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Environmental fate & pathways

Adsorption / desorption

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Administrative data

Endpoint:
adsorption / desorption, other
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-06-19 to 2017-09-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report date:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.18 (Adsorption / Desorption Using a Batch Equilibrium Method)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
batch equilibrium method
Media:
soil/sewage sludge

Test material

Constituent 1
Chemical structure
Reference substance name:
D-Glucitol, 1-deoxy-1-(dimethylamino)-
EC Number:
810-394-3
Cas Number:
76326-99-3
Molecular formula:
C8H19NO5
IUPAC Name:
D-Glucitol, 1-deoxy-1-(dimethylamino)-
Test material form:
other: solution in methanol (liquid)
Details on test material:
Batch Number CFQ43125
Radiochemical purity 99.4%
Specific activity 57 mCi/mmol
Radiochemical concentration 270 µCi/mL; 10.0 MBq/mL
Molecular formula C8H19NO5
Molecular Weight 211.1 g/mol (at this specific activity)
Expiry date Not specified, radiochemical purity was verified to be ≥ 95 %.
Radiolabelling:
yes

Study design

Test temperature:
nominal: 20 ± 2 °C

Batch equilibrium or other method

Analytical monitoring:
yes
Details on sampling:
Test Procedure
Test item:
N,N-Dimethyl-D-[1-14C]glucamine

Test concentrations:
Tier 1: 100.1 µg/L (1 MBq/L), 878 µg/L (8.57 MBq/L), 2402 µg/L (24 MBq/L)
Fresh spikes: 50000 Bq/replicate and 80000 Bq/replicate
Tier 2: 100.1 µg/L (1000000 Bq/L)
Tier 3: 50.0 µg/L (500000 Bq/L), 10.0 µg/L (100000 Bq/L), 5.00 µg/L (50000 Bq/L), 1.00 µg/L (10000 Bq/L)

Stock solutions:
Stock solutions N,N-Dimethyl-D-[1-14C]glucamine in methanol were prepared. 0.1 volume-% of these stock solutions (7 µL for sludge and 10 µL for soils), related to the volume of the aqueous phase (7 mL for sludge and 10 mL for soils) in the soil / sludge suspensions, were used for spiking.

Dispersion treatment:
Agitation

Sample Preparation
Matrix for the adsorption experiments:
The soil / sludge samples were equilibrated by shaking with an appropriate volume (7 mL for sludge and 10 mL for soils) of 0.01 M CaCl2 solution overnight (12 h minimum). Afterwards 0.1 volume-% of the stock solutions, related to the volume of the aqueous phase in the soil / sludge suspensions were added in order to adjust the test concentrations. The distribution of the test item between aqueous phase and soil / sludge was analytically verified by radiometric analysis.

Matrix for the desorption experiments:
Test systems from the adsorption experiments were used for this purpose. After completion of the adsorption experiments the test systems were centrifuged and the supernatant was replaced by fresh 0.01 M CaCl2 solution. Then the test systems were agitated again to investigate the desorption behavior of the test item. The degree of desorption was determined by radiometric analysis.

Replicates:
All samples were prepared in duplicate.
Samples at t0 and for four further sampling points were prepared for the adsorption experiments.
t1 = 1 h
t2 = 2 h
t3 = 3 h
t4 = 4 h
Samples for four sampling points were prepared for desorption kinetic experiments.
t1 = 1 h
t2 = 2 h
t3 = 3 h
t4 = 4 h

For the adsorption and desorption isotherms, the samples were agitated for 4 h. 

Controls and Blanks

CONTROLS
CaCl2-solution was agitated with the matrices followed by separation of the aqueous phase after centrifugation. Then the aqueous phase was fortified acc. to the amended test concentrations and agitated as long as the test item sample with the longest agitation period.

Replicates
Duplicates

BLANK
Blank samples were prepared for all matrices as described for the test item samples but without fortification with the test item. The samples were agitated as long as the samples with the longest agitation period.

Replicates
Duplicates (tier 1), Single (tier 2)

Sample Preparation:

Aqueous phase (LSC)
Appropriate volumes of the aqueous phase were mixed with Ultima Gold XR in a LSC vial followed by analysis via LSC. Exact volumes were documented in the raw data.

Aqueous phase (radio-HPLC, tier 1)
0.1 mL of the sample were measured by radio-HPLC.

Soil extraction - ASE
The soil was extracted by using an accelerated solvent extractor (ASE). After decantation of the aqueous phase, the soil was used for extraction. Each sample was extracted with methanol : HPLC water (50 : 50) + 1 % formic acid. For parameters of the extraction method see below. Extracts were transferred quantitatively into a 50 mL measuring flask and filled up to 45 mL with methanol : HPLC water (50 : 50) + 1 % formic acid. If possible, the samples were extracted twice. Appropriate volumes of the extracts were mixed with Ultima Gold XR in a LSC vial followed by analysis by LSC. For radio-HPLC 0.1 mL of the sample were measured.

Parameters of the ASE method
Preheat: 2 min
Heat: 6 min
Static: 10 min
Flush: 40 % (v/v)
Purge: 60 sec
Cycles: 2
Pressure: 100 bar
Temperature: 125 °C
Solvent: methanol : HPLC water (50 : 50) + 1 % formic acid

Samples for method validation:
Samples were conditioned as described above. The aqueous phases were decanted and filtrated (if necessary). The aqueous phases were spiked with test item at 1 x LOQ level.
Matrix propertiesopen allclose all
Matrix no.:
#1
Matrix type:
other: silty sand
% Clay:
8.6
% Silt:
29.3
% Sand:
62.1
% Org. carbon:
0.412
pH:
5.9
CEC:
4.9 other: mval/100 g
Matrix no.:
#2
Matrix type:
clay loam
% Clay:
25.2
% Silt:
42.3
% Sand:
32.6
% Org. carbon:
1.74
pH:
7.4
CEC:
22 other: mval/100 g
Matrix no.:
#3
Matrix type:
loamy sand
% Clay:
10.2
% Silt:
31.1
% Sand:
58.7
% Org. carbon:
0.916
pH:
7.3
CEC:
10 other: mval/100 g
Matrix no.:
#4
Matrix type:
other: silty sand
% Clay:
4.25
% Silt:
9.5
% Sand:
86.3
% Org. carbon:
0.564
pH:
5.9
CEC:
<= 1.3 other: mval/100 g
Matrix no.:
#5
Matrix type:
loamy sand
% Clay:
8.5
% Silt:
11.3
% Sand:
80.2
% Org. carbon:
1.47
pH:
6.1
CEC:
7.6 other: mval/100 g
Matrix no.:
#6
Matrix type:
other: Dystric Cambisol
% Clay:
17
% Silt:
36.8
% Sand:
46.4
% Org. carbon:
3.01
pH:
6.1
CEC:
18.3 other: mval/100 g
Matrix no.:
#7
Matrix type:
other: Sewage sludge from Hildesheim
% Org. carbon:
40
pH:
6.3
Matrix no.:
#8
Matrix type:
other: Sewage sludge from Hannover
% Org. carbon:
39
pH:
5
Details on matrix:
Reason for the selection
These matrices vary considerably in their sorption relevant physico-chemical properties. Therefore these matrices are suitable for the conduction of the study because all parameters with impact on the adsorption / desorption behaviour of a chemical substance were considered.

Origin of soil / sludge
Landwirtschaftliche Untersuchungs- und Forschungsanstalt (LUFA) Speyer, Obere Langgasse 40, 67346 Speyer, Germany
European Commission, Joint Research Centre, Institute for Reference Materials and Measurements IRMM Retieseweg, B-2440 Geel, Belgium
Sewage treatment plant, Kanalstraße 50, 31137 Hildesheim, Germany
Sewage treatment plant, Dünenweg 20, 30419 Hannover, Germany

Storage at test facility
Eurosoils: Room temperature, in brown glass bottles
Sludge: Room temperature, in closed containers
LUFA soils: Room temperature, in closed containers

Expiry Dates of Matrices:
Matrix Batch Expiry date
LUFA 2.1 F2.1 3414 (tier 2 and 3) 2020-09-01
LUFA 2.2 F2.2 4016 (tier 1, 2 and 3) 2021-10-24
LUFA 2.3 F2.3 4116 (tier 1) 2021-10-24
LUFA 2.4 F2.4 4116 (tier 1) 2021-10-24
LUFA 5M F5M 5015 (tier 1) 2020-12-17
Eurosoil 3 0119 (tier 1),0055 (tier 2 and 3) 2019-07-21, 2022-05-12
Sewage sludge from Hildesheim - 2020-03-03
Sewage sludge from Hannover - 2020-03-19
Details on test conditions:
CaCl2-solution Demineralized water was used to prepare the CaCl2-solution (0.01 M).

Matrix / Solution ratio The highest technically feasibly matrix / solution ratios were used
Soils: 1:1
Sludge: 1:7

Agitation By horizontal shaker and overhead shaker
Frequency was adjusted to avoid sedimentation of soil particles during treatment.

Test temperature The temperature was in the range of 20 ± 2 °C during the course of the study.

Results and discussion

Adsorption coefficientopen allclose all
Key result
Sample No.:
#1
Type:
Kd
Value:
0.12 L/kg
pH:
5.2
Temp.:
20 °C
Matrix:
LUFA 2.1 matrix/solution ratio 1:1
% Org. carbon:
0.564
Key result
Sample No.:
#1
Type:
Koc
Value:
21.3 L/kg
pH:
5.2
Temp.:
20 °C
Matrix:
LUFA 2.1 matrix/solution ratio 1:1
% Org. carbon:
0.564
Key result
Sample No.:
#2
Type:
Kd
Value:
0.831 L/kg
pH:
6.2
Temp.:
20 °C
Matrix:
LUFA 2.2 matrix/solution ratio 1:1
% Org. carbon:
1.47
Key result
Sample No.:
#2
Type:
Koc
Value:
56.5 L/kg
pH:
6.2
Temp.:
20 °C
Matrix:
LUFA 2.2 matrix/solution ratio 1:1
% Org. carbon:
1.47
Key result
Sample No.:
#3
Type:
Kd
Value:
0.731 L/kg
pH:
5.6
Temp.:
20 °C
Matrix:
Eurosoil 3 Matrix/solution ratio 1:1
% Org. carbon:
3.01
Key result
Sample No.:
#3
Type:
Koc
Value:
24.3
pH:
5.6
Temp.:
20 °C
Matrix:
Eurosoil 3 matrix/solution ratio 1:1
% Org. carbon:
3.01
Key result
Sample No.:
#2
Type:
other: Kdes
Value:
7.78 L/kg
pH:
6.2
Temp.:
20 °C
Matrix:
LUFA 2.2 matrix/solution ratio 1:1
% Org. carbon:
1.47
Key result
Sample No.:
#3
Type:
other: Kdes
Value:
24.5
pH:
5.6
Temp.:
20 °C
Matrix:
Eurosoil 3 matrix/solution ratio 1:1
% Org. carbon:
3.01

Results: Batch equilibrium or other method

Adsorption and desorption constants:
Freundlich Adsorption Coefficients KFads and KFOC and Regression Coefficients 1/n for N,N-Dimethyl-D-[1-14C]glucamine in Different Matrices
Equilibration time [h]: 4 for soils and 48 for sludges
Nominal application concentration [µq/L]: 100.1, 50.0, 10.0, 5.00, 1.00

Parameter LUFA 2.1 LUFA 2.2 Eurosoil 3
Matrix / Solution Ratio 1:1 1:1 1:1
Organic Carbon [%] 0.564 1.47 3.01
R2 0.7944 0.9843 0.9843
1/n 0.509 0.877 0.816
KFAds [µg1-1/n(mL)1/ng-1] 0.0162 0.399 0.338
KFOC [µg1-1/n(mL)1/ng-1] 2.88 27.2 11.2
Mass balance (%) at end of adsorption phaseopen allclose all
Sample no.:
#1
Duration:
4 h
% Adsorption:
11
Remarks on result:
other:
Remarks:
LUFA 2.1 matrix/solution ratio 1:1
Sample no.:
#2
Duration:
2 h
% Adsorption:
45
Remarks on result:
other:
Remarks:
LUFA 2.2 matrix/solution ratio 1:1
Sample no.:
#3
Duration:
4 h
% Adsorption:
42
Remarks on result:
other:
Remarks:
Eurosoil 3 matrix/solution ratio 1:1
Mass balance (%) at end of desorption phaseopen allclose all
Sample no.:
#1
Duration:
4 h
% Desorption:
12
Remarks on result:
other:
Remarks:
LUFA 2.2 matrix/solution ratio 1:1
Sample no.:
#2
Duration:
4 h
% Desorption:
4
Remarks on result:
other:
Remarks:
Eurosoil 3 matrix/solution ratio 1:1

Any other information on results incl. tables

Matrix Dry Weights

The matrix dry weight of each type used in tier 2 and 3 was determined at least in duplicates after drying at 105 °C for at least three hours.

 

Matrix Dry Weights

Mean values (n = 2 for LUFA soils, n = 3 for Eurosoil 3 and sludges)

 

Matrices

LUFA 2.1

LUFA 2.2

Eurosoil 31)

Sludge
Hildesheim2)

Sludge
Hannover2)

matrix dry weight [%]

98.1

98.8

97.7

94.1

94.8

1)        determined for batch number 102;value cited from a separate study (study ID 160706AD/CAD17245)

2)        value cited from a separate study (study ID 160406RD/CAD17144)

pH Values

The pH of the aqueous phase was measured once before and after contact with the matrix and after addition of the test item in the test concentration with the highest test item loading.

pH Values of the Aqueous Media

Matrix / solution ratio 1:1 (soils) and 1:7 (sludges)

 

Soils

LUFA 2.1

LUFA 2.2

Eurosoil 3

Sludge
Hildesheim

Sludge
Hannover

0.01 M CaCl2

6.1

after soil contact

5.9

6.1

6.1

6.3

5.0

after addition of the test item

5.2

6.2

5.6

5.0

4.9

Tier 1–Fresh Spikes

Soil samples were conditioned for at least 12 h, centrifuged and decanted. The soil was spiked with test item and extracted once with ASE . These extracts were analysed by radio-HPLC.

Tier 2 and 3 were conducted with LUFA 2.1, LUFA 2.2 and Eurosoil 3 due to the lower recoveries in the other soils.

 

Tier 1– Fresh Spikes

Extraction medium: methanol : HPLC water (50:50) + 1 % formic acid

n = 1

Matrix

N,N-Dimethyl-D-[1-14C]glucamine

nominal Activity

[Bq]

radio-HPLC purity

[%]

Activity

[Bq]

Recovery to nominal

[%]

LUFA 2.1

50000

97

54030

108

LUFA 2.2

80000

94

73050

91

LUFA 2.3

50000

81

42113

84

LUFA 2.4

80000

53

33563

42

LUFA 5M

50000

59

26925

54

Eurosoil 3

50000

93

36743

73

Sludge Hildesheim

80000

100

70860

89

Sludge Hannover

50000

100

48473

97

Activity                        = measured radioactivity ofN,N-Dimethyl-D-[1-14C]glucamineinthe test item with radio-HPLC, dilution factor taken into account

Tier 1– Mass Balance

The mass balance was calculated from the measured amounts of the test item in the aqueous phase, the matrix extracts and oxidized extracted matrices. Extraction of the test vessel surfaces was done with 5 mL methanol (time: 15 min, shaker: 175 rpm) for two soils and one sludge. Adsorption of the test item on test vessel surfaces did not occur. Matrix samples after extraction (0.6 g for soils and 0.4 g for sludge) were combusted using a sample oxidizer.The mass balances in all matrices were from 106 to 113 %.

 

Mass Balance

n = 1 (2 for sludge Hannover)

Nominal activity (0 h):                         120000 Bq



 

Matrix

 

LUFA 2.1

LUFA 2.2

Eurosoil 3

Sludge Hildesheim

Sludge Hannover

Sampling [h]

4

24

Recovery rate

aqueous phase
[%]

97

65

70

105

104

solid phase1)
[%]

10

37

41

1

2

oxidizer
[%]

1

4

2

6

3

Mass Balance
[%]

108

106

113

112

109

1)           ASE Extraction with methanol : HPLC water (50:50) + 1 % formic acid

Tier 2–Adsorption Kinetics

The following table shows the amount of test item measured in the aqueous phase and based on this value the calculated amount adsorbed to the solid matrix (indirect method) was derived. The percentage of adsorption, the distribution coefficientsKdand the corresponding organic carbon normalized distribution coefficientsKOCwere calculated by considering the values obtained for sampling points 1 to 4 h (LUFA 2.1), 1 and 2 h (LUFA 2.2) and 4 h (Eurosoil 3).

 

Equilibrium Time, Measured Amounts in Aqueous Phase, Calculated Amount for Solid Matrices, Percent of Adsorption and Distribution CoefficientsKdandKOC

Applied test item concentration: 100.1 µg/L, n = 2
equilibration time: 4 h (LUFA 2.1 and Eurosoil 3), 2 h (LUFA 2.2)

Matrix

mmatrix
[g]

Loss of mass [%]

Vaq
[mL]

madsaq(eq)

[µg]

madss(eq)

[µg]

Kd

[mL/g]

KOC

[mL/g]

Adsorption

[%]

LUFA 2.1

9.81

-

10

0.895

0.106

0.120

21.3

11

LUFA 2.2

9.88

0.550

0.451

0.831

56.5

45

Eurosoil 3

4.89

5

0.292

0.208

0.731

24.3

42

mmatrix              = used amount of matrix (dry weight), loss of mass taken into account for sludges

Loss of mass  = Loss of matrix mass after/during agitation for sludges

Vaq                   = used volume of aqueous phase

madsaq              = amount of test item in the aqueous phase at equilibrium

madss                 = amount of test item in the matrix at equilibrium

Tier 3– Desorption Kinetics

The desorption behavior of the test item was determined after 4 h adsorption and a desorption time of 4 h. The following table show the desorption coefficientsKdes.

Percent of Desorption and Desorption CoefficientKdes 

Applied test item concentration: 100.1 µg/L

Matrix

mmatrix[g]

Vaq[mL]

mdesaq(eq) [µg]

madss(eq) [µg]

Kdes[mL/g]

Desorption [%]

LUFA 2.2

9.88

10

0.363

0.0472

7.78

12

Eurosoil 3

4.89

5

0.200

0.00835

24.5

4

mmatrix              = used amount of matrix (dry weight)

Vaq                  = used volume of aqueous phase

mdesaq               = amount test item measured in the aqueous phase after desorption step (without pore water)

madss                = amount of test item adsorbed to matrix at equilibrium

Tier 3– Adsorption Isotherms

The adsorption isotherms were determined with concentrations of 1.00 µg/L, 5.00 µg/L, 10.0 µg/L, 50.0 µg/L and 100.1 µg/L after an adsorption phase of 4 h for soils and 48 h for sludges.Table15shows the Freundlich adsorption coefficientKadsFand the organic carbon normalized Freundlich adsorption coefficientKOCF.For sludges no adsorption in matrix samples could be determined and no endpoints could be calculated.

 

Freundlich Adsorption Isotherms

Applied test item concentrations: 100.1, 50.0, 10.0, 5.00, 1.00 µg/L

Matrix

mmatrix[g]

Vaq[mL]

R2

1/n

KadsF

KOCF

LUFA 2.1

9.81

10

0.7944

0.509

0.0162

2.88

LUFA 2.2

9.88

0.9843

0.877

0.399

27.2

Eurosoil 3

4.89

5

0.9843

0.816

0.338

11.2

mmatrix = used amount of matrix (dry weight) [g]

Vaq      = used volume of aqueous phase

n         = regression constant

%OC   = percentage of organic carbon content in the matrix

KadsF    = Freundlich adsorption coefficient [µg1-1/n(mL)1/ng-1]

KOCF     = Freundlich adsorption coefficient normalized to content of organic carbon [µg1-1/n(mL)1/ng-1]

Applicant's summary and conclusion

Executive summary:

The adsorption / desorption behavior of the test item N,N-Dimethyl-D-[1-14C]glucamine was investigated in six different soils and returned sludge from two sewage treatment plants according to OECD guideline 106 and council regulation (EC) C.18 from 2017‑06‑19 to 2017-09-02 at Noack Laboratorien GmbH, 31157 Sarstedt, Germany.

The relevant characteristics of the used matrices and their representative values are summarized in the table below. The soils given in the first were not used for the further experiments inTier 2 and Tier 3 due to a limited chemical stability (< 90%) of the test item in these soils when samples of the aqueous phase and samples of the matrix extracts were analysed by radio-HPLC.

Relevant Characteristics of Test Matrices only used in Tier 1

Parameters

LUFA 2.3

LUFA 2.4

LUFA 5M

Soil Type (LUFA Soils), acc. to German DIN

Silty sand

Clayey loam

Loamy sand

Batch

F2.3 4116

F2.4 4116

F5M 5015

pH (0.01 M CaCl2)2)

5.9

7.4

7.3

Organic Carbon [%]1)

0.412

1.74

0.916

Clay (<0.002 mm)[%]1)

8.6

25.2

10.2

Silt (0.002-0.063 mm)[%]1)

29.3

42.3

31.1

Sand (0.063-2 mm)[%]1)

62.1

32.6

58.7

Cation Exchange Capacity [mval/100g]1)

4.9

22

10

1)     determined atAgrolab Agrar und Umwelt GmbH(non-GLP)

2)     obtained from LUFA Speyer

 


 

Relevant Characteristics of Test Matrices used in Tier 1, Tier 2 and Tier 3

 

Parameters

 

LUFA 2.11)

LUFA 2.21)

Eurosoil 3

Sewage sludge from Hildesheim

Sewage sludge from Hannover

Soil Type (LUFA Soils), acc. to German DIN,FAO soil unit (Eurosoil)

Silty sand

Loamy sand

Dystric Cambisol

n.a.

n.a.

Batch

F2.1 3414

F2.2 4016

01194), 0055

-

-

pH (0.01 M CaCl2)2)

5.9

6.1

6.1

6.3

5.0

Organic Carbon [%]

0.5646)

1.471)

3.017)

40

39

Clay (<0.002 mm)[%]

4.251)

8.51)

17.05)

n.a.

n.a.

Silt (0.002-0.063 mm)[%]

9.501)

11.31)

36.85)

n.a.

n.a.

Sand (0.063-2 mm)[%]

86.31)

80.21)

46.45)

n.a.

n.a.

Cation Exchange Capacity [mval/100g]

≤1.31)

7.61)

18.35)

n.a.

n.a.

1)     determined atAgrolab Agrar und Umwelt GmbH(non-GLP)

2)  determined during the course of the study (tier 2)

3)     obtained from LUFA Speyer

4)  only used fortier 1

5)      data taken from Gawlik and Muntau, Eurosoils II Laboratory and Reference Materials for Soil-related Studies, Environment Institute 1999

6)      mean value of two replicates

7)      actual certified value on the corresponding soil certificate

 

Tier 1 

Experiments during Tier 1 were performed with the soils LUFA 2.1, 2.2, 2.3, 2.4, 5M and Eurosoil 3 as well as returned sludge from two sewage treatment plants Hildesheim and Hannover. Suitable matrix / solution ratios, the required time for the adsorption experiments and the parental mass balance (chemical stability) were investigated in all matrices by analyzing samples of the aqueous phase and soil extracts with LSC and radio-HPLC. The mass balances determined by LSC were > 90% in all matrices. No adsorption of the test item on test vessel surfaces took place. Decreased chemical stability of the test item was observed in extracts of samples from LUFA 2.3 (67%) and LUFA 2.4 (18%) already after 4h of agitation. Radio-HPLC chromatograms showed additional peaks in the void time of the chromatographic system. Additionally, spiked soil samples were analysed to figure out if these void time peaks are also present in soil samples when processed immediately after spiking. These experiments showed also additional peaks in samples obtained from soils LUFA 2.3, 2.4 and 5M. For this reason, these soils were not further used for the subsequent experiments inTier 2 and Tier 3. The agitation time was limited to four hours in the further experiments for Eurosoil 3, LUFA 2.1 and 2.2 to maximise the chemical stability according tothe opinion published by the scientific committee on plants and methods for the determination of the organic carbon adsorption coefficient (KOC) for a plant protection product active substance (SCP/KOC/002).This opinion describes to limit the agitation with the aim to maximize the chemical stability of the test item as much as possible.

The adsorption was only low (approx. 10%) even with a soil / solution ratio of 1:1 in the soil LUFA 2.1. The test item adsorption was > 20% in the soils LUFA 2.2 and Eurosoil 3 with a soil/solution ratio of 1:1. The further experiments in Tier 2 and Tier 3 with the soils were performed with an agitation of 4 h and soil /solution ratios of 1:1 based on these results.

No test item adsorption was observed in experiments with returned sludge form sewage treatment plants Hildesheim and Hannover when the highest technical possible matrix / solution ratio of 1:7 was used. For this reason, no endpoints to describe the adsorption and desorption behaviour in these matrices could be derived.

 

Tier 2 

The adsorption kinetic experiments (single concentration of 100 µg/L) indicated that an agitation time of 4 h is sufficient to obtain the adsorption equilibrium. The decline of the test item in the aqueous phase was measured by LSC to determine the % of adsorption (indirect method). A distribution coefficient Kd of 0.120 mL/g was obtained for the experiments in the soil LUFA 2.1. An adsorption of 11% was obtained in equilibrium. As a result, the desorption behaviour was not investigated in Tier 3 with this soil. The decline of the test item in the aqueous phase or the increase in the soil by adsorption was too low and therefore inside the range of the analytical error of the analytical methods for the aqueous phase and soil. The adsorption isotherms were determined by the direct method (analysis of soil and aqueous phase) in Tier 3 according to the guideline because the product of Kd and soil / solution ratio of 1:1 was < 0.3.The corresponding distribution coefficients Kd for LUFA 2.2 (0.831 mL/g) and Eurosoil 3 (0.731 mL/g) were > 0.3 (product of Kd and soil / solution ratio of 1:1). In consequence, the indirect method could be further used for the experiments in Tier 3.

 

Tier 3 

The adsorption isotherms were determined with five concentrations from 1 to 100 µg/L.Coefficients of variation R2 from 0.7944 to 0.9843 were obtained for the adsorption isotherms. The Freundlich adsorption constants 1/n ranged from 0.509 to 0.877. Freundlich adsorption coefficients KFads from 0.0162 to 0.399 [µg1-1/n(mL)1/ng-1] and organic carbon normalized Freundlich adsorption coefficients KFOC from 2.88 to 27.2 [µg1-1/n(mL)1/ng-1] resulted.

 

Freundlich Adsorption Coefficients KFads and KFOCand Regression Coefficients 1/n for N,N-Dimethyl-D-[1-14C]glucamine in Different Matrices

Equilibration time [h]: 4 for soils and 48 for sludges

Nominal application concentration [µq/L]:         100.1, 50.0, 10.0, 5.00, 1.00

Parameter

LUFA 2.1

LUFA 2.2

Eurosoil 3

Matrix / Solution Ratio

1:1

Organic Carbon [%]

0.564

1.47

3.01

R2

0.7944

0.9843

0.9843

1/n

0.509

0.877

0.816

KFAds[µg1-1/n(mL)1/ng-1]

0.0162

0.399

0.338

KFOC[µg1-1/n(mL)1/ng-1]

2.88

27.2

11.2

 

The desorption kinetic experiments in Eurosoil 3 showed only a desorption < 5%. No desorption isotherms were determined for Eurosoil 3 because no accurate determination is possible. The increase of the test item in the aqueous phase or the decrease in the soil by desorption was too low and therefore inside the range of the analytical error of the analytical methods for the aqueous phase and soil. For LUFA 2.2, a desorption of approx. 10% was calculated and desorption isotherms were additionally determined after an adsorption time for 4 h.

Freundlich Desorption Coefficients KFDes and Regression Coefficients 1/n for N,N-Dimethyl-D-[1-14C]glucamine in Different Matrices

Nominal application concentration [µq/L]:         100.1, 50.0, 10.0, 5.00, 1.00

Parameter

LUFA 2.2

Soil / Solution Ratio

1:1

Organic Carbon [%]

1.47

R2

0.9183

1/n

0.741

KFDes[µg1-1/n(mL)1/ng-1]

1.58

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