Paraquat-dichloride

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Remarks:

field studies

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1984 to 1986

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The adsorption properties of unlabelled test substance were determined in 230 European soils covering a wide range of textural classes as well as a wide range of physical and chemical characteristics. The soils were collected from sites in Denmark, Germany, Greece, Italy, the Netherlands and the UK with a known history of the test substance use on various crop types.

GLP compliance:

not specified

Type of method:

other: not reported

Media:

soil

Radiolabelling:

no

Test temperature:

Not reported

Analytical monitoring:

not specified

Details on sampling:

Samples of soil were generally taken down to between 10 and 30 cm. At most sites, 20 samples were taken at random by coring, at a few sites up to 50 samples were taken. At 1 site 5 samples were taken using a 10 cm diameter corer. All other samples were cored using 2 to 3 cm diameter corers. Samples were occasionally collected using a trowel. At each site, the soil was bulked and a sub-sample of approximateyl 1 kg was sent for analysis.

Details on matrix:

In 'Any other information on results incl. tables' a table is included presenting the soil textural classes, soil characteristics and adsorption coefficients of all 230 tested soils.

Details on test conditions:

The adsorption coefficients were measured at much higher application rates than those applied during normal agricultural use, because the concentration in solution at normal rates is below the limit of determination. Adsorption steps of at least 16 hours were employed to equilibrate soil slurries of the test substance between soil and solution phases. For the adsorption steps, at least 6 nominal concentrations were used. After adsorption, the soil slurries were centrifuged and the supernatants were assayed using wheat seedling bioassays. The soil adsorption coefficients were determined. 

Computational methods:

Not reported

Key result

Type:

Koc

Value:

>= 8 400 - <= 40 000 000 dimensionless

Remarks on result:

other: See 'Any other information on results incl. tables' for a complete overview of the results

Type:

Kd

Value:

>= 980 - <= 400 000 dimensionless

Remarks on result:

other: See 'Any other information on results incl. tables' for a complete overview of the results

Transformation products:

not measured

Statistics:

Not reported

The partition adsorption coefficients (Kd values) in the soils ranged from 980 to 400000. Kd values adjusted for the organic carbon content of the soil (Koc) ranged from 8400 to 40000000. The average Koc value is 1635797 and median Koc value is 405500. The data showed adsorption of the test substance to be predominantly related to clay content, the adsorption to clay being so strong that it masked any relationship between adsorption and soil organic matter content. Using the McCall classification scale to assess the potential mobility of chemicals in soil, the test substance is classified as immobile in all the soils studied and therefore has no potential to leach from soils. Results from the individual soils is presented below.

Table: Soil Textural Classes, Characteristics and Adsorption Coefficients

	Particle Size Distribution				CEC (meq/100g)	%OM	%OC	pH	Kd	Koc
Textural Class	%Coarse Sand	%Fine Sand	%Silt	%Clay
Soils from Denmark
Coarse Sand	66	26	2	6	6.1	2.7	1.6	6.4	8900	570000
Loamy Sand	36	50	7	7	11.1	4.6	2.7	6.2	25000	930000
Sand	52	41	3	4	8.2	5.6	3.2	6.4	2500	76000
Sand	50	43	3	4	7.8	4.7	2.7	6.5	4500	160000
Very Fine Sand	4	89	2	5	5.6	2.4	1.4	6.3	2300	160000
Loamy Fine Sand	26	60	7	7	5.9	1.8	1	6	16000	1500000
Loamy Sand	32	56	5	7	6.8	2.8	1.6	5	9500	580000
Loamy Fine Sand	24	55	11	10	7.9	2.4	1.4	7	18000	1300000
Sandy Loam	19	47	16	18	15.8	3.4	2	6.9	110000	5600000
Loamy Sand	27	53	12	8	9	3.1	1.8	7.8	19000	1100000
Loamy Fine Sand	22	55	12	11	10.7	5.2	3	6.3	12000	400000
Fine Sand	18	72	5	5	5.1	2.9	1.7	5.6	7000	410000
Loamy Fine Sand	18	62	12	8	7.6	2.5	1.5	5.7	14000	960000
Loamy Fine Sand	5	64	17	14	10	2.3	1.3	5.6	28000	2100000
Loamy Fine Sand	21	54	14	11	8.6	2.3	1.3	7.2	26000	1900000
Loamy Fine Sand	21	52	14	13	7.4	2.2	1.3	6.8	30000	2300000
Loamy Fine Sand	15	58	15	12	8.2	2.2	1.3	6	21000	1600000
Sandy Loam	18	48	17	17	9.9	2.8	1.6	6.8	22000	1400000
Peat	8	48	25	19	41	24.5	14.2	6.2	56000	390000
Loamy Fine Sand	19	54	14	13	8.8	2.7	1.6	6.5	17000	1100000
Loamy Sand	33	50	9	8	13.3	11.1	6.4	5.6	12000	190000
Soils from Germany
Silty Loam	1	48	32	19	3.8	14.5	8.4	6.9	23000	273000
Fine Sandy Loam	2	53	22	23	1.9	9.1	5.3	7.6	28000	529000
Sandy Loam	33	35	21	11	2.9	8.3	4.8	5.6	14000	290000
Fine Sandy Loam	6	48	28	18	2.2	11	6.4	7.1	44000	888000
Loamy Fine Sand	3	68	16	13	3.2	6.7	3.9	7.5	34000	872000
Very Find Sandy Loam	5	59	14	22	4	15.3	8.9	7.5	87000	978000
Fine Sandy Loam	7	56	19	18	2.4	9.2	5.3	7.3	44000	804000
Sandy Loam	16	43	24	17	3	10.2	5.9	7.1	24000	404000
Sandy Loam	16	44	24	16	2.9	10.4	6	6.9	14000	231000
Loam	11	36	31	22	1.5	11	6.4	6.6	59000	922000
Clay Loam	1	40	26	33	3.8	18	10.4	7.4	74000	707000
Fine Sandy Loam	4	51	22	23	3.2	10	5.8	7.9	24000	412000
Fine Sandy Loam	1	52	23	24	2.4	11.7	6.8	7.6	33000	558000
Fine Sandy Loam	14	50	23	13	1	5.9	3.4	7.4	27000	787000
Fine Sandy Loam	8	54	20	18	1.6	6.8	3.9	8	28000	7080000
Very Fine Sandy Loam	1	54	24	21	2.5	7.8	4.5	7.9	38000	838000
Very Fine Sandy Loam	1	54	24	21	1.9	8.6	5	8	34000	680000
Sandy Loam	25	34	25	16	3.8	12.4	7.2	7.2	35000	485000
Very Fine Sandy Loam	<1	63	21	16	3	6.5	3.8	7.8	45000	1190000
Loamy Sand	31	45	12	12	2	5.5	3.2	7.8	10980	343000
Sandy Loam	3	55	23	19	4.1	18.5	10.7	7.8	125000	1160000
Silty Loam	2	48	33	17	3.2	11	6.4	6.8	8980	140000
Very Fine Sandy Loam	<1	53	26	21	2.1	8.8	5.1	7.9	34000	664000
Fine Sandy Loam	9	52	19	20	1.7	7.6	4.4	7.9	28000	633000
Sandy Loam	20	38	27	17	2.1	10.8	6.3	7.2	20980	334000
Fine Sandy Loam	2	49	24	25	3	13.2	7.7	7.9	38000	495000
Silty Loam	2	51	30	17	3.9	13.4	7.8	6.9	18000	231000
Fine Sandy Loam	1	48	25	26	2.9	11.6	6.7	7.9	38000	583000
Very Fine Sandy Loam	<1	58	24	18	2	6.9	4	7.5	30000	747000
Fine Sandy Loam	6	48	22	24	2.6	8.8	5.1	7.9	36000	703000
Fine Sandy Loam	3	52	23	22	1.5	8.1	4.7	7.9	41000	870000
Sandy Loam	1	46	22	21	1.2	7	4.1	8	40000	982000
Fine Sandy Loam	1	50	24	25	2.1	11.8	6.8	7.7	15500	225000
Clay Loam	1	35	27	37	3.3	17.1	9.9	7.6	78000	784000
Fine Sandy Loam	2	52	22	24	2.7	9.4	5.5	7.9	48000	878000
Silt Loam	6	34	41	19	2.5	10.4	6	7.9	32000	529000
Silt Loam	4	33	31	32	4.6	15.6	9	7.8	40980	452000
Very Fine Sandy Loam	3	59	21	17	1.8	7.4	4.3	8	40000	929000
Clay Loam	1	38	27	34	4.1	20.7	12	7.6	49000	407000
Loamy Coarse Sand	40	36	11	13	2.1	5.8	3.4	7.6	13000	385000
Fine Sandy Loam	1	53	25	21	2.7	10.9	6.3	7.8	35000	552000
Fine Sandy Loam	5	51	21	23	3.1	10.6	6.1	7.6	14000	227000
Sandy Loam	20	37	25	18	1.8	13.1	7.6	6.7	25000	328000
Fine Sandy Loam	2	55	24	19	2.3	7.5	4.4	7.9	34000	779000
Coarse Sandy Loam	24	36	26	14	1.5	7	4.1	4.9	16000	393000
Silty Loam	4	50	30	16	2.5	10.2	5.9	7.3	26000	438000
Fine Sandy Loam	1	50	25	24	2.8	10.2	5.9	7.7	22000	371000
Fine Sandy Loam	1	55	21	23	1.8	10.4	6	7.8	40000	861000
Silty Loam	1	51	29	19	2.8	9.8	5.7	7.8	29000	509000
Silt Loam	1	33	39	27	4.9	19	11	7.6	49000	443000
Fine Sand	19	77	2	2	2.4	3.8	2.2	5.3	2480	112000
Sand	45	49	3	3	5.7	9.2	5.3	5.7	1480	27700
Fine Sand	9	82	4	5	6	7.7	4.5	5.4	7980	178000
Sand	29	62	6	3	3.7	4.9	2.8	5.7	1180	41400
Loamy Sand	42	40	12	6	1.3	4.7	2.7	6.4	9980	365000
Fine Sand	20	73	3	4	7.3	8.1	4.7	5.3	4980	106000
Fine Sand	13	91	3	3	3.3	7.8	4.5	5.7	4480	98800
Fine Sand	13	80	3	4	6.2	8.8	5.1	6	2480	48400
Fine Sand	22	71	5	2	4.5	9.8	5.7	5.2	2980	52300
Sand	37	58	2	3	4.9	8.8	5.1	5.8	1580	30800
Very Fine Sand	4	89	4	3	4.7	9.6	5.6	5.2	4980	89200
Fine Sand	21	73	3	3	2.5	5.6	3.2	6.3	3980	122000
Sand	28	65	5	2	7.6	9	5.2	5.9	1080	20600
Coarse Sand	60	28	7	5	4.1	8.5	4.9	6.5	2980	60300
Fine Sand	15	78	4	3	6.6	11.2	6.5	5.7	2980	45800
Fine Sand	10	81	5	4	10	9.8	5.7	5.3	4980	87400
Fine Sand	10	77	7	6	5.8	10.5	6.1	5.9	26000	426000
Fine Sand	18	76	2	4	4.5	10.3	6	5.6	3980	66500
Sand	45	44	6	5	3	4.4	2.6	5.4	3980	156000
Peat	N/A	N/A	N/A	N/A	41	38	22	5.3	8980	40800
Sand	43	45	6	6	2.9	5.6	3.2	5.6	5480	168000
Fine Sand	13	82	2	3	5	6.8	3.9	5.8	3980	100600
Sand	33	61	1	5	4.8	9.9	5.7	5.4	2180	37900
Fine Sand	9	78	4	9	5.8	9.4	5.5	5.9	38000	595000
Coarse Sand	56	38	2	4	5.1	9.4	5.5	6	2480	45400
Fine Sand	25	67	4	4	4.2	7.8	4.5	5.8	5980	132000
Fine Sand	12	77	3	8	10.7	19.8	11.5	6	9980	86700
Sand	43	47	4	6	3.6	6.7	3.9	5.9	3980	102000
Sand	41	53	3	3	6.1	6.6	3.8	4.8	1880	43800
Sand	44	44	6	6	2.8	4.8	2.8	5.4	3960	143000
Coarse Sand	58	31	8	5	1.5	2.8	1.6	6.1	4480	275000
Sand	37	57	2	4	11.4	13.6	7.9	5.2	4980	63000
Fine Sand	13	82	2	3	2.8	4.2	2.4	6.2	2480	102000
Fine Sand	21	72	3	4	3.8	7.4	4.3	6.4	2980	69200
Sand	45	45	6	4	1.8	2.9	1.7	6.5	3480	20700
Sand	48	45	3	4	4.7	9.4	5.5	6	1880	34400
Sand	46	42	8	4	2	3.6	2.1	6.8	4980	283000
Fine Sand	20	68	6	6	12.2	20.2	11.7	5.7	11000	93500
Sand	46	44	6	4	1.8	4	2.3	6.8	5980	257000
Loamy Sand	37	48	10	5	1.9	4.3	2.5	7.2	4980	199000
Sand	55	38	4	3	5.5	9.8	5.7	5.9	1380	24200
Sand	35	52	6	7	3.8	5.4	3.1	6.2	5980	190000
Sand	31	59	6	4	6.8	8.2	4.8	5.4	960	20600
Fine Sand	20	71	4	5	4.6	6.4	3.7	6	3980	107000
Loamy Coarse Sand	53	33	8	6	2.5	5.1	3	6.6	5980	202000
Sand	49	44	4	3	8.4	8.8	5.1	4.4	1080	21100
Fine Sand	11	83	3	3	4.7	6	3.5	5.6	1580	45200
Fine Sand	18	77	1	4	4.8	6.2	3.6	6	3180	88200
Sand	54	34	8	4	1.9	3.7	2.1	6.7	3480	162000
Sand	46	44	5	5	3.6	5.8	3.4	5.9	4980	153000
Coarse Sand	60	33	5	2	3.8	5	2.9	6.7	2980	103000
Loamy Sand	43	44	7	6	9.8	13.6	7.9	5.9	3980	50300
Coarse Sand	58	36	2	4	7.3	12.2	7.1	6	2480	35000
Sand	45	49	3	3	7.1	11.6	6.7	5.7	2480	36800
Loamy Sand	38	48	7	9	3.7	9.8	5.7	6	16000	280000
Loamy Sand	46	42	6	6	4.8	7	4.1	5.3	4480	110000
Loamy Fine Sand	27	60	7	6	5.2	9.2	5.3	5.7	4980	93100
Sand	33	59	3	5	7.8	12.8	7.4	5.7	3980	53500
Loamy Sand	33	52	8	7	5.6	9.4	5.5	6.3	7980	146000
Loamy Fine Sand	26	58	9	7	6	10	5.8	6.4	5980	104000
Loamy Fine Sand	25	62	8	5	4.8	8.2	4.8	6.4	4480	94000
Peat	N/A	N/A	N/A	N/A	N/A	63.8	37	5.5	4480	12100
Peat	N/A	N/A	N/A	N/A	55	49.8	28.9	5.2	3980	13800
Loamy fine Sand	17	70	7	6	19.2	26	15.1	4.6	3980	26300
Fine Sand	12	82	2	4	4.7	6.6	3.8	5.9	6980	182000
Very Fine Sand	1	89	6	4	8.6	9.2	5.3	5.7	4480	83800
Fine Sand	18	77	3	2	5.1	10	5.8	5.5	2480	42700
Loamy Fine Sand	15	73	7	5	4.1	7.4	4.3	5.8	12000	278000
Peat	N/A	N/A	N/A	N/A	75.4	85	49.3	5	4480	9070
Peat	N/A	N/A	N/A	N/A	90.3	50.8	29.5	5.4	2480	8430
Peat	N/A	N/A	N/A	N/A	59	90	52.2	4.9	4480	8560
Loamy Very Fine Sand	8	78	7	7	12.2	18	10.4	7	3980	38000
Soils from Greece
Sandy Loam	16	45	22	17	8.2	2.3	1.3	8	54000	4040000
Loamy Find Sand	19	53	14	14	4.4	0.8	0.5	8.2	62000	13300000
Clay Loam	3	44	25	28	11.1	2.3	1.3	8.2	92000	6880000
Silty Clay Loam	<1	25	29	45	15.8	2.3	1.3	8.1	188000	14060000
Clay Loam	<1	29	23	48	18.3	2.8	1.8	8.2	170000	10400000
Clay Loam	<1	38	22	40	16.2	3.1	2.1	7.8	176000	9760000
Silty Loam	6	45	31	18	9.8	3.7	1.9	7.3	39000	1810000
Silt Loam	<1	39	35	26	11.5	3.3	2.1	7.8	89000	4640000
Fine Sandy Loam	6	49	19	26	9.3	3.7	1.6	6.9	41000	190500
Clay Loam	<1	30	25	45	23.6	2.8	1.7	7.7	194000	11900000
Silt Loam	4	38	31	27	18.5	3	2.1	6.6	197000	11300000
Clay Loam	3	34	26	37	18.3	3.7	2.6	7.9	225000	10500000
Fine Sandy Loam	8	52	15	25	13.8	4.4	1	5.3	152000	5940000
Loamy Fine Sand	12	61	14	13	7.6	1.8	1.1	5	52000	4970000
Loamy Fine Sand	7	65	13	15	11.7	1.9	1	7.4	59000	5340000
Loamy Fine Sand	12	67	10	11	6.1	1.7	1.3	5.5	48000	4850000
Loamy Fine Sand	4	73	10	13	7.8	2.2	1.7	7.9	25000	1950000
Clay Loam	3	46	16	35	13.5	2.9	1.6	7.9	59000	3500000
Clay Loam	6	47	15	32	10.6	2.8	1.7	8.1	45000	2980000
Clay Loam	5	44	18	33	13.9	2.9	1	7.8	51000	3020000
Soils from Italy
Silty Clay	<1	8	32	60	25.9	1.7	1.2	8.2	400000	40500000
Silty Clay	<1	12	33	55	22	2.1	2.1	7.8	76000	6220000
Clay	1	10	19	70	26.2	3.6	0.8	7.9	89000	4250000
Loamy Very Fine Sand	5	73	6	16	6.8	1.4	0.8	7.7	16000	1960000
Very Fine Sand	1	88	4	7	3.8	1.3	0.8	8.1	7480	990000
Loamy Very Fine Sand	1	79	6	14	7.9	1.8	1	8	30000	2860000
Silty Clay Loam	7	19	34	40	16.2	2.5	1.5	4.9	34000	2340000
Silty Clay Loam	10	16	37	37	18.5	3.7	2.1	5.1	34000	1580000
Silty Clay Loam	8	17	41	34	22.9	4.5	2.6	5.2	35000	1340000
Silty Clay Loam	5	30	31	34	16.2	2.2	1.3	8	230000	18000000
Soils from The Netherlands
Organic Very Find Sand	8	85	3	4	15.6	10	5.8	5.6	3980	68500
Organic Fine Sand	8	80	6	6	22.5	15	8.7	5.5	5980	68500
Organic Fine Sand	9	78	4	9	19.9	13.6	7.9	6.1	7980	100900
Organic Fine Sand	10	82	4	4	16.4	10.1	5.9	6	4980	84800
Peaty Fine Sand	9	79	5	7	59.7	19.6	11.4	5.7	6480	56900
Fine Sand	17	75	3	5	7.4	3.2	1.9	5.8	4480	240800
Fine Sand	17	77	3	3	6.2	3	1.7	5.5	3480	200000
Fine Sand	18	76	3	3	7.2	3.4	2	5.7	5480	277000
Fine Sand	10	82	4	4	7.5	3.3	1.9	6.2	1980	103000
Fine Sand	9	82	5	4	7.4	3.2	1.9	6.8	1980	106000
Sand	29	65	2	4	9.2	4.4	2.6	5.8	5980	234000
Fine Sand	16	75	3	6	6.4	3.3	1.9	6.1	8480	442000
Fine Sand	19	73	3	5	7.9	3.3	1.9	6.2	7480	390000
Fine Sand	15	78	3	4	6.9	3.2	1.9	5.4	3980	214000
Fine Sand	15	79	2	4	6.5	3	1.7	6.2	3480	200000
Fine Sand	18	78	1	4	3	1.1	0.6	7	7980	1250000
Fine Sand	15	82	1	2	3.1	1.2	0.7	7.3	7480	1070000
Fine Sand	16	81	1	2	3.1	1.2	0.7	6.7	5980	857000
Sand	33	64	1	2	1.3	0.6	0.3	7.6	2980	854000
Sand	40	57	1	2	4.1	1.6	0.9	7.4	2980	320000
Sand	45	52	<1	2	0.7	0.1	0.1	8.6	2480	4270000
Fine Sand	14	76	5	5	7.5	3.6	2.1	5.8	5480	262000
Fine Sandy Loam	<1	52	19	29	14.2	3.3	1.9	7.6	151000	7870000
Peaty Clay Loam	10	31	23	36	48	24	13.9	6	25000	179000
Clay Loam	8	36	24	32	17.9	2.5	1.5	6.6	99000	6810000
Sand	48	46	2	4	2.4	2.2	1.3	7	6980	546000
Sand	41	53	3	3	2	1.4	0.8	7.4	6980	858000
Very Fine Sandy Loam	<1	63	23	14	9.6	2.5	1.5	5.5	28000	1925000
Peaty Fine Sand	26	66	5	3	21	15.1	8.8	4.8	2980	33900
Sand	34	63	<1	2	7.4	4.3	2.5	5.4	2480	99200
Sand	28	80	4	8	7.3	1.4	0.8	7.3	29000	3560000
Loamy Very Fine Sand	<1	75	9	16	7.1	2.1	1.2	7.9	72000	5900000
Loamy Very Fine Sand	<1	75	4	21	7	1.9	1.1	8	60000	5430000
Very Fine Sandy Loam	<1	60	15	25	12.2	2	1.2	7.6	128000	11000000
Sandy Clay Loam	<1	59	8	33	12.4	2.1	1.2	7.6	94000	7700000
Very Fine Sandy Loam	<1	57	23	20	13.7	2.2	1.3	7.4	160000	12500000
Clay Loam	2	45	20	33	15.7	3.9	2.3	7.9	174000	7670000
Soils from the UK
Peat	N/A	N/A	N/A	N/A	73	59	34.2	7	34000	99100
Peat	N/A	N/A	N/A	N/A	86	83	48.1	5.6	7480	15500
Peaty Clay	4	13	23	60	41	24	13.9	7.5	29000	208000
Loamy Sand	38	46	4	12	12.5	4.8	2.8	7.5	17000	609000
Loamy Sand	31	46	6	17	15.4	5.3	3.1	7.6	33000	1070000
Sand	37	51	4	8	5.1	1.4	0.8	7.9	15000	1840000
Fine Sand	18	69	3	10	8.7	3.7	2.1	7.4	18000	836000
Fine Sand	23	71	2	4	3.7	2.2	1.3	6.5	4980	389000
Peat	N/A	N/A	N/A	N/A	65	58	33.6	5.2	9980	29600
Peat	N/A	N/A	N/A	N/A	73	74	42.9	5	9450	22000
Peat	N/A	N/A	N/A	N/A	58	54	31.3	5.4	14000	44500
Peat	N/A	N/A	N/A	N/A	66	71	41.2	5.2	16000	38700
Loamy Very Fine Sand	5	74	11	10	8.9	3.5	2	7.3	32000	1570000
Loamy Fine Sand	19	66	6	9	7.2	2.9	1.7	6.4	9980	592000
Loamy Fine Sand	19	66	6	9	8.5	3.5	2	6.1	9480	486000
Silty Loam	4	44	31	21	13.6	2.9	1.7	6.3	25000	1480000
Fine Sandy Loam	9	52	22	17	10.1	3.4	2	5.5	13000	657000
Sandy Loam	11	43	26	20	18.4	9.7	5.6	6.1	14000	248000
Sandy Loam	24	44	17	15	10.1	3.5	2	6.2	16000	785000
Fine Sand	14	72	4	10	6.7	1.9	1.1	7	20000	1810000
Sand	46	36	9	9	6.5	2.5	1.5	6.8	6980	480000
Sand	47	36	9	8	4.3	1.5	0.9	6.8	5980	686000
Loamy Sand	43	38	12	7	4.4	1.7	1	7.8	5980	605000
Loamy Sand	43	35	11	11	6.8	2	1.2	6.6	32000	2750000
Loamy Very Fine Sand	2	73	11	14	6.1	1.9	1.1	6.4	60000	5430000
Loamy Fine Sand	21	54	14	11	5.6	1.6	0.9	6.4	11000	1180000
Loamy Sand	25	49	15	11	5.1	1.4	0.8	6.4	9980	1230000
Loamy Sand	34	48	10	8	4.5	1.3	0.8	5.5	9480	1250000
Laomy Coarse Sand	54	28	8	10	5.6	1.6	0.9	6.6	18000	1930000
Loamy Fine Sand	6	64	17	13	8.1	2.8	1.6	7.1	12000	736000
								average		1635797
								median		405500

Validity criteria fulfilled:

not specified

Conclusions:

The partition adsorption coefficients (Kd values) in the soils ranged from 980 to 400000. Kd values adjusted for the organic carbon content of the soil (Koc) ranged from 8400 to 40000000.

Executive summary:

The adsorption properties of the unlabelled test substance were determined in 230 European soils covering a wide range of textural classes as well as a wide range of physical and chemical characteristics. The soils were collected from sites in Denmark, Germany, Greece, Italy, the Nethlerands and the UK with a known history of use of the test substance on various crop types.  Adsorption steps of at least 16 hours were employed to equilibrate soil slurries of the test substance between soil and solution phases. For the adsorption steps, at least 6 nominal concentrations were used. After adsorption, the soil slurries were centrifuged and the supernatants were assayed using wheat seedling bioassays. The soil adsorption coefficients were determined. The partition adsorption coefficients (Kd values) in the soils ranged from 980 to 400000. Kd values adjusted for the organic carbon content of the soil (Koc) ranged from 8400 to 40000000. The average Koc value is 1635797 and median Koc value is 405500. 

Description of key information

Median Koc value is determined to be 405500 (8400 - 40000000) in 230 representative soils, Dyson, 1994.

All available data was assessed and the study by Dyson is considered representative of the adsorption/desorption properties of the test substance. Other studies are included as supporting information.

Key value for chemical safety assessment

Koc at 20 °C:

405 500

Additional information

Table: Overview of available data on adsorption / desorption of the test susbtance

Method	Guideline / GLP	Endpoint	Value	Reference
Adsorption / desorption determined in 230 representative soils	No guideline followed	Kfoc-Ads	8400 - 40000000	Dyson, 1994