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Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water and sediment: simulation testing, other
Type of information:
experimental study
Adequacy of study:
key study
Study period:
22-07-2008 - 22-08-2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: SETAC (Europe): Procedures for assessing the enviornmental fate and ecotoxicity of pesticides Part 1, Section 8.2, March 1995
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: Commission Directive 91/414/EEC, Annex II; Paragraph 7.2.1.3.2; amended by Commission Directive 95/36/EC July 14, 1995
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
EPA Subdivision N Pesticide Guideline 162-4 (Aerobic Aquatic Metabolism)
Principles of method if other than guideline:
Guidelines & Limitations
1. The label position does not allow to establish the degradation pathway (especially the occurrence of phenyl and imidazole moiety containing degradation products).
This discussion on labelling position and analytical methods is also dealt with at the phys/chem. and analytical methods experts.
The fact that the imidazole ring is oxidised by CYP450 enzymes to give in the end at least acids. Several enzymes like oxygen and amine oxidases and alcohol/aldehyde dehydrogenases are also involved in the biotransfomation of the imidazole moiety. Imidazole itself also has been shown to undergo oxidation to the 2-imidazolone metabolite, which upon further oxidation and ring cleavage yields the hydantoin and N-(carboxymethyl) urea is agreed. Nevertheless because very little metabolites are identified and the fact that there is only 1 labelling position it cannot be excluded that other degradation pattern exist.
acceptable without information.
2. The study is acceptable and the DT50 endpoints reliable provided remark 1 is adequately addressed by the notifier. If so, these endpoints may be used for risk assessment. The study is not conclusive with respect to the assessment of relevant metabolites.
GLP compliance:
yes
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
- Details on collection (e.g. location, sampling depth, contamination history, procedure):
The water/sediment systems were sampled from a river (Rhine river, Mumpf AG, Switzerland) and from a pond (Fröschweiher pond, Möhlin AG, Switzerland) and consisted of natural water filtered through a 0.2 mm sieve.
- pH at time of collection:
Surface water #1 (river Rhine, Switzerland): 7.91
Surface water #2 (Fröschweiher Pond, Switzerland): 7.75
- Organic carbon (%):
Surface water #1 (river Rhine, Switzerland): 1.28 mg TOC/L
Surface water #2 (Fröschweiher Pond, Switzerland): 4.52 mg TOC/L
Details on source and properties of sediment:
- Details on collection (e.g. location, sampling depth, contamination history, procedure):
The water/sediment systems were sampled from a river (Rhine river, Mumpf AG, Switzerland) and from a pond (Fröschweiher pond, Möhlin AG, Switzerland) and the upper 10 cm layer of sediment sieved through a 2 mm mesh.
- Textural classification (i.e. %sand/silt/clay):
Sediment #1 (river Rhine, Switzerland): loamy sand: 81% sand/ 12% silt/ 7% clay (USDA)
Sediment #2 (Fröschweiher Pond, Switzerland): silt loam: 21% sand/ 54% silt/ 25%c lay (USDA)
- pH at time of collection:
Sediment #1 (river Rhine, Switzerland): 7.38
Sediment #2 (Fröschweiher Pond, Switzerland): 7.07
- Organic carbon (%):
Sediment #1 (river Rhine, Switzerland): 0.70 mg TOC/L
Sediment #2 (Fröschweiher Pond, Switzerland): 4.22 mg TOC/L
- microbial biomass (start):
Sediment #1 (river Rhine, Switzerland): 497 g C/g
Sediment #2 (Fröschweiher Pond, Switzerland): 1281 g C/g
- microbial biomass (end):
Sediment #1 (river Rhine, Switzerland): 584 g C/g
Sediment #2 (Fröschweiher Pond, Switzerland): 2277 g C/g
Duration of test (contact time):
152 d
Initial conc.:
ca. 40 µg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Volume of test solution/treatment: Imazalil was applied to the water surface of each aquatic sample at a dose of about 0.04 mg item per litre water
- Composition of medium: 200g sediment (wet weight) and 600mL water
- Test temperature: 20 +/-2 °C
- Aeration of dilution water: yes
- Suspended solids concentration:
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: open glas-flow-through-system in 1000 mL glass metabolism flasks
- Number of culture flasks/concentration: dublicate per test system
- method used to create aerobic conditions: the water phase was aerated by a stream of air through the sample whilst the sediment remained undisturbed
- Measuring equipment: HLPC
- Test performed in open system: yes

SAMPLING
- Sampling frequency: time 0 and on 1, 7, 14, 28, 56, 100 and 152 of incubation
- Sampling method used per analysis type: The supernatant (practically the total amount of water) was removed from the sediment with a pipette without disturbing the underlying sediment . The small residual pore water was treated as sediment in further processing
Key result
Compartment:
entire system
DT50:
97.4 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #1 river
Key result
Compartment:
entire system
DT50:
79.6 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #2 pond
Key result
Compartment:
natural water: freshwater
DT50:
3.17 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #1 river
Key result
Compartment:
natural water: freshwater
DT50:
2.35 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #2 pond
Key result
Compartment:
natural sediment: freshwater
DT50:
159 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #1 river
Key result
Compartment:
natural sediment: freshwater
DT50:
187 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #2 pond
Transformation products:
not specified
Validity criteria fulfilled:
yes
Conclusions:
In two water/sediment systems, treated with 14C-imazalil at a concentration of 40 μg/L and incubated at 20°C in the dark for 152 days, the radioactivity level in water decreased to <10% AR on day 14 and was 1.7-4.6% AR after 152 days. Sediment radioactivity reached a maximum after 56 days (92-96% AR) and decreased to 85-91% AR at the end of the study (day 152). The non-extractable fraction in the sediment increased to a maximum of 35-46% AR at study end. CO2 was 2.9-3.9% AR at study end and no other volatiles were produced. The level of imazalil in water was 4.5-8.0% AR on day 14 and 2.1% AR at study end. The levels of imazalil reached a maximum in sediment of 62-69% AR on day 14 and were 37-40% AR on day 100. Metabolites in water were 2.2% AR. The most important metabolite in sediment was maximum 9.9% AR (day 28). Other sediment metabolites were always 5.0% AR. One metabolite was identified as R014821 (maximum 0.7% AR in water and 5.0% AR in sediment). For persistence, the following level P-I endpoints are estimated: Total system DegT50: 97.4 and 79.6 days, water column DT50: 3.17 and 2.35 days and sediment DT50: 159 and 187 days. It was therefore concluded that in aerobic aquatic systems, 14C-imazalil rapidly dissipates from the water phase by adsorption tot the sediment. Once in the sediment, its degradation proceeds at a slow rate. Degradation proceeds via numerous minor metabolites, bound residues and finally mineralization.
Endpoint:
biodegradation in water and sediment: simulation testing, other
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Data from the related substance imazalil base is used to cover this endpoint. The justification for read across is attached in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Key result
Compartment:
entire system
DT50:
97.4 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #1
Key result
Compartment:
entire system
DT50:
79.6 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #2
Key result
Compartment:
natural water: freshwater
DT50:
3.17 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #1
Key result
Compartment:
natural water: freshwater
DT50:
2.35 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #2
Key result
Compartment:
natural sediment: freshwater
DT50:
159 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #1
Key result
Compartment:
natural sediment: freshwater
DT50:
187 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: location #2
Transformation products:
not specified
Endpoint:
biodegradation in water and sediment: simulation testing, other
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
Deviations:
no
GLP compliance:
yes
Radiolabelling:
yes
Oxygen conditions:
aerobic/anaerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
aquatic system #1 Rhine river (Speyer, Germany)
aquatic system #2 Natural ditch (Schifferstadt, Germany)
- The water/sediment systems were first acclimated under aerobic conditions in the dark for about 3 weeks prior to treatment
- the aqueous phases were aerobic htoughout the incubation period
- water was filtered through a 0.15 mm sieve
-pH at the sampling site/time of collection:
#1 Rhine river #2 natural ditch
7.31 at 8.6°C 6.83 at 8.8°C
-pH in the laboratory: #1 Rhine river #2 Natural ditch
#1 Rhine river #2 natural ditch
7.50 7.43
- total organic carbon:
#1 Rhine river #2 natural ditch
4.7 mg/L 2.6 mg/L
- oxygen saturation at the sampling site:
#1 Rhine river #2 natural ditch
7.1 mg/L 9.62 mg/L
- redox potential at the sampling site:
#1 Rhine river #2 natural ditch
216 mV 236 mV- Details on collection (e.g. location, sampling depth, contamination history, procedure):
Details on source and properties of sediment:
aquatic system #1 Rhine river (Speyer, Germany): silt loam
aquatic system #2 Natural ditch (Schifferstadt, Germany): sand
- The water/sediment systems were first acclimated under aerobic conditions in the dark for about 3 weeks prior to treatment
- the sediments were anaerobic from the beginning of the test period
- sediment was sieved through a 2.0 mm sieve
-pH (Cacl2):
#1 Rhine river #2 natural ditch
7.49 5.98
-pH (H2O):
#1 Rhine river #2 natural ditch
8.05 6.48
- total organic carbon:
#1 Rhine river #2 natural ditch
4.75 % 0.66 %
- cation exchange capacity potential per 100 g dry weight:
#1 Rhine river #2 natural ditch
26.0 mval Ba 3.3 mval Ba
- optimum amount of glucose:
#1 Rhine river #2 natural ditch
6000 2000
- microbial biomass (mg Cmicrobial/kg dry soil) per two measurements:
Day #1 Rhine river #2 natural ditch
0 57.47 / 70.16 13.67 / 10.35
100 (with test item) 65.63 / 64.04 8.69 / 8.69
100 (without test item) 91.11 / 94.29 13.69 / 13.69
100 (with solvent) 81.56 / 81.56 3.70 / 5.37
- maximum water holding capacity per100 g dry soil
#1 Rhine river #2 natural ditch
94.7 g H2O 28.9 g H2O
- Textural classification (i.e. %sand/silt/clay):
#1 Rhine river #2 natural ditch
19.2/68.0/12.8 94.0/4.7/1.3
Duration of test (contact time):
100 d
Initial conc.:
0.8 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Volume of test solution/treatment:
Each test system was filled with wet sediment raching a height of 2-2.5 cm corresponding to approximately 230 g dry weight (300 g wet weight) and 90 g dry weight (220 g wet weight) for ditch and river, respectively. Afterwards 6 cm of the corresponding water were layered over the sediment. The volume of the applied water was determined by weighing to an amount of approximately 500 mL. Therefore, the water:sediment ratio in the test systems was approximately 3:1 (v:v).
- Test temperature: 20 +/- 2°C
- pH: 8.03 - 8.17 in the river system 7.77 - 8.07 in the ditch system
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: air tight cylindrical 1L metabolism flask
- Details of trap for CO2 and volatile organics if used: The incubation flasks were connected to a trapping system which was filled with soda lime (adsorbent for 14C CO2) and oil wetted quartz wool (adsorbent of volatile organic compounds)


SAMPLING
- Sampling frequency: time 0, and after 2, 7, ,13, 28, 58 and 100 days of incubation
- number of samples: duplicates

Compartment:
entire system
% Recovery:
100
Remarks on result:
other: river system: phenyl label
Compartment:
entire system
% Recovery:
100
Remarks on result:
other: river system: imidazole label
Compartment:
entire system
% Recovery:
97.2
Remarks on result:
other: ditch system: phenyl label
Compartment:
entire system
% Recovery:
98.2
Remarks on result:
other: ditch system: phenyl label
Key result
% Degr.:
100
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other: river water/sediment system
% Degr.:
100
Parameter:
radiochem. meas.
Sampling time:
100 d
Remarks on result:
other: analysis in water in the ditch/water sediment system
Compartment:
natural water / sediment: freshwater
DT50:
1.8 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: river
Compartment:
natural water / sediment
DT50:
140.5 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: River
Compartment:
natural water / sediment
DT50:
48.2 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Ditch
Compartment:
natural water / sediment: freshwater
DT50:
1.9 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: Ditch
Transformation products:
yes
No.:
#1
No.:
#2
Details on transformation products:
R014821 and Unk metabolites were identified, only in minor concentrations (3.1% max)
Volatile metabolites:
not measured
Residues:
yes

Table 1.Distribution of the radioactivity after application of [14 C]-Imazalil (imidazole- label) in the river water/sediment system (% applied radioactivity) AR = apllied radioactivity, NER = non-extractable radioactivity, n.m. not measured, n.d. = not detected

 Time (days)  Water Phase (% AR) Sediment extractables (% AR)  14C CO2 (% AR)   Organic Volatiles  NER  Mass Balance
 0 85.90 9.35  n.m.  n.m.  1.19  96.44 
 2 47.33  43.34  0.03  n.d.  10.81  101.52 
 7 17.69  74.79  0.14 n.d.  19.28  111.90 
 13 8.37  79.13 0.36  n.d.  20.82  108.69 
 28 5.35  76.50  0.82  n.d.  24.35  107.03 
 58 2.05  67.60  3.43  n.d.  27.84  100.93 
 100 1.16  62.98  5.69  n.d.  33.03  102.85
 

Table 2.Distribution of the radioactivity after application of [14C]-Imazalil (phenyl- label) in the river water/sediment system (% applied radioactivity) AR = apllied radioactivity, NER = non-extractable radioactivity, n.m. not measured, n.d. = not detected

 Time (days)  Water Phase (% AR) Sediment extractables (% AR)  14C CO2 (% AR)   Organic Volatiles  NER  Mass Balance
 0 89.61  4.77 n.m.  n.m.  0.64 95.02 
 2

35.86 

56.21

0.01

n.d. 

11.95

104.03

 7

12.66

69.89 

0.07

n.d. 

22.38 

105.00 

 13

9.15

78.79

0.18 

n.d. 

18.42 

106.54 

 28

6.23

73.35 

0.49

n.d. 

26.06 

106.13 

 58

5.43

61.32 

2.05 

n.d. 

28.93 

97.73

 100

2.06

56.82 

4.70 

n.d. 

37.51 

101.10 

 

Table 3.Distribution of the radioactivity after application of [14C]-Imazalil (imidazole- label) in the ditch water/sediment system (% applied radioactivity) AR = apllied radioactivity, NER = non-extractable radioactivity, n.m. not measured, n.d. = not detected

 Time (days)

 Water Phase (% AR)

Sediment extractables (% AR) 

14C CO2 (% AR) 

 Organic Volatiles

 NER

 Mass Balance

 0

87.98

9.03 

n.m. 

n.m. 

0.25

97.27

 2

44.48 

49.01 

0.08

n.d. 

2.98 

96.54

 7

11.17

74.17

0.30

n.d. 

12.47

98.10

 13

8.54

72.31

0.74

n.d. 

17.11

98.71

 28

10.74

58.79

1.45

n.d.

24.61

95.60

 58

7.15

47.30

4.15

n.d. 

37.04

95.66

 100

7.76

41.92 

6.26

n.d. 

42.80

98.75

 

Table 4.Distribution of the radioactivity after application of [14C]-Imazalil (phenyl- label) in the ditch water/sediment system (% applied radioactivity) AR = apllied radioactivity, NER = non-extractable radioactivity, n.m. not measured, n.d. = not detected

 Time (days)  Water Phase (% AR) Sediment extractables (% AR)  14C CO2 (% AR)   Organic Volatiles  NER  Mass Balance
 0 90.23 5.77  n.m.  n.m.  0.24 96.23
 2 45.93 48.56  n.d. n.d.  4.31 98.80
 7

12.37

74.02 

0.08

n.d. 

13.70 

100.18 

 13

7.93

72.74

0.25 

n.d. 

18.73 

99.65 

 28

10.16

61.54 

0.64 

n.d. 

25.54

97.88

 58

7.36

46.29 

2.35

n.d. 

41.08 

97.07

 100

9.30

35.62

4.66

n.d. 

48.29

97.87

 

Validity criteria fulfilled:
yes
Conclusions:
Two different ring labeeled 14C imazalil compounds were tested in two different water/sediment systems to unravel the route of degradation. The results showed that no additional major metabolites were formed under the tested condititions. The DT50 in the sediment ranged between 140.5 d for a river and 48.2 in a ditch.

Description of key information

No study was available on the biodegradation of the test substance imazalil sulfate in water and sediment. Therefore, read across is performed using a study from the related substance imazalil. The study by Mégel (2008) was considered as the key study to cover this endpoint (Klimisch 1).The biodegradability source substance was determined according to OECD Guideline 308. Under the conditions of the test, the geomean (n=4) of DT50 water persistence endpoint was 2.2 d at 20 °C and the DT50 sediment Persistence endpoint was 172.5 d at 20 °C (159 d for the river sample and 187 d for the pond sample). The total sediment/water system had a DT50 (geomean = 4) of 94.7 d.

Key value for chemical safety assessment

Half-life in freshwater:
2.2 d
at the temperature of:
20 °C
Half-life in freshwater sediment:
172.5 d
at the temperature of:
20 °C

Additional information