Ethyl [2-(4-phenoxyphenoxy)ethyl]carbamate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Remarks:

batch equilibrium method

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 Jul 1994 to 7 Sep 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: EPA 163-1

Version / remarks:

October 18,1982

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

25 ± 1 °C

Analytical monitoring:

yes

Details on sampling:

- Adsorption: At the equilibrium time, the tubes were removed from the incubator and centrifuged at ~1000G for 15 minutes to pellet the soil. The supernatant was decanted, retained in silylated liquid scintillation vials, and triplicate 0.5 mL aliquots removed for LSC analysis. LSC analysis of the supernatant determined the equilibration concentrations (Ce) of the test substance in all test solutions. The actual concentration of the test substance adsorbed (x/m) was determined by difference subtracting the radioactivity observed in supernatant from added to each tube prior to adsorption. The supernatant from each concentration for each soil type was analysed for pH determination. Additionally, the supernatant from one replicate per soil type at the highest concentration (1.841 ppm) was analysed by TLC and HPLC.
- Desorption: At the equilibrium time, the tubes were removed from the incubator, centrifuged at ~1000G for 15 minutes to pellet the soil, and the supernatant was removed. Triplicate 2 mL aliquots each supernatant were and analysed by to determine the equilibration concentrations (Ce) of the test substance. Desorption soil concentration (x/m) was by combustion of the residual soil with correction for the amount of radioactivity present in the solution remaining with each soil sample (i. e. radioactivity present in the interstitial water). Additionally, the desorption supernatant from one replicate per soil type at the highest concentration (1.841 ppm) was analysed by TLC and HPLC.

Matrix no.:

#1

Matrix type:

clay

% Clay:

47

% Silt:

32

% Sand:

21

% Org. carbon:

1.798

pH:

6.6

CEC:

33.4 meq/100 g soil d.w.

Bulk density (g/cm³):

1.06

Matrix no.:

#2

Matrix type:

sand

% Clay:

3

% Silt:

8

% Sand:

89

% Org. carbon:

0.232

pH:

6

CEC:

3.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.54

Matrix no.:

#3

Matrix type:

sandy loam

% Clay:

11

% Silt:

24

% Sand:

65

% Org. carbon:

1.798

pH:

7.7

CEC:

14.9 meq/100 g soil d.w.

Bulk density (g/cm³):

1.25

Matrix no.:

#4

Matrix type:

silt loam

% Clay:

15

% Silt:

60

% Sand:

25

% Org. carbon:

0.986

pH:

6.7

CEC:

14.1 meq/100 g soil d.w.

Bulk density (g/cm³):

1.14

Matrix no.:

#5

Matrix type:

loam

% Clay:

11

% Silt:

44

% Sand:

45

% Org. carbon:

1.914

pH:

6.8

CEC:

21.4 meq/100 g soil d.w.

Bulk density (g/cm³):

1.15

Details on matrix:

Soil characterisations are presented in Table 1 in 'Any other information on materials and methods incl. tables'
COLLECTION AND STORAGE
- Soil preparation: All five soils were air dried at ambient laboratory temperatures and sieved through a 2 mm sieve prior to characterization and use in the study to assure uniform particle size. A representative subsample of each soil was removed for soil characterization by laboratories.
- Storage conditions: Air dried soils were maintained (stored) at ambient temperature from receipt until use.

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 mL Oak Ridge Teflon centrifuge tubes (including screw cap); Prior to use, all centrifuge tubes were autoclaved for 1 hour at 121°C and 15 psig.
- Test water: The water used in this study was drinking water provided by the City of Frederick, Maryland. The drinking water was filtered, deionized, boiled, and distilled prior to use. This test water was used to prepare the 0.01M calcium ion solutions.
- Silylation of glassware: All glassware used in the study was silylated according to Agrisearch Incorporated Standard Operating Procedure NO. 13.C.2.1. The procedure uses a solution of dichlorodimethylsilane in dichloromethane (DCM) to block all available binding sites on the glassware. After sitting for 30 minutes, the glassware is rinsed three times with methanol, 3 times with DCM and oven baked at 100 to 110°C for 2 hours.
- Soil/sediment/sludge-water ratio: 20 mL solution to 1 g for all soils except the Maryland sand which was at a ratio of 5 mL solution to 1 g soil.
- Amount of soil/sediment/sludge-water: ~ 2 g each soil type with 40 mL solution, except sand ~ 4 soil with 20 mL solution
- Number of reaction vessels/concentration: 2
- Method of preparation of test solution: The 0.01M calcium chloride solution was prepared by adding 7.75 g of calcium chloride dihydrate to 4 liters of water and stirring until dissolved (1.94 g calcium chloride dihydrate per liter of water). The resultant solution (0.01M calcium ion concentration) was sterilized by filtration through a 0.2 micron membrane filter into autoclaved glassware. The sterile calcium ion solution was covered with aluminium foil to maintain sterility. The pH of the CaCl2 aqueous solution measured after preparation was 5.44 and 5.77 (prepared twice).
For the definitive phase, 400 mL aliquots of prepared sterile 0.01M calcium ion solution were placed into a series of six sterile silylated 1 L Erlenmeyer flasks. To each flask, a total of 2.86 mL of acetonitrile was added. The acetonitrile addition was in the form of pure solvent to attain the 0.0 µg/mL dose level or up to 2.86 mL of stock solution to attain the 2 µg/mL (ppm) dose level. Intermediate dose levels were prepared by using various combinations of pure solvent plus 14C-labelled test substance stock solution. In all cases, the amount of cosolvent present was equivalent to 0.72%. The final concentrations for the definitive phase of the study were: 0.0, 0.099, 0.203, 0.947, and 1.841 µg/mL. All test solutions were prepared immediately prior to use. The actual test solution concentration, solubility and homogeneity, of three aliquots were determined prior to use by LSC. The concentration of radioactivity in each LSC aliquot was within of the respective mean concentration and the radioactivity was considered to be homogeneously dispersed in the test solution. The of each test solution was also measured prior to use. Aliquots of each of the test solutions were analysed by TLC and HPLC.

- Adsorption: Based upon the equilibrium time and test solution to soil ratios as determined in the preliminary phase, the definitive adsorption phase of the study was performed. The selected solution to soil ratio based on the preliminary phase was 20 mL solution to 1 g for all soils except the Maryland sand which was at a ratio of 5 mL solution to 1 g soil. Duplicate samples of air dried soil ( ~ 2 g each soil type with 40 mL solution, except sand ~ 4 soil with 20 mL solution) were weighed into centrifuge tubes for each test solution concentration. An appropriate volume of the test solution at 0.0, 0.099, 0.203, 0.474, 0.947, and 1.841 ppm was transferred to the appropriate centrifuge tubes and capped. The pH of the test solution was determined on a portion of each test solution and that portion was not added to any centrifuge tube. The 0.0 ppm concentration served as a control for determination of background radioactivity from undosed soil. Values obtained from these were to that the soil had not previously exposed to radiocarbon. The entire sample set was shaken in the dark for the equilibrium time (8 hours) using an shaker at 175 to 200 rpm in a constant temperature incubator at 25 ± 1 °C incubator).

- Desorption: Desorption was performed on the soil samples following adsorption. chloride aqueous solution at a concentration of 0.01M without test was added to all centrifuge tubes containing soil pellets for adsorption. The volume of 0. 01M CaCl2 solution added was same as volume used for the (definitive) adsorption phase. The soil pellet was then suspended by vortexing and shaking until dispersed. Soil samples at the 0.0 ppm level were also desorbed to demonstrate radiocarbon free calcium ion solution and no radiocarbon desorption from the control soils. The entire sample set was shaken in the dark for the equilibrium time (8 hours) using an Eberbach shaker at 175 to 200 rpm in a constant temperature incubator at 25 ± 1 ˚C.
The material balance was calculated for every sample by adding the total dpm in adsorption supernatant, plus the dpm in the desorption supernatant, plus the dpm in the combusted soils. The target recovery was > 90% and ≤ 110%. The soil pellet from the highest level (2 ppm) of each soil type was extracted by treating the soil with a 1:1 solution of 80 : 20 MeOH: 0.1N NaOH (aq, pH ≈13) and homogenizing for approximately 5 minutes at about 12000 - 15000 rpm using a tissue homogenizer. The samples were then centrifuged at for 15 minutes to pellet the soil. The extract was decanted, and the soil was homogenized/centrifuged two more times. The combined extract was radioassayed in triplicate (100 µL aliquots). The remaining soil pellet was air dried at ambient temperatures in a laboratory hood. Aliquots of the air-dried soil pellet were oxidized by combustion and the resulting radioactive carbon dioxide analysed by LSC. Additionally, an aliquot of the pooled extract was analysed by to determine the amount of test substance remaining in the soil after adsorption.

Duration:

8 h

Temp.:

25 °C

Remarks:

Applicable to all tested concentrations

Duration:

8 h

Temp.:

25 °C

Remarks:

Applicable to all tested concentrations

Key result

Sample No.:

#1

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

2 599 L/kg

pH:

6.6

Temp.:

25 °C

Matrix:

Clay

% Org. carbon:

1.798

Key result

Sample No.:

#2

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

1 883 L/kg

pH:

6

Temp.:

25 °C

Matrix:

Sand

% Org. carbon:

0.232

Key result

Sample No.:

#3

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

1 251 L/kg

pH:

7.7

Temp.:

25 °C

Matrix:

Sandy loam

% Org. carbon:

1.798

Key result

Sample No.:

#4

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

1 639 L/kg

pH:

6.7

Temp.:

25 °C

Matrix:

Silt loam

% Org. carbon:

0.986

Key result

Sample No.:

#5

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

1 710 L/kg

pH:

6.8

Temp.:

25 °C

Matrix:

Loam

% Org. carbon:

1.914

Sample No.:

#1

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

3 304 L/kg

Temp.:

25 °C

pH:

6.6

Matrix:

Clay

% Org. carbon:

1.798

Sample No.:

#2

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

2 368 L/kg

Temp.:

25 °C

pH:

6

Matrix:

sand

% Org. carbon:

0.232

Sample No.:

#3

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

1 769 L/kg

Temp.:

25 °C

pH:

7.7

Matrix:

sandy loam

% Org. carbon:

1.798

Sample No.:

#4

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

2 376 L/kg

Temp.:

25 °C

pH:

6.7

Matrix:

silt loam

% Org. carbon:

0.986

Sample No.:

#5

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

2 546 L/kg

Temp.:

25 °C

pH:

6.8

Matrix:

loam

% Org. carbon:

1.914

Adsorption and desorption constants:

An overview of the results is presented in Table 5 in ‘Any other information on results incl. tables’.
- Adsorption: Using the empirical Freundlich isotherm, values of n and Kd were determined from the adsorption data. The correlation coefficients for the adsorption phase were 0.9940 to 0.9998. These high correlation coefficients demonstrate that the adsorption model was studied and that the Freundlich equation was applicable to the test system. The logarithmic plots of Ce (equilibrium solution concentration) versus x/m ( equilibrium soil concentration) are presented as straight lines for the adsorption phase. The adsorption soil constants (Kd) were found to be 4.4 (MD sand) to 46.7 (MS clay) for the five soil textures tested. Calculation of the Koc ( adsorption coefficient based on organic carbon) yielded values of 1251 (MD sandy loam to 2599 (MS clay). These Koc values placed the test substance in the low to slight mobility class (Koc = 500 – 5000).
- Desorption: The correlation coefficients obtained for the desorption phase were 0.9938 to 0.9997. The desorption soil constants (Kd) were found to be 5.5 (MD sand) to 59.4 (MS clay) for the five soil textures tested. Calculation of the Koc (desorption coefficient based on organic carbon) yielded values of 1769 (MD sandy loam) to 3304 (MS clay). These Koc values placed the test substance in the low to slight mobility class (Koc = 500 - 5000).

Recovery of test material:

An overview of the results is presented in Table 2 - Table 4 in ‘Any other information on results incl. tables’.
- Mass balance: The average radiocarbon balance for each soil type ranged from 92.1 to 100.3% of applied with individual replicates demonstrating a range of 88.5 to 110.0%.
- Soil Extraction: Following completion desorption definitive phase, the soil samples remaining at the highest tested concentration (1.841ppm) were extracted. The extraction of the soil pellet was
performed to determine the amount of test substance remaining in the soil following adsorption and desorption. Extractability varied ranging from 74.4 to 122.6% of the available radioactivity.
Combustion of the non-extracted residue accounted for the remaining radiocarbon balance. Total balance for the residual soil, extraction, and combustion average 106.1% (range 99.6 to 125.6%).
- TLC results: One replicate of the highest concentration for adsorption and desorption from each soil type was analysed by two dimensional TLC. Each dose solution for the definitive phase and aliquots of each post desorption soil extract were analysed by two dimensional TLC. In all cases, the scanner quantitated the test substance at 96.8% or greater.
- HPLC results: The quantitation results from the RAMONA radioactivity monitor for analysis of the definitive phase dose solutions, adsorption solutions, desorption solutions, and the extractions the soil remaining after desorption. In all cases the quantitated the test substance at 97.9% or greater.

Sample no.:

#1

Duration:

8 h

% Adsorption:

>= 56.8 - <= 76

Remarks on result:

other: all tested concentrations

Sample no.:

#2

Duration:

8 h

% Adsorption:

>= 21 - <= 35.7

Remarks on result:

other: all tested concentrations

Sample no.:

#3

Duration:

8 h

% Adsorption:

>= 38.7 - <= 59.4

Remarks on result:

other: all tested concentrations

Sample no.:

#4

Duration:

8 h

% Adsorption:

>= 28.2 - <= 43.6

Remarks on result:

other: all tested concentrations

Sample no.:

#5

Duration:

8 h

% Adsorption:

>= 46.4 - <= 63.9

Remarks on result:

other: all tested concentrations

Sample no.:

#1

Duration:

8 h

% Desorption:

>= 7.4 - <= 13.6

Remarks on result:

other: all tested concentrations

Sample no.:

#2

Duration:

8 h

% Desorption:

>= 13 - <= 17.5

Remarks on result:

other: all tested concentrations

Sample no.:

#3

Duration:

8 h

% Desorption:

>= 9.4 - <= 16.7

Remarks on result:

other: all tested concentrations

Sample no.:

#4

Duration:

8 h

% Desorption:

>= 10.8 - <= 16.9

Remarks on result:

other: all tested concentrations

Sample no.:

#5

Duration:

8 h

% Desorption:

>= 12.3 - <= 17.2

Remarks on result:

other: all tested concentrations

Transformation products:

not specified

Details on results (Batch equilibrium method):

- Preliminary phase: Solution equilibrium was achieved within 8 hours as demonstrated by only slight changes in the concentration of test substance in the subsequent aqueous sample. Therefore, the equilibrium shaking time selected for the definitive phase was 8 hours. The estimated Kd values indicated a Kd of all soils except Maryland sand would range from 10 to 50. Sand soil estimated Kd value was < 10. Based on this estimated value, a solution to soil ratio of 20:1 (40 mL solution to 2 g of soil) was selected for the definitive phase for all soils except Maryland sand. The solution to soil ratios selected for Maryland sand was 5:1 (20 mL solution to 4 g of soil). Mass balance for the preliminary phase was determined by summation of the total radioactivity in the equilibration solution plus the total radioactivity in the combusted soils. This total activity recovered was divided by the total activity dosed to determine the mass balance. The mass balance obtained during the preliminary investigations 88.3 to 105.7%. The soil-less "blank" tubes demonstrated no adsorption of the test substance with 96.5 to 99.4% accountability of radioactivity at the end of the 24 hour equilibrium period.

Table 2. Radiocarbon balance

Adsorption test solution concentration (µg/mL)		Percent of dose*
		soil	Water		total
Mississippi Clay soil	Replicate		adsorption	desorption
0.099	1	76.0	17.1	7.7	100.8
	2	74.2	17.5	7.4	99.1
0.203	1	67.1	18.1	8.2	93.4
	2	69.4	18.8	8.5	96.7
0.474	1	67.4	19.7	12.1	99.2
	2	62.8	22.0	10.5	95.3
0.947	1	63.4	24.4	12.0	99.8
	2	64.1	22.1	11.1	97.3
1.841	1	56.80	27.10	13.00	96.9
	2	60.50	25.50	13.60	99.6
Average ± SD	97.8± 2.3
Maryland sand soil
0.099	1	33.6	45.9	13.0	92.5
	2	35.7	44.4	14.4	94.5
0.203	1	30.0	46.5	15.2	91.7
	2	29.1	47.1	13.8	90.0
0.474	1	29.3	48.3	15.8	93.4
	2	31.3	48.2	15.6	95.1
0.947	1	24.4	51.0	15.9	91.3
	2	25.9	50.1	15.9	91.9
1.841	1	22.7	52.0	13.8	88.5
	2	21.0	54.0	17.5	92.5
Average ± SD	92.1± 2.0
Maryland sand loam soil
0.099	1	57.3	33.9	9.4	100.6
	2	59.4	33.2	9.4	102
0.203	1	53.1	35.7	11.4	100.2
	2	47.3	36.9	11.4	95.6
0.474	1	51.3	36.8	13.4	101.5
	2	43.3	42.2	13.7	99.2
0.947	1	42.9	41.9	15.5	100.3
	2	45.4	38.8	15.2	99.4
1.841	1	39.5	44.6	16.1	100.2
	2	38.7	46	16.7	101.4
Average ± SD	100.1± 1.8
Maryland silt loam soil
0.099	1	33.1	45.2	14.2	92.5
	2	43.6	55.6	10.8	110.0
0.203	1	37.6	48	14.9	100.5
	2	35.1	50.4	14.7	100.2
0.474	1	35.1	49.5	15.7	100.3
	2	34.7	48.7	15.1	98.5
0.947	1	30.5	51.8	16.2	98.5
	2	29.5	51.1	16.1	96.7
1.841	1	29.2	50.9	16.9	97.0
	2	28.2	53.9	16.8	98.9
Average ± SD	99.3± 4.4
Wahington loam soil
0.099	1	63.9	25.5	12.4	101.8
	2	60.9	25.2	12.3	98.4
0.203	1	53.9	26.5	13.2	93.6
	2	57.9	28	13.8	99.7
0.474	1	55.6	29.9	15.1	100.6
	2	58.1	29.9	15.4	103.4
0.947	1	56.7	32.5	16.4	105.6
	2	52.6	33.2	15.4	101.2
1.841	1	46.4	34.3	17.2	97.9
	2	53	34.4	13.9	101.3
Average ± SD	100.3± 3.3

* soil = radiocarbon remaining on soil following desorption.

Adsorption water = radiocarbon remaining in adsorption calcium ion solution and not adsorbed to soil.

Desorption Water = radiocarbon in calcium ion solution following desorption.

Table3. AMBIS radioanalytical results

	percent radiocarbon detected as the test substance
Soil	replicate	adsorption solution	desoprtion solution	soil extraction
MS-Clay	1	98.9		98.3
	2		98.2	98.0
MD-Sand	1			98.9
	2	99.0	99.5	98.9
MD-Silt loam	1			96.8
	2	98.9	97.8	97.0
MD-sandy loam	1	99.4		98.5
	2		99.0	98.3
WA-loam	1	99.9		98.0
	2		99.1	98.1

Table 4. RAMONA radioanalytical results (All samples from the highest test concentration (1.841 ppm initial dose)).

	percent radiocarbon detected as the test substance
Soil	replicate	adsorption solution	desoprtion solution	soil extraction
MS-Clay	1	99.8	99.8	99.3
	2			98.9
MD-Sand	1	98.7	99.5	99.5
	2			99.8
MD-Silt loam	1	100.0	99.3	97.9
	2			99.2
MD-sandy loam	1	99.6	98.9	99.4
	2			98.5
WA-loam	1	99.9	99.5	99.6
	2			99.2

Table 5. Overview of adsorption and desorption results (All samples from the highest test concentration (1.841 ppm initial dose)).

	Adsorption			Desorption
Soil type	Kd	Koc	n	Kd	Koc	n
MS-Clay	46.7	2599	1.192	59.4	3304	1.296
MD-Sand	4.4	1883	1.099	5.5	2368	1.214
MD-Silt loam	16.2	1639	1.04	23.4	2376	1.229
MD-sandy loam	22.5	1251	1.153	31.8	1769	1.345
WA-loam	32.7	1710	1.146	48.7	2546	1.148

 

 

 

Validity criteria fulfilled:

yes

Conclusions:

In an adsorption/desorption study, performed in accordance with guideline EPA 163 - 1, Freundlich coefficients (KFOC) were calculated to be 2599, 1883, 1639, 1251 and 1710 L/kg in Leland Mississippi (Clay), Burtonsville Maryland (sand), Lime Kiln Maryland (Silt loam), Middletown Maryland (sandy loam) and Yakima Washington (Loam) soils, respectively.

Executive summary:

The adsorption and desorption properties of [phenyl-ring-14C]-labelled test substance were studied in five soils: Leland Mississippi (Clay), Burtonsville Maryland (sand), Lime Kiln Maryland (Silt loam), Middletown Maryland (sandy loam) and Yakima Washington (Loam).

The study was performed in accordance with guidance EPA 163-1 and in compliance with GLP criteria. A preliminary test was performed with an initial test substance concentration of 1.82 μg/mL to determine the time required to achieve equilibrium in the adsorption phase and establish an appropriate soil-to-solution ratio. In the definitive test, a solution to soil ratio of 20:1 (40 mL solution to 2 g of soil) was used for all soils except Maryland sand. The solution to soil ratios selected for Maryland sand was 5:1 (20 mL solution to 4 g of soil). Test substance was added to the soil slurries in amounts that resulted in five targeted rates of application (i.e. 0.099, 0.203, 0.474, 0.947 and 1.841 μg/mL). Adsorption and desorption isotherms were established for each soil equilibrated over 8 hours at 25 ± 1˚C for all evaluated soils. After equilibration, the phases were separated by centrifugation with the test substance concentration determined by liquid scintillation counting (LSC) of the aqueous phases and by difference for the soil phase. The soil phases were next desorbed with 0.01M calcium ion solution free of the test substance and concentrations determined by combustion and LSC following centrifugation. Soil characteristics were obtained. The soil sorption coefficients Kd and the Freundlich sorption constants KOC were determined for each soil.

Overall mean recoveries of applied radioactivity from each soil type were in the range 92.1 to 100.3 %. The Freundlich coefficients (KFOC) were calculated to be 2599, 1883, 1639, 1251 and 1710 L/kg in Leland Mississippi (Clay), Burtonsville Maryland (sand), Lime Kiln Maryland (Silt loam), Middletown Maryland (sandy loam) and Yakima Washington (Loam) soils, respectively.

Description of key information

Arithmetic mean Log Koc = 3.4 L/kg (Koc = 2440 L/kg) based on four studies covering 9 soils, equilibrium batch method, EPA guideline 163 -1 or no guidance followed, Spare 1995 and Pryde et al., 1982.

Key value for chemical safety assessment

Koc at 20 °C:

2 440

Additional information

Table. Summary of the Kfoc values for the substance

USDA	Name / Origin	OC*	pH	Kf*	Kfoc*	1/n	Author / Year
Sandy loam	Dielsdorf, CH	2.5	6.9	49	1965	0.873	Pryde /1982
Loam	Steinmaur, CH	3.3	7.5	77	2371	0.924	Pryde /1982
Sandy loam	Commugny, CH	1.2	7.2	77	6321	0.990	Pryde /1982
Sandy loam	Wallis, CH	0.8	7.9	18	2217	0.941	Pryde /1982
Clay	Leland, Mississippi, USA	1.8	6.6	47	2599	0.839	Spare et al./1995
Sand	Butonsville, Maryland, USA	0.2	6.0	4	1883	0.910	Spare et al./1995
Sandy loam	Lime Kiln, Maryland USA	1.8	7.7	16	1639	0.962	Spare et al./1995
Silt loam	Middeltown, Maryland, USA	1.0	6.7	23	1251	0.867	Spare et al./1995
Loam	Yakima, Washington, USA	1.9	6.8	33	1710	0.873	Spare et al./1995
Arithmetic mean Koc (n=9)				38	2440	0.909