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Biodegradation in water and sediment: simulation tests

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Reference
Endpoint:
biodegradation in water and sediment: simulation testing, other
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
Deviations:
yes
Remarks:
TOC of the water phase and of the sediments and pH of the sediments were not measured after the end of prolongation because no untreated samples were available. This deviation did not affect the validity or integrity of the study.
GLP compliance:
yes (incl. certificate)
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment
Details on source and properties of surface water:
- Details on collection:
River system: Birs, 4243 Dittingen, Switzerland
Pond system: Fröschweiher, 4310 Rheinfelden, Switzerland

The sampling was performed in accordance to draft ISO Guidance on sampling of bottom sediments.
The sampling locations were not in areas that received effluent discharges. Surface water was collected from the same site and at the same time as the sediment.
The samples were transported to the laboratory in sealed containers. The water was passed through a 0.2 mm screen. The water/sediment systems were then stored together, water-logged (>5 cm water layer) at about 4 °C in the dark for one week until use.

Parameters for river surface water:
- Temperature (°C) at time of collection: 16.0°C
- pH:
at time of collection: 8.1 (water)
start of test: 8.0-8.3
end of test: 7.8-8.1
average during test: 8.1 ± 0.3
- Total organic carbon (TOC):
at time of collection: not available
start of test: 4.6 mg/L
during test (day 101): 32.2 mg/L
end of test: not available
- Redox potential:
at time of collection: 385 mV
start of test: 366-369 mV
end of test: 364-393 mV
average during test: 362 ± 32 mV
- Oxygen concentration:
at time of collection: 9.9 mg/L
start of test: 8.0-8.2 mg/L
end of test: 9.0-11.0 mg/L
average during test: 8.5 ± 1.3 mg/L

Parameters for pond surface water:
- Temperature (°C) at time of collection: 20.2 °C
- pH:
at time of collection: 7.3 (water)
start of test: 8.5-8.7
end of test: 7.7-8.3
average during test: 8.2 ± 0.3
- Total organic carbon (TOC):
at time of collection: not available
start of test: 16.7 mg/L
during test (day 101): 20.5 mg/L
end of test: not available
- Redox potential:
at time of collection: 284 mV
start of test: 360-362 mV
end of test: 356-408 mV
average during test: 360 ± 31 mV
- Oxygen concentration:
at time of collection: 6.1 mg/L
start of test: 8.5-8.9 mg/L
end of test: 9.9-11.7 mg/L
average during test: 8.8 ± 1.3 mg/L
Details on source and properties of sediment:
- Details on collection:
River system: Birs, 4243 Dittingen, Switzerland
Pond system: Fröschweiher, 4310 Rheinfelden, Switzerland

The sampling was performed in accordance to draft ISO Guidance on sampling of bottom sediments.
The sampling locations were not in areas that received effluent discharges. Sediments were taken from the top 10 cm sediment layer.
The samples were transported to the laboratory in sealed containers. The sediments were passed through a 2.0 mm sieve. The water/sediment systems were then stored together, water-logged (>5 cm water layer) at about 4 °C in the dark for one week until use.

river system:
- Textural classification (i.e. %sand/silt/clay):
Clay: 10.36%
Silt: 16.54%
Sand: 73.10%
soil (sediment) type (USDA): sandy loam
- pH at time of collection: 7.32 (CaCl2)
- Total organic carbon (TOC:
at time of collection: not available
start of test: 10.3 mg/g
during test (day 101): 25.5 mg/g
end of test: not available
- Redox potential:
at time of collection: not available
start of test: 45-92 mV
end of test: 43-115 mV
average during test: 63 ± 24 mV
- Biomass:
at time of collection: 392 mg microbial C/kg dry sediment
start of test: 528 mg/kg
during test (day 101): 691 mg/kg
end of test: 209 mg/kg

pond system:
- Textural classification (i.e. %sand/silt/clay):
Clay: 26.50%
Silt: 57.36%
Sand: 16.14%
soil (sediment) type (USDA): silty loam
- pH at time of collection: 7.27 (CaCl2)
- Total organic carbon:
at time of collection: not available
start of test: 30.3 mg/g
during test (day 101): 32.3 mg/g
end of test: not available
- Redox potential:
at time of collection: not available
start of test: 29-34 mV
end of test: 1-53 mV
average during test: 46 ± 20 mV
- Biomass:
at time of collection: 704 mg microbial C/kg dry sediment
start of test: 686 mg/kg
during test (day 101): 943 mg/kg
end of test: 395 mg/kg
Duration of test (contact time):
189 d
Initial conc.:
131.7 other: µg/flask
Based on:
test mat.
Initial conc.:
0.65 other: µg/g wet river sediment
Based on:
test mat.
Initial conc.:
0.57 other: µg/g wet pond sediment
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Test solutions: An aliquot of the test item was mixed with unlabelled test item (prepared in Milli-Q water). No organic solvent was used. Five aliquots of 600 µL each were measured by LSC. Based on the results, the radioactivity content of the application solution was 50’582’500 dpm/mL or 0.843 MBq/mL. The specific radioactivity of the application solution was 4.12 MBq/mg, corresponding to 0.204 mg test item/mL. The application volume was 600 µL, corresponding to a concentration122 µg per aquatic system. Control flasks were treated with the corresponding amount of water.
- Setup of test flasks:
For each time interval and test system duplicate test systems were prepared. 18 flasks each were treated with the test item, other 6 flasks were treated with Milli-Q water only and used as controls (determination of parameters and microbial biomass).
- Sample preparation:
Water-sediment samples were prepared for the study by sieving (2 mm sieve, sediment) and filtering (0.2 mm screen, water). The test systems consisted of 1 L all-glass metabolism flasks (inner diameter: approx. 10.6 cm) filled with wet sediment to a height of approx. 2.3 cm (corresponding to 202.5 ± 5.4 g river sediment and 232.0 ± 4.7 g pond sediment, respectively). Thereafter, approx. 6.8 cm water of the corresponding system (559 ± 22 mL) was added to reach a sediment/water volume ratio of approx. 1:3. The samples were left to acclimatise for about 3 weeks ventilated with moistened air at 20.9 ± 0.2°C in the dark to achieve constant redox potential and oxygen conditions.
After application of the test item the flasks were connected to a series of two volatiles traps, the first trap containing ethylene glycol and the second trap consisting of 2M NaOH (volume: approximately 50 mL each). For sampling on day 0, no absorption traps were set up.
- Test temperature: The test systems were incubated at 20.9 ± 0.2°C in the dark, ventilated with moistened air.

TEST SYSTEM
- Test concentration: The target concentration of the test item was 122 µg per aquatic system.
The amount of radioactivity applied to each sample averaged 131.7 µg test item per flask (107.9% of target). This resulted in an average application rate of 0.65 µg/g wet river sediment. The corresponding application rate in the pond system was 0.57 µg/g wet sediment, respectively.

SAMPLING
- Sampling frequency: 0, 3, 7, 14, 32, 60, 101, 154 and 189 days
- Sampling method: The aqueous phase was withdrawn from the flasks using a pipette.

STATISTICAL METHODS:
DT50 and DT90 values for 14C-THEIC were calculated using single first-order kinetics. Kinetics evaluation for metabolite M4 was not feasible as the number of data points from maximum onwards was too low.
CAKE software developed by TessellaPlc, Abingdon, Oxfordshire, UK
The rate of degradation of 14C-THEIC were calculated according to FOCUS (2006) „Guidance Document on Estimating Persistence and degradation Kinetics from Environmental Fate Studies on Pesticides in EU Registration“ Report of the FOCUS Work Group on Degradation Kinetics, EC Document Reference Sanco/10058/2005/version 2.9, 434 pp.
Reference substance:
not required
Compartment:
other: water / sediment, material (mass) balance
Remarks on result:
other: The total mean recoveries were 95.0 ± 3.4% and 95.6 ± 1.6% of the applied radioactivity for river and pond water/sediment systems, respectively.
% Degr.:
95.2
St. dev.:
2.8
Parameter:
test mat. analysis
Sampling time:
189 d
Remarks on result:
other: in the entire river system
% Degr.:
97.7
St. dev.:
0.4
Parameter:
test mat. analysis
Sampling time:
189 d
Remarks on result:
other: in the entire pond system
Compartment:
water
DT50:
16.9 d
Type:
(pseudo-)first order (= half-life)
Temp.:
21 °C
Remarks on result:
other: river system; r2=0.9709, DT90=56.0 d
Compartment:
sediment
DT50:
40.94 d
Type:
(pseudo-)first order (= half-life)
Temp.:
21 °C
Remarks on result:
other: river system; r2=0.8849, DT90=136 d
Compartment:
entire system
DT50:
29.3 d
Type:
(pseudo-)first order (= half-life)
Temp.:
21 °C
Remarks on result:
other: river system; r2=0.9578, DT90=97.2 d
Compartment:
water
DT50:
16.7 d
Type:
(pseudo-)first order (= half-life)
Temp.:
21 °C
Remarks on result:
other: pond system; r2=0.9631, DT90=55.3 d
Compartment:
sediment
DT50:
50.3 d
Type:
(pseudo-)first order (= half-life)
Temp.:
21 °C
Remarks on result:
other: pond system; r2=0.8158, DT90=167 d
Compartment:
entire system
DT50:
27.8 d
Type:
(pseudo-)first order (= half-life)
Temp.:
21 °C
Remarks on result:
other: pond system; r2=0.9407, DT90=92.3 d
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3
No.:
#4
No.:
#4
No.:
#5
No.:
#6
No.:
#7
Details on transformation products:
The results are summarised in Tables 4 to 9 (see Attached background material: Tables.pdf).
The amount of 14C-THEIC in total river test system decreased from 92.5% AR on day 0 to 4.4% AR at the end of incubation (sampling day 189). The corresponding values for total pond test system were 93.1% AR on day 0 and 2.1% AR at the end of incubation.
In both systems, 14C-THEIC was mainly present in the aqueous phase. The amount of 14C-THEIC in the aqueous phase of the river system decreased from 92.5% AR (sampling day 0) to 56.2% AR on sampling day 14, and reached 1.8% AR at the end of incubation. The corresponding values in the aqueous phase of the pond system were 93.1%, 64.3% and 0.4% AR, respectively. In sediment extracts of the river and pond system, 14C-THEIC reached maximum mean levels of 24.0% and 23.0% AR (sampling day 14). Thereafter, the amount of 14C-THEIC decreased to 2.5% and 1.7% AR at the end of incubation, respectively.
14C-THEIC degraded into 7 radioactive fractions. In both systems, radioactive fraction M4 was a major metabolite mainly present in the aqueous phase. The first occurrence of M4 in the aqueous phase of river system was on sampling day 7, with M4 accounting for 7.0% of the applied radioactivity (AR). The amount of M4 in the aqueous phase increased over time to a maximum level of 69.3% (sampling day 101), followed by a decrease to 6.6% AR at the end of incubation. The same pattern was observed in the extracts of river sediments, with M4 accounting for 1.0% (sampling day 7), 8.6% (sampling day 101) and 0.8% AR (end of incubation). In the pond system, M4 also first occurred on sampling day 7. The amount of M4 in the aqueous phase increased over time from 1.5% AR (day 7) to a maximum level of 68.2% AR (end of incubation). In the corresponding sediment extracts, M4 also increased over time, and accounted for 13.8% AR at sampling day 189. Based on LC-MS and MS/MS analysis of M4, the proposed identity of M4 was (3,5-Bis-carboxymethyl-2,4,6-trioxo-[1,3,5]triazinan-1-yl)-acetic acid. Kinetics evaluation for metabolite M4 was not feasible as the number of data points from maximum onwards was too low.
In the total river system, radioactive fraction M2 exceeded 5% AR at three consecutive sampling intervals (sampling day 7, 14 and 32), with a maximum level of 6.8% AR at sampling day 7. In the pond system, radioactive fraction M2 reached a maximum level of 4.9% AR in total test system (sampling day 7). In both test systems, M2 was not detected anymore from sampling day 101 onwards.
The other 5 radioactive fractions were detected only intermittently and never reached 5% AR.
Part of the radioactivity in the aqueous phase of the river system consisted of volatile radioactivity (see also "Any other information on results incl. tables"). It was attempted to trap volatiles after acidifying two aliquots of the water phase. Originally, 35.3% of the radioactivity applied was measured in the water phase of replicate A. After acidifying and stripping, 24.8% AR remained in the water, 2.5% AR was trapped in sodium hydroxide solution, and about 8.0% AR was not recovered. The latter radioactivity could be 14CO2 not being trapped or other unknown volatile substances. The experiment was done twice with the same result.
Replicate B of interval day 189 showed less radioactivity in water (A: 35.3% AR, B: 16.7% AR), but at the same time much more 14CO2 (A: 38.4% AR, B: 60.0% AR).
The whole amount of radioactivity in the NaOH-traps was confirmed as 14CO2 by precipitation as barium carbonate. Therefore, it can be concluded that the lost radioactivity in replicate A was either 14CO2 or a volatile substance that would have been completely mineralised. HPLC chromatograms of replicate A and B from sampling day 189 further confirmed that the degradation/mineralisation of replicate B was faster than in replicate A. Parent and metabolite M4 already had completely disappeared from replicate B. Consequently, the end of the degradation process leads to complete mineralisation.
Evaporation of parent compound:
no
Volatile metabolites:
no
Residues:
yes
Details on results:
TEST CONDITIONS
- Aerobicity, moisture, temperature and other experimental conditions maintained throughout the study: Yes

MAJOR AND MINOR TRANSFORMATION PRODUCTS
See "Details on transformation products" and Attached background material: Tables.pdf.

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT:

EXTRACTABLE RESIDUES
- % of applied amount at day 0: river 3.0%, pond 1.5%
- % of applied amount at end of study period: river 3.5%, pond 15.5%

NON-EXTRACTABLE RESIDUES
- % of applied amount at day 0: river 0.8%, pond 0.5%
- % of applied amount at end of study period: river 8.2%, pond 7.6%

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: river 49.2%, pond 5.0%

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: <0.1% in both systems

Distribution of radioactivity

The results are summarised in Tables 1 to 3 (see Attached background material: Tables.pdf).

1. Water

Immediately after treatment (day 0), 94.8% and 95.5% AR was present in the aqueous phase of river and pond systems. Thereafter, the amount of radioactivity in the aqueous phase decreased in both aquatic sediment systems. At 7 days of incubation, 68.7% and 68.1% AR were recovered from river and pond water, respectively. The amount of radioactivity in the aqueous phase of the river system remained constant between approx. 60% and 70% AR until 154 days of incubation. Thereafter, radioactivity in the aqueous phase rapidly decreased, and accounted for 26.0% AR at 189 days of incubation. The amount of radioactivity in the aqueous phase of the pond system remained constant between approx. 60% and 70% AR until the end of the incubation.

The aqueous phases of the river system contained dissolved volatile radioactivity (Table 2, Attached background material - Tables.pdf). This volatile radioactivity derived from a degradation process finally leading to complete mineralisation. This formation of volatile degradates explained the loss of radioactivity during the work-up process, i.e. the separation of the water phase from the sediment. As a consequence, the total radioactive balances of both samples were slightly below 90% AR, i.e. 86.9% AR (mean value). Aliquots of the aqueous phase were concentrated before chromatographic analysis. Further loss of radioactivity was observed, indicating more dissolved volatile radioactivity. It was attempted to quantitatively remove the volatiles and identify them as 14CO2. The results are reported in the field "Details on transformation products".

2. Sediment

2.1 Extractable Radioactivity

The amount of radioactivity extracted from river sediments at room temperature increased over time from 3.0% AR (day 0) to a maximum of 19.1% AR at 7 days of incubation. Thereafter, the amount decreased, accounting to 1.8% AR at the end of the incubation (day 189). Radioactivity recovered by Soxhlet extraction slightly increased over time, reaching 7.8% AR at 32 days of incubation, followed by a decrease to 1.7% AR at the end of incubation.

Radioactivity extracted at room temperature from pond sediments increased from 1.5% AR (day 0) to a maximum of 19.5% AR at 7 days of incubation and remained relatively constant until sampling day 60. Thereafter, the amount decreased to 12.7% AR at 189 days of incubation. Radioactivity recovered by Soxhlet extraction slightly increased from 2.7% AR (day 3) to a maximum of 6.6% AR (day 32), followed by a decrease to 2.8% AR at sampling days 189.

2.2 Non-Extractable Radioactivity

On day 0, the amount of non-extractable radioactivity was below ≤0.8% AR in both water/sediment systems. In the river system, bound residues increased over time to a maximum of 8.4% AR (day 101), and accounted for 8.2% AR at the end of incubation. In the pond system, bound residues reached a maximum of 10.2% AR at sampling day 60, and accounted for 7.6% AR at the end of incubation.

3. Volatiles

Mineralisation of 14C-THEIC in the river water/sediment was initially rather slow. The amount of 14CO2 increased from 0.4% AR at sampling day 3 to 7.3% AR at day 154. Thereafter, the amount of 14CO2 strongly increased to 49.2% AR at sampling day 189. Mineralisation of 14C-THEIC in the pond water/sediment system was minor. The amount of 14CO2 increased continuously, accounting for 5.0% AR at the end of the incubation.

The majority of the radioactivity in sodium hydroxide could be identified as 14CO2. The amount of radioactivity which could not be precipitated with barium hydroxide accounted for < 0.5% AR.

Organic volatile products absorbed in the ethylene glycol traps did not exceed 0.1% AR in both aquatic sediment systems tested.

Validity criteria fulfilled:
yes
Conclusions:
The rate of degradation of 14C-THEIC was investigated in two different aquatic systems (a river and a pond) under aerobic conditions. 14C-THEIC degraded in aquatic systems with a half-life of between 27.8 and 29.3 days. The degradation proceeded mainly via formation of Metabolite M4 ((3,5-Bis-carboxymethyl-2,4,6-trioxo-[1,3,5]triazinan-1-yl)-acetic acid) and ultimately by formation of CO2.
Executive summary:

The route and rate of degradation of14C-THEIC (i.e. tris(2-hydroxyethyl)-1,3,5-triazinetrione[Ring-14C(U)]) was investigated in two different aquatic sediment systems: a river (Birs, Switzerland) and a pond (Fröschweiher, Switzerland).14C-THEIC was applied at a rate of 131.7 µg test item per system (107.9% of target). This resulted in an average application rate of 0.64 µg/g wet river sediment and 0.57 µg/g wet pond sediment, respectively.

The aquatic sediment systems were incubated under aerobic conditions in the laboratory in the dark at 20.9 ± 0.2 °C for 189 days. Treated samples were continuous ventilated with moistened air and the exiting air was passed through a trapping system consisting of a flask with ethylene glycol and a flask with sodium hydroxide in series. Duplicate samples were taken for analysis after 0, 3, 7, 14, 32, 60, 101, 154 and 189 days of incubation.

 

The aqueous phase was withdrawn from the flasks and the radioactivity measured by Liquid Scintillation Counting (LSC). Chromatographic profiling was performed by High-Performance Liquid Chromatography (HPLC). Thin-Layer Chromatography (TLC) was used as confirmatory method for chromatographic profiling of selected samples.

Sediments were extracted up to three times with acetonitrile/water (4:1, v/v), followed by Soxhlet extraction with acetonitrile/water (4:1; v/v). Extracts were combined, concentrated in a rotary evaporator at about 35 °C and analysed by LSC for recovery. Chromatographic profiling was performed by HPLC. Selected samples were analysed by TLC.

Non-extractable radioactivity was determined by combustion of homogenised sediments. Volatile radioactivity trapped in ethylene glycol and sodium hydroxide solutions was determined by LSC.

 

The total mean recoveries were 95.0 ± 3.4% and 95.6 ± 1.6% of the total radioactivity applied (AR) for river and pond water/sediment systems, respectively.

Immediately after treatment (day 0), 94.8% and 95.5% AR was present in the aqueous phase of river and pond systems. The amount of radioactivity in the aqueous phase initially decreased in both aquatic sediment systems to approx. 60 - 70% AR within one week. Thereafter, the amount of radioactivity in the aqueous phase of the pond system remained constant until the end of the incubation. In the river system, however, radioactivity only remained constant until sampling day 154. Thereafter, it rapidly decreased to 26.0% AR at 189 days of incubation.

The amount of radioactivity extracted from river sediments increased over time from 3.0% AR (day 0) to a maximum of 25.8% AR at 14 days of incubation. Thereafter, the amount decreased again to 3.5% AR at the end of the incubation (day 189). The corresponding values for the pond system were 1.5% (day 0), 26.1% (day 32) and 15.5% (day 189).

On day 0, the amount of non-extractable radioactivity was below ≤0.8% AR in both water/sediment systems. In the river system, bound residues increased over time to 8.2% AR at the end of incubation. In the pond system, bound residues reached a maximum of 10.2% AR at sampling day 60, and accounted for 7.6% AR at the end of incubation.

Mineralisation of14C-THEIC in the river water/sediment was initially rather slow. The amount of14CO2increased from 0.4% AR at sampling day 3 to 7.3% AR at day 154, followed by a strong increase to 49.2% AR at sampling day 189. Mineralisation of14C-THEIC in the pond water/sediment system was minor, reaching 5.2% AR at the end of the incubation. Organic volatile products absorbed in the ethylene glycol traps did not exceed 0.1% AR in both aquatic sediment systems tested.

The amount of14C-THEIC in total river test system decreased from 92.5% AR on day 0 to 4.4% AR at the end of incubation (sampling day 189). The corresponding values for total pond test system were 93.1% AR on day 0 and 2.1% AR at the end of incubation.

In both systems,14C-THEIC was mainly present in the aqueous phase. The amount of14C-THEIC in the aqueous phase of the river system decreased from 92.5% AR (sampling day 0) to 56.2% AR on sampling day 14, and reached 1.8% AR at the end of incubation. The corresponding values in the aqueous phase of the pond system were 93.1%, 64.3% and 0.4% AR, respectively. In extracts of the river and pond system,14C-THEIC reached maximum mean levels of 24.0% and 23.0% AR (sampling day 14). Thereafter, the amount of14C-THEIC decreased to 2.5% and 1.7% AR at the end of incubation, respectively.

 

14C-THEIC degraded into 7 radioactive fractions. In both systems, radioactive fraction M4 was a major metabolite, which was mainly present in the aqueous phase. The first occurrence of M4 in the aqueous phase of river systems was on sampling day 7, with M4 accounting for 7.0% AR. The amount of M4 in the aqueous phase increased over time to a maximum level of 69.3% (sampling day 101), followed by a rapid decrease to 6.6% AR at the end of incubation. The same pattern was observed in the extracts of river sediments, with M4 accounting for 1.0% (sampling day 7), 8.6% (sampling day 101) and 0.8% AR (end of incubation).

In the pond system, M4 also first occurred on sampling day 7. The amount of M4 in the aqueous phase increased over time from 1.5% AR (day 7) to a maximum level of 68.2% AR (end of incubation). In the corresponding sediment extracts, M4 also increased over time, and accounted for 13.8% AR at sampling day 189. Based on LC-MS and MS/MS analysis of M4, the proposed identity of M4 was (3,5-Bis-carboxymethyl-2,4,6-trioxo-[1,3,5]triazinan-1-yl)-acetic acid.

 

The calculated DT50and DT90values for14C-THEIC in aqueous phase, sediments and total test system were based on single first-order kinetics and are given in the table below.

 

System

14C-THEIC

 

 

DT50[d]

DT90[d]

chi2-error [%]

r2

Prob > t

River

Aqueous phase

16.9

56.0

10.52

0.9709

2.639E-08

Sediment

40.94

136

10.51

0.8849

0.0001573

Total system

29.3

97.2

9.11

0.9578

8.138E-08

Pond

Aqueous phase

16.7

55.3

12.27

0.9631

1.507E-07

Sediment

50.3

167

7.83

0.8158

0.0007712

Total system

27.8

92.3

12.31

0.9407

1.113E-06

 

In conclusion,14C-THEIC degraded in aquatic systems with a half-life of between 27.8 and 29.3 days. The degradation proceeded mainly via formation of Metabolite M4 ((3,5-Bis-carboxymethyl-2,4,6-trioxo-[1,3,5]triazinan-1-yl)-acetic acid) and ultimately by formation of CO2.

Description of key information

Biodegradation in water and sediment: simulation tests (OECD TG 308, aerobic degradation in two aquatic systems): DT50 28-29 days in the total system; 17 days in water, 41-50 days in the sediment.

Key value for chemical safety assessment

Half-life in freshwater:
17 d
at the temperature of:
21 °C
Half-life in freshwater sediment:
50 d
at the temperature of:
21 °C

Additional information

During degradation of THEIC several well water soluble metabolites were detected. The major metabolite was identified as (3,5-Bis-carboxymethyl-2,4,6-trioxo-[1,3,5]triazinan-1-yl)-acetic acid. Ultimately, THEIC was mineralised to CO2.