cyproconazole (ISO); (2RS,3RS;2RS,3SR)-2-(4-chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)butan-2-ol

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: sediment simulation testing

Remarks:

whole-system

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3 Jul 1996 to 9 Oct 1997

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

Natural waters (Rhine river and Judenweiher pond) and sediment were used to expose the substance at initial concentration of 65.8 µg/L for 259 days. The biodegradation of the substance in the whole system and water phase were studied.

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

An overview of parameters for water phase is provided in Table 1 in 'Any other information on materials and methods incl. tables'
- General: Water and sediment were sampled from two different locations, (pond and river) known not to be submitted to discharges of effluents or near human activity. The following two test systems were used:
System I: River water/Sediment from Rhine (Mohlin AG/Switzerland); sampled on 11 June 1996
System II: Pond water/Sediment from Judenweiher (Rheinfelden AG/Switzerland); sampled on 24 June 1996

- System Plot History: The water was sampled down to a depth of 10 - 30 cm and the sediment was sampled from the top 5 - 10 cm of each system. This sampling was located 1 - 2 m from firm land. The systems were transported to the test facility in sealed containers and were stored at about 4 °C for 1 to 4 days, until the start of equilibration.

- Sampling of water and sediment: Before sampling, the temperature, the pH, the oxygen content and the redox potential of the water were measured just below the surface and about 5 cm above the sediment and the redox potential of the sediment was determined. The systems were sampled from different locations throughout the plot to assure a homogeneous distribution. From the sampled water the NO3-N, NO2-N, NH4-N, the orthophosphate concentration and the hardness were immediately determined at the sampling sites.

Details on source and properties of sediment:

See 'Details on source and properties of surface water'
An overview of parameters for sediment phase is provided in Table 2 in 'Any other information on materials and methods incl. tables'

Details on inoculum:

At the test facility, the water/sediment systems were stored at about 4 °C for one day after sampling. Thereafter, the sediment was passed through a 2.0 mm sieve, the water was passed through a 0.2 mm sieve, and total phosphorous, total organic carbon (TOC) and total nitrogen of the water were determined. The sediment was allowed to settle down after sieving before its further characterisation by determination of pH, organic carbon content, cation exchange capacity, particle size distribution, total nitrogen and total phosphorous content.

Duration of test (contact time):

259 d

Initial conc.:

65.8 µg/L

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Details on study design:

TEST CONDITIONS
- Test temperature: 20 ± 1 °C
- Continuous darkness: Yes
- pH: 7.64 - 8.05

TEST SYSTEM
- Culturing apparatus: 1000 mL glass metabolism flasks (inner diameter: about 10.6 cm, area: about 88.2 cm2).
- Amount of sediment: Sediment was filled into the bottles to a height of 2.4 cm, corresponding to a wet weight of 180 g for each system.
- Amount of water: The respective water phases were added to the sediments to reach a height of about 6 cm (550 mL).
- Number of culture flasks/concentration: Per test system, 31 flasks were set up comprising:
20 treated flasks (i.e. 10 possible sampling intervals in duplicate with 18 flasks to be analysed and 2 flasks as reserves)
4 treated flasks with water/sediment system, which were heat sterilised before application
2 untreated flasks to determine the biomass at the beginning of the study
2 untreated controls, which were used to determine the biomass at the end of the study
3 untreated reserve flasks, which might have been used for a possible pre-test or for any other purpose relevant to the study.
- Acclimation: On June 25, 1996, the sediment and thereafter the water were placed in the metabolism flasks. Thereafter, the sediment was left to settle down. From July 03, 1996 on, all flasks were ventilated with CO2-free, moistened air with simultaneous gentle agitation of the water layer by stirring from the top with a "suspended" magnetic stirrer without disturbing the sediment. A gentle agitation of the water surface is recommended by the guideline. On August 5, 1996, 33 days after the start of the acclimation period (day 0), the equilibriumobtained was considered to be sufficient to apply the test substance. At this date, the water phases of all flasks to be treated and the two control flasks were analysed for their oxygen concentration, pH and redox potential
- Test performed in open system: Yes, open gas-flow-system
- Details of trap for CO2 and volatile organics if used: The flasks were connected to a series of two traps. The first trap contained 50 mL ethylene glycol followed by a trap containing 50 mL 2 N NaOH.
- Preparation of application solution: An amount of 1.3 mg of the purified labelled test substance (dissolved in acetonitrile/water) was transferred to a 50 mL volumetric flask and the solvent was evaporated under a gentle stream of nitrogen. Then an amount of 1.27 mg unlabelled test substance was added and dissolved in deionised water. The volumetric flask was made up to volume with deionised water.
The content of radioactivity was determined by liquid scintillation counting (LSC) of diluted aliquots to be 5.3175E+8 dpm. Based on the new calculated specific radioactivity of 3.4 MBq/mg, the amount of [14C]-labelled test substance was found to be 2.594 mg in 50 mL application solution.
A volume of 705 μL of the application solution was calculated to be applied, corresponding to 36.7 μg test substance per flask. This concentration of the active ingredient (a.i.) was obtained by applying the maximum recommended field rate (200 g a.i./ha) and assuming a homogeneous distribution of the test substance in the top 30 cm of the water column (= 36.7 μg a.i./550 mL water). Before, in the middle and after application of the incubation flasks the application volume was applied to 50 mL water in order to check the actual amount applied. An amount of 7'421'100 dpm was determined and taken as the 100% value per flask.

WATER PARAMETERS
- pH, oxygen concentration and redox potential of the water phase and the redox potential in the sediment were measured during the acclimation period in the control flasks and at the day of application (day 0) in all flasks to be treated. The same parameters were determined in the flask to be sampled and in the control flasks at each sampling interval. At the end of the incubation period, i.e. after 259 days, the parameters of the water and of the sediment from the control flasks, for river as well as for pond, were measured. Before analysis of the biomass, the total phosphorous content, the total nitrogen content, the organic carbon content, the hardness and the dry mass of the sediment of both control flasks was mixed.

SAMPLING
- Sampling frequency: After 0, 3, 7, 14, 28, 42, 70 and 105 days of incubation, two flasks (duplicate samples) of each system were taken for analysis. Furthermore one treated flask of each system was taken for analysis: 154, 210 and 259 days after application. One sterilised sample for each test system was taken at 171 and 259 days of incubation. The sterility of the samples was analysed at each sampling interval.
- Sterility check if applicable: Plate Counts Agar as well as a mixture of standard Plate Counts Agar and bacteriological agar, dissolved in bi-distilled water, were sterilised for 20 minutes at 120 °C. Thereafter, the temperature of the respective agar was lowered below 50 °C in a water bath and 20 ml was added to a Petri-dish for each single sterility test. After solidification and cooling, the Petri-dishes were incubated in an incubator overnight at 37 °C for a sterility check. Thereafter, aliquots of 0.5 mL of the sample solutions were applied on top of the agar plates and uniformly distributed on the surface of the agar. Manipulation was performed near to flame on a desk sterilised with ethyl alcohol. Thereafter, the plates were incubated at 37 °C. The number of colonies developed on the plates was counted after 48 and 72 hours of exposure.
- Water samples: After determination of pH, O2-content and redox potential, a pipette was used to separate the water from the sediment and the water volume was recorded. The water phase was gently mixed and aliquots of 200 mL water for each sample were taken immediately after sampling for analysis, whereas the remaining volume was stored in the freezer at about -20 °C. The radioactivity content was determined by liquid scintillation counting (LSC). Thereafter, the aqueous phase was submitted to chromatographic analysis by TLC and HPLC. Samples containing low radioactivity were concentrated prior to analyses by a gentle steam of nitrogen.
- Sediment samples: After removing the water phase from the test system, the sediment was extracted at room temperature four times with acetonitrile/water (8/2, v/v). Individual extracts were measured by LSC and then combined. Pooled extracts containing low radioactivity were concentrated prior to analysis by TLC and HPLC. The solvent was either evaporated in a stream of nitrogen or under reduced pressure on a rotavap. The residue was then dissolved in acetonitrile/water (1/1, v/v) before chromatographic analysis. The recoveries were in the range of 90.2 to 108.2%. Beginning with day 7, sediment still containing radioactivity after cold extraction was further extracted in a Soxhlet apparatus with the same solvent. These extracts were also analysed by LSC, TLC and HPLC as for the cold extracts. The residual sediments were dried, weighed, homogenised, and their radiocarbon content was determined by combustion of 0.3 to 1.1 g aliquots and LSC.
- Volatiles: Prior to the determination of radioactivity the volume of the liquid in each trap was recorded. All NaOH traps and all ethylene glycol traps were monitored for radioactivity by LSC at the respective sampling intervals or about once a month, whichever was shorter, until the end of the incubation period.

Compartment:

natural water / sediment: freshwater

% Total extractable:

94.3

% Non extractable:

3.8

% CO2:

0.4

% Other volatiles:

< 0.1

% Recovery:

98.5

Remarks on result:

other: River system, on day 259

Compartment:

natural water / sediment: freshwater

% Total extractable:

87.4

% Non extractable:

10

% CO2:

0.3

% Other volatiles:

< 0.1

% Recovery:

97.7

Remarks on result:

other: Pond system, on day 259

Parent/product:

parent

Compartment:

total system

% Degr.:

9.7

Parameter:

radiochem. meas.

Sampling time:

259 d

Remarks on result:

other: River system

Parent/product:

parent

Compartment:

total system

% Degr.:

16.5

Parameter:

radiochem. meas.

Sampling time:

259 d

Remarks on result:

other: Pond system

Key result

Compartment:

natural water / sediment: freshwater

DT50:

1 480 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: River; Whole system

Key result

Compartment:

natural water / sediment: freshwater

DT50:

741 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: Pond; Whole system

Compartment:

natural water / sediment: freshwater

DT50:

4.2 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: River, Water phase

Compartment:

natural water / sediment: freshwater

DT50:

5 d

Type:

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

Temp.:

20 °C

Remarks on result:

other: Pond; Water phase

Other kinetic parameters:

third / second order rate constant

pseudo-first order rate constant

Transformation products:

no

Details on transformation products:

An overview of the results is provided in Table 4 in 'Any other information on results incl. tables'.
DISTRIBUTION OF METABOLITES
- River test system (water): On day 0, the test substance amounted to 95.8% of the radioactivity applied or 0.063 mg p.e. per litre water. It decreased continuously over the incubation period to 16.1% or 0.011 mg p.e. (parent equivalent)/L on day 259.
Besides the parent compound, five minor unknown metabolites were found. None of them exceeded 1.5% (0.001 mg p.e./L) during the experiment.

- River test system (Sediment): The test substance increased from 2.4% or 0.005 mg p.e. per kilogram sediment to maximum 77.5% (0.156 mg p.e./kg) on day 154. Thereafter it decreased to 72.4% (0.146 mg p.e./kg) on day 259. Besides the parent compound, five minor unknown metabolites were found. None of them exceeded 2.2% (0.004 mg p.e./kg) during the experiment.

- River test system (Whole System): The amount of test substance in the whole river system decreased from 98.2% of the radioactivity applied or 0.049 mg p.e. per kilogram whole system on day 0 to 88.5% or 0.044 mg p.e./kg at the end of the experiment (day 259).
Five minor unknown radioactive components were detected. None of them exceeded 3.4% (0.002 mg p.e./kg) during the experiment.

- Pond test system (water): On day 0 the test substance amounted to 94.6% of the radioactivity applied or 0.062 mg p.e. per litre water. It decreased continuously over the incubation period to 6.4% or 0.004 mg p.e./L on day 259.
Besides the parent compound, six minor unknown metabolites were found. None of them exceeded 2.6% (0.002 mg p.e./L) during the experiment.

- Pond test system (sediment): The test substance increased from 1.5% or 0.003 mg p.e. per kilogram sediment to a maximum of 80.9% (0.163 mg p.e./kg) on day 63. Thereafter it decreased to 73.2% (0.147 mg p.e./kg) on day 259. Besides the parent compound, six minor unknown metabolites were found. None of them exceeded 3.2% (0.006 mg p.e./kg) during the experiment.

- Pond test system (whole system): The amount of the test substance in the whole pond system decreased from 96.1 % of the radioactivity applied or 0.048 mg p.e. per kilogram whole system on day 0 to 79.6% or 0.039 mg p.e./kg at the end of the experiment (day 259).
Six minor radioactive components were detected. None of them exceeded 4.4% (0.002 mg p.e./kg) during the experiment.

Evaporation of parent compound:

not specified

Volatile metabolites:

yes

Remarks:

14CO2

Residues:

yes

Details on results:

An overview of the results is provided in Table 3, Table 5 - Table 7 in 'Any other information on results incl. tables'.

- Recovery of radioactivity: The total mean recoveries of radioactivity were 98.6% ± 1.3% for river and 98.1% ± 1.5% for pond. The individual recoveries ranged between 96.3% and 101.3% for river and between 95.0% and 100.8% for pond.

DISTRIBUTION OF RADIOACTIVITY
The radioactivity in the small volume of water which remained in the sediment phase after separation of the aqueous phase was counted as radioactivity in the sediment.

- Radioactivity in the River Test System: The level of radioactivity in the water decreased from 97.1 % of the radioactivity applied on day 0 to 19.5% on day 259. In the sediment the radioactivity increased from 2.7% on day 0 to 76.4% on day 28. Thereafter, a plateau value of about 80% was observed until the end of incubation. Radioactive carbon dioxide was below the detection limit (< 0.1%) until day 63 and increased slightly thereafter to 0.4% until day 259.

- Radioactivity in the Pond Test System: The level of radioactivity in the water decreased from 97.2% on day 0 to 9.3% on day 259. The level of radioactivity in the sediment increased from 1. 7% on day 0 to 84.1 % on day 28. Thereafter, a plateau value of about 85% was observed until the end of incubation like for the river test system. Radioactive carbon dioxide was below the detection limit(< 0.1 %) until day 28 and increased slightly thereafter to 0.3% until day 259.

CHARACTERISATION OF RADIOACTIVITY
- Extractability of Radioactivity from Sediment: The total radioactivity extracted from the river sediment increased from 2.4% on day 0 to a maximum of 79.2% on day 154 and decreased afterwards slightly to 74.8% on day 259. Soxhlet extractions recovered a maximum of 10.6% (day 210) of the applied radioactivity. The non-extracted radioactivity increased over time, from 0.3% on day 0 to 3.8% on day 259.

The total radioactivity extracted from the pond sediment increased from 1.5% on day 0 to a maximum of 83.6% on day 21 0 and decreased afterwards slightly to 78.1 % on day 259.
Soxhlet extractions recovered a maximum of 22.7% (day 210) of the radioactivity applied. The non-extracted radioactivity increased with time, from 0.2% on day 0 to 10.0% on day 259.

- Rate of Degradation of 14C-labelled test substance from the Aquatic Systems: See Table 4 in ‘Any other information on results incl. tables’

STERILE RIVER AND POND SYSTEMS
Sterile samples were analysed after 171 and 259 days of incubation for river and pond aquatic systems, respectively. The sterility test showed, no or clearly less growth of microorganisms at day 171 and for day 259.
The recovery of radioactivity was 102.6% and 101.0% for river and 93.4% and 94.8% for pond. The distribution of radioactivity in the water phase and sediment of the sterile river and pond systems was similar to that of the non-sterile systems. However, the metabolic pattern of the sterile systems showed that more parent compound was still present in the systems compared to the non-sterile part. Amounts of 91.9% and 83.1 % of applied radioactivity remained as the test substance after 259 days of incubation in river and pond systems, respectively.
Compared to the non-sterile systems, the number of metabolites in water or extracts is smaller, i.e. four unknown metabolites and their concentrations are lower. None of the metabolites in the river and pond systems exceeded 4.6% of applied radioactivity.

Table 3. Balance of radioactivity for the river and pond water/sediment system after treatment with 14C-labelled test substance. Values in percent of the radioactivity applied.

a)

RIVER	INCUBATION DAYS
	0	3	7	14	28	42	63	105	154	210	259
Radioactivity in water	97.1	53.3	46.5	33.9	23.3	21.6	16.8	19.9	19.0	18.4	19.5
Total radioactivity in sediment	2.7	44.7	52.0	63.9	76.4	76.6	79.5	79.2	82.1	79.7	78.6
Extractables*	2.4	43.1	49.2	60.5	70.4	69.4	71.9	70.0	71.8	66.4	64.7
Soxhlet**	n.p.	n.p.	2.3	3.0	5.2	5.4	5.6	7.0	7.4	10.6	10.1
Total extractables from sediment	2.4	43.1	51.5	63.5	75.6	74.8	77.5	77.0	79.2	77.0	74.8
Water + Extractables	99.5	96.4	97.9	97.3	98.8	96.4	94.3	96.9	98.2	95.4	94.3
Non-Extractables (Sediment)	0.3	1.6	0.5	0.5	0.9	1.8	2.0	2.3	2.9	2.7	3.8
14CO2	n.p.	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	0.1	0.2	0.1	0.4
Other Volatiles	n.p.	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1
TOTAL	99.7	98.0	98.4	97.8	99.7	98.2	96.3	99.2	101.3	98.2	98.5
AVERAGE	98.6±1.3

 

b)

POND	INCUBATION DAYS
	0	3	7	14	28	42	63	105	154	210	259
Radioactivity in water	97.2	62.2	36.8	24.7	14.6	15.2	11.6	10.8	11.2	9.5	9.3
Total radioactivity in sediment	1.7	38.6	62.4	72.8	84.1	83.8	85.3	83.9	86.6	89.5	88.1
Extractables*	1.5	36.9	57.7	67.3	73.6	71.1	72.4	67.7	67.7	60.9	57.2
Soxhlet**	n.p.	n.p.	4.2	4.3	8.8	10.6	9.4	14.7	14.2	22.7	20.9
Total extractables from sediment	1.5	36.9	61.9	71.6	82.4	81.7	81.7	82.4	81.9	83.6	78.1
Water + Extractables	98.7	99.1	98.7	96.2	97.0	96.9	93.3	93.2	93.1	93.1	87.4
Non-Extractables (Sediment)	0.2	1.8	0.5	1.2	1.7	2.1	3.6	1.5	4.7	5.9	10.0
14C02	n.p.	<0.1	<0.1	<0.1	<0.1	0.2	0.1	0.4	0.2	0.3	0.3
Other Volatiles	n.p.	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1
TOTAL	97.2	100.8	99.2	97.4	98.7	99.1	96.9	95.0	98.0	99.3	97.7
AVERAGE	98.1±1.5

*Extracted with acetonitrile/water (80/20;v/v) up to four times

** soxhlet with acetonitrile/water (80+20; v/v)

n.p.: not performed

Table 4. Distribution of 14C-labelled test substance and metabolites in water (A), sediment (B) and entire system (D) of the river and pond test systems. Values given in percent of the radioactivity applied

a)

River	INCUBATION TIME IN DAYS
Radioactive fraction	type of sample	0	3	7	14	28	42	63	105	154	210	259
The test substance	A	95.8	52.4	44.9	32.8	22.4	20.3	16.4	18.1	16.7	15.9	16.1
	B	2.4	43.1	51.5	63.0	73.3	74.8	76.2	74.6	77.5	72.7	72.4
	D	98.2	95.5	96.4	95.8	95.7	95.1	92.5	92.6	94.1	88.6	88.5
U0	A	1.3	0.*	1.5	1.1	0.8	1.2	0.4	1.2	1.5	1.0	1.1
	B				0.4	2.2		0.9	2.2	0.6	1.1	0.9
	D	1.3	0.9	1.5	1.5	3.1	1.2	1.3	3.4	2.1	2.1	2.1
U1	A								0.4	0.5	1.0	1.3
	B									0.6	0.7	1.0
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.4	1.1	1.7	2.3
U2	A								0.2	0.1	0.2	0.6
	B							0.4	0.2	0.6	0.4	0.5
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.4	0.5	0.7	0.7	1.1
U3	A									0.2	0.2	0.3
	B										2.0
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.2	2.2	0.3
U4	A										0.1
	B
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.1	n.d.
U5	A
	B
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.
Total		99.5	96.4	97.9	97.3	98.8	96.3	94.3	96.9	98.2	95.4	94.3

 

b)

Pond	INCUBATION TIME IN DAYS
Radioactive fraction	type of sample	0	3	7	14	28	42	63	105	154	210	259
The test substance	A	94.6	61.4	35.6	23.6	13.4	14.2	10.2	8.6	9.5	7.3	6.4
	B	1.5	36.9	61.1	71.1	81.1	79.4	80.9	79.2	76.8	78.2	73.2
	D	96.1	98.2	96.7	94.7	94.5	93.6	91.1	87.7	86.3	85.5	79.6
U0	A	2.6	0.8	1.2	1	1.2	1	1.4	1.9	0.4	0.6	0.8
	B	0	0.7	0.4	1.2	2.2	0.8	2.5	3.2	1.1	1.2
	D	2.6	0.8	1.9	1.4	2.5	3.2	2.2	4.4	3.7	1.7	2
U1	A	0.2	1	1.4	1.7
	B	1.3	2.7	2.8
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.2	2.2	4.1	4.6
U2	A	0.1	0.1
	B	0.7	0.6	0.8	0.8
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.8	0.7	0.8	0.8
U3	A	0.2	0.3
	B	0.2
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.2	0.5
U4	A	0.1
	B	0.3
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.4	n.d.
U5	A
	B	0.4	0
	D	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	0.4	0
Total		98.7	99.0	96.2	97.0	96.9	93.9	93.3	93.2	93.0	93.1	87.5

A: water

B: sediment

D: entire system

n.d.: not detected

Table 5. Balance of radioactivity for the sterile river and pond water/sediment system after treatment with 14C-labelled test substance. Values in percent of the radioactivity applied 

	Pond		River
	INCUBATION TIME IN DAYS
	171	259	171	259
Radioactivity in water	15.0	11.8	19.5	14.0
Total radioactivity in sediment	78.4	83.0	83.0	87.0
Extractables* Soxhlet**	59.5 16.1	59.2 17.5	61.0 19.6	60.9 18.8
Total extractables from sediment	75.6	76.7	80.6	79.7
Water+ Extractables	90.6	88.5	100.1	93.7
Non-Extractables (Sediment)	2.8	6.3	2.4	7.3
14CO2	<0.1	<0.1	<0.1	<0.1
Other Volatiles	<0.1	<0.1	<0.1	<0.1
TOTAL	93.4	94.8	102.6	101.0

* Extracted with acetonitrile/water (80/20;v/v) up to four times

** soxhlet with acetonitrile/water (80+20; v/v)

  Table 6. Distribution of 14C-labelled test substance and metabolites in water (A), sediment (B) and entire system (D) of the sterile river and pond test system. Values given in percent of the radioactivity applied.

Radioactive fraction		Pond		River
	type of   sample	INCUBATION TIME IN DAYS
		171	259	171	159
Test substsance	A B D	14.8 75.1 89.9	11.7 71.4 83.1	19.2 74.9 94.1	14.0 77.9 91.9
U0	A B D	0.1 0.5 0.6	0.1 0.7 0.8	0.3 0.9 1.2	0.5 0.5
U1	A B D	n.d.	n.d.	3.4 3.4	0.6 0.6
U2	A B D	n.d.	4.6 4.6	1.4 1.4	0.7 0.7
U3	A B D	0.1   0.1	n.d.
U4	A B D	n.d.	n.d.	n.d.	n.d.
U5	A B D	n.d.	n.d.	n.d.	n.d.
Total		90.6	88.5	100.1	93.7

A: water

B: sediment

D: entire system

n.d.: not detected

Table 7. Kinetic results

	River		Pond
	Water phase	Whole system	Water phase	Whole system
DT50 (days)	4.2	1480	5.0	741
DT90 (days)	344	2755	129	1381
R squared (correlation)	0.9906	0.9146	0.9986	0.9739
Model used	sqrt 2nd-order	linear regression	2-compartment	linear regression

 

Validity criteria fulfilled:

yes

Conclusions:

Under aerobic conditions at 20°C the test substance was quickly adsorbed to the sediment. The test substance adsorbed to the sediment was slowly but continuously degraded. The DT50 values in the whole river system and whole pond system were determined to be 1480 days and 741 days, respectively. End point of the degradation pathway was the formation of bound residues and to a lower extent the mineralisation to carbon dioxide.

Executive summary:

The degradation of the 14C-labelled test substance was investigated in two aquatic systems (Rhine River and Judenweiher Pond). The study was performed in accordance with scientifically valid standards and GLP criteria. Additionally, the test procedures and results are well documented, so that the study is considered as reliable (with restrictions). The two systems were treated with 65.8 µg/L14C-labelled substance corresponding to a field rate of 197 g a.i./ha for 259 days. The incubation was under aerobic conditions at 20 ± 2 °C in the darkness in the laboratory. The system were continuously aerated using moistened air. The surface of the water layer was gently agitated by a stirrer without disturbing the sediment.

The overall recovery comprising the soil extracts, non-extractable residues and volatile products was between 95.0% and 101.3% with an average of 98.6% for the river and 98.1 % for the pond test system. The test substance was quickly adsorbed to the sediment and slowly degraded in both water/sediment systems. At the end of the study, the test substance amounted to 88.5% of the applied radioactivity in the river system (water and sediment) and 79.6% in the pond system. The mineralisation of the test compound was very low in both test systems. At the end of the incubation, 14CO2 accounted for 0.4% and 0.3% of the applied radioactivity for river and pond, respectively. Besides parent, five to six minor unknown degradates were formed, none of them exceeded 4.6% of the radioactivity applied at any time interval. The amount of non-extractable radioactivity increased slightly during the study. On day 259, 3.8% of the applied radioactivity remained unextracted for river and 10.0% for pond.

Based on the findings, the DT50 values in the whole river system and whole pond system were determined to be 1480 days and 741 days, respectively. The DT50 values in the water phase of the river system and pond system were determined to be 4.2 days and 5.0 days, respectively. End point of the degradation pathway was the formation of bound residues and to a lower extent the mineralisation to carbon dioxide.

 

Description of key information

All available data was assessed. The study that follows standard test conditions is included here as the key study. The other study is included as supporting information.

- Freshwater: The study was waived. Based on the available information, the CSA does not reveal a need for further investigation (the environmental risk assessment for all intended uses shows that the risk is controlled). In addition, a scientifically valid study showed that the substance was quickly adsorbed from the water phase to the sediment phase (Völkel 1997).

- Freshwater/sediment whole system: The DT50 ranged from 741 to 1480 days (geometric mean of 1047 days), no guideline followed (Völkel 1997).

Key value for chemical safety assessment

Whole System

Half-life in whole system:

1 047 d

at the temperature of:

20 °C

Type of system:

fresh water and sediment

Additional information

Two studies under aerobic conditions are available for this endpoint. The study follows standard test conditions is included as the key study (Völkel 1997, Reliability 2). The effect values from this study were used in a weight of evidence approach for the CSA. The test condition, results and effect values are summarised in the Table below. The other study is used as supporting information.

 

Test system	Test conditions	Mineralisation / Non-extractable residues/ Major metabolites (% applied)	Compartment	DT50 [d] - Kinetic model	Author / Year
River Rhine, CH	180 g wet sediment + 550 mL corresponding water. Incubation in the dark for 259 days at 20 °C under aerobic conditions with 11 sampling intervals	Miner.: max. 0.4 % AR Non-extr.: max. 3.8 % AR Maj. met.: None, all below 4.6 % AR	Water Total system	4.2 days – Sqrt 2nd order 1480 days – linear regression	Völkel 1997
Pond, Judenweiher, CH	180 g wet sediment + 550 mL corresponding water. Incubation in the dark for 259 days at 20 °C under aerobic conditions with 11 sampling intervals	Miner.: max. 0.4 % AR Non-extr.: max. 10.0 % AR Maj. met.: None, all below 4.6 % AR	Water Total system	5.0 days – two-comp 741 days – linear regression	Völkel 1997

 

The supporting study followed Dutch guideline G.2 and complied with GLP criteria (Reliability 1). Two field soils and 1 pond sediment system were treated with 14C-labelled substance for 3 months under aerobic conditions and ambient temperature. The waster-sediment system test conditions, results and effect values were included in the Table below.

 

Test system	Test conditions	Mineralisation / NER / Major metabolites (% applied)	Compartment	DT50 [d] – Kinetic model	Author/ Year
Sediment and water from pond in Anwil, CH	20 g sediment and 200 mL filtered surface water. Aerobic incubation for up to 3 months with 4 sampling intervals	Miner.: up to 20 % AR NER: up to 8 % AR Maj. met.: None	Sediment	About 7 months – zero order	Gampp 1989