 1:1

 0.3117

 0.9330

y = 0.9330x - 0.5063

 0.9978

 Anhui fluvo-aquic soil

 1:1

 0.2826

0.9775

y = 0.9775x - 0.5488

 0.9892

Table 4: Results of desorption isotherms test

 Soil type  Soil-/Solution ratio KF(desorption)

1/n

Freundlich equation 

 

 Jiangxi red soil

 1:1

0.3061 

1.026

y = 1.026x - 0.5142

 0.9635

 Heilongjiang black soil

 1:1

0.6793

1.046 

y = 1.046x - 0.1679 

0.9918

 Xinjiang sierozem

 1:1

0.3831

0.9715

y = 0.9715x - 0.4167

 0.9470

 Hubei paddy soil

 1:1

 0.3896

 0.9599

y = 0.9599x - 0.4094

0.9647

 Anhui fluvo-aquic soil

 1:1

 0.4490

1.086

y = 1.086x - 0.3478

0.9686

Validity criteria fulfilled:
yes
Remarks:
In analytical methods, the recovery of the aqueous phase fell within the criterion of 80%-110%, and the recovery of the soils fell within the criterion of 70%-110%.
Conclusions:
Koc values calculated based on results of a soil adsorption/desorption batch study (OECD 106):
Results for five different soils: Koc = 18.4, 19.4, 10.3, 10.4, 13.6. Mean value (n = 5) for Koc: 14.42.
log Koc = 1.26, 1.29, 1.01, 1.02, 1.13. Mean value (n = 5) for log Koc = 1.142.
The total desorption is less than 75% of the amount adsorbed, the adsorption is considered to be irreversible, so the test substance was irreversibly adsorbed on five types of soil.
Executive summary:

This adsorption/desorption batch study (in accordance with OECD Guideline 106) aimed to evaluate the ad- and desorption of the test compound on different soil types with a varying range of organic carbon content, clay content and soil texture, and pH. It comprises three tiers.

Tier 1: Preliminary study in order to determine: the soil/solution ratio; the equilibration time for adsorption and the amount of test substance adsorbed at equilibrium; the adsorption of the test substance on the surfaces of the test vessels and the stability of the test substance during the test period.

Tier 2: Screening test: the adsorption is studied in five different soil types by means of adsorption kinetics at a single concentration and determination of distribution coefficients Kd and Koc.

Tier 3: Detennination of Freundlich adsorption isotherms to detennine the influence of concentration on the extent of adsorption on soils . Study of desorption by means of desorption kinetics/Freundlich desorption isotherms.

Koc values calculated based on results of this soil adsorption/desorption batch study (OECD 106): Results for five different soils:

Koc =18.4, 19.4, 10.3, 10.4, 13.6. Mean value (n = 5) for Koc: 14.42
log Koc = 1.26, 1.29, 1.01, 1.02, 1.13. Mean value (n = 5) for log Koc = 1.142.

The total desorption is less than 75% of the amount adsorbed, the adsorption is considered to be irreversible, so the test substance was irreversibly adsorbed on five types of soil.

Description of key information

Koc values calculated based on results of a soil adsorption/desorption batch study (OECD 106):

Results for five different soils:
Koc (mL/g) = 18.4, 19.4, 10.3, 10.4, 13.6. Mean value (n = 5) for Koc: 14.42
log Koc = 1.26, 1.29, 1.01, 1.02, 1.13. Mean value (n = 5) for log Koc = 1.142.

Key value for chemical safety assessment

Koc at 20 °C:
14.42

Additional information

[LogKoc: 1.142]