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

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:

03 Nov 1999 to 11 Aug 2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)

Version / remarks:

OECD Guidelines for Testing of Chemicals: Aerobic and Anaerobic Transformation in Water-Sediment Systems; Draft Proposal for a new Guideline, July 1997

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Dutch registration Guideline, Section G2

Version / remarks:

Dutch registration Guideline, Section G2: Behaviour in Water; Ministry of Agriculture and Fisheries, Ministry of Public Health and Environmental Hygiene, Ministry of Social Affairs. January 1987

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment: freshwater

Details on source and properties of surface water:

Specifications of water is provided in Table 1 in 'Any other information on materials and methods incl. tables'
- Sample date: October 22, 1999
- Source: River and pond system
- Details on collection: Water was sampled down to a depth of 5 - 10 cm with a plastic container. The sampling site was located about 5 m from shore.
- Storage conditions and length: After transportation to the test facility, the water was aerated. Water was kept at room temperature until filling into the flasks.

Details on source and properties of sediment:

Specifications of sediment is provided in Table 1 in 'Any other information on materials and methods incl. tables'
- Sample date: October 22, 1999
- Source: River and pond system
- Details on collection: Sediment was sampled with a shovel from the top 5 - 10 cm for each system. The sampling site was located about 5 m from shore. The sediment was directly sieved into plastic containers.
- Storage conditions and length: After transportation to the test facility, the sediment was covered with the corresponding river or pond water.

Duration of test (contact time):

120 d

Initial conc.:

0.15 other: kg/ha

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Details on study design:

TEST CONDITIONS
- Amount of sediment and volume of water: Sediment was filled into 1-litre glass metabolism flask to a height of about 2 to 2.5 cm corresponding to 318 g fresh weight for river and 240 g for pond. Afterwards, 500 mL of water were layered upon the corresponding sediment, reaching a height of about 6 cm.
- Aeration: The systems were continuously aerated with moistened air at a flow rate of about 30 mL/min.
- Test temperature: 20 ± 2 °C.
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 1-L glass metabolism flask
- Number of culture flasks/concentration ( River System): 18 flasks (7 sampling points in duplicate + 1 sampling point single and 3 reserve flasks).
- Number of culture flasks/concentration (Pond System): 26 flasks (7 sampling points in duplicate 1 sampling point single and 11 reserve flasks).
- Number of control: For each system type, two reference flasks (not treated; for pH, O2 and redox potential measurement)). Biomass before start: Three flasks (untreated) per system.
- Preparation of the Treatment Solution: A stock solution of the 14C-labelled test substance dissolved in acetone (20 mL) was prepared. The accurate amount of the test substance determined by liquid scintillation counting (LSC) was 0.432 mg/mL (432 ppm). The radiochemical purity of the stock solution was determined by HPLC.
- Treatment and Incubation: For treatment, individual aliquots of the application solution (on average 0.118 mg for each sample) were placed into vials (weight control) and kept deep-frozen until application. The stability during storage was checked by HPLC. The aliquots were evenly applied onto the water surface of the aquatic systems by means of a syringe. Finally, all application devices were rinsed, the radioactivity determined by LSC and the actual amount applied calculated. The nominal concentration of the test substance in the water layer corresponded to a field application rate of 0.15 kg a.i./ha. The concentration of acetonitrile was < 0.1 % of the amount of water.
- Test performed in open system: Yes; After completion of the treatment, the incubation flasks were connected to the open airflow systems and incubated in climatic chambers at 20°C. During incubation, the systems were aerated and gently stirred from the top without disturbing the sediment.
- Details of trap for CO2 and volatile organics if used: The effluent air was passed through a trapping system consisting of one absorption bottle filled with 50 mL ethylene glycol and of two absorption bottles each containing 50 mL 2N NaOH.

SAMPLING
- Sample intervals: on day 0, 3, 7, 14, 28/29, 57, 98 and 119
- Water and Sediment: Seven sampling intervals were processed and analysed in duplicate, and one as single.
- Absorption solutions: The absorption solutions were exchanged in about weekly intervals during the first month and thereafter in intervals of about two weeks.
- Redox Potential, pH and Oxygen Concentration of Aquatic Systems: Redox potential, pH and oxygen concentration of the aquatic system were determined on untreated reference flasks and on treated flasks at the sampling days. Prior to treatment, the parameters had periodically been measured in reference flasks (two samples per system) for three weeks.

Test performance:

At the end of the four weeks equilibration period redox potentials indicated aerobic conditions for both water layers (+ 103 mV and + 82 mV) and anaerobic conditions for the sediments of both systems (-229 mV and — 380 mV). The oxygen content was 7.7 and 6.6 mg/L for river and pond, respectively and the pH-value 8.3 and 8.2 for both systems. During incubation, the mean redox parameters in the water phase indicated aerobic conditions (+ 85 mV for river and + 69 mV for pond), whereas the values for redox potential in sediment confirmed anaerobic conditions (- 254 mV for river and – 314 mV for pond) throughout the study. The average oxygen concentration of the aqueous phases ranged at the same time from 7.5 to 6.6 mg/L and the average pH was 8.2 and 8.1 for river and pond, respectively. There was no significant difference observed between the parameters of untreated (reference) and treated samples for both aquatic system types.

Compartment:

natural water / sediment: freshwater

% Total extractable:

5.1

% Non extractable:

49.5

% CO2:

40.4

% Recovery:

95.9

Remarks on result:

other: River Aquatic System; on day 119

Compartment:

natural water / sediment: freshwater

% Total extractable:

5.5

% Non extractable:

52.1

% CO2:

36.3

% Recovery:

94.4

Remarks on result:

other: Pond Aquatic System; on day 119

Parent/product:

parent

Compartment:

total system

% Degr.:

93.7

Parameter:

radiochem. meas.

Sampling time:

29 d

Remarks on result:

other: Rhein River Aquatic System

Parent/product:

parent

Compartment:

total system

% Degr.:

90.2

Parameter:

radiochem. meas.

Sampling time:

28 d

Remarks on result:

other: Pond Aquatic System

Key result

Compartment:

natural water / sediment: freshwater

DT50:

5.95 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: Total system; River

Key result

Compartment:

natural water / sediment: freshwater

DT50:

6.54 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: Total system; pond

Compartment:

natural water / sediment: freshwater

DT50:

1.99 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: water; River

Compartment:

natural water / sediment: freshwater

DT50:

1.43 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: water; pond

Compartment:

natural water / sediment: freshwater

DT50:

6.18 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: sediment; River

Compartment:

natural water / sediment: freshwater

DT50:

11.46 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: sediment; pond

Mineralization rate (in CO2):

0.34 other: %/day

Transformation products:

not specified

Remarks:

M2

Details on transformation products:

An overview of the results is provided in Table 4 - Table 5 in 'Any other information on results. incl. tables'.
- Pattern and Identity of Metabolites: In both aquatic systems, no major metabolites (> 5 % of the applied radioactivity) were found. Mainly minor metabolites (13), mostly of transient nature, were detected. One of them could be identified by co-chromatography as M2.
- River System: The amount of the test substance in river water decreased continuously from 95.0 % (given as average of duplicates) to below the limit of detection at study end. M2 increased to 2.7% on day 7 and decreased to 0.3% on day 119. in the sediment the amount of the test substance first increased to 32.4 % on day 3 and decreased thereafter to 4.2 % on day 119. M2 amounted to 2.4% on day 3 and decreased to 0.3% at the end of the study. In the entire river aquatic system the test substance decreased from 97.7 % to 4.2% of the applied radioactivity at day 119. M2 concentration increased up to 5.0 % at day 3 and declined thereafter to 0.3 % at the end of the study. The concentration of any other metabolite did not exceed 3.7 % of the radioactivity applied to the total river system.
- Pond System: In the pond system the same metabolites were detected as in the river system. The concentration of the test substance in pond water continuously decreased from 94.5 % to below the limit of detection at study end. The concentration of M2 declined from 3.8% (day 3) to < LD (day 57). The concentration of the test substance increased to 37.1 % on day 3 and decreased to 2.6 % on day 119. M2 amounts increased to 3.5 % on day 7 and decreased to 0.7% at the end of the study. In the total pond system the concentration of the test substance declined from 97.8 % after application to 2.6 % of the applied radioactivity at day 119. The concentration of M2 reached 7.5% on day 3 and 0.7% at the end of the study.

Evaporation of parent compound:

not specified

Volatile metabolites:

yes

Residues:

yes

Details on results:

An overview of the results is provided in Table 2 - Table 6 in 'Any other information on results. incl. tables'.
- Microbial Biomass of the Sediments: At study start, the sediment biomass was 18.6 and 105.6 mg microbial carbon per 100 g sediment for river and pond system, respectively.
- Overall Recovery: In both systems the overall recovery (mean duplicate) comprising the water layers, the sediment extracts, non-extractable residues and volatile products ranged from 90.1 % to 98.2 % of the applied radioactivity.
- Balance of Radioactivity in the River System: In the water layer the amount of radioactivity decreased continuously from 95.0 % (average of duplicates) to 1.0 % at day 119. The extractable radioactivity from the sediment extracts increased from 2.9 % at the beginning of the study and reached 34.1% at 3 days and decreased to 5.1 % at the end of the study. In addition, only 0.2 % of the applied radioactivity could be extracted by harsh extraction procedures (performed on day 29). Non-extractable radioactivity increased steadily from 0.1 % to 56.2 % at day 29 and decreased to 49.5% at the end of the study after 119 days. Organic matter fractionation of non-extractable residues (sampling day 29) revealed that 7.9 %, 8.9 % and 38.1 % were associated with the humic acid, fulvic acid and humin fractions, respectively. The mineralisation of the test substance was high. The production of amounted to 40.4 % after 119 days of incubation. Organic volatiles were found to be negligible (< 0.1 %).
- Balance of Radioactivity in the Pond System: Similar results as for the river system were obtained for pond. The radioactivity in the water declined from 94.4% (average of duplicates) to 0.6 % at the end of the study. The extractable radioactivity was 3.6 % at study start and reached 41.3 % at day 3 and declined rapidly to 5.5 % after 119 days. In addition, only 0.5 % of the applied radioactivity could be extracted by harsh extraction procedures (performed on day 28). Non-extractable radioactivity steadily increased reaching 54.9 % of the applied dose at day 14 and decreased to 52.1% at the end of the study after 119 days. Organic matter fractionation of non-extractable residues (sampling day 28) revealed that 13.7 %, 6.0 % and 33.3 % were associated with the humic acid, fulvic acid and humin fractions, respectively. The production of 14CO2 amounted to 36.3 % at day 119 of incubation. Organic volatiles were found to be < 0.1 %.
- Disappearance Rate of the test substance from water: The test substance disappeared from the water layer of the Rhine and pond aquatic system with a DT50 of 2.0 and 1.4 days, respectively. The corresponding DT90 values were 6.6 and 4.8 days.
- Disappearance Rate of the test substance from sediment: The degradation of the test substance (DT50) in the sediments of both aquatic systems was 6.2 and 11.5 days for pond and Rhine sediments, respectively. Observed DT90 values were in the same sediments 20.5 and 38.0 days.
- Disappearance Rate of the test substance in total system: The test substance was degraded rapidly with half-life times of 6.0 and 6.5 days in the Rhine-river and pond aquatic systems, respectively. The corresponding DT90 values were 25.8 and 22.8 days.

Table 2. Balance of the Radioactivity applied to River Aquatic system

Incubation time (day)		Aqueous phase	Extractables	14CO2	Organic volatiles	Non-extractable (2)	Recovery (1)
	0	96.9	2.8	n.a.	n.a.	0.0	99.7
	0	93.00	3	n.a.	n.a.	0.1	96.1
Mean	0	95.00	2.9	n.a.	n.a.	0.1	97.9
(3)	3	47.00	34.1	0.5	<LD	12.7	94.3
	7	23.00	29.5	3.5	<LD	34.3	90.3
	7	22.7	29.7	3.2	<LD	35.6	91.2
Mean	7	22.9	29.6	3.4	<LD	35.0	90.8
	14	9.9	22.5	9.9	<LD	49.8	92.1
	14	9.00	17.5	12.6	<LD	53.1	92.2
Mean	14	9.5	20	11.3	<LD	51.5	92.2
	29	3.4	7.9	25.6	<LD	57.9	94.8
	29	5.2	9.1	25.4	<LD	54.5	94.2
Mean	29	4.3	8.5	25.5	<LD	56.2	94.5
	57	1.5	8.2	31.7	<LD	53.3	94.7
	57	1.5	7.1	31	<LD	52.7	92.3
Mean	57	1.5	7.7	31.4	<LD	53.0	93.5
	98	1.1	6.3	38.6	<LD	50.3	96.3
	98	0.9	5.5	41.7	<LD	49.2	97.3
Mean	98	1.00	5.9	40.2	<LD	49.8	96.8
	119	1.00	5.1	40.3	<LD	50.0	96.4
	119	0.90	5.1	40.5	<LD	48.9	95.4
Mean	119	1.00	5.1	40.4	<LD	49.5	95.9

(1) Recovery values were not corrected for the amount of the test substance binding excessively to the glassware calculated to be 4.5% (according to a separate experiment).

(2) Day 7 N.E. are the sum of bound residues and NaOH extractables

(3) Day 3 has just one flask

Table 3. Balance of the Radioactivity applied to pond Aquatic system

Incubation time (day)		Aqueous phase	Extractables	14CO2	Organic volatiles	non-extractable	Recovery (1)
	0	95.5	3.3	n.a.	n.a.	0.1	98.9
	0	93.4	3.90	n.a.	n.a.	0.2	97.4
Mean	0	94.40	3.6	n.a.	n.a.	0.1	98.2
(2)	3	29.90	41.3	0.4	<LD	20.4	92
	7	8.5	29.30	10.9	<LD	39.1	87.9
	7	15.2	48.5	3.6	<LD	27.5	94.8
Mean	7	11.9	38.9	7.3	<LD	33.3	91.4
	14	6.1	13.1	14.2	<LD	56.6	90.0
	14	6.9	17.40	12.7	<LD	53.2	90.2
Mean	14	6.5	15.2	13.4	<LD	54.9	90.1
	28	2.6	12.5	21	<LD	54	90.1
	28	2.7	15.8	19.8	<LD	52.8	91.2
Mean	28	2.7	14.2	20.4	<LD	53.4	90.6
	57	2.3	14.7	23.3	<LD	51.3	91.5
	57	0.7	9.4	29	<LD	52.7	91.8
Mean	57	1.5	12	26.2	<LD	52.0	91.6
	98	0.6	6.8	37.8	<LD	50.9	96.0
	98	0.6	5.6	33	<LD	54.4	93.7
Mean	90	0.60	6.2	35.4	<LD	52.6	94.8
	119	0.5	5.50	35.6	<LD	51.8	93.5
	119	0.6	5.60	36.9	<LD	52.3	95.3
Mean	119	0.60	5.5	36.3	<LD	52.1	94.4

(1) Recovery values were not corrected for the amount of the test substance binding excessively to the glassware calculated to be 4.5% (according to a separated experiment).

(2) Day 3 has just one flask

Table 4. Pattern of Metabolites in Rhein River Aquatic System treated with 14C-labelled test substance (% applied radioactivity)

			Metabolites
Incubation time (day)	cold extract (1)	Parent	1	2	3	4	5	6	M2	8	9	10	11	12	13
0	Aqueous phase	96.9
	Extractables	2.6
	Total	99.5
0	Aqueous	93
	Extraclables	2.8
	Total	95.8
Mean 0	Aqueous phase	95
	Extraclables	2.7
	Total	97.7
3	Aqueous phase	42.5	0.3	<LD	<LD	0.4	0.4	<LD	2.6	0.3	0.6	0.2	0.3	<LD	<LD
	Extraclables	32.4	<LD	<LD	<LD	<LD	<LD	<LD	2.4	<LD	<LD	<LD	<LD	<LD	<LD
	Total	74.9	0.3	<LD	<LD	0.4	0.4	<LD	5.0	0.3	0.6	0.3	0.3	<LD	<LD
7	Aqueous phase	16.6	0.8	0.6	0.0	0.3	0.3	0.2	2.4	1.0	0.4	0.3	<LD	<LD	<LD
	Extraclables	26.1	<LD	<LD	<LD	<LD	<LD	<LD	<LD	2.7	0.6	0	<LD	<LD	<LD
	Total	42.7	0.8	0.6	0	0.3	0.3	0.2	2.4	3.7	1	0.3	<LD	<LD	<LD
7	Aqueous phase	16	0.6	0.6	0.7	0	0	0	2.7	1	0.5	0.2	0.3	<LD	<LD
	Extraclables	25.7	<LD	<LD	<LD	<LD	<LD	<LD	<LD	2.5	1	0.5	<LD	<LD	<LD
	Total	41.7	0.6	0.6	0.7	0	0	0	2.7	3.5	1.5	0.7	<LD	<LD	0
Mean 7	Aqueous phase	16.3	0.7	0.6	0.3	0.2	0.2	0.1	2.6	1	0.4	0.3	0.2	<LD	<LD
	Extraclables	25.9	<LD	<LD	<LD	<LD	<LD	<LD	<LD	2.6	0.8	0.2		<LD	<LD
	Total	42.2	0.7	0.6	0.3	0.2	0.2	0.1	2.6	3.6	1.3	0.5	0.2	<LD	<LD
14	Aqueous phase (2)	3.8	3.2	<LD	<LD	<LD	<LD	<LD	<LD	1	<LD	<LD	<LD	<LD	<LD
	Extraclables	18.8	0	<LD	<LD	<LD	<LD	<LD	1.9	1.4	<LD	0.3	<LD	<LD	<LD
	Total	22.6	3.2	<LD	<LD	<LD	<LD	<LD	1.9	2.4	<LD	0.3	<LD	<LD	<LD
14	Aqueous phase (3)	1.8	5.6	<LD	<LD	<LD	<LD	<LD	<LD	0.7	<LD		<LD	<LD	<LD
	Extraclables	14.3	0.3	<LD	<LD	<LD	<LD	<LD	1.7	1	<LD	0.2	<LD	<LD	<LD
	Total	16.1	5.9	<LD	<LD	<LD	<LD	<LD	1.7	1.7	<LD	0.2	<LD	<LD	<LD
Mean 14	Aqueous phase	2.8	4.4	<LD	<LD	<LD	<LD	<LD	<LD	0.9	<LD		<LD	<LD	<LD
	Extraclables	16.6	0.1	<LD	<LD	<LD	<LD	<LD	1.8	1.2	<LD	0.3	<LD	<LD	<LD
	Total	19.4	4.5	<LD	<LD	<LD	<LD	<LD	1.8	2.1	<LD	0.3	<LD	<LD	<LD
29	Aqueous phase (4)	0	3.4	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD
	Extraclables	5.9	0.2	0.1	<LD	<LD	<LD	<LD	0.5	0.4	0.1	0.3	0.2	0.2	0.2
	Total	5.9	3.6	<LD	<LD	<LD	<LD	<LD	0.5	0.4	0.1	0.3	0.2	0.2	0.2
29	Aqueous phase (5)	0.1	5		<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD
	Extraclables	6.7	0.2	0.2	<LD	<LD	<LD	<LD	0.7	0.5	0.1	0.2	0.3	0.02	0.2
	Total	6.8	5.2	0.2	<LD	<LD	<LD	<LD	0.7	0.5	0.1	0.2	0.3	0.2	0.2
Mean 29	Aqueous phase	0.1	4.2	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD
	Extraclables	6.3	0.2	0.2	<LD	<LD	<LD	<LD	0.6	0.4	0.1	0.3	0.3	0.2	0.2
	Total	6.3	4.4	0.2	<LD	<LD	<LD	<LD	0.6	0.4	0.1	0.3	0.3	0.2	0.2
57	Extraclables	6.9	0.1	<LD	<LD	<LD	0.4	0.3	0.2	<LD	<LD	0.2	<LD	<LD	<LD
57	Extraclables	5.6	2	<LD	<LD	<LD	0.4	0.3	0.3	<LD	<LD	0.4	<LD	<LD	<LD
Mean 57	Extraclables	6.2	0.2	<LD	<LD	<LD	0.4	0.3	0.2	<LD	<LD	0.3	<LD	<LD	<LD
98	Extraclables	5.2	0.1	0.1	0.1	<LD	<LD	<LD	0.5	0.2	<LD	0.2	<LD	<LD	<LD
98	Extraclables	4.7	0	0.1	<LD	<LD	<LD	<LD	0.3	0.1	<LD	0.2	<LD	<LD	<LD
Mean 98	Extraclables	5	0	0.1	<LD	<LD	<LD	<LD	0.4	0.2	<LD	0.2	<LD	<LD	<LD
119	Extraclables	0.1	<LD	0.1	<LD	<LD	<LD	<LD	0.3	0.1	0	0.1	0.2	<LD	<LD
119	Extraclables	4.2	<LD	0.1	<LD	<LD	<LD	<LD	0.3	0.1	0.1	0.2	0.1	<LD	<LD
Mean 119	Extraclables	4.2	<LD	0.1	<LD	<LD	<LD	<LD	0.3	0.1	0.1	0.2	0.1	<LD	<LD

(1) Due to very low amount of radioactivity (< 1%) Aqueous phase from 57 days up to 119 days was not analysed.

(2)TLC-Metabolites uk4, uk5. ukG, uk7, ukB, uk10, uk12 and uk13 representing 0.1, 0.2, 0.2,0.1, 0.4, 0.3, 0.1 and 0.6 % applied radioactivity were also found.

(3) TLC-Metabolites uk5, uk8 and uk10 representing 0.4. 0.3 and 0.2 % applied radioactivity were also found

(4) TLC-Metabolites uk4, and uk5 representing 0.04, 0.03% applied radioactivity were also found

(5)TLC-Metabolites uk4. and uk5 representing 0.05, 0.03% applied radioactivity were also found

Table 5. Pattern of Metabolites in Pond Aquatic System treated with 14C-labelled test substance (% applied radioactivity)

			Metabolites
Incubation time	cold extract (1)	Parent	1	2	3	4	5	6	M1	8	9	10	11	12	13
0	Aqueous phase	95.5
	Extractables	3
	Total	98.5
0	Aqueous	93.4
	Extraclables	3.6
	Total	97
Mean 0	Aqueous phase	94.5
	Extraclables	3.3
	Total	97.8
3	Aqueous phase	19.4	1.3	0.3	0.3	1.3	0.9	<LD	3.8	1.7	0.3	<LD	0.4	0.2	<LD
	Extraclables	37.1	<LD	<LD	<LD	<LD	<LD	<LD	3.7	1.9	<LD	<LD	<LD	<LD	<LD
	Total	56.5	1.3	0.3	0.3	1.3	0.9	<LD	7.5	3.6	0.3	<LD	0.4	0.2	<LD
7	Aqueous phase (2)	0.2	7.2		<LD	<LD	<LD	<LD	0	0	<LD	<LD	<LD	<LD	<LD
	Extraclables	21.5	0.2	0.2	0	0	<LD	<LD	3.3	1.6	<LD	1.8	0.8	<LD	<LD
	Total	21.7	7.4	0.2	0	0	<LD	<LD	3.3	1.6	<LD	1.8	0.8	<LD	<LD
7	Aqueous phase (3)	7.4	4.5							1.3	<LD	<LD	<LD	<LD	0
	Extraclables	38.3	0.0	0.0	0.6	0.6			3.8	3.9	<LD	0.6	0.7	<LD	0
	Total	45.7	4.5	0.0	0.6	0.6	0.0	0.0	3.8	5.2	<LD	0.6	0.7	<LD	<LD
Mean 7	Aqueous phase	3.8	5.9		0	0	<LD	<LD	0	0.7	<LD	<LD	<LD	<LD	<LD
	Extraclables	29.9	0.1	0.1	0.3	0.3	<LD	<LD	3.5	2.7	<LD	1.2	0.8	<LD	<LD
	Total	33.7	6.0		0.3	0.3	<LD	<LD	3.5	3.4	<LD	1.2	0.8	<LD	<LD
14	Aqueous phase (4)	0.6	4.5		<LD	<LD	<LD	<LD		0	<LD	<LD	<LD	<LD	<LD
	Extraclables	9.2	0.4		<LD	<LD	<LD	<LD	1.1	0.9	<LD	0.5	0.9	<LD	<LD
	Total	9.8	4.9		<LD	<LD	<LD	<LD	1.1	0.9	<LD	0.5	0.9	<LD	<LD
14	Aqueous phase (5)	0.4	5.0		<LD	<LD	<LD	<LD		0.4	<LD	<LD	<LD	<LD	<LD
	Extraclables	12.3	0.4		<LD	<LD	<LD	<LD	0.9	1.9	<LD	0.6	1.4	<LD	<LD
	Total	12.8	5.4		<LD	<LD	<LD	<LD	0.9	2.3	<LD	0.6	1.4	<LD	<LD
Mean 14	Aqueous phase	0.5	4.8	0.0	<LD	<LD	<LD	<LD	0	0.2	<LD	0	<LD	<LD	<LD
	Extraclables	10.8	0.4	0.0	<LD	<LD	<LD	<LD	1	1.4	<LD	0.6	1.2	<LD	<LD
	Total	11.3	5.2		<LD	<LD	<LD	<LD	1	1.6	<LD	0.6	1.2	<LD	<LD
28	Aqueous phase (4)	0.0	2.5		<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD
	Extraclables	8.3	0.4		<LD	<LD	<LD	0.6	0.8	0.8	<LD	0.5	1.0	<LD	<LD
	Total	8.3	2.9		<LD	<LD	<LD	0.6	0.8	0.8	<LD	0.5	1.0	<LD	<LD
28	Aqueous phase (5)	0.0	2.7		<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD
	Extraclables	11.3	0.1		<LD	<LD	<LD	0.0	0.9	1.9	<LD	0.6	1.4	<LD	<LD
	Total	11.3	3.1	0.0	<LD	<LD	<LD	<LD	0.9	1.9	<LD	0.6	1.4	<LD	<LD
Mean 28	Aqueous phase	0.0	2.6		<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD	<LD
	Extraclables	9.8	0.4	0.0	<LD	<LD	<LD	0.3	0.9	1.3	<LD	0.6	1.2	<LD	<LD
	Total	9.8	3.0		<LD	<LD	<LD	0.3	0.9	1.3	<LD	0.6	1.2	<LD	<LD
57	Extraclables	11	0.2		<LD	<LD	<LD	0	1.2	0.4	<LD	0.8	1.1	<LD	<LD
57	Extraclables	6.0	0.3		<LD	<LD	<LD	0.4	0.7	0.5	<LD	0.6	0.8	<LD	<LD
Mean 57	Extraclables	8.5	0.3		<LD	<LD	<LD	0.2	0.9	0.5	<LD	0.7	1.0	<LD	<LD
98	Extraclables	3.8	0.1	0.2	<LD	0.4	<LD	<LD	0.9	0.4	0.0	1.1	0.0	<LD	0.0
98	Extraclables	2.5	0	0.2	<LD	0.3	<LD	<LD	0.2	0.6	0.3	0.9	0.3	<LD	0.2
Mean 98	Extraclables	3.8	0.1	0.2	<LD	0.4	<LD	<LD	0.6	0.5	0.2	1	0.2	<LD	0.1
119	Extraclables	2.7	0.0	0.2	0.0	0.3	0.0	<LD	0.6	0.2	<LD	0.8	0.5	0.1	0.1
119	Extraclables	2.5	0.1	0.2	0.1	0.1	0.2	<LD	0.8	0.2	<LD	0.9	0.4	0.1	0.1
Mean 119	Extraclables	2.6	0.1	0.2	0.1	0.2	0.1	<LD	0.7	0.2	<LD	0.9	0.4	0.1	0.1

(1) Due to very low amount of radioactivity (< 1%) Aqueous phase from 57 days up to 119 days was not analysed.

(2)TLC-Metabolites uk5. uk6, uk7 and uk8 representing 0.5, 0.3. 0.1 and 0.2% applied were also found

(3) TLC-Metabolites uk4, uke and uk8 representing 0.2 ,0.2, and 1.7% applied were also found

(4) TLC-Metabolites uk5. uk6 and uk8 representing 0.5, 0.2 and 0.3% applied were also found

(5)TLC-Metabolites ukS, uk6 and ukB representing 0.5, 0.3 and 0.4% applied were also found

(6) TLC-Metabolite uk5 representing 0.1% applied radioactivity was also found

(7) TLC-Metabolite uk5 representing 0.1% applied radioactivity was also found

Table 6. Overview of results 

	COMPARTMENT	C1 [%]	C2 [%]	K01	K02	DT-50 [days]	DT-90 [days]
RIVER	WATER	95.0	-	0.348	-	1.99	6.61
	SEDIMENT	2.7		0.112		6.18	20.54
	TOTAL SYSTEM	92.1	7.8	0.130	0.005	5.95	25.80
POND	WATER	95.0	-	0.485	-	1.43	4.75
	SEDIMENT	3.3		0.060		11.46	38.04
	TOTAL SYSTEM	85.6	12.1	0.209	0.009	6.54	22.78

 

Validity criteria:

The total recovery (mass balance) at the end of the experiment should be between 90% and 110% for radiolabelled substances.

Observed value:

River system = 90.8 - 97.9%; Pond system = 90.1 - 98.2%

Validity criteria fulfilled:

yes

Conclusions:

In a biodegradation study with fresh water-sediment systems, performed in accordance with a draft of OECD guideline for Testing of Chemicals: Aerobic and Anaerobic Transformation in Water-Sediment Systems, the 14C-labelled test substance very rapidly disappeared from the water layer of both aquatic systems. The DT50 of the test substance was calculated to be 5.95 days in the total river system and 6.54 days in the total pond system. In both aquatic systems, no major metabolites (> 5 % of the applied radioactivity) were found. The identified metabolite (M2) degraded mainly through mineralisation and formation of bound residues. In pond and river systems, CO2 and bound residues amounted at the end of the study to 36.3% - 40.4% and 52.1% - 49.5%, respectively.

Executive summary:

The degradation of [phenoxy-U-14C]-labelled test substances were investigated in two aerobically incubated fresh water-sediment systems, Rhine river and pond. The study was performed with following a draft OECD guideline for Testing of Chemicals: Aerobic and Anaerobic Transformation in Water-Sediment Systems and the Dutch national registration guideline (Section G2), and the study was in compliance with GLP criteria. There were318 g and 240 g fresh weight sediment for river and pond systems, respectively. The water volume in both system was approximately 500 mL. The 14C-labelled test substance was applied to the river and pond systems at a concentration corresponding to a field rate of about 0.15 kg/ha and incubated at 20 ± 2°C over a period of 120 days. The systems were continuously aerated with moistened air at a flow rate of about 30 ml/min. Samples were analysed at 0, 3, 7, 14, 28/29 (pond/river), 57, 98 and 119 days. At each sampling interval, the distribution of 14C-labelled test substance and its metabolites was determined in the surface water and sediment layers after separation of the two phases using HPLC and 2D-TLC. 

After 120 days incubation, in both systems, the overall recovery (mean duplicate) comprising the water layers, the sediment extracts, non-extractable residues and volatile products ranged from 90.1 % to 98.2 % of the applied radioactivity. No major metabolites (> 5% of the applied radioactivity) were found in any of the systems. Mainly minor metabolites (13 in total), mostly of transient nature, were detected. One of them could be identified by co-chromatography as M2. In the entire river system, the test substance decreased from 97.7 % to 4.2% of the applied radioactivity at day 119. M2 concentration increased up to 5.0 % at day 3 and declined thereafter to 0.3 % at the end of the study. The concentration of any other metabolite did not exceed 3.7 % of the radioactivity applied to the total river system. In the total pond system, the concentration of the test substance declined from 97.8% after application to 2.6% of the applied radioactivity at day 119. The concentration of M2 reached 7.5% on day 3 and 0.7% at the end of the study. In both systems, CO2 and bound residues amounted at the end of the study to 36.3% - 40.4% and 52.1% - 49.5%, respectively. It was concluded that the test compound very rapidly disappeared from the water layer of both aquatic systems with DT-50 values between 1.4 and 2.0 days. Degradation in the sediment was less rapid with DT-50 values between 6.2 and 11.5 days. The DT50 values in the whole river system and whole pond system were determined to be 5.95 days and 6.54 days, respectively.

Description of key information

All available data was assessed. The study representing the worst-case effects of the water-sediment system was included here and its effect values were used as key values in a weight of evidence approach.

Geometric mean DT50 in freshwater-sediment = 6.24 d, 20 °C, a draft OECD guideline for Testing of Chemicals: Aerobic and Anaerobic Transformation in Water-Sediment Systems and the Dutch national registration guideline (Section G2) followed study, Nicollier 2000.

Key value for chemical safety assessment

Whole System

Half-life in whole system:

6.24 d

at the temperature of:

20 °C

Type of system:

fresh water and sediment

Additional information

Table. DT50 values for the substance in freshwater-sediment system under aerobic standard test conditions

Test system	Test condition	Mineralisation / Non-extractable residues / Major metabolites (% applied)	Compartment	DT50 (d) – Kinetic model	Author/ year
River system, Rhine, CH	Aerobic, 20°C, darkness	Min.: 40.4% after 119d Non-extr.: 49.5% after 119d Maj. Met.:none	Water Total system	1.99 - SFO 5.95 - SFO	Nicollier, 2000
Pond system, Rheinfelden, CH	Aerobic, 20°C, darkness	Min.: 36.3% after 119d Non-extr.: 54.9% after 14d, 52.1% after 119d Maj. Met.:none	Water Total system	1.43 - SFO 6.54 - SFO	Nicollier, 2000
		Geomean DT50 (days)	Water	1.69
		Geomean DT50 (days)	Total system	6.24