cyproconazole (ISO); (2RS,3RS;2RS,3SR)-2-(4-chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

9 Sep 1985 to 16 Oct 1985

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EPA, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate, Series 163-1

Deviations:

no

GLP compliance:

yes

Remarks:

The study was initiated prior to full implementation of a Quality Assurance Unit, inspected phases were the General laboratory facilities, Notebook and record keeping, Protocol (retrospective) and the Final Report.

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

25 ºC

Analytical monitoring:

yes

Details on sampling:

Samples were taken after 16 hours adsorption equilibrium.

Matrix no.:

#1

Matrix type:

loam

% Clay:

20.2

% Silt:

43.8

% Sand:

36

% Org. carbon:

1.3

pH:

6.4

CEC:

25.7 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

other: Sediment

% Clay:

20.7

% Silt:

34.2

% Sand:

45.1

% Org. carbon:

1.3

pH:

7.4

CEC:

16.1 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

sandy loam

% Clay:

8.4

% Silt:

34.4

% Sand:

57.2

% Org. carbon:

0.8

pH:

7

CEC:

14.1 meq/100 g soil d.w.

Matrix no.:

#4

Matrix type:

clay

% Clay:

43

% Silt:

37.4

% Sand:

19.6

% Org. carbon:

6.6

pH:

6.2

CEC:

33 meq/100 g soil d.w.

Matrix no.:

#5

Matrix type:

loamy sand

% Clay:

11.6

% Silt:

1.5

% Sand:

86.9

% Org. carbon:

2.3

pH:

5.1

CEC:

11.1 meq/100 g soil d.w.

Matrix no.:

#6

Matrix type:

sand

% Clay:

1

% Silt:

2

% Sand:

97

% Org. carbon:

0

pH:

6.7

CEC:

2.2 meq/100 g soil d.w.

Details on matrix:

Soil characteristics are described in Table 1 in 'Any other information on materials and methods incl. tables'
- Location: The Gilroy loam and sediment were obtained from agricultural sites near Gilroy, CA which are representative of certain proposed use sites. The German soil is a German BBA standard-soil ; all other soils were obtained in California. The Gilroy loam is currently being used in an aerobic soil metabolism study of the test substance and was used in the column leaching study presented here.
- Preparation: All soils were air-dried and passed through a 2--mm screen prior to use.

Details on test conditions:

Adsorption-desorption test
TEST SYSTEM
- Type, size and further details on reaction vessel: Kimax tubes (25 x 150 mm) with Teflon-lined screw caps
- Amount of soil per treatment: 10 g of soil
- Exposure method: mixtures of soil with 10 mL of a 0.01N CaCl2 solution which contained radiolabeled test substance at the following concentrations: 0.10, 0.50, 2.50, 12.5, and 62.5 ppm.
- Number of reaction vessels/concentration: 2

TEST CONDITIONS
- Test performed in closed vessels: In order to attain adsorption equilibrium, the tubes were tightly capped, sealed with Parafilm, vortexed for 1 min, then placed horizontally in a shaker and shaken for 16 hrs at 25°C.
- Desorption: The desorption experiments utilized the same samples. Desorption was determined by replacement of the 3.5 mL of supernatant removed for adsorption determinations with 3.5 mL of 0.02N CaCl2 solution followed by reequilibration. This procedure was repeated a total of five times. Desorption was not determined for Monterey sand because of extremely low adsorption.


Mobility test
- Column leaching: A soil column was used to study the mobility of the test substance in a loam soil. The split column technique was employed. A 60-cm section of polyvinyl chloride pipe (7.5 cm internal diameter) was cut in half longitudinally, taped back together, the seam caulked, and the bottom of the column secured with a screen and a layer of glass wool. The column was then uniformly packed to a height of 42 cm with 2.50 kg of dry Gilroy loam and the soil then saturated with water and allowed to drain for one day to establish "field capacity." An additional 50 g of dry soil was added to the column and treated with 2 mL of methanol containing 14C-labelled test substance and technical grade test substance for a dose rate equal to 0.1 kg/ha (0.09 lb/acre). After the methanol had evaporated, a disc of filter paper and glass wool were placed on top of the column and 2,320 mL of deionized water (equal to 51 cm of rainfall) were added to the column over seven days. The flow rate ( ~14 mL/hr) was controlled by the use of a buret.

Duration:

16 h

Temp.:

25 °C

Remarks:

Applicable to all test concentrateds and soils

Remarks:

Not specified

Key result

Sample No.:

#1

Type:

Koc

Value:

309 L/kg

pH:

6.4

Temp.:

25 °C

Matrix:

Gilroy loam

% Org. carbon:

1.3

Key result

Sample No.:

#2

Type:

Koc

Value:

369 L/kg

pH:

7.4

Temp.:

25 °C

Matrix:

Gilroy Sediment

% Org. carbon:

1.3

Key result

Sample No.:

#3

Type:

Koc

Value:

173 L/kg

pH:

7

Temp.:

25 °C

Matrix:

Keaton Sandy loam

% Org. carbon:

0.8

Key result

Sample No.:

#4

Type:

Koc

Value:

258 L/kg

pH:

6.2

Temp.:

25 °C

Matrix:

Briggs Clay

% Org. carbon:

6.6

Key result

Sample No.:

#5

Type:

Koc

Value:

711 L/kg

pH:

5.1

Temp.:

25 °C

Matrix:

German Loamy sand

% Org. carbon:

2.3

Remarks on result:

not measured/tested

Adsorption and desorption constants:

An overview of the results is provided in Table 2 – Table 4 in ‘Any other information on results incl. tables’
Adsorption
Adsorption of the test substance increased in the order of Keaton sandy loam< Gilroy loam< Gilroy sediment< German loamy sand~ Biggs clay on the basis of both the actual amounts adsorbed and Kads. Two of the soil characteristics were correlated with Kads by linear regression analysis; organic natter content was correlated directly and pH was correlated inversely (significance levels of 0.05).
The Freundlich adsorption constant (KF) for the various soils ranged from 1.3 for the Keaton sandy loam to 17 for the Biggs clay. The adsorption adjusted for the organic carbon content of the soils, KFOC ranged from 173 for the Keaton sandy loam to 711 for the German loamy sand. Any adsorption to the Monterey sand was too low to be measured due to its lack of organic matter. The median KFOC for the five remaining soils is 309 mL/g. Slopes (1/n) for the adsorption isotherms were in the range 0.84 to 0.87 for all but the German loamy sand (0.9).

Desorption
The percent and total desorption of the test substance at various initial concentrations showed that desorption decreases as the organic matter and clay content increase. This observation seem to apply for most pesticides. Thus, the order for desorption of the test substance from soil was as follows: Keaton sandy loam > Gilroy loam ~ Gilroy sediment > German loamy sand - Biggs clay.

Recovery of test material:

Not specified

Concentration of test substance at end of adsorption equilibration period:

See Table 2 in 'Any other information on results incl. tables'

Concentration of test substance at end of desorption equilibration period:

See Table 2 in 'Any other information on results incl. tables'

Remarks on result:

not determinable

Sample no.:

#1

Duration:

16 h

% Desorption:

30.9

Remarks on result:

other: 62.5 µg/g treatment

Sample no.:

#2

Duration:

16 h

% Desorption:

26.8

Remarks on result:

other: 62.5 µg/g treatment

Sample no.:

#3

Duration:

16 h

% Desorption:

60.4

Remarks on result:

other: 62.5 µg/g treatment

Sample no.:

#4

Duration:

16 h

% Desorption:

10.9

Remarks on result:

other: 62.5 µg/g treatment

Sample no.:

#5

Duration:

16 h

% Desorption:

8.9

Remarks on result:

other: 62.5 µg/g treatment

Transformation products:

not measured

Details on results (Batch equilibrium method):

An overview of the results is provided in Table 6 in 'Any other information on results incl. tables'
- Mobility in Soil: When eluted with the equivalent of 51 cm (20 inches) of rain, 74% of the test substance remained in the top 6 cm of the column with levels of the test substance diminishing at lower column depths. The test substance degradates were not used in a leaching study (as in the EPA registration guidelines) because concurrent studies indicate there is minimal degradation of the test substance after 30 days (extractable degradates represent <3% of the applied dose).

Table 2. Adsorption - Desorption of the test substance by Six Soils

Gilroy loam
Initial adsorption1	0.088	0.437	2.12	9.92	42.7
solution concentration 2	0.012	0.063	0.38	2.58	19.8
adsorpti n afterJ extractions1	0.074	0.399	1.85	8.08	29.5
total desorption1	0.014	0.038	0.27	1.84	13.2
% desorption	15.9	8.70	12.7	18.5	30.9
Gilroy sediment
initial adsorption	0.089	0.442	2.17	10.2	47.1
solution concentration	0.011	0.058	0.33	2.30	15.4
adsoprtion after 6 extractions	0.077	0.389	1.88	8.31	34.5
total desorption	0.012	0.053	0.29	1.89	12.6
% desorption	13.5	12.0	13.4	18.5	26.8
Keaton sandy loam
initial adsorption	0.065	0.327	1.43	6.59	27.0
solution concentration	0.035	0.173	1.07	5.91	35.5
adsorption after 6 extractions	0.042	0.207	0.814	3.03	10.7
total desorption	0.023	0.12	0.616	3.56	16.3
% desorption	35.4	36.7	43.1	54.0	60.4
Biggs clay
initial adsorption	0.098	0.486	2.41	11.9	57.6
solution concentration	0.002	0.014	0.09	0.6	4.9
adsorption after 6 extractions	0.096	0.473	2.31	11.2	51.3
total desorption	0.002	0.013	0.10	0.70	6.3
% desorption	2.04	2.68	4.15	5.88	10.9
German loamy sand
initial adsorption	0.096	0.481	2.40	11.9	57.3
solution concentration	0.004	0.019	0.10	0.6	5.2
adsorption after 6 extractions	0.091	0.457	2.28	11.2	52.2
total desorption	0.005	0.024	0.12	0.70	5.1
% desorption	5.21	4.99	5.00	5.88	8.9
Monterey sand
initial adsorption	0.002	(0.001	<0.01	(0.1	6.6
solution concentration	0.098	0.506	2.57	12.8	55.9

1. µg test substance/g soil

2. µg test substance/mL water

Table 3. Distribution Adsorption Constants (Kd values*) for Adsorption of the test substance onto Five Soils

	Initial concentration µg/g
Soil	0.1	0.5	2.5	12.5	62.5
Gilroy loam	7.3	6.9	5.6	3.8	2.2
Gilroy sediment	8.1	7.6	6.6	4.4	3.1
Keaton sandf loam	1.9	1.9	1.3	1.1	0.76
Biggs clay	49	35	27	20	12
German loamy sand	24	25	24	20	11

* Kd values are the ratio of pesticide adsorbed (µg/g) to pesticide solution concentration (µg/mL), at equilibrium.

 

Table 4. Freundlich Equation Parameters and Correlation Coefficients for Adsorption of the test substance onto Five Soils 

Soil	KF(mL/g)	1/n	R^2
Gilroy loam	4.1	0.84	1.00
Gilroy sediment	4.9	0.86	1.00
Keaton sandy loam	1.3	0.87	1.00
Biggs clay	17	0.84	1.00
German loamy sand	16	0.90	1.00

Table 5. Sample Calculations of the test substance Equilibrium Adsorption Concentrations in Gilroy Loam

Initial concentration (µg/g)	Total radioactivity in solution (dpm)1	Specific activity (dpm/µg)	Total µg in solution	µg/mL in solution	µg/g adsorbed 2
0.1	22,300	190,000	0.117	0.012	0.088
0.5	23,800	38,000	0.626	0.063	0.437
2.5	28,800	7,600	3.79	0.38	2.12
12.5	39,200	1,520	25.8	2.58	9.92
62.5	60,100	304	198	19.8	42.7

1. Total radioactivity in solution was calculated by multiplying the average dpm in 3.5 mL of the equilibrium solution for duplicate samples by 2.86.

2. The amount adsorbed (µg/g) was determined by subtracting the amount in solution (µg/mL) from the initial concentration of the test substance

Table 6. Vertical Distribution of Surface-Applied test substance in a Soil Column of Gilroy Loam Following Elution with a Volume of Water Equivalent to 51 cm of Rainfall

Depth of soil	% of total applied dose*
0 – 6 cm	74
6 – 12 cm	7
12 – 18 cm	4
18 – 24 cm	4
24 – 30 cm	3
30 – 36 cm	1
36 – 42 cm	1
> 42 cm	< 0.5

Total recovery equals 95%

 

Validity criteria fulfilled:

yes

Conclusions:

Adsorption constants (Koc values) of 309, 369, 173, 258 and 711 in Gilroy loam, Gilroy sediment, Keaton sandy loam, Briggs clay and German loamy sand soils, respectively.

Executive summary:

Adsorption, desorption and mobility of [14C]-substance were determined using six soil types which varied in cation exchange capacity (CEC), percent organic matter (OM), and texture. The study was conducted in accordance with EPA N Series 163-1 but and in compliance with GLP criteria (with deviations).

Aqueous test solutions of [14C]substance in 0.01 N calcium chloride (CaCl2 were prepared at the concentrations of 0.1, 0.5, 2.5, 12.5 and 62.5 ppm. The adsorption phase was conducted at 25 °C for 16 hours in a shaking water bath with 10 g soil plus 10 mL of test solution in Teflon centrifuge tubes that capped and sealed with parafilm. At the end of the equilibration period, the samples were centrifuged for 10 min. 3.5 mL of the supernatant was subsequently removed for quantification of the radiolabel using LSC. This procedure was repeated five times in total. Desorption was not determined for the Monterey sand because of extremely low adsorption. For the other five soils, desorption was accomplished by replacing the supernatant that was withdrawn after centrifugation with an equivalent volume of fresh 0.01 N calcium chloride solution followed by equilibration

The result showed that adsorption of the test substance increased in the order of Keaton sandy loam< Gilroy loam< Gilroy sediment< German loamy sand~ Biggs clay on the basis of both the actual amounts adsorbed and Kads. Two of the soil characteristics were correlated with Kads by linear regression analysis; organic matter content was correlated directly and pH was correlated inversely (significance levels of 0.05). The percent and total desorption of the test substance at various initial concentrations showed that desorption decreases as the organic matter and clay content increase. This observation seem to apply for most pesticides. Thus, the order for desorption of the test substance from soil was as follows: Keaton sandy loam > Gilroy loam ~ Gilroy sediment > German loamy sand - Biggs clay. Adsorption constants (Koc values) of 309, 369, 173, 258 and 711 in Gilroy loam, Gilroy sediment, Keaton sandy loam, Briggs clay and German loamy sand soils, respectively. The mobility test showed that the test substance is not particularly mobile in the Gilroy (loam) soil with 74 % of the applied radioactivity remaining in the top 6 cm of a soil column containing a loam soil after the equivalent of 510 mm rain was added.

Description of key information

Arithmetic mean = 364 L/kg based on a study covering 5 soils (Gilroy loam, Gilroy sediment, Keaton sandy loam, Briggs clay and German loamy sand), EPA 163-1, Skinner et al. 1985

Key value for chemical safety assessment

Koc at 20 °C:

364

Additional information

There is one study available for this endpoint. The study followed EPA 163 -1 guideline, and was in compliance with GLP criteria (Reliability 1). It covered 5 types of soil and used the equilibrium batch method. The soil types, test conditions, and results are summarised in the table below.

 

USDA	Name/ Origin	OC	pH	Kf/Kd(mL/g)	Koc (mL/g)	1/n
Loam	Gillroy / US	1.3	6.4	4.1	309	0.84
Loam (sediment)	Gilroy / US	1.3	7.4	4.9	369	0.86
Sandy Loam	Keaton / US	0.8	7.0	1.3	173	0.87
Clay	Briggs / US	6.6	6.2	17	258	0.84
Loamy sand	BBA 2.2 / De	2.3	5.1	16	711	0.90
Arithmetic mean					364