Pirimiphos-methyl

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

8 Mar 1993 to 27 Jul 1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Qualifier:

according to guideline

Guideline:

other: BBA Part IV 5-1

Version / remarks:

December 1990

Deviations:

not specified

GLP compliance:

yes

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment: freshwater

Details on source and properties of surface water:

- Two different water/sediment systems were used:
1) 'Old Basing', River Loddon, Old Basing, Basingstoke, Hampshire, OS Ref SU660 527.
2) 'Virginia Water', The Great Park (Crown Estate), Virginia Water, Berkshire, OS Ref SU984 697.

- Preparation of water: Water from the two sites was passed through a 212 μm sieve.
The water and sediments were supplied by the Study Sponsor. Details of the location, sampling, handling and properties of each test system are given in Table 1 and 2 in 'Any other information on materials and methdos incl. tables'.

Details on source and properties of sediment:

The properties of sediment are provided in 'Details on source and properties of surface water', Table 1 and Table 2 in 'Any other information on materials and methods incl. tables'.

- Preparation of sediment: Each sediment was passed through a 2 mm sieve.

Duration of test (contact time):

100 d

Initial conc.:

1.5 other: kg/ha

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Details on study design:

TEST CONDITIONS
- Acclimation period: Water/sediment systems were set up in the laboratory and allowed to acclimatise for about one month.
- Acclimation condition: Vessels were plugged with cotton wool and temporarily stored for about 5 days in an incubator at approximately 20 ± 2°C. For acclimatisation each test vessel was incorporated into a separate gas-flow system allowing humidified air to pass over the surface of the water. The glass tube bringing the air-flow into the test vessel was positioned about 3 cm above the water surface. The flow rate was 50 mL/min. The vessels were maintained in the dark at 19.5 ± 0.6°C. During acclimatisation, the pH and oxygen concentration in the water and the redox potential in the water and sediment were measured. Duplicate determinations were made at least twice a week for each water/sediment system until a measurable equilibrium in these parameters was established. The acclimatisation period was 33 days except for time zero, which was 36 days.
- Test substance application: The radiolabelled application solution was prepared by dissolving 14C-labelled test substance in acetonitrile at a nominal concentration of 2.95 mg/mL. An aliquot (90 μL) of the application solution was applied to 40 water/sediment test systems (20 of each sediment type). After application each vessel was gently agitated, taking care to minimise any disturbance of the sediment.
- Test temperature: 19.5 ± 0.6°C
- Continuous darkness: Yes
- pH: 6.1 - 8.4 (Old Basing); 5.8 - 8.1 (Virginia Water)
- Oxygen concentration: 25 - 50% (Old Basing); 22 - 45% (Virginia Water)
- Redox potential: -20 to -138 mV (Old Basing); -48 to -157 mV (Virginia Water)
- Initial biomass of sediment: 463.8 μg C/g sediment (Old Basing); 142.6 μg C/g sediment (Virginia Water)
- Biomass of sediment at the end of the test: 346.9 μg C/g sediment (Old Basing); 114.1 μg C/g sediment (Virginia Water)

TEST SYSTEM
- Culturing apparatus: 250 mL glass vessels, diameter 5 cm
- Weight of sediment per vessel: Approximately 58 g and 66 g wet weight of sediment from Old Basing and Virginia Water, respectively. (filled to a depth of 2 - 2.5 cm of the test vessel)
- Number of culture flasks/sediment: 32
- Volume of water per vessel: Approximately 150 mL (give a depth of about 6 cm above the surface of the sediment in the test vessel)
- Method used to create aerobic conditions: During acclimatisation period, the flow rate of humidified air above the surface of the water was increased to 200 mL/min in order to maintain aerobic conditions in the water phase.
- Test performed in closed vessels due to significant volatility of test substance:
- Details of trap for CO2 and volatile organics if used: Polyurethane foam bungs was used to trap neutral, volatile organic compounds including any volatilised test substance. Ethyl digol trap was used to trap organic volatiles. The 1 M aqueous potassium hydroxide with phenolphthalein indicator and ethanolamine : 2-ethoxyethanol (1 : 3 V/V) were used to to trap 14CO2.

SAMPLING
- Sampling frequency: For each water/sediment type duplicate test vessels were taken for analysis immediately and at 0.25, 1, 2, 7, 14, 30, 59 and 100 days after test substance application. Trapping solutions and polyurethane foam bungs were taken for analysis at each sampling interval and at Day 65. Additionally, polyurethane foam bungs were taken for analysis 3 days after test substance application. At each sampling interval, the water and sediment were separated prior to analysis. Further water/sediment test systems were set up for determination of microbial biomass at the start and end of the test period.
- Anlysis of samples: Duplicate test vessels of each sediment type were analysed at each sampling time. At the time of sampling the oxygen concentration, pH and temperature of the water and the redox potential of the water and sediment were measured.
- Sample storeage: The water and sediment were separated on the day of sampling. Both were stored at < -15°C prior to analysis. The sediment extracts were stored at < -15°C prior to analysis by HPLC and TLC. The water and sediment extracts were analysed within 8 weeks of sampling.

MEASUREMENTS
- Oxygen: The oxygen concentration of the water was measured using an oxygen meter connected to a suitable probe. The probe was calibrated at 0 and 100% oxygen saturation. 100 % saturation was achieved by shaking a sample of the ditch water for 30 seconds. The probe was inserted and gently agitated in the saturated water until an equilibrium was achieved. The meter was adjusted to read 100%. Nitrogen was blown through a second portion of ditch water. The probe was inserted and after equilibration the meter was adjusted to zero. The probe was then inserted in the water samples to be measured and gently agitated until a constant reading was achieved. The temperature of the water sample was also measured.
- pH: The pH of the water samples was measured using a combination electrode fitted to a pH meter. The probe was calibrated at pH 7 and pH 4 prior to use.
- Redox potentials: The redox potential of the water and sediment was measured using a platinum sensor with silver/silver chloride reference system. To measure samples the probe was inserted into the water about 2 cm below the surface and allowed to stabilise before taking the reading. The probe was then inserted into the sediment and again allowed to stabilise before recording the redox potential.
- Microbial biomass: Six untreated water/sediment systems for each sediment type were analysed for microbial biomass at the time of test substance application. Further water/sediment systems were treated with unlabelled test substance and kept under the same conditions as the test vessels. The microbial biomass was measured following the last sampling time (100 days).

Compartment:

natural water / sediment: freshwater

% Other volatiles:

12.2

% Recovery:

99.15

Remarks on result:

other: Mean total recovery from Old Basing water and sediment system after 100 days application of the test substacne. Details of information on recovery see Table 3 in 'Any other information on results incl. tables'.

Compartment:

natural water / sediment: freshwater

% Other volatiles:

30.2

% Recovery:

94.95

Remarks on result:

other: Mean total recovery from Virginia Water water and sediment system after 100 days application of the test substacne. Details of information on recovery see Table 4 in 'Any other information on results incl. tables'.

Parent/product:

parent

% Degr.:

99.4

Parameter:

radiochem. meas.

Sampling time:

100 d

Remarks on result:

other: From Old Basing system

Key result

Compartment:

natural water / sediment: freshwater

DT50:

5.5 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Old Basing; Total system

Compartment:

natural water / sediment: freshwater

DT50:

4.9 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Virginia Water; Total system

Compartment:

natural water / sediment: freshwater

DT50:

5.7 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Old Basing; Water

Compartment:

natural water / sediment: freshwater

DT50:

4.1 d

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: Virginia Water; Water

Mineralization rate (in CO2):

2 other: %

Other kinetic parameters:

pseudo-first order rate constant

Transformation products:

not specified

Remarks:

See additional information provided in overall endpoint summary.

Details on transformation products:

An overview of the results is provided in Table 8 - Table 11 in 'Any other information on results incl. tables'.
Water and extracts of sediment were analysed separately. The pattern of degradation was qualitatively similar in water and sediment for both Old Basing and Virginia Water. HPLC analysis revealed three distinct areas of radioactivity, other than the test substance. The first of these was an area associated with polar radioactivity (retention time 2 - 4 minutes). The radioactivity associated with peak 1 ('polars') accounted for a maximum 2% AR in water and 4.5% AR in the sediment from both Old Basing and Virginia Water. The pattern of formation of HPLC peak 2 (unidentified) (retention time, 9 minutes) was similar in both water/sediment systems. This component appeared almost exclusively in water and was transient, peaking at 30 days after application at about 14 - 16% AR and then declining rapidly. Co-chromatography by HPLC revealed the presence of metabolite M1 as the majority of the peak 3 although this peak appeared to contain another, as yet unidentified, component which was resolved by TLC. A similar pattern of formation of this peak was seen in the water/sediment systems of both Old Basing and Virginia Water. Metabolites M3 and M5 were not detected in either water or sediment.

Generally the results from TLC and HPLC analysis where comparable were in good agreement. Normal phase TLC co-chromatography with available reference compounds confirmed the presence of the test substance, whilst reverse phase TLC co-chromatography confirmed the presence of the test substance and metabolite M1. The resolution of metabolite M1 in TLC allowed it to be quantified by this method. Metabolites M3 and M5 were not detected in either water or sediment. Reverse phase TLC analysis showed that the rates of formation of metabolite M1 and peak 6 were similar in both water/sediment systems. The combined values for metabolite M1 and peak 6 are in good agreement with values calculated for peak 3 from HPLC analysis. Metabolite M1 showed a steady increase in both water and sediment, accounting for approximately 40 - 60% of the total applied radioactivity in systems sampled after 30 days or later. Peak 6 generally represented less than 4% AR in water and sediment combined.

Peak 7 (from TLC analysis) was shown by autoradiography to contain one major component and a number of minor unidentified components. The major component in peak 7 (TLC analysis) appeared to be resolved by HPLC analysis and was designated as peak 2. The minor components from peak 7 (TLC) were probably contained in the region of polar radioactivity eluted during 2 - 4 minutes period of HPLC analysis. Therefore HPLC analytical data was used to quantify the unidentified component Peak 2. It was a transient compound reaching a maximum, at 30 days after application, of about 20 % of the applied radioactivity. In water, this component disappeared rapidly whereas in sediment it was degraded at a much slower rate. By 100 days this component represented 2 - 4% of applied radioactivity. Up to 5 other unidentified components were detected none of which accounted for greater than 6% applied radioactivity at 100 days.

Evaporation of parent compound:

yes

Volatile metabolites:

yes

Residues:

yes

Details on results:

An overview of the results is provided in Table 3 - Table 7 in 'Any other information on results incl. tables'.

- Recovery of radioactivity: For each water/sediment test system the material balance was calculated as a percentage of the total radioactivity applied (% AR). In the following section results are the mean of replicate vessels analysed at each time. Total recoveries of radioactivity from Old Basing water/sediment systems treated with 14C-labelled test substance were in the range 94.2% AR to 100.1 % AR. Total radioactivity in the water increased from 6.8% AR at time zero to 49.6% AR after 30 days. After 100 days incubation, this had decreased to 37.9% AR. There was a corresponding decrease in the total radioactivity recovered from the sediment. This
decreased from 89.2% AR at time zero to 49.1 % AR after 100 days. Non-extractable radioactivity from sediment increased from 0.4% AR at time zero to 8.7% AR after 1 00 days. Volatile radioactivity amounted to 12.2% AR after 100 days. Of this a large portion was trapped on the polyurethane foam bungs (10.6% AR) and was subsequently characterised as the test substance using TLC.
Total recoveries of radioactivity from Virginia Water, water/sediment test system were in the range 93.7 - 102.9% AR. Total radioactivity in water increased from 13.3% AR at application to 46.1 % AR after 30 days. This declined to 34.1 % AR after 100 days. There was a decrease in the total radioactivity recovered in sediment from 82.3% AR at time zero to 30.7% AR after 100 days. Non-extractable radioactivity from sediment increased from 0.2 % AR at time zero to 6.1 % AR after 100 days. Volatile radioactivity amounted to 30 .2 % AR after 100 days, of which 27. 8 % was characterised as the test substance using TLC. A similar pattern of evolution to that seen in Old Basing was observed.

- Quantification of the test substance in water and sediment: In water/sediment test systems from Old Basing the test substance was rapidly degraded in both water and sediment. In water, the test substance showed an exponential decline from 5.4% AR at time zero to < 0.1 % AR 100 days after application. An exponential decline in the amount of the test substance in sediment was also observed with the level falling from 85.7% AR at application to 0.6% AR after 100 days incubation. The DT50 of the test substance in water calculated from this data was 5.7 days and the DT90 was 18.8 days. The DT50 of the test substance in water and sediment calculated from this data was 5.5 days, with a DT90 of 18.1 days. Total test substance in the whole test system declined from 91.1 % AR at application to 0.6% AR at 100 days.
In water/sediment test systems from Virginia Water the degradation of the test substance was again rapid in both water and sediment. In water, the test substance declined from 11.4% AR at time zero to < 0.1 % AR at 100 days. The amount of the test substance in sediment also decreased with time from 80.1 % AR at application, to 0.6% AR at 100 days. The DT50 of the test substance in water was calculated as 4.1 days with a DT90 of 13.5 days. The DT50 of the test substance in water and sediment was calculated as 4.9 days, with a DT90 of 16.4 days. Total test substance in the whole test system declined from 91.5 % at application to 0.6% at 100 days.
Both water/sediment systems showed a rapid decrease in the quantity of the test substance present between 14 and 30 days. A possible explanation for this may be due to the induction of microbial activity towards the test substance.

Table 3.Extraction and recovery of radioactivity from Old Basing water and sediment after application of 14C-labelled test substance at a nominal rate of 15 μg/cm2. Results are expressed as % applied radioactivity

Time after application (days)	Sample number	Total water	Sediment			Total sediment	Volatiles	Total recovery
			Extract 1	Extract 2	Not extracted
0	A33 A34	7.7 5.8	88.3 88.2	0.6 0.5	0.3 0.5	89.2 89.2	ND ND	96.9 95.0
0.25	A3 A4	5.7 6.1	93.0 91.7	0.5 0.3	0.3 0.3	93.8 92.3	1.5 0.7	101.0 99.1
1	A5 A6	6.7 8.0	86.6 85.9	0.3 0.5	0.2 0.3	87.1 86.7	5.2 1.9	99.0 96.6
2	A7 A8	7.4 8.9	77.4 83.7	0.6 0.4	0.4 0.3	78.4 84.4	4.0 5.3	89.8 98.6
7	A9 A10	12.4 11.9	73.8 70.1	0.9 1.2	1.1 1.2	75.8 72.5	10.7 10.0	98.9 94.4
14	A11 A12	27.9 23.0	49.0 57.9	1.3 1.3	2.5 1.8	52.8 61.0	16.7 11.3	97.4 95.3
30	A13 A14	50.2 48.9	31.6 31.7	3.0 2.8	4.2 3.5	38.8 38.0	8.6 8.5	97.6 95.4
59	A15 A16	36.3 42.0	28.4 34.5	3.1 3.3	7.0 5.9	38.5 43.7	24.4 14.8	99.2 100.5
100	A17 A18	39.2 36.6	33.4 36.3	6.2 4.9	9.1 8.3	48.7 49.5	9.6 14.7	97.5 100.8

 ND Not detected, no traps were sampled at Day 0

Table 3.Extraction and recovery of radioactivity from Old Basing water and sediment after application of 14C-labelled test substance at a nominal rate of 15 μg/cm2. Results are expressed as % applied radioactivity

Time after application (days)	Sample number	Total water	Sediment			Total sediment	Volatiles	Total recovery
			Extract 1	Extract 2	Not extracted
0	A33 A34	7.7 5.8	88.3 88.2	0.6 0.5	0.3 0.5	89.2 89.2	ND ND	96.9 95.0
0.25	A3 A4	5.7 6.1	93.0 91.7	0.5 0.3	0.3 0.3	93.8 92.3	1.5 0.7	101.0 99.1
1	A5 A6	6.7 8.0	86.6 85.9	0.3 0.5	0.2 0.3	87.1 86.7	5.2 1.9	99.0 96.6
2	A7 A8	7.4 8.9	77.4 83.7	0.6 0.4	0.4 0.3	78.4 84.4	4.0 5.3	89.8 98.6
7	A9 A10	12.4 11.9	73.8 70.1	0.9 1.2	1.1 1.2	75.8 72.5	10.7 10.0	98.9 94.4
14	A11 A12	27.9 23.0	49.0 57.9	1.3 1.3	2.5 1.8	52.8 61.0	16.7 11.3	97.4 95.3
30	A13 A14	50.2 48.9	31.6 31.7	3.0 2.8	4.2 3.5	38.8 38.0	8.6 8.5	97.6 95.4
59	A15 A16	36.3 42.0	28.4 34.5	3.1 3.3	7.0 5.9	38.5 43.7	24.4 14.8	99.2 100.5
100	A17 A18	39.2 36.6	33.4 36.3	6.2 4.9	9.1 8.3	48.7 49.5	9.6 14.7	97.5 100.8

 ND Not detected, no traps were sampled at Day 0

Table 5. Quantity of the test substance present in total volatile radioactivity following application to water/sediment at a nominal rate of 15 μg/cm2. Results are expressed as % applied radioactivity

Time after application (days)	Old Basing			Virginia Water
	Sample number	Total radioactivity	Test substance^a	Sample number	Total radioactivity	Test substance^a
0	A33 A34	ND ND	ND ND	B33 B34	ND ND	ND ND
0.25	A3 A4	1.5 0.7	1.3 0.6	B3 B4	1.4 4.0	1.3 3.9
1	AS A6	5.2 1.9	5.0 1.8	B5 B6	5.8 3.7	5.7 3.7
2	A7 A8	4.0 5.3	3.9 5.2	B7 B8	9.4 3.7	9.2 3.4
7	A9 A10	10.7 10.0	10.4 9.8	B9 B10	18.6 30.9	18.1 30.5
14	A11 A12	16.7 11.3	16.2 10.9	B11 B12	32.4 21.1	31.8 20.8
30	A13 A14	8.6 8.5	8.1 8.2	B13 B14	25.4 24.0	24.8 23.4
59	A15 A16	24.4 14.8	23.4 14.3	B15 B16	35.0 23.6	33.1 23.0
100	A17 A18	9.6 14.7	9.0 12.1	B17 B18	29.2 31.2	25.8 29.8

a. The test substance concentrations from TLC analysis

Table 6. Concentrations of total radioactivity and the test substance in water after application of 14C-labelled test substance at a nominal rate of 15 μg/cm2. Results are expressed as μg equivalents test substance/mL

Time after application (days)	Sample number	Old Basing		Sample numbers	Virginia Water
		Total radioactivity	Test substance		Total radioactivity	Test substance
0	A33 A34	0.13 0.10	0.104 0.081	B33 B34	0.22 0.23	0.183 0.202
0.25	A3 A4	0.09 0.10	0.049 0.055	B3 B4	0.24 0.25	0.177 0.157
1	A5 A6	0.10 0.13	0.071 0.080	B5 B6	0.28 0.30	0.154 0.167
2	A7 A8	0.12 0.14	0.067 0.081	B7 B8	0.27 0.28	0.185 0.174
7	A9 A10	0.21 0.21	0.026 0.024	B9 B10	0.38 0.30	0.062 0.046
14	A11 A12	0.48 0.39	0.008 0.020	B11 B12	0.35 0.47	0.021 0.049
30	A13 A14	0.89 0.83	0.001 0.002	B13 B14	0.81 0.81	0.001 0.001
59	A15 A16	0.64 0.72	< 0.001 < 0.001	B15 B16	0.57 0.71	0.001 0.001
100	A17 A18	0.65 0.68	0.001 < 0.001	B17 B18	0.65 0.63	< 0.001 < 0.001

 

Table 7. Mean quantities of the test substance in water and sediment from Old Basing and Virginia water at various times after application at a nominal rate of 15µg/cm2

Time after application (days)	Old Basing			Virginia water
	Water	Sediment	Total	Water	Sediment	Total
0	5.4	85.7	91.1	11.4	80.1	91.5
0.25	3.2	90.9	94.1	10.0	78.1	88.1
1	4.9	83.9	88.8	9.5	72.3	81.8
2	4.7	78.4	83.1	10.2	77.6	87.8
7	1.5	66.7	68.2	3.0	47.2	50.2
14	0.8	41.2	42	2.0	34.4	36.4
30	0.1	1.6	1.7	< 0.1	1.1	1.1
59	< 0.1	0.8	0.8	0.1	1.0	1.1
100	< 0.1	0.6	0.6	< 0.1	0.6	0.6

Mean quantities derived from HPLC analysis

Table 8. Quantities of radioactive components in water and sediment from Old Basing after application of 14C-labelled test substance at a nominal rate of 15 μg/cm(Components were separated by HPLC)

Radioactive component	Approximate retention time	Time after application in days (sample number)
	(min)	0		0.25		1		2		7		14		30		59		100
		A33	A34	A3	A4	A5	A6	A7	A8	A9	A10	A11	A12	A13	A14	A15	A16	A17	A18
Water
1 Polars^a	2-apr	0.1	<0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	<0.1	0.4	1.7	1.1	0.2	0.1	2.2	0.7
2	9	0.2	0.2	0.5	0.5	0.6	0.9	1.1	1.0	3.8	3.5	15.4	7.8	16.0	12.8	0.8	2.7	1.2	0 .7
3^b	13	0.6	0.4	1.1	1.3	0.8	1.7	1.8	2.2	6.5	6.4	11.6	13.0	31.1	34	34.7	38.0	35.0	34.5
4	17-19	0.1	0.1	0.2	0.3	0.1	0. 1	0.1	0.1	<0.1	0.1	0.1	0.2	0.1	<0.1	<0.1	0.1	<0.1	0.1
5	19-21	0.3	0.2	0.4	0.4	0.2	0.2	0.2	0.2	0.1	0.1	<0.1	0.1	0.1	<0.1	<0.1	<0.1	<0.l	<0.1
test substance		6.1	4.7	3.1	3.3	4.8	4.9	4.1	5.2	1.5	1.4	0.4	1.2	0.1	0.1	<0.1	<0.1	0.1	<0.1
Others^c		0.2	0.1	0.2	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.3	0.3	1.4	0.9	0.4	1.1	0.6	0.4
Sediment
1 Polars^a	2-apr	0.4	0.4	0.3	0.4	1.3	0.4	0.5	0.5	1.7	1.1	3.5	2.1	4.5	4.5	2.6	4.3	3.0	4.2
2	9	0.3	0.3	0.1	0.1	0.2	0. 1	0.2	0.1	0.1	0.1	1.0	0.6	2.8	1.2	1.8	2.3	2.0	4.2
3^b	13	0.6	0.5	0 . 5	0.5	0.4	0.8	0.9	0.8	4 . 1	4.1	9.4	9.2	24.2	26.5	25.1	28.1	32.1	29.1
4	17-19	0.3	0.2	0. 1	0.1	0.1	0.1	0.1	<0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.3	0.8	0.2	0.2
5	19-21	0.4	0.4	0.4	0.4	0.3	0.3	0.3	0.3	0.4	0.4	0.3	0.4	0.1	0.1	0.1	0.1	0.2	0 .2
test substance		85.4	85.9	91.5	90.2	83.9	83.9	75.1	81.7	68.2	65.2	35.7	46.7	1.6	1.5	0.7	0.8	0.7	0.5
Others^c		0.9	0.6	0.2	0.2	0.3	0.3	0.5	0.3	0.3	0.4	0.4	0.2	1.3	0.6	1.0	1.6	1.3	2.8

a. Polars - radioactivity containing more than one component

b. Contains mainly metabolite M1

c. Others - radioactivity distributed through regions of the chromatogram other than those specified and which did not contain any discrete radioactive peaks

 

Table 9. Quantities of radioactive components in water and sediment from Virginia water after application of 14C-labelled test substance at a nominal rate of 15 μg/cm (Components were separated by HPLC). Results are expressed as % applied radioactivity.

Radioactive component	Approximate retention time	Time after application in days (sample number)
	(min)	0		0.25		1		2		7		14		30		59		100
		B33	B34	B3	B4	B5	B6	B7	B8	B9	B10	B11	B12	B13	B14	B15	B16	B17	B18
Water
1 Polars^a	2 4	0.1	0.1	0.2	0.1	0.4	0.5	0.2	0.2	0.3	0.2	0.1	0.2	0.6	0.4	<0.1	0.7	0.3	0.2
2	9	0.2	0.2	0.5	0.8	1.0	1.0	1.2	1.9	3.9	3.4	7.2	6.4	15.6	16	1.7	3.5	0.9	0.7
3^b	13	1.0	0.6	1.6	3.0	3.5	3.7	2.4	3.0	12.8	9.5	10.3	16.9	29.0	28.4	30.9	36.8	34.8	30.3
4	17-19	0.3	0.1	0.5	0.9	1.2	1.4	0.4	0.3	0.1	0.1	0.3	0.2	0.4	0.3	0.1	0.1	<0.1	0.1
5	19-21	0.5	0.4	0.6	0.8	1.0	1.1	0.5	0.4	0.2	0.2	0.2	0.2	0.1	<0.1	0.2	<0.1	<0.1	<0.1
test substance		11.2	11.5	9.9	10.0	9.0	10.0	10.5	9.9	3.4	2.5	1.2	2.8	<0.1	<0.1	<0.1	0.1	<0.1	<0.1
Others^c		0.1	0.1	0.2	0.3	0.3	0.3	0.2	0.2	0.3	0.3	0.4	0.3	0.7	0.5	0.5	0.5	0.4	0.3
Sediment
1 Polars^a	2-apr	0.3	0.4	0.3	0.3	0.4	0.5	0.3	0.5	0.5	0.4	1	1.1	1.4	1.5	3	2.9	3.7	2.3
2	9	0.2	0.3	0.1	<0.1	0.1	0.1	0.2	0.2	0 . 2	0. 1	0.2	0.3	3.5	3	2.2	2.2	2. 3	1.4
3^b	13	0.6	0.6	0.6	0.6	0.9	1.0	0.9	1.3	4.7	3.9	4.7	5.8	16.1	15.7	16.7	17.8	19.8	16.4
4	17-19	<0.1	<0.1	0.1	0.1	0 . 3	0.3	0.1	0.1	0.1	<0.1	0.2	0.1	0.4	0.2	0.1	0.1	0.2	0.1
5	19-21	0.3	0.3	0.3	0.3	0.6	0.6	0.3	0.2	0.2	0.2	0.3	0.2	0.2	1.1	0.1	<0.1	0.1	<0.1
test substance		77.4	82.8	82.1	74	70.1	74.5	15.9	79.3	51.8	42.5	31.5	37.3	1.0	1.2	1.1	0.8	0.8	0.4
Others^c		0.2	0.2	0.3	0.1	0.6	0 .5	0 .4	0.3	0.3	0 .3	0.4	0.3	0.5	0 . 8	0.8	0.7	1.2	0.5

a.Polars - radioactivity containing more than one component

b. Contains mainly metabolite M1

c. Others - radioactivity distributed through regions of the chromatogram other than those specified and which did not contain any discrete radioactive peaks

 

Table 10. Quantities of radioactive components in water and sediment from Old Basing after application of 14C-labelled test substance at a nominal rate of 15μg/cm2 (Components were separated by TLC). Results are expressed as % applied radioactivity.

Radioactive component	Approximate	Time after application in days (sample number)
	Rf	0		0.25		1		2		7		14		30		59		100
		A33	A34	A3	A4	A5	A6	A7	A8	A9	A10	A11	A12	A13	A14	A15	A16	A17	A18
Water
Test substance	0.29	4.6	4.2	2.0	2.8	4.3	4.8	3.9	4.7	1.3	1.4	0.5	0.5	0.2	< 0.1	0.1	0.2	0.3	0.1
6	0.44	0.2	0.2	0.6	0.5	0.3	< 0.1	0.4	0.5	1.1	0.5	0.3	0,5	1.2	3.4	1.8	1.9	1.1	2.1
M1	0.63	0.2	0.6	1.1	1.3	1.0	1.5	1.5	2	5.2	5.6	10.3	13.2	28.3	31.4	32.6	36.1	33.8	29.2
7	0.85	0.2	0.2	0.6	0.7	0.5	0.9	1.1	1.1	3.9	2.8	15.8	7.6	16.4	12.1	0.2	1.9	1.5	3.0
Others^a		2.5	0.5	1.5	0.8	0.6	0.8	0.4	0.5	0.9	1.6	1.0	1.2	4	1.9	1.6	1.9	2.5	2.2
Sediment
Test substance	0.29	86.5	85.5	91.1	89.4	84.7	84	74.7	81.4	67.4	65.3	37	48.1	2.2	1.8	1.2	0.9	2.6	0.8
6	0.44	0.4	0.4	0.1	0.1	0.1	< 0.1	0.3	0.3	0.4	0.3	0.2	0.3	0.1	0.4	0.3	0.7	0.2	0.5
M1	0.63	0.5	0.5	0.4	0.5	0.2	0.5	0.8	0.8	3.7	3.7	8.9	8.0	23.1	24.7	23.3	27.6	30.5	28.7
7	0.85	0.4	0.4	0.3	0.3	< 0.1	< 0.1	0.5	0.5	1.2	1.1	3.3	1.2	6.0	4.6	3.4	5.1	3.8	7.6
Others^a		0.5	1.4	1.0	1.4	1.6	1.3	1.1	0.7	1.2	1.0	0.9	1.5	3. 1	3.0	3.3	3.5	2.6	3.6

a. Others - radioactivity distributed through regions of the chromatogram other than those specified and which did not contain any discrete radioactive peaks

 

Table 11. Quantities of radioactive components in water and sediment from Virginia water after application of 14C-labelled test substance at a nominal rate of 15μg/cm2 (Components were separated by TLC). Results are expressed as % applied radioactivity.

Radioactive component	Approximate	Time after application in days (sample number)
	Rf	0		0.25		1		2		7		14		30		59		100
		B33	B34	B3	B4	B5	B6	87	88	B9	B10	B11	B12	B13	B14	B15	B16	B17	B18
Water
Test substance	0.29	9.2	11.7	8.8	10.2	8.8	8.4	8.8	10.1	2.6	2.2	1.3	1.7	0.2	<0.1	<0.1	0.2	0.1	0.1
6	0.44	1.0	0.4	0.8	0.9	1.2	1.4	0.6	0.5	2.1	0.6	1.1	1.3	6.6	3.7	0.2	0.8	0.5	3.5
M1	0.63	1.5	0.6	1.8	2.3	3.4	3.8	2.9	2.8	11.4	9.2	10.7	16.7	20.9	26.1	30.4	35.5	33.3	24.2
7	0.85	0.8	0.2	0.7	1.2	0.9	1.2	1.0	1.7	3.7	3.7	5.5	5.9	14.6	14.1	1.4	3.4	0.8	2.2
Others^a		0.9	0.3	1.4	1.3	2.1	3.3	2.1	0.9	1.1	0.7	1.0	1.3	4.0	1.8	1.4	2.0	1.8	1.7
Sediment
Test substance	0.29	76.7	81	81.6	73.4	70.4	74.1	75.2	78.8	45	39.9	32.l	38	10	1.3	1.2	0.8	0.8	0.5
6	0.44	0.3	0.5	0.1	0.3	0.5	0.8	0.4	0.3	0.8	0.6	0.3	0.2	0.1	0.2	0.2	<0.1	0.1	0.1
M1	0.63	0.7	0.6	0.8	0.6	0.9	1.0	1.1	1.3	4.7	3.6	4	4.7	16.2	15.9	16.5	17.2	19.2	15.3
7	0.85	0.5	0.8	0.3	0.4	0.4	0.6	0.5	0.8	0.9	0.5	0.8	1.1	4.5	4.7	4.5	3.8	5.2	4.1
Others^a		0.8	1.6	1.1	0.7	0.8	1.1	0.9	0.9	6.3	3.0	1.0	1.1	l.3	1.4	l.5	26	2.7	1.2

 a. Others - radioactivity distributed through regions of the chromatogram other than those specified and which did not contain any discrete radioactive peaks

 

 

Validity criteria fulfilled:

yes

Conclusions:

The test substance was degraded in both sediment and water and varying amounts up to 33 % of the applied compound were dissipated by volatilisation. About 1 % of the initial test substance remained in the test systems after 100 days incubation. The DT50 values in Old Basing and Virginia Water systems were 5.5 and 4.9 days, respectively. Corresponding DT90 values were 18.1 and 16.4 days, respectively. The test substance was degraded via hydrolysis of the phosphorothioic ester function to yield M1 as a major metabolite (up to 61 % applied radioactivity). A further unknown degradation product reached a maximum of about 20% applied radioactivity after 30 days and declined to 2 - 4% after 100 days. Up to 5 other components were detected, none of which accounted for greater than 6% applied radioactivity at 100 days.

Executive summary:

The metabolism and degradation of the test substance have been studied in two different water/sediment systems. The study was in accordance with national guideline BBA Part IV, 5-1 and was compliance with GLP criteria. In this study, water/sediment was collected from two locations in the UK, Old Basing and Virginia Water. Water/sediment systems were set up in cylindrical glass vessels in the dark at 20°C. The nominal rate of application to the water surface was 15 μg radiolabelled test substance/cm2 equivalent to a field application of 1.5 kg/ha. Duplicate samples of each sediment type were taken for analysis at 0, 0.25, 1, 2, 7, 14, 30, 59 and 100 days post application.

 

The total mean recovery of radioactivity from each test system at each sampling time was greater than 93% of the applied radioactivity in all cases. After 100 days incubation, means of 49.1 % and 30.7% applied radioactivity were measured in the sediment for Old Basing and Virginia Water, respectively. Means of 37.9% and 34.1% applied radioactivity remained in the water from the two locations, respectively. The test substance was degraded in both sediment and water and varying amounts up to 33 % of the applied compound were dissipated by volatilisation. About 1 % of the initial test substance remained in the test systems after 100 days incubation. Throughout the study, two degradation products, which accounted for more than 10 % of the applied radioactivity at any time were detected by HPLC and TLC of water and sediment extracts. The main degradation product was identified in water and sediment from both locations as M1. This compound accounted for up to ca 60 % applied radioactivity. An unidentified product accounted for a maximum of about 20% applied radioactivity after 30 days, but decreased to 2 - 4% after 100 days. The DT50 values of the test substance in Old Basing and Virginia Water systems were 5.5 and 4.9 days, respectively.

Description of key information

Freshwater sediment, geomean DT50 = 5.5 d, 20 °C, BBA Part IV 5 -1, aerobic, Kirkpatrick 1994

Key value for chemical safety assessment

Whole System

Half-life in whole system:

5.5 d

at the temperature of:

20 °C

Type of system:

fresh water and sediment

Additional information

Table. DT50 values for the test substance in surface water under aerobic test conditions

Test system	Test condition	Mineralisation / Non-extractable residues / Major metabolites (% applied)	Compartment	DT50 [d] – Kinetic model	Author / Year
Old basing, Hampshire, UK	Aerobic, 20°C, darkness	Mineralisation: 1.6% after 100d Volatile: 19.6% after 59 d (b) Non-extr.: 8.7% after 100 d Maj. met.: M1 – max. 61% after 100d	Water	5.7 – SFO (c)	Kirkpatrick, 1994
Old basing, Hampshire, UK	Aerobic, 20°C, darkness	Mineralisation: 1.6% after 100d Volatile: 19.6% after 59 d (b) Non-extr.: 8.7% after 100 d Maj. met.: M1 – max. 61% after 100d	Total system	5.5 – SFO	Kirkpatrick, 1994
Virginia Water, Berkshire, UK	Aerobic, 20°C, darkness	Mineralisation: 2.4% after 100 d Volatile: 30.2% after 100d (b) Non-extr.: 6.1% after 100d Maj. met.: M1 – max. 50% after 60d	Water	4.1 – SFO (c)	Kirkpatrick, 1994
Virginia Water, Berkshire, UK	Aerobic, 20°C, darkness	Mineralisation: 2.4% after 100 d Volatile: 30.2% after 100d (b) Non-extr.: 6.1% after 100d Maj. met.: M1 – max. 50% after 60d	Total system	4.9 – SFO	Kirkpatrick, 1994