Cyclopropanecarboxylic acid, 3-[(1Z)-2-chloro-3,3,3-trifluoro-1-propen-1-yl]-2,2-dimethyl-, (1R,3R)-rel-

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2004-10-11 to 2005-06-23

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Deviations:

yes

Remarks:

Only three soils investigated; centrifugation shorter and at lower force than recommended

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 1°C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: preliminary test: 0.55 mg/L; advanced test: 2.024, 1.017, 0.413, 0.099 and 0.020 mg/L
- Sampling interval: preliminary test: 2, 5, 24, and 48 hours; advanced test: 24 hours
- Sample storage before analysis: none

Details on matrix:

COLLECTION AND STORAGE: #1: soil I (18 Acres); #2: soil II (Gartenacker); #3: soil III (Marsillargues)
- History of the field sites: none of the soils were fertilised or treated with pesticides for at least 12 months prior to sampling
- Geographic location: soil I: Jealotts Hill Research Station (Bracknell, Berkshire/UK, 51°26' N, 0°42' W); soil II: Les Barges (Vouvry VS, Switzerland, 46°20' N, 6°53' E); soil III: near F-34590 Marsillargues (France, 43°39' N, 4°10' E)
- Collection procedures: collected from different agricultural areas; sampling and handling performed under consideration of ISO 10381-6
- Sampling depth (cm): I: top 5-10 cm; II: top 20 cm; III: top 5-15 cm
- Storage conditions: not reported in detail, according to ISO 10381-6
- Storage length: 13-20 days
- Soil preparation: sieved to 2 mm, air-dried, equilibrated with 0.01 M CaCl2 for at least 48 h

PROPERTIES
- Soil texture: I: sandy clay loam; II: loam; III: loam
- % sand: soil I: 50.35%; II: 44.64; III: 30.13%
- % silt: soil I: 27.15%; II: 44.73%; III: 49.84%
- % clay: soil I: 22.50%; II: 10.63%; III: 20.03%
- Horizon: agricultural soil, top layer
- Soil taxonomic classification: I: sandy clay loam; II: loam; III: loam
- Soil classification system: USDA
- Soil series (batch): 09/04
- pH (CaCl2): soil I: 5.38; II: 7.13; III: 7.61
- Organic carbon (%, g/100g): soil I: 3.23; II: 2.50; III: 0.58
- CEC (mmol/kg soil): soiI I: 21.3; II: 13.5; III: 9.11
- Nitrogen content (g/100g soil): soil I: 0.29 ; II: 0.34; III: 0.11
- Organic matter (g/100g soil): soil I: 5.6; II: 4.3; III: 1.0
- C/N ratio: soil I: 11.1; II: 7.3; III: 5.3
- Carbonate as CaCO3 (g/100g soil): soil I: 0.3; II: 9.2; III: 42.5
- Extractable Cations (Ca, Mg, Na, K, H) (MEQ/100 g): not reported
- Moisture (after heating at 120°C to weight constancy): determined in three aliquots per soil, but not reported; dry weight used in calculations
- Bulk density (g/cm3): not reported
- Biomass (e.g. in mg microbial C/100 mg, CFU or other): not reported

Details on test conditions:

TEST CONDITIONS
- Buffer: 0.01 N CaCl2, not buffered
- pH: aqueous phase before contact with soils: 6.19; after contact with soils: 4.45 (soil I), 6.05 (soil II), 7.50 (soil III)
- Suspended solids concentration: preliminary test: 1 or 5 g soil / 25 mL 0.01 M CaCl2 solution, or 10 g soil / 10 mL 0.01 M CaCI2 solution; advanced test: 1 g soil / 25 mL 0.01 M CaCl2 solution
- other: air-dried soil samples pre-equilibrated with aqueous phase (about 90% of targeted volume) by shaking >= 48 hours prior to application

TEST SYSTEM
- Type, size and further details on reaction vessel: sealed Teflon centrifuge tubes, shaken horizontally (about 150 strokes / minute) in the dark
- Water filtered: no
- Amount of soil and water per treatment: preliminary test: 1 or 5 g soil / 25 mL, or 10 g soil / 10 mL; advanced test: 1 g soil / 25 mL
- Soil/sediment/sludge-water ratio (if simulation test): preliminary test: 1:25, 1:5, 1:1; advanced test: 1:1
- Number of reaction vessels/concentration: 2
- Measuring equipment: LSC, HPLC
- Test performed in closed vessels due to significant volatility of test substance: no (test item non-volatile)
- Test performed in open system: yes
- Method of preparation of test solution: Prliminary test: 110 microliter of the radiolabelled test item (in acetonitrile) evaporated under nitrogen in a volumetric flask, redissolved in 0.01 M CaCI2 (by ultrasonication), and made-up to 50 mL; amount of 14C-labelled test item determined by LSC to be 40'680'000 dpm or 0.280 mg per 50 mL application solution (specific radioactivity: 2.42 MBq/mg). Advanced test: 220 microliter evaporated and redissolved in 25 mL; amount 81'930'000 dpm or 0.56 mg per 25 mL application solution I; thereof, serial dilutions were prepared to yield application solutions II-V.
- Application of test solution: to surface of supernatant, with subsequent shaking of the test tube
- Are the residues from the adsorption phase used for desorption: yes

Sample No.:

#1

Duration:

48 h

Initial conc. measured:

13.8 mg/kg soil d.w.

pH:

4.45

Temp.:

20 °C

Remarks:

Temp.: 20 ± 1 °C

Sample No.:

#1

Duration:

48 h

Initial conc. measured:

2.8 mg/kg soil d.w.

pH:

4.45

Temp.:

20 °C

Remarks:

Temp.: 20 ± 1 °C

Sample No.:

#1

Duration:

48 h

Initial conc. measured:

0.55 mg/kg soil d.w.

pH:

4.45

Temp.:

20 °C

Remarks:

Temp.: 20 ± 1 °C

Sample No.:

#2

Duration:

48 h

Initial conc. measured:

0.55 mg/kg soil d.w.

pH:

6.05

Temp.:

20 °C

Remarks:

Temp.: 20 ± 1 °C

Sample No.:

#3

Duration:

48 h

Initial conc. measured:

0.55 mg/kg soil d.w.

pH:

7.5

Temp.:

20 °C

Remarks:

Temp.: 20 ± 1 °C

Sample no.:

#1

Duration:

48 h

Conc. of adsorbed test mat.:

1.04 mg/kg soil d.w.

pH:

4.45

Sample no.:

#1

Duration:

48 h

Conc. of adsorbed test mat.:

1.06 mg/kg soil d.w.

pH:

4.45

Sample no.:

#1

Duration:

48 h

Conc. of adsorbed test mat.:

0.43 mg/kg soil d.w.

pH:

4.45

Sample no.:

#2

Duration:

48 h

Conc. of adsorbed test mat.:

0.196 mg/kg soil d.w.

pH:

6.05

Sample no.:

#3

Duration:

48 h

Conc. of adsorbed test mat.:

0.042 mg/kg soil d.w.

pH:

7.5

Computational methods:

- Adsorption and desorption coefficients (Kd): [Kd = m(ads)s (eq) * Vo] / [m(ads)aq (eq) * m(soil) ], with: m(ads)s (eq) = mass of test item adsorbed on soil at equilibrium; Vo = initial volume of aqueous phase; m(ads)aq (eq) = mass of test item in solution at equilibrium; m(soil) = dry mass of soil phase

- Freundlich adsorption coefficient: log C(ads)s (eq) = log KF(ads) + 1/n * log C(ads)aq (eq), with: C(ads)s (eq) = mass concentration of test item adsorbed on soil at equilibrium; KF(ads) = Freundlich adsorption coefficient; 1/n = Freundlich exponent; C(ads)aq (eq) = mass concentration of test item in aqueous phase at equilibrium

- Freundlich desorption coefficient: log C(des)s (eq) = log KF(des) + 1/n * log C(des)aq (eq), with: C(des)s (eq) = mass concentration of test item remaining adsorbed on soil at desorption equilibrium; KF(des) = Freundlich desorption coefficient; 1/n = Freundlich exponent; C(des)aq (eq) = mass concentration of test item in aqueous phase at desorption equilibrium
C(des)s (eq) = [m(ads)s (eq) - m(des)aq (eq)] / m(soil), using:
m(des)aq (eq) = [m(des)m (eq) * Vo / VFr ] – m(A)aq, with m(des)m (eq) =mass of test item determined analytically in aqueous phase at desorption equilibrium; VFr = volume of supernatant taken for test item measurement at desorption equilibrium; m(A)aq = mass of test item left due to incomplete volume replacement

- Slope of Freundlich adsorption/desorption isotherms: slope of the linear regression line for the double logarithmic equation for log C(ads)s (eq)

- Adsorption coefficient per organic carbon (Koc): Koc = Kd / foc, with foc = fraction of organic carbon in soil

- Adsorption coefficient per organic matter (Kfom): Kfom = Kfoc / 1.724

- Regression coefficient of Freundlich equation: regression coefficient for the linear regression of the double logarithmic equation for log C(ads)s (eq)

- Other: Mass balance MB = [ Vrec * C(ads)aq (eq) + m(E) ] * 100 / [ Vo * Co ], with Vrec = volume of supernatant recovered after adsorption equilibrium, m(E) = mass of test item extracted from soil, Co = initial mass concentration of test item in aqueous phase

Key result

Type:

Kd

Remarks:

Soil I: sandy clay loam

Value:

2.969 dimensionless

Temp.:

20 °C

% Org. carbon:

3.23

Remarks on result:

other: Soil pH: 5.38, clay 22.5%, sand 50.35%

Key result

Type:

Koc

Remarks:

Soil I: sandy clay loam

Value:

91.9 dimensionless

Temp.:

20 °C

% Org. carbon:

3.23

Key result

Type:

Kd

Remarks:

Soil II: loam

Value:

0.345 dimensionless

Temp.:

20 °C

% Org. carbon:

2.5

Remarks on result:

other: Soil pH: 7.13, clay 10.63%, sand 44.64%

Key result

Type:

Koc

Remarks:

Soil II: loam

Value:

13.8 dimensionless

Temp.:

20 °C

% Org. carbon:

2.5

Key result

Type:

Kd

Remarks:

Soil III: loam

Value:

0.094 dimensionless

Temp.:

20 °C

% Org. carbon:

0.58

Remarks on result:

other: Soil pH: 7.61, clay 20.03%, sand 30.13%

Key result

Type:

Koc

Remarks:

Soil III: loam

Value:

16.2 dimensionless

Temp.:

20 °C

% Org. carbon:

0.58

Adsorption and desorption constants:

Soil I: 18 Acres, sandy clay loam:
Adsorption / desorption constants KF = 3.011 / 3.417 ; slope 1/n = 1.01 / 1.03 ; regression coefficient r2 = 0.9999 / 0.9962
Soil II: Gartenacker, loam
Adsorption / desorption constants KF = 0.314 / 0.263 ; slope 1/n = 0.95 / 0.92 ; regression coefficient r2 = 0.9954 / 0.9952
Soil III: Marsillargues, loam
Adsorption / desorption constants KF = 0.079 / 0.103 ; slope 1/n = 0.89 / 0.82 ; regression coefficient r2 = 0.9920 / 0.9963
See Table 1

Recovery of test material:

Mass balance in % of radioactivity, after 24 hours of adsorption (advanced test):
Soil / solution ratio 1:1, initial concentration 2.02 mg/L (20.2 microgram), soil extraction with acetonitrile/water (4/1; v/v)
Soil I (sandy clay loam): recovery 92.8 +/- 0.49 %, supernatant 24.9%, extract 64.0%, non-extracted 3.8%
Soil II: (loam): recovery 94.3 +/- 1.34 %, supernatant 74.4%, extract 17.3%, non-extracted 2.6%
Soil III: (loam): recovery 101.4 +/- 1.27 %, supernatant 95.1%, extract 4.6%, non-extracted 1.7%
See Table 2

Concentration of test substance at end of adsorption equilibration period:

Concentrations of test substance at the end of the 24-h adsorption equilibration period:
Concentrations in liquid phase, measured (average of 2):
Soil I: 0.005 – 0.500 microgram/mL
Soil II: 0.014 – 1.589 microgram/mL
Soil II: 0.018 – 1.886 microgram/mL
Concentrations in solid phase, calculated by difference (total applied - concentration in solution):
Soil I: 0.015 – 1.524 microgram/g
Soil II: 0.006 – 0.435 microgram/g
Soil III: 0.002 – 0.139 microgram/g
See Table 3

Concentration of test substance at end of desorption equilibration period:

Concentrations of test substance at the end of the 24-h desorption equilibration period:
Concentrations in liquid phase, measured (average of 2):
Soil I: 0.004 – 0.402 microgram/mL
Soil II: 0.009 – 0.964 microgram/mL
Soil II: 0.008 – 0.844 microgram/mL
Concentrations in solid phase, calculated by difference (total applied - concentration in solution):
Soil I: 0.013 – 1.363 microgram/g
Soil II: 0.004 – 0.249 microgram/g
Soil III: 0.002 – 0.099 microgram/g
See Table 4

Sample no.:

#1

Duration:

24 h

% Adsorption:

>= 74.3 - <= 75.3

Sample no.:

#2

Duration:

24 h

% Adsorption:

>= 21.5 - <= 29.1

Sample no.:

#3

Duration:

24 h

% Adsorption:

>= 6.8 - <= 12.3

Transformation products:

no

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- Sample purity: 99.1 % radiochemical
- Weighed soil: air dried; moisture content determined by drying three aliquots at 120°C to weight constancy
- Volume of CaCl2 solution: 25 and 10 mL
- Initial test substance concentration: 0.55 mg/L
- Analytical test substance concentration in final solution (after adsorption): soil I: 0.51, 0.34, 0.12 mg/L; soil II: 0.36 mg/L; soil III: 0.51 mg/L
- Test material stability during adsorption phase (2 - 48 h): 98.7 - 101.0 %
- Adsorption/desorption kinetics: see Table 5

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase (24 h, 0.020 - 2.024 mg/L): 99.2 - 101.4 %
- Experimental conditions maintained throughout the study: Yes
- Buffer/test substance interactions affecting sorption: test item stable in 0.01 M CaCI2, HPLC purity 98.2% before application, 98.4% after 24 hours (control samples ).
- Further chemical interactions: no adsorption of the test item on the surface of the test vials observed
- Buffer-catalyzed degradation of test substance: none detectable in HPLC
- Anomalies or problems encountered: none

TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount: none detectable in HPLC; radioactivity in test item peak after desorption: supernatant 97.11% (soil I), 100% (soil II), 98.17% (soil III); eluate from soil: 98.85% (soil I), 96.54% (soil II), 98.45% (soil III)

RESIDUES
- Total unidentified radioactivity (range) of applied amount: 0 - 3.5% by HPLC
- Extractable residues, excluding pore water (% of applied amount at end of adsorption period 24 h): 64.0% (soil I), 17.3% (soil II), 4.6% (soil III)
- Non-extractable residues (% of applied amount at end of adsorption period 24 h): 3.8% (soil I), 2.6% (soil II), 1.7% (soil III)

VOLATILIZATION
- none observed

Statistics:

- mean value of duplicate experiments
- linear regression of mean results to linear Freundlich equation (advanced test)
- coefficients of determination (r2) for the linear regression of the linear form of the Freundlich equation

Table 1: Freundlich Parameters after adsorption (soil to solution ratio: 1/1)
Parameter		Soil I: 18 Acres	Soil II: Gartenacker	Soil III: Marsillargues	Mean values
		sandy clay loam	loam	loam
% Organic carbon	%OC	3.23	2.50	0.58
% Organic matter	%OM	5.57	4.31	1.00
pH (after equilibration)		4.45	6.05	7.50
Adsorption
Distribution coefficient	Kd	2.969	0.345	0.094
Adsorption coefficient normalized to organic carbon	Koc	91.9	13.8	16.2	40.6
Freundlich adsorption coefficient	KF	3.011	0.314	0.079
Freundlich ads. coeff. per org. C	KFOC	93	13	14	40
Freundlich ads. coeff. per org. matter	KFOM	54	7	8	23
Freundlich exponent	1/n	1.01	0.95	0.89	0.95
Freundlich regression coefficient	r2	0.9999	0.9954	0.9920
Desorption
Distribution coefficient	Kd	3.124	0.315	0.162
Desorption coefficient normalized to organic carbon	Koc	96.7	12.6	28.0	45.8
Freundlich desorption coefficient	KF,des	3.417	0.263	0.103
Freundlich ads. coeff. per org. C	KFOC,des	106	11	18	45
Freundlich ads. coeff. per org. matter	KFOM,des	61	6	10	26
Freundlich exponent	1/n	1.03	0.92	0.82	0.92
Freundlich regression coefficient	r2	0.9962	0.9952	0.9963

Table 2: Mass balance in % of radioactivity, after 24 hours of adsorption
Soil / solution ratio 1:1, initial concentration 2.02 mg/L (20.2 microgram)
	% in	% in	% in	% in	% in	%	standard
Soil	total aq.	pore	total	extract with-	residue	recovery	deviation
	phase	water	extract	out pore water	(combustion)
I: sandy clay loam	24.9	10.8	74.8	64.0	3.8	92.8	0.49
II: loam	74.4	33.2	50.5	17.3	2.6	94.3	1.34
III: loam	95.1	32.6	37.2	4.6	1.7	101.4	1.27

Table 3: Advanced test:
Distribution of test item between aqueous and soil phase after 24 h adsorption
Soil I: sandy clay loam; soil/solution ratio 1/1
Concentration Ci [microgram/mL]	2.024	1.017	0.413	0.099	0.020
Mean mass adsorbed m(ads)s [microgram]	15.24	7.56	3.09	0.74	0.15
Mean mass adsorbed [% of applied]	75.3%	74.4%	74.9%	75.1%	74.3%
C(ads)s = m(ads)s / m(soil) [microgram/g]	1.524	0.756	0.309	0.074	0.015
log C(ads)s	0.183	-0.121	-0.510	-1.129	-1.826
C(ads)aq [microgram/mL]	0.500	0.261	0.104	0.025	0.005
log C(ads)aq	-0.301	-0.584	-0.984	-1.609	-2.287
Soil II: loam; soil/solution ratio 1/1
Concentration Ci [microgram/mL]	2.024	1.017	0.413	0.099	0.020
Mean mass adsorbed m(ads)s [microgram]	4.35	2.78	1.06	0.24	0.06
Mean mass adsorbed [% of applied]	21.5%	27.4%	25.7%	24.2%	29.1%
C(ads)s = m(ads)s / m(soil) [microgram/g]	0.435	0.278	0.106	0.024	0.006
log C(ads)s	-0.362	-0.556	-0.975	-1.621	-2.233
C(ads)aq [microgram/mL]	1.589	0.738	0.307	0.075	0.014
log C(ads)aq	0.201	-0.132	-0.513	-1.125	-1.846
Soil III: loam; soil/solution ratio 1/1
Concentration Ci [microgram/mL]	2.024	1.017	0.413	0.099	0.020
Mean mass adsorbed m(ads)s [microgram]	1.39	0.83	0.33	0.07	0.02
Mean mass adsorbed [% of applied]	6.8%	8.2%	8.0%	7.4%	12.3%
C(ads)s = m(ads)s / m(soil) [microgram/g]	0.139	0.083	0.033	0.007	0.002
log C(ads)s	-0.858	-1.081	-1.480	-2.133	-2.606
C(ads)aq [microgram/mL]	1.886	0.934	0.380	0.092	0.018
log C(ads)aq	0.275	-0.030	-0.420	-1.038	-1.754

Table 4: Advanced test:
Distribution of test item between aqueous and soil phase after 24 h desorption
Soil I: sandy clay loam; soil/solution ratio 1/1
Concentration Ci before adsorption [microgram/mL]	2.024	1.017	0.413	0.099	0.020
Mean mass remaining after desorption m(des)s [microgram]	13.629	6.569	2.829	0.629	0.130
Mean mass remaining [% of applied]	67.3%	64.6%	68.5%	63.5%	64.4%
C(des)s = m(des)s / m(soil) [microgram/g]	1.363	0.657	0.283	0.063	0.013
log C(des)s	0.134	-0.183	-0.548	-1.202	-1.888
C(des)aq [microgram/mL]	0.402	0.226	0.076	0.023	0.004
log C(des)aq	-0.396	-0.646	-1.118	-1.635	-2.348
Soil II: loam; soil/solution ratio 1/1
Concentration Ci before adsorption [microgram/mL]	2.024	1.017	0.413	0.099	0.020
Mean mass remaining after desorption m(des)s [microgram]	2.490	1.519	0.575	0.129	0.037
Mean mass remaining [% of applied]	12.30%	14.94%	13.92%	13.01%	18.54%
C(des)s = m(des)s / m(soil) [microgram/g]	0.249	0.152	0.057	0.013	0.004
log C(des)s	-0.604	-0.819	-1.240	-1.890	-2.429
C(des)aq [microgram/mL]	0.964	0.482	0.197	0.046	0.009
log C(des)aq	-0.016	-0.317	-0.706	-1.341	-2.061
Soil III: loam; soil/solution ratio 1/1
Concentration Ci before adsorption [microgram/mL]	2.024	1.017	0.413	0.099	0.020
Mean mass remaining after desorption m(des)s [microgram]	0.990	0.499	0.227	0.067	0.022
Mean mass remaining [% of applied]	4.89%	4.91%	5.49%	6.73%	11.01%
C(des)s = m(des)s / m(soil) [microgram/g]	0.099	0.050	0.023	0.007	0.002
log C(des)s	-1.004	-1.302	-1.644	-2.177	-2.655
C(des)aq [microgram/mL]	0.844	0.427	0.166	0.040	0.008
log C(des)aq	-0.074	-0.370	-0.779	-1.397	-2.092

Table 5: Preliminary test:
Adsorption / Desorption kinetics, initial concentration 0.55 mg/L
Adsorption: Radioactivity adsorbed in % of radioactivity applied (mean)
			Adsorption time (h)
Soil	Ratio	2	5	24	48
I: sandy clay loam	1/25	6.2%	5.6%	8.9%	7.5%
	1/5	30.8%	32.9%	35.4%	38.5%
	1/1	71.9%	74.9%	75.3%	77.5%
II: loam	1/1	27.7%	31.9%	35.0%	35.3%
III: loam	1/1	5.6%	8.3%	7.5%	7.6%
Desorption: Mass desorbed as % of amount adsorbed (mean)
			Desorption time (h)
Soil	Ratio	2	5	24	48
I: sandy clay loam	1/1	8.5%	7.3%	7.0%	6.6%
II: loam	1/1	39.9%	36.5%	32.1%	34.6%
III: loam	1/1	19.3%	27.0%	22.1%	22.7%

Validity criteria fulfilled:

yes

Conclusions:

A mean adsorption Freundlich isotherm KFOC of 40 (range 13 – 93) and a mean desorption KFOC of 45 (11 – 106) were determined.
Higher K values found in desorption isotherms indicate a partial irreversibility; small fractions of the total radioactivity could not be extracted with organic solvents and remained irreversibly bound to the soil.
Freundlich isotherms showed near linear adsorption for all soils studied (1/n values 0.89 to 1.01).
High organic carbon content combined with an acidic pH of the soil seems to enhance the adsorption of the test item to the soil.
The potential mobility of the test item was determined to be high (soil I) to very high (soils II and III).
The study report is relevant, adequate and reliable for risk assessment, classification and labeling.

Executive summary:

Adsorption and desorption of the 14C-labeled test substance was determined by the batch equilibrium method according to OECD Guideline 106, in three soils (sandy clay loam and two types of loam), using liquid scintillation counting.

In a preliminary test at a concentration of 0.55 mg/L, the optimal soil/solution ratio was determined to be 1/1; adsorption and desorption reached equilibrium within 5 hours. No degradation of the test item in the aqueous phase was detectable by HPLC analysis, and no adsorption to the tube walls was observed. Soils I, II, and III showed 77.5%, 35.3%, and 7.6% adsorption, respectively.

In the advanced test, adsorption and desorption isotherms were determined using five concentrations (2.024, 1.017, 0.413, 0.099 and 0.020 mg/L, agitation time 24 hours, soil/solution ratio 1/1). The recovery of radioactivity (mass balance) was between 92.8% and 101.4% for all soils; small fractions of the total radioactivity applied (1.7 – 3.8 %) could not be extracted with organic solvents and remained irreversibly bound to the soil.

Freundlich adsorption constants of 3.011, 0.314, and 0.079, and desorption constants of 3.417, 0.263, and 0.103 were found for the three soils, resulting in a mean adsorption KFOC of 40 (range 13 – 93) and a mean desorption KFOC of 45 (11 – 106). The higher K values in desorption isotherms indicate a partial irreversibility; near linear adsorption was seen in all three soils (1/n values 0.89 to 1.01).

The rather high adsorption of the test item to soil I correlated with the acidic soil pH (4.45); soils II (pH 6.05) and III (pH 7.50) showed a rather low adsorption. High organic carbon content combined with an acidic pH enhances the adsorption. According to the classification of McCall et al. [Test Protocols for Environmental Fate and Movement of Toxicants, Proceedings of AOAC Symposium, AOAC Washington 1981], the potential mobility of the test item was determined to be high (soil I) to very high (soils II and III).

Description of key information

Adsorption/desorption soil: Koc 40.6 (13.8 - 91.9), batch equilibrium method, three soils, OECD 106, Voelkel 2005

Key value for chemical safety assessment

Koc at 20 °C:

40.6

Additional information

Adsorption / Desorption:

One batch equilibrium adsorption/desorption study on three soils, conducted under GLP according to guideline OECD 106, is available (Voelkel 2005). The study is considered to be relevant, reliable (Klimisch 1) and adequate for the purposes of risk assessment, classification and labelling.

Adsorption and desorption of the 14C-labeled test substance was determined in three soils (sandy clay loam and two types of loam), using liquid scintillation counting.

In a preliminary test at a concentration of 0.55 mg/L, the optimal soil/solution ratio was determined to be 1/1; adsorption and desorption reached equilibrium within 5 hours. No degradation of the test item in the aqueous phase was detectable by HPLC analysis, and no adsorption to the tube walls was observed. Soils I, II, and III showed 77.5%, 35.3%, and 7.6% adsorption, respectively.

In the advanced test, adsorption and desorption isotherms were determined using five concentrations (2.024, 1.017, 0.413, 0.099 and 0.020 mg/L, agitation time 24 hours, soil/solution ratio 1/1). The recovery of radioactivity (mass balance) was between 92.8% and 101.4% for all soils; small fractions of the total radioactivity applied (1.7 – 3.8 %) could not be extracted with organic solvents and remained irreversibly bound to the soil.

Freundlich adsorption constants of 3.011, 0.314, and 0.079, and desorption constants of 3.417, 0.263, and 0.103 were found for the three soils, resulting in a mean adsorption KFOC of 40 (range 13 – 93) and a mean desorption KFOC of 45 (11 – 106). The higher K values in desorption isotherms indicate a partial irreversibility; near linear adsorption was seen in all three soils (1/n values 0.89 to 1.01).

The rather high adsorption of the test item to soil I correlated with the acidic soil pH (4.45); soils II (pH 6.05) and III (pH 7.50) showed a rather low adsorption. High organic carbon content combined with an acidic pH enhances the adsorption. According to the classification of McCall et al. [Test Protocols for Environmental Fate and Movement of Toxicants, Proceedings of AOAC Symposium, AOAC Washington 1981], the potential mobility of the test item was determined to be high (soil I) to very high (soils II and III).

Other adsorption coefficient indicated as dimensionless:
- other: Freundlich adsorption KFOC ,40.0 at the temperature 20.0°C
- other: Freundlich desorption KFOC ,45.0 at the temperature 20.0°C