1-(allyloxy)-2-methyl-1-oxopropan-2-yl 2-chloro-5-[3-methyl-2,6-dioxo-4-(trifluoromethyl)-3,6-dihydropyrimidin-1(2H)-yl]benzoate

Adsorption / desorption

Description of key information

Kf = 4.1 to 34.0,  Koc= 251 to 462, substance strongly to very strongly adsorbed in Cumulic humaquept and strongly adsorbed in Typic and Rhodic hapludox soils, OECD 106, Brandelli 2001
Kf = 1.01 to 4.06, mean Koc = 269, the substance is strongly adorbed in Speyer2.1 and Gartenacker soils, OECD 106, Schulze-Aurich 1998
Kd = 1.1 (MD sandy loam) to 4.1 (MD sand), Koc = 69 (MD silt loam) to 2347 (MD sand), main degradates CGA-293731 (2.2 to 14.4% of dose on soil columns, 7.5 to 44.6% in leachates) and CGA-293730 (0.1 to 1.1% of dose on soil columns, 0.1 to 4.6% in leachates), EPA N 163-1, Spare 1996a 
Main degradates were CGA-293731 (4.8 to 7.2% of dose on soil columns, 45.7 to 55% in leachates) and CGA-293730 (0 to 0.8% of dose on soil columns, 2.7 to 25.2% in leachates). Average Kd = 0.6 to 0.9 and average Koc = 24 to 524, The aged-substance and its degradates classified very high to low mobility, EPA N 163-1, Spare 1996b
Adorption: Kd = 0.961 (MD Sand) to 11.1 (IL Clay Loam),  Koc= 149 (MD Sandy Loam) to 581 (IL Clay Loam), the primary degradate observed was CGA-293731 (maximum 29.7% of dose, MD silt loam) with minor amounts of CGA-293730 (maximum 3. 1% of dose, MD silt loam). The substance and its degradates classified low to high mobility, EPA N 163-1, Spare 1996c
In four soils substance mean relative mobility factor (RMF) = 0.66, mean Koc = 298 ml/g, the mobility of substance was considered to be low (mobility class II), only degradates M4 (CGA 293731) and MX were found in the leachates, Reischmann, 1998
Aged- substance in two soils, four metabolites were identified, CGA 293730 (67.5-80.4% AR), CGA 380963 (11.4-16.8% AR), CGA 293731 (1.7-1.9% AR), CGA 98166 (1.9-1.0% AR). For the major metabolites, mean relative mobility factors were <1.7 CGA 293730 and <1.6 CGA 380963 with corresponding Koc values of 63 and 70. These soil metabolites are classified as considerably mobile (mobility class IV), Morgenroth, 1998.
The arit. mean KOC of 331 l/kg was used in the ERA

Key value for chemical safety assessment

Koc at 20 °C:

331.3

Additional information

OECD 106, Brandelli 2001: This study was performed in accordance with the OECD guideline for the testing of chemicals, number 106, 2000. The adsorption/desorption characteristics and the Freundlich adsorption/desorption isotherms of test substance were determined in the following Brazilian soils: Typic hapludox, Cumulic humaquept and Rhodic hapludox.  

Adsorption: Typic hapludox Kf ads= 4.8; Koc = 462 / Cumulic humaquept Kf ads= 34.0; Koc = 255 / Rhodic hapludox Kf ads= 4.1; Koc = 253

Desorption: Typic hapludox Kf des= 14.0; Koc = 1346 / Cumulic huinaquept Kf des= 57.4; Koc = 431 / Rhodic hapludox Kf des= 8.3; Koc = 512

Based on these results, the substance is strongly adsorbed in Cumulic humaquept, Typic hapludox and Rhodic hapludox soils.

 

OECD 106, Schulze-Aurich 1998: The adsorption and desorption of the test substance, was studied according to OECD Guideline For Testing of Chemicals, No. 106, Adsorption/Desorption, adopted May 12,1981 with two soil types (Gartenacker and Speyer 2.1 soils). Obtained data were compared to other compounds. Pre-test data showed that adsorption reached equilibrium within less than 4 hours of exposure.

The Freundlich adsorption constants kads varied between 1.01 ml/g of soil Speyer 2.1 and 4.06 ml/g of soil Gartenacker. The mean adsorption constant based on the organic carbon content (OC) of all soils was Koc = 269 ml/g OC. With respect to the organic matter (OM) of the soils the mean adsorption constant was calculated to Kom = 156 ml/g (OM). This classifies the substance as a strongly soil adsorbed compound, as e.g. Metolachlor or Terbutryn. The compound is therefore considered to be only little mobile.

Desorption of substance was to a large extent reversible in the tested soils. Ranging from 1.33 ml/g of soil Speyer 2.1 to 4.88 ml/g of soil Gartenacker, the desorption constants were close to the corresponding adsorption constants. The average desorption constants (Koc) were 343 ml/g OC (1st desorption) and 410 ml/g OC (2nd desorption).

Analysis of the soil extracts showed no degradation products. The amounts of non-extractable radioactivity were found to be low (1.2% and 1.36% for Gartenacker and Speyer 2.1 soil, respectively). The amount of radioactivity found (mean values) after adsorption in the aqueous phase ranged from 44.11 % (Speyer 2.1) to 62.69 % (Gartenacker).

 

EPA N 163-1, Spare 1996a: The adsorption and desorption of test substance was studied according to EPA Guideline Subdivision N163 -1 (Leaching and Adsorption/Desorption) with four soil types (Maryland [MD] sand, MD sandy loam, Illinois [IL] clay loam and MD silt loam). Pure [phenyl-U-14C]test substance was prepared in solution. The dose solution was applied directly to four different soil types prepared in twelve inch soil columns at field capacity. Following leaching, average radiocarbon recoveries ranged from 92.2 (MD sand) to 102.0 (MD silt loam) percent of dose.

After elution, the leachate from each column was recovered and analyzed for total radioactivity. The average radioactivity in the leachates accounted for 19.9% of dose for IL clay loam soil, 48.3% for MD sandy loam soil, 42.5% for MD silt loam soil, and 13.3% for MD sand soil. In leachates from the MD sand and one of the MD silt loam columns, test substance was detected intact. Parent represented an average 5.6% of dose in the MD sand leachates and 0.3% of dose in the MD silt loam. Approximately 7.5 to 44.6 average percent of dose in the leachates was identified as CGA-273731 and 0.2 to 4.6 average percent of dose was CGA-293730. Small amounts of several other products (up to three) were observed at a maximum of 0.4 average percent of dose.

Each soil column was segmented into the treated layer and five 6 cm sections after elution and all sections were extracted. The average amount of radioactivity retained on the columns was 78.5% of dose for IL clay loam, 59.3% for MD silt loam, 52.2% for MD sandy loam, and 78.8% for MD sand. In all cases extracted radioactivity was primarily test substance. CGA-293731 was detected at 0.2 to 3.7 percent of dose per column segment. Minor amounts of CGA-293730, CGA-368221, CGA-321432, and CGA-368220 (maximum 0.4% of dose) were detected.

Considering the total radioactivity detected in the leachate, sorption constants, Kd (mL/g), and sorption coefficients based upon organic carbon, Koc (mL/g organic carbon), were estimated for test substance and its degradation products for each soil type. Average sorption constants (Kd) ranged from 1.1 (MD sandy loam) to 4.1 (MD sand) and average sorption coefficients (Koc) ranged from 69 (MD silt loam) to 2347 (MD sand). Based upon the range of sorption coefficients (Koc), test substance and its degradates would be classified as having high to slight mobility. Main degradates were CGA-293731 (2.2 to 14.4% of dose on soil columns, 7.5 to 44.6% of dose in leachates) and CGA-293730 (0.1 to 1.1% of dose on soil columns, 0.1 to 4.6% of dose in leachates).

 

EPA N 163-1, Spare 1996b: The adsorption and desorption of aged test substance was studied according to EPA Guideline Subdivision N163 -1 (Leaching and Adsorption/Desorption) with four soil types (Maryland [MD] sand, MD sandy loam, Illinois [IL] clay loam and MD silt loam). Pure [phenyl-U-14C]test substance was prepared in solution. The dose solution was applied to four different soil types at 0.10 to 0.11 ppm, aged until the approximate soil half-life (0.8 days for sandy loam and silt loam, 1.2 days for clay loam soil, and 2.2 days for sand soil) at 25±1°C and 75% of 1/3 bar field moisture capacity (FMC), and tested for leaching characteristics. Approximately twelve inch soil columns in duplicate were tested with a volume of 0.01M aqueous calcium chloride solution equal to at least twenty inches times the cross sectional area of the column at an infiltration rate of no more than one inch per hour. Following leaching, radiocarbon recoveries were 93.8% to 104.6% percent of dose.

After elution, the leachate from each column was recovered and analyzed for total radioactivity. The average radioactivity in the leachates accounted for 60.8% of dose for IL clay loam soil, 70.5% for MD sandy loam soil, 80.2% for MD silt loam soil, and 49.2% for MD sand soil. Intact test substance was detected only in leachates from MD sand soil columns at an average of 0.8% of dose. CGA-293731 accounted for the majority of radioactivity in the leachates: 45.7% MD sand, 47.2% IL clay loam, 50.4% MD sandy loam, and 55.0% MD silt loam. The remaining activity in the leachates was CGA-293730 accounting for 2.7% in MD sand, 13.6% in IL clay loam, 20.0% MD sandy loam, and 25.2% in the MD silt loam. No other products were observed.

Each soil column was segmented into the treated layer (top) and 6 cm sections after elution and all sections were extracted. The average amount of radioactivity retained on the columns was 43.7% of dose for IL clay loam, 19.5% for MD silt loam, 24.8% for MD sandy loam, and 44.5% for MD sand. In all cases radioactivity extracted from the soil column sections was primarily test substance. The remaining activity on the soil columns was mainly CGA-293731 at 5 to 8% of dose. No other product was detected at greater than 1.0% of dose.

Considering the total radioactivity detected in the leachate, sorption constants, Kd (mL/g), and sorption coefficients based upon organic carbon, Koc (mL/g organic carbon), were estimated for test substance and its degradation products for each soil type. Average sorption constants (Kd) ranged from 0.6 (MD sandy loam and MD silt loam) to 0.9 (MD sand and IL clay loam) and average sorption coefficients (Koc) ranged from 24 (MD silt loam) to 524 (MD sand). Based upon the range of sorption coefficients (Koc), test substance and its degradates would be classified as having very high to low mobility.

 

EPA N 163-1, Spare 1996c: The adsorption and desorption of test substance was studied according to EPA Guideline Subdivision N163 -1 (Leaching and Adsorption/Desorption) in four soils (Maryland [MD] sand, MD sandy loam, Illinois [IL] clay loam and MD silt loam) with varying in organic matter and texture were tested using the batch equilibrium technique (adsorption/desorption). Analytical grade uniform phenyl-ring-labelled test substance was prepared in aqueous 0.01M calcium ion solution added to soil, and allowed to equilibrate in the dark while shaking at a controlled temperature of 25±1°C. After equilibration, the phases were separated by centrifugation with test substance concentrations determined by liquid scintillation counting (LSC) of the aqueous phases and by difference for the soil phases. The soil phases were next desorbed with aqueous 0.01M calcium ion solution free of test substance and concentrations determined by combustion of the soil and LSC of the aqueous phase following centrifugation.

All data were evaluated using the Freundlich equation and values for Koc (sorption coefficient-organic carbon), Kd (sorption constant) and n were determined. The results demonstrated that the Freundlich isotherm was applicable to analysis of adsorption and desorption of test substance. TLC and HPLC analysis demonstrated significant degradation of test substance to CGA-293731 and to a lesser extent CGA-293730 during this study. Degradation of test substance occurred during adsorption and was dependent on soil type with MD sand showing the least degradation and MD silt loam demonstrating the greatest. All radioactivity was identified as parent test substance or its degradates CGA-293731 (maximum 29.7 percent of dose) or CGA-293730 (maximum 3.1% of dose). Other minor products were observed (maximum total <1% of applied dose). Logarithmic plots of data yielded a straight line for all 4 soil types tested. Test substance and its degradates were classified as having a low to high mobility with Koc values between 149 and 581.

 

Reischmann 1998: The substance leaching behaviour was examined in a study according to Commission Directive 95/36/EC of 14 July 1995 7.1. -7.1.3.1, in a soil column model experiment and compared to monuron which is known to be moderately mobile in the field. The mobility of the test substance was investigated in a sand (Speyer 2.1 (FRG)), a loamy sand (Pappelacker (CH)), in three silt loams (Gartenacker (CH), Vetroz (CH), and lbaragi-Ushiku (J)), and a loam (Hyogo-Ono(J)). For this purpose, the 14C-Iabelled test substance was applied at a rate corresponding to about 0.5 kg a.i. I ha onto the top of 30-cm soil columns and thereafter submitted to artificial rain of 200 mm (constant head method). Results were compared with those of a reference substance (monuron) tested simultaneously on the same columns.

By far the majority of the radioactivity was found in the first three soil layers accounting for 78.7 % (Pappelacker) to 94.1 % (Vetroz) of the dose applied. The radioactivity found in the soil extracts consisted of parent substance (44.5- 96.0 %) and of two degradates M4 (0.5- 33.3 %) and MX (2.9- 5.2 %). Metabolite M4 was tentatively characterised as CGA 293731. The total amount of radioactivity found in the leachates ranged from 0.02% to 8.2 %, corresponding to 0.0204 μg/mL in maximum. Only the degradates M4 and MX were found in the leachates.

The penetration depth of test substance into the soil profile was 5 - 30 cm for all investigated soils, whereas the leaching distance of monuron was 10 to > 30 cm. The mean relative mobility factor (RMF) was calculated to be 0.66. Based on these findings, and considering the estimated Koc of 298 ml/g, the substance can be considered to have low mobility in the soil (mobility class II).

 

Morgenroth 1998: The substance leaching and its main soil metabolites behaviour was examined in a study according to Commission Directive 95/36/EC of 14 July 1995 7.1. -7.1.3.1, in a soil column model experiment and compared to monuron which is known to be moderately mobile in the field. For this purpose, a loamy sand (Pappelacker) and a loam (Gartenacker) was treated separately with the 14C-phenyl-ring labelled test substance at a dose corresponding to a field rate of approximately 0.65 - 0.71 kg a.i./ ha and aged under aerobic conditions at 20°C for 13 days in a metabolism apparatus at a soil moisture of 40 % MWC. After ageing, the soil was analysed for amount of parent molecule and number and nature of metabolites. Thereafter, aliquots of soil were taken and the reference compound monuron was incorporated into the aged soil aliquots. Finally, the soils were applied as 2-cm layers onto the top of untreated soil columns.

Artificial rain of 100 and 200 mm was applied onto the soil columns. The objective for the additional use of a lower percolation volume (100 mm) was to prevent the wash-out of metabolites from the column thus allowing an estimate of their mobility and soil adsorption constants by comparison with the reference compound. The leachates were collected and the radioactivity determined. The penetration depth of the radioactive fractions were compared to the one of the reference substance (monuron) tested simultaneously on the same columns. The metabolite pattern after 13 days of ageing under aerobic conditions was similar for both soils. The main fractions in the soil extracts were M2 (CGA 293730), with 80.4% (Pappelacker) and 67.5% (Gartenacker) and M1 (CGA 380963), with 11.4% and 16.8 %, accordingly. The concentration of parent substance was 2.4 % (Pappelacker) and 1.0 % (Gartenacker). Metabolite M4 (CGA 293731), represented 1.7 and 1.9% of the applied radioactivity, whereas M7A (CGA 98166), accounted for 1.9% and 1.0% for soils Pappelacker and Gartenacker, respectively. After percolation of 200 mm artificial rain, the leachates mainly contained metabolites M2 (CGA 293730) and M1 (CGA 380963) accounting for 78.3 % (54.9 % for Gartenacker) and 11.2 % (13.4 % for Gartenacker) of the radioactivity applied, respectively. The concentrations measured for M4 (CGA 293731) and M7A (CGA 98166) were 2.0% and 1.6% (0.7% and 0.5% for Gartenacker), respectively. No parent substance was found in any of the leachates. With the percolation 100 mm artificial rain, practically no radioactivity was found in the leachates under these conditions (<0.1% and 0.8%, respectively, not further analysed).

Analysis of the extractables of the soil layers showed that, M2 (CGA 293730) was the predominant radioactive fraction found in both soil types followed by M1 (CGA 380963). Parent substance (test substance) was found in the upper soil layer only (1.8 and 1.5 %). The sum amounts found for M4 (CGA 293731) and M7A (CGA 98166) in Pappelacker were 1.1 % (0.2 % for Gartenacker) and 2.3 % (below the detection limit for Gartenacker), respectively. The penetration depth of M2 (CGA 293730) into the soil profile was 28 and >30 cm for Pappelacker and Gartenacker, whereas the leaching distance of monuron was >20 and >16 cm. The penetration depth of M1 (CGA 380963) into the soil profile after an irrigation of 100 mm artificial rain was 28 cm for both soils.

The mean relative mobility factors (RMF) were calculated to be <1.7 for CGA 293730 and <1.6 for CGA 380963 with corresponding Koc values of 63 and 70. Based on their relative mobility factors, the major soil metabolites of the test substance (CGA 293730 and CGA 380963) can be considered to be highly mobile (mobility class IV).

[LogKoc: 2.52]