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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
2000
Deviations:
not specified
GLP compliance:
no
Remarks:
Published study from a peer-reviewed journal.
Type of method:
batch equilibrium method
Media:
sediment
Radiolabelling:
no
Test temperature:
21 ± 2 °C
Analytical monitoring:
yes
Remarks:
The concentration of the UV filters sorbed onto the sediments was not detected but instead calculated from the aqueous concentration based on mass balance.
Details on sampling:
- Concentrations: All test concentrations (2, 5, 10, 25, 50, 100 μg/L) and the control.
- Sampling interval: The concentrations of the UV filters in the aqueous phase at equilibrium for both sorption and desorption experiments were measured after certain sample preparation steps.
- Sample storage before analysis: Samples were extracted after sampling and eluates were stored at −20 °C until further analysis.
Matrix no.:
#1
Matrix type:
other: Yangtze River
% Clay:
5.04
% Silt:
13.17
% Sand:
81.79
% Org. carbon:
0.53
pH:
7.83
CEC:
13.06 not specified
Matrix no.:
#2
Matrix type:
other: Qinhuai River
% Clay:
16.98
% Silt:
23.7
% Sand:
59.31
% Org. carbon:
1.1
pH:
7.47
CEC:
14.98 not specified
Matrix no.:
#3
Matrix type:
other: Xuanwu Lake
% Clay:
13.52
% Silt:
48.99
% Sand:
37.48
% Org. carbon:
1.74
pH:
7.52
CEC:
22.45 not specified
Matrix no.:
#4
Matrix type:
other: Mochou Lake
% Clay:
8.86
% Silt:
57.01
% Sand:
34.13
% Org. carbon:
2.61
pH:
7.3
CEC:
22.45 not specified
Details on matrix:
- Details on collection (e.g. location, depth, contamination history, procedure: Natural water and sediment samples were collected from four main urban aqueous systems in the city of Nanjing, China, namely Yangtze River, Qinhuai River, Xuanwu Lake, and Mochou Lake. Sediments were taken from the surface layer (≤20 cm in depth) by a Van Veen grab sampler (25 ×40× 30 cm). At each sampling point, water samples were collected at three different depths from the surface to the bottom, and then mixed together.
- Storage conditions: All sediments were freeze-dried, gently ground to pass through a sieve (2 mm), and then stored at 4 °C. Water samples were filtered through 0.45-μm glass fiber filters and kept cool (4 °C) until their use within 3 days.
- Electrical conductivity: Yangtze River 589 dS/cm; Qinhuai River 592 dS/cm; Xuanwu Lake 570 dS/cm; Mochou Lake 561 dS/cm
Details on test conditions:
TEST SYSTEM
- Type, size and further details on reaction vessel: 250-mL Erlenmeyer flasks
- Water filtered: No
- Amount of soil/sediment/sludge and water per treatment: 50 mL of an autoclaved CaCl2 solution and 1 g of autoclaved sediment
- Soil/sediment/sludge-water ratio: Sediment/solution ratio of 1:50
- Number of reaction vessels/concentration: 2
- Measuring equipment: UPLC-ESI
- Test performed in open system: Not reported
- Method of preparation of test solution: Freeze-dried and sieved sediments were autoclaved for 20 min at 121 °C and 1.3 bar before use. The sediments were equilibrated by shaking with 0.01 M CaCl2 solutions overnight at 21 ± 2 °C before the day of the experiment. Subsequently, 25 μL of the UV filter stock solution was added into the aqueous phase, and the methanol added is less than 0.1 % (v/v) of the total solution
volume.
- Are the residues from the adsorption phase used for desorption: Yes
- Other: 8 h equilibration time for adsorption and desorption experiments.
Key result
Type:
log Koc
Value:
3.7 dimensionless
Temp.:
21 °C
Matrix:
Natural sediment
% Org. carbon:
0.53 - 2.61
Remarks on result:
other: Mean log Koc for the four natural sediments. log Koc standard deviation: 0.06
Sample No.:
#1
Type:
log Koc
Value:
3.77 dimensionless
Temp.:
21 °C
Matrix:
Yangtze River
% Org. carbon:
0.53
Remarks on result:
other: log Koc standard deviation: 0.14
Sample No.:
#2
Type:
log Koc
Value:
3.73 dimensionless
Temp.:
21 °C
Matrix:
Qinhuai River
% Org. carbon:
1.1
Remarks on result:
other: log Koc standard deviation: 0.17
Sample No.:
#3
Type:
log Koc
Value:
3.63 dimensionless
Temp.:
21 °C
Matrix:
Xuanwu Lake
% Org. carbon:
1.74
Remarks on result:
other: log Koc standard deviation: 0.11
Sample No.:
#4
Type:
log Koc
Value:
3.65 dimensionless
Temp.:
21 °C
Matrix:
Mochou Lake
% Org. carbon:
2.61
Remarks on result:
other: log Koc standard deviation: 0.23
Sample No.:
#1
Type:
Kd
Value:
31.36 dimensionless
Temp.:
21 °C
Matrix:
Yangtze River
% Org. carbon:
0.53
Remarks on result:
other: Kd standard deviation: 7.80
Sample No.:
#2
Type:
Kd
Value:
58.87 dimensionless
Temp.:
21 °C
Matrix:
Qinhuai River
% Org. carbon:
1.1
Remarks on result:
other: Kd standard deviation: 8.14
Sample No.:
#3
Type:
Kd
Value:
75.26 dimensionless
Temp.:
21 °C
Matrix:
Xuanwu Lake
% Org. carbon:
1.74
Remarks on result:
other: Kd standard deviation: 10.32
Sample No.:
#4
Type:
Kd
Value:
116.13 dimensionless
Temp.:
21 °C
Matrix:
Mochou Lake
% Org. carbon:
2.61
Remarks on result:
other: Kd standard deviation: 16.40
Recovery of test material:
The loss in the control group was 4.82 ± 0.09%. The recovery of the initial concentration was over 80% after an equilibration time of 8 h if corrected by method recovery.
Concentration of test substance at end of desorption equilibration period:
Only 13 to 40% of the sorbed concentration desorbed.
Transformation products:
not measured
Details on results (Batch equilibrium method):
PRELIMINARY TEST
- Weighed soil: 1 g
- Volume of CaCl2 solution: 50 mL
- Initial test substance concentration: 100 μg/L
Statistics:
Standard deviations were calculated for Kd and log Koc values.

Table 1. Freundlich parameters

 Sample  Kf  n  R2
 #1  22.74 ± 1.67  1.13 ± 0.09 0.983 
 #2  52.78 ± 1.58  1.05 ± 0.06 0.994 
 #3  77.18 ± 2.18  0.97 ± 0.02 0.977 
 #4  122.55 ± 4.25  0.96 ± 0.04 0.991 

The Freundlich equation is Cs = Kf x (Cw)^n where Cs (μg/g) and Cw (μg/L) are the sorbed and the aqueous concentrations of the UV filters respectively, while Kf is the Freundlich affinity constant giving the capacity of sorption, and n is a linearity factor that describes the nonlinearity of sorption. The distribution coefficient (Kd =Cs/Cw) was determined by the mean value from a set of six tested concentration levels. The values of the organic carbon-normalised distribution coefficients (Koc) were calculated by Koc=Kd/foc.

Validity criteria fulfilled:
not specified
Conclusions:
The mean log Koc was determined to be 3.70 ± 0.06.
Executive summary:

The adsorption/desorption of the test material was determined according to OECD Guideline 106 using natural sediment. Sediment was collected from Yangtze River, Qinhuai River, Xuanwu Lake and Mochou Lake, in China. Sediments were exposed to nominal concentrations of 2, 5, 10, 25, 50, 100 μg/L of the test item in CaCl2 solution and equilibrated for 8 hours at 21 ± 2 °C in the adsorption experiment. Subsequently, the test solution was replaced with fresh CaCl2 solution and the test system was equilibrated for another 8 hours in the desorption experiment. The Kd values were determined to be 31.36 ± 7.80, 58.87 ± 8.14, 75.26 ± 10.32 and 116.13 ± 16.40 for sediment from the Yangtze River, Qinhuai River, Xuanwu Lake and Mochou Lake, respectively, and the log Koc values were 3.77 ± 0.14, 3.73 ± 0.17, 3.63 ± 0.11 and 3.65 ± 0.23, respectively. The mean log Koc of the four natural sediments was determined to be 3.70 ± 0.06. This study is reliable with restrictions (Klimisch 2) as it was conducted according to guideline, however there were minor limitations in reporting.

Description of key information

The mean log Koc was determined to be 3.70 ± 0.06 at 21°C.

Key value for chemical safety assessment

Koc at 20 °C:
5 011.87

Additional information

The adsorption/desorption of the test material was determined according to OECD Guideline 106 using natural sediment (2016). Sediment was collected from Yangtze River, Qinhuai River, Xuanwu Lake and Mochou Lake, in China. Sediments were exposed to nominal concentrations of 2, 5, 10, 25, 50, 100 μg/L of the test item in CaCl2 solution and equilibrated for 8 hours at 21 ± 2 °C in the adsorption experiment. Subsequently, the test solution was replaced with fresh CaCl2 solution and the test system was equilibrated for another 8 hours in the desorption experiment. The Kd values were determined to be 31.36 ± 7.80, 58.87 ± 8.14, 75.26 ± 10.32 and 116.13 ± 16.40 for sediment from the Yangtze River, Qinhuai River, Xuanwu Lake and Mochou Lake, respectively, and the log Koc values were 3.77 ± 0.14, 3.73 ± 0.17, 3.63 ± 0.11 and 3.65 ± 0.23, respectively. The mean log Koc of the four natural sediments was determined to be 3.70 ± 0.06. This study is reliable with restrictions (Klimisch 2) as it was conducted according to guideline, however there were minor limitations in reporting.

[LogKoc: 3.7]

[LogKoc: 3.7]

[LogKoc: 3.7]