5,7-dichloro-4-(4-fluorophenoxy)quinoline;quinoxyfen (ISO)

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

EPA Subdivision N Pesticide Guideline 162-4 (Aerobic Aquatic Metabolism)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Quinoxyfen-2-14C (Inv. number: 1461)
Purity: 98.6%

Quinoxyfen-phenyl-UL-14C (Inv. number 1453)
Purity: 99%

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural sediment

Duration of test (contact time):

100 d

Initial conc.:

0.4 other: µg/mL

Parameter followed for biodegradation estimation:

radiochem. meas.

Reference substance:

other: 4- fluorophenol

Compartment:

natural sediment

% Recovery:

93.9

Remarks on result:

other: for phenyl labelled at 100 DAT

Compartment:

natural sediment

% Recovery:

95.8

Remarks on result:

other: for quinoline at 100 DAT

Key result

Parameter:

radiochem. meas.

Sampling time:

100 d

Remarks on result:

other: led to mineralization up to 13.4 % of applied observed with the phenyl-label

Key result

Parameter:

radiochem. meas.

Sampling time:

100 d

Remarks on result:

other: led to mineralization up to 4.8 % of applied with the quinoline-label

Key result

Compartment:

natural sediment

DT50:

34 d

Type:

other: Non-linear, first order regression

Temp.:

25 °C

Key result

Compartment:

natural sediment

DT50:

49.5 d

Type:

other: Linear, first order regression

Temp.:

25 °C

Other kinetic parameters:

other: Apparent adsorption coefficients (Kd): 148.7 to 622.1 mL/g

Transformation products:

yes

Remarks:

Major metabolites: 3-OH-quinoxyfen

Residues:

yes

Remarks:

Unextracted residues were slightly greater for the quinoline-labelled form than the phenyl-labelled form with 23.1 and 19.8 % of applied, respectively.

Validity criteria fulfilled:

yes

Conclusions:

The test substance will reside mostly sorbed to the sediment phase if accidentally introduced to surface waters.

Executive summary:

The aerobic aquatic metabolism of the test substance was investigated at 25°C in a flooded sediment from California to fulfill data requirements found in US EPA Subdivision N § 162-4. Samples were fortified with test substance 14C-labelled in the phenyl or quinoline ring at an initial concentration of 0.4 µg/ml, which is equivalent to a yearly total application of 600 g a.i./ha. One sample of each labelled form of the test substance was taken at 0, 3, 7, 14, 28, 48, 70 and 100 days after fortification. The dissolved oxygen, redox potential and pH of samples indicated that the samples remained aerobic. 

The test substance was transformed into one major metabolite, 3-OH-test substance, that attained a maximum of 43.8 % of applied at 48 DAT. Several minor metabolites were observed that remained at or below 2 % of applied. High Performance Liquid Chromatography and thin layer chromatography confirmed that 3-OH-test substance and DCHQ (a minor metabolite that attained 1.2 % of applied) were present. Mineralization of the test substance was greater for the phenyl-labelled form than the quinoline-labelled form with 13.4 and 4.8 % of applied, respectively. Unextracted residues were slightly greater for the quinoline-labeled form than the phenyl-labelled form with 23.1 and 19.8 % of applied, respectively. 

The aerobic aquatic metabolism of the test substance and 3-OH-test substance occurred at a moderate rate. Non-linear, first order regression analysis was used to calculate the half-life and DT90 values. The half-life and DT90 for the test substance were 34.0 and 113.1 days, respectively. The half-life and DT90 for 3-OH-test substance were 54.2 and 180.0 days, respectively. Linear, first order regression gave a test substance half-life of 49.5 days. Apparent Kd values for the test substance ranged from 148.7 to 622.1 mL/g, for 3-OH-test substance from 9.5 to 429.5 mL/g and for DCHQ from 9.5 to 28.3 mL/g. These apparent Kd values suggest that the test substance, 3-OH-test substance and DCHQ will reside mostly sorbed to the sediment phase if accidentally introduced to surface waters.  

Reference 2

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

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

Guideline:

OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Radiolabelled substance
DE-795-quinoline-2-14C
Lot number: 54290-06-10 (INV302950)
Radiochemical purity: 100%

DE-795-phenoxy-UL-14C
Lot number: DE3-133876-91 (INV304377)
Radiochemical purity: 99.8%

Non-Radiolabelled substance
Lot number: F50-E1662-51 (TSN104816)
Purity: 99.8%

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water: freshwater

Details on source and properties of surface water:

- Details on collection (location, contamination history): 4310 Rheinfelden, Switzerland; 47.5435 °N / 7.8179 °E. The sampling location was known not to be subjected to any effluent discharges.
- Sampling depth: Surface
- Storage conditions: 4 °C in a plastic barrel with free access to air in the dark
- Storage length: Up to 22 days
- Temperature (°C) at time of collection: 17.8 and 14.8 for for Q- and P-label, respectively
- pH at time of collection: 7.76 and 7.69 for Q- and P-label, respectively
- Redox potential (mv) initial: 196 and 197 for Q- and P-label, respectively
- Oxygen concentration (mg/l) initial: 6.31 and 8.79 for Q- and P-label, respectively
- Water filtered: Yes
- Type and size of filter used: 0.2 mm screen

Duration of test (contact time):

60 d

Initial conc.:

0.5 µg/L

Based on:

test mat.

Remarks:

Low dose system

Initial conc.:

5 µg/L

Based on:

test mat.

Remarks:

High dose system

Initial conc.:

5 µg/L

Based on:

test mat.

Remarks:

High dose sterile system

Parameter followed for biodegradation estimation:

radiochem. meas.

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: 100 µL
- Test temperature: 21.0 ± 0.1°C
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 300 mL Erlenmeyer flasks
- Number of culture flasks/concentration: 26 (high and low doses); 13 (sterilised)
- Method used to create aerobic conditions: Each flask was aerated with moistened air pushed through the system.
- Method used to control oxygen conditions: Agitation facilitated oxygen transfer from headspace to liquid, in a way that aerobic conditions were maintained.
- Measuring equipment: Triplicate LSC

- Details of trap for CO2 and volatile organics if used: The exhaust air was passed through a volatile trapping system equipped with two absorption traps, one containing ethylene glycol (50 mL) and the other 2 M NaOH (50 mL), in this sequence per flask, to trap organic volatiles and 14CO2, respectively
- Test performed in open system: The flasks were connected to the continuously ventilated gas-flow system

SAMPLING
- Sampling frequency: Samples (two replicates for non-sterile systems, single samples for sterile systems) were taken for analysis immediately after treatment (day 0). Additional samples were taken after 7, 14, 21, 27/28, 41/42 and 60 days of incubation. Single samples treated with [14C(U)]benzoic acid were taken and analysed after 7 and 14 days of incubation.

DESCRIPTION OF CONTROL AND/OR BLANK TREATMENT PREPARATION
CONTROL AND BLANK SYSTEM
- Abiotic sterile control: To prepare the application solution (Q-label, high dose), 173 μL from the corresponding stock solution was added to 5.0 mL of acetone and submitted to ultrasonic treatment for three minutes. The radioactivity content as determined by triplicate LSC measurements was 58’275 dpm/50 μL, corresponding to 4.856 μg/mL. To prepare the application solution (Plabel, high dose), 576 μL from the corresponding stock solution was added to 5 mL of acetone and submitted to ultrasonic treatment for two minutes. The radioactivity content as determined by triplicate LSC measurements was 67’197 dpm/50 μL, corresponding to 4.967 mg/mL.
- Toxicity control: A aliquot of 3 μL of [14C(U)]benzoic acid solution (dissolved in ethanol as delivered by the supplier) was diluted in 5 mL Milli-Q water and submitted to ultrasonic treatment for three minutes. The radioactivity content of the application solution was 347’950 dpm/50 μL (mean of triplicate LSC measurements), or 3.063 μg/mL. This application solution was used to treat pond water collected for treatment with the Q-label of the test item. A second application solution containing benzoic acid was prepared in order to treat pond water collected for treatment with the P-label of the test item. Therefore, 3 μL of [14C(U)]benzoic acid solution (dissolved in ethanol as delivered by the supplier) was diluted in 5 mL Milli-Q water and submitted to ultrasonic treatment for three minutes. The radioactivity content of the application solution was 172.340 dpm/50 μL (mean of triplicate LSC measurements), or 1.517 μg/mL.

Reference substance:

other: [14C(U)]benzoic acid

Compartment:

other: High dose system (Q-label test substance)

Remarks on result:

other: 101.7±4.1

Compartment:

other: High dose sterile system (Q-label test substance)

% Recovery:

100

St. dev.:

5.7

Compartment:

other: Low dose system (Q-label test substance)

% Recovery:

97.8

St. dev.:

6.3

Compartment:

other: High dose system (P-label test substance)

% Recovery:

97

St. dev.:

8.7

Compartment:

other: High dose sterile system (P-label test substance)

% Recovery:

98.1

St. dev.:

6.8

Compartment:

other: Low dose system (P-label test substance)

% Recovery:

96

St. dev.:

5.3

Key result

% Degr.:

74.3

Parameter:

radiochem. meas.

Sampling time:

60 d

Remarks on result:

other: High dose system (Q-label test substance)

Key result

% Degr.:

93.3

Parameter:

radiochem. meas.

Sampling time:

60 d

Remarks on result:

other: High dose sterile system (Q-label test substance)

Key result

% Degr.:

70.1

Parameter:

radiochem. meas.

Sampling time:

60 d

Remarks on result:

other: Low dose system (Q-label test substance)

Key result

% Degr.:

79.5

Parameter:

radiochem. meas.

Sampling time:

60 d

Remarks on result:

other: High dose system (P-label test substance)

Key result

% Degr.:

89.4

Parameter:

radiochem. meas.

Sampling time:

60 d

Remarks on result:

other: High dose sterile system (P-label test substance)

Key result

% Degr.:

78.7

Parameter:

radiochem. meas.

Sampling time:

60 d

Remarks on result:

other: Low dose system (P-label test substance)

Key result

Compartment:

other: High dose system

DT50:

128.6 d

Type:

other: Single first-order

Temp.:

21 °C

Key result

Compartment:

other: High dose sterile system

DT50:

318.6 d

Type:

other: Single first-order

Temp.:

21 °C

Key result

Compartment:

other: Low dose system

DT50:

115 d

Type:

other: Single first-order

Temp.:

21 °C

Transformation products:

yes

Remarks:

Major metabolites: 2-oxo-quinoxyfen and DCHQ (5,7-dichloro-4-hydroquinoline)

No.:

#1

No.:

#2

Details on transformation products:

- Formation and decline of each transformation product during test: Q-label: Over the course of the incubation period in the high dose system, the test substance degraded into six minor metabolites. Metabolite M2 was identified as 2-oxo-quinoxyfen and M4 as DCHQ (5,7-dichloro-4-hydroquinoline), respectively. M2 increased from 2.0% on day 21 to a maximum of 9.9% AR after 41 days, and amounted 9.3% AR at the end of the 60-day incubation period. M4 was first observed after 28 days (2.2% AR), but remained below the level of quantification on day 41, while amounting 2.0% AR at the last sampling interval (day 60). Three other metabolites (M3, M5 and M6) were detected in very low quantities and were therefore not characterised further. Metabolite fraction M1 reached mean radioactivity recoveries of 8.0% AR (41 days) and 7.1% AR (60 days).
In the high dose sterile samples, degradation of the Q-label test substance was insignificant over the course of the 60-day incubation period. Recovery of the test item was initially 103.4% AR, and still amounted for 93.3% AR after 60 days of incubation. Two metabolites (M1 and M4) were detected once, but they were both below the limit of quantification and therefore not characterised further.
In the low dose samples, the test substance degraded into four metabolites. One of them, M2, could be classified as a major metabolite and was identified as 2-oxo-quinoxyfen. This metabolite reached 16.9% AR after 28 days before dissipating slightly to 7.8% AR at the final sampling interval. Reproducibility between replicates A and B was not achieved probably due to differences of the microbial activity in the individual flasks. Another metabolite (M4) was detected and previously identified as DCHQ, but remained below the limit of quantification for low dose samples. Two other minor metabolites, M1 and M3, were detected at different intervals, but were neither identified nor characterized further.
P-label: In the high dose samples, the test substance degraded into two radioactive fractions. The main metabolite (M2), identified as 2-oxo-quinoxyfen, accounted for 1.5% AR after 42 days and 6.0% AR at the end of the 60-day incubation period. The other metabolite (M1) was detected at various intervals, but remained below the limit of quantification at each interval, and was therefore not characterised further. In the high dose sterile samples, no metabolites detected over the course of the study period. In the low dose samples, the test item degraded into a major and a minor radioactive fraction. The major metabolite (M2), identified as 2-oxoquinoxyfen, accounted for 33.3% AR after 27 days, 16.2% AR after 42 days and 7.5% AR at the end of the 60-day incubation period. The minor metabolite (M1) was detected after 27 and 60 days. But as with the Q-label variant of the test item, M1 was detected but was always below the limit of quantification and therefore not characterised further.
- Pathways for transformation: The test substance breaks down 2-oxo-quinoxyfen (M2) and DCHQ (M4), along with other unidentified minor metabolites. In the low dose systems for each label (Q-label and P-label), 2-oxo-quinoxyfen (M2) could be classified as a major metabolite, reaching maximums of 16.9% AR and 33.3% AR for Q-label and P-label treated systems, respectively.

Volatile metabolites:

yes

Remarks:

Mean formation of radioactive carbon dioxide as well as other volatile products remained low and did not exceed mean amounts of 2.2% and 4.4% in the Q-label and P-label test systems, respectively, throughout the study.

Details on results:

TEST CONDITIONS
- Oxygen concentrations measured in the surface water of treated samples confirmed aerobic conditions during the incubation period. The pH values during incubation showed stability of the system. The mean temperature during incubation was 21.0 ± 0.1 °C for all systems.

MAJOR TRANSFORMATION PRODUCTS (P-label high dose)
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: The main metabolite (M2), identified as 2-oxo-quinoxyfen, accounted for 1.5% AR after 42 days
- Range of maximum concentrations in % of the applied amount at end of study period: 6.0% AR at the end of the 60-day incubation period

MAJOR TRANSFORMATION PRODUCTS (P-label low dose)
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: The major metabolite (M2), identified as 2-oxoquinoxyfen, accounted for 33.3% AR after 27 days, 16.2% AR after 42 days
- Range of maximum concentrations in % of the applied amount at end of study period: 7.5% AR at the end of the 60-day incubation period.

MAJOR TRANSFORMATION PRODUCTS (Q-label high dose)
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: M2 increased from 2.0% on day 21 to a maximum of 9.9% AR after 41 days
- Range of maximum concentrations in % of the applied amount at end of study period: M2 amounted 9.3% AR at the end of the 60-day incubation period

MAJOR TRANSFORMATION PRODUCTS (Q-label low dose)
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: M2 reached 16.9% AR after 28 days
- Range of maximum concentrations in % of the applied amount at end of study period: M2 reached 7.8% AR at the final sampling interval.

MINOR TRANSFORMATION PRODUCTS (Q-label high dose)
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: M4 was first observed after 28 days (2.2% AR), but remained below the level of quantification on day 41. Metabolite fraction M1 reached mean radioactivity recoveries of 8.0% AR (41 days)
- Range of maximum concentrations in % of the applied amount at end of study period: M4 amounting to 2.0% AR at the last sampling interval (day 60). Three other metabolites (M3, M5 and M6) were detected in very low quantities and were therefore not characterised further. Metabolite fraction M1 reached mean radioactivity recoveries of 7.1% AR (60 days)

MINOR TRANSFORMATION PRODUCTS (Q-label low dose)
- Another metabolite (M4) was detected and previously identified as DCHQ, but remained below the limit of quantification for low dose samples. Two other minor metabolites, M1 and M3, were detected at different intervals, but were neither identified nor characterized further.

STERILE TREATMENTS
- Q-label: In the high dose sterile samples, degradation of the Q-label test item was insignificant over the course of the 60-day incubation period. Recovery of the test item was initially 103.4% AR, and still amounted for 93.3% AR after 60 days of incubation. Two metabolites (M1 and M4) were detected once, but they were both below the limit of quantification and therefore not characterised further.
- P-label: In the high dose sterile samples, no metabolites detected over the course of the study period.

Results with reference substance:

The reference substance benzoic acid had degraded completely within 7 days of incubation, indicating high microbial activity in the test water.

Conclusions:

The DT50 values for 14C-labelled test substance in surface water under aerobic conditions, using SFO kinetics, were calculated to be 128.6 days for the high dose, 318.6 days for the high dose sterile, and 115.0 days for the low dose experiment. Respective DT90 values were 427.1, 1058 and 382.1 days for the high dose, high dose sterile and low dose, respectively.

Executive summary:

Aerobic mineralization of 14C-test substance in surface water was investigated under defined laboratory conditions as per the guideline OECD 309. For this purpose, samples of natural pond water were treated with two separate labels of the test item: Test substance-quinoline-2-14C (Q-label) and test substance phenoxy- UL-14C (P-label). For both labels, the tests were performed in duplicate using a high test substance concentration of about 5 μg/L and a low test item concentration of about 0.5 μg/L. Additionally, for both labels at the same sampling intervals, single replicate samples using the high dose test item concentration were incubated under sterile conditions in order to gain information about abiotic degradability of the test item. The flasks were connected to a volatiles trapping system consisting of flasks with ethylene glycol and sodium hydroxide in series. The applied systems were incubated in the dark under aerobic conditions for a period of 60 days at 21.0 ± 0.1°C. Microbial activity of the test system was confirmed using a degradability check of [14C(U)]benzoic acid.

Duplicate samples per test concentration were removed for analysis after 0, 7, 14, 21, 27 (28 days for Q-label), 42 (41 days for Q-label) and 60 days of incubation. Phase partitioning using an ethyl acetate phase and a water phase was performed for the extractions. The remaining water phase from the partitioning was only analysed for specific intervals showing >5% recovery of applied radioactivity. Oxygen concentrations and pH were monitored in the aqueous phase. The amount of radioactivity in the aqueous phase and trapping solutions was determined by Liquid Scintillation Counting (LSC).

Aliquots of the ethyl acetate phase were analysed by Thin-Layer Chromatography (TLC) in order to quantify the amount of test item and metabolites present. The remaining water phase for selected samples was analysed by High-Performance Liquid Chromatography (HPLC). For the Q-label test item, the total mean recoveries were 101.7 ± 4.1% of applied radioactivity (AR) for the high dose, 100.0 ± 5.7% AR for the high dose sterile and 97.8 ± 6.3% AR for the low dose experiment. For the P-label test item, the total mean recoveries were 97.0 ± 8.7% AR for the high dose, 98.1 ± 6.8% AR for the high dose sterile and 96.0 ± 5.3% AR for the low dose experiment.

For the Q-label test item, immediately after treatment (time 0) and partitioning, mean values of 98.0%, 103.4% and 95.6% AR were measured in the ethyl acetate phases of the high dose, high dose sterile and low dose system, respectively. Corresponding values for the water phase were 6.1%, 3.9% and 8.6% AR. Similarly, for the P-label test item, immediately after treatment (time 0) and partitioning, mean values of 107.3%, 108.3% and 97.7% AR were measured in the ethyl acetate phase of the high dose, high dose sterile and low dose system, respectively. For the water phases, measurements were below the limit of quantification for high dose and low dose samples, and a mean value of 2.0% AR for the high dose sterile system.

For the Q-label test item, the amount in the radioactivity in the ethyl acetate phase decreased slowly over the study and represented 85.8%, 94.0% and 80.7% AR in the high dose, high dose sterile and low dose systems by the end of the 60-day incubation period. Corresponding values for the water phases were 11.9%, 3.9% and 9.0%. Similarly, for the P-label test item, after 60 days of incubation, mean values of 86.0%, 89.4% and 86.8% AR were measured in the ethyl acetate phases of the high dose, high dose sterile and low dose systems, respectively. Values for the water phases were 2.2%, and 2.5% AR for the high and low dose systems, respectively, whereas the value for the high dose sterile system was below the limit of quantification.

Mean formation of radioactive carbon dioxide as well as other volatile products remained low and did not exceed mean amounts of 2.2% and 4.4% in the Q-label and P-label test systems, respectively, throughout the study.

In the test system incubated with Q-label test item, test substance represented 98.0%, 103.4% and 95.6% AR in the high dose, high dose sterile and low dose experiment respectively at the first sampling interval (time 0). Test substance later represented 74.3%, 93.3% and 70.1% AR in both high dose, high dose sterile and low dose systems, respectively, after 60 days of incubation.

In the high dose system treated with the Q-label, the test item degraded into six minor metabolites, two of which were identified as 2-oxo-quinoxyfen and DCHQ (5,7-dichloro-4- hydroquinoline). One unidentified metabolite (M1) reached mean recovery values of 8.0 and 7.1% AR after 41 and 60 days of incubation, respectively, but was shown to be multicomponent and each individual component <5% AR. In the high dose sterile system, two metabolites, unidentified M1 and M4 (DCHQ), were detected once, but they were both below the limit of quantification and therefore not characterised further. In the low dose system, the only major metabolite (M2, maximum of 16.9% AR at 28 days after treatment (DAT)) was identified as 2-oxo-quinoxyfen (5,7-dichloro-4-(4-fluorophenoxy)-1H-quinolin-2-one). In addition, one minor metabolite (M4) was detected and previously identified as DCHQ, but remained below the limit of quantification for low dose samples. Two other unidentified minor metabolites, M1 and M3, were detected at different intervals, but were not characterized further.

At the first sampling interval (time 0), the P-label test item represented 107.1%, 108.3% and 97.7% of AR in the high dose, high dose sterile and low dose system, respectively. Test substance-phenyl-UL-14C (P-label) degraded to 79.5%, 89.4% and 78.7% AR by the end of the 60-day incubation period.

In the high dose system treated with the P-label, the test item degraded into two minor metabolites, of one metabolite remained below the limit of quantification at all intervals. The second metabolite (M2) was identified as 2-oxo-quinoxyfen (5,7-dichloro-4-(4- fluorophenoxy)-1H-quinolin-2-one). There were no metabolites detected in the high dose sterile system. In the low dose system, the test item degraded into two radioactive fractions, one major and one minor metabolite. The major metabolite (M2) was identified as 2-oxoquinoxyfen, which accounted for 33.3% AR after 27 days, 16.2% AR after 42 days and 7.5% AR at the end of the 60-day incubation period. The minor metabolite (M1) was detected at 27 and 60 days, but remained below the level of quantification at both intervals.

The rate of degradation for test substance in surface water was calculated using single first-order (SFO) kinetics (data of both labels fitted together). For all three test systems, i.e. the high dose, high dose sterile and low dose system, SFO fitted results were visually and statistically acceptable, whereas FOMC fitted results were only visually, but not statistically acceptable. Therefore, SFO was chosen as best fit.

The DT50 values for 14C-labelled test substance in surface water under aerobic conditions, using SFO kinetics, were calculated to be 128.6 days for the high dose, 318.6 days for the high dose sterile, and 115.0 days for the low dose experiment. Respective DT90 values were 427.1, 1058 and 382.1 days for the high dose, high dose sterile and low dose, respectively.

Reference 3

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

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

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.4300 (Aerobic Aquatic Metabolism)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Radiolabelled test substance name: DE-795-phenoxy-UL-14C and DE-795-quinoline-14C
Lot #: YB1-4100780-062 (Phenyl labelled); 54290-06-10 (quinoline labelled)
Radiochemical purity: 98.9% (Phenyl labelled); 100% (quinoline labelled)

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

- Details on collection (location): The Golden Lake Sediment was collected from Steel County, North Dakota and the Goose River Sediment was collected from Grand Forks County, North Dakota.
- Sampling Depth: 0-5 cm
- Storage conditions: Stored in the dark in an incubator set at 4 ± 2°C
- Storage length: Until used

Golden lake water:
- pH at time of collection: 8.6
- Calcium (ppm): 98
- Magnesium (ppm): 98
- Sodium (ppm): 98
- Hardness mg equivalent (CaCO3/L): 655
- Conductivity (mmhos/cm): 1.41
- Sodium Adsorption Ratio (SAR): 1.68
- Total Dissolved Solids: 1276 ppm
- Turbidity: 42.2 NTU

Goose river water:
- pH at time of collection: 8.5
- Calcium (ppm): 153
- Magnesium (ppm): 106
- Sodium (ppm): 163
- Hardness mg equivalent (CaCO3/L): 824
- Conductivity (mmhos/cm): 1.79
- Sodium Adsorption Ratio (SAR): 2.48
- Total Dissolved Solids: 1616 ppm
- Turbidity: 31.4 NTU

Details on source and properties of sediment:

- Details on collection (location): The Golden Lake Sediment was collected from Steel County, North Dakota and the Goose River Sediment was collected from Grand Forks County, North Dakota.
- Sampling Depth: 0-5 cm
- Storage conditions: Stored in the dark in an incubator set at 4 ± 2°C
- Storage length: Until used

Golden lake sediment:
- Textural classification (i.e. %sand/silt/clay): Sand (89 / 4 / 7%)
- Sediment samples sieved: 2.0 mm sieve
- Bulk Density (disturbed), g/cc: 1.21
- Cation exchange capacity, meq/100 g: 9.2
- % Moisture at 1/3 bar: 7.5
- % Organic Carbon: 0.76
- pH in 1:1 sediment: water ratio: 8.3

Goose river sediment:
- Textural classification (i.e. %sand/silt/clay): Clay loam (27 / 40 / 33%)
- Sediment samples sieved: 2.0 mm sieve
- Bulk Density (disturbed), g/cc: 0.85
- Cation exchange capacity, meq/100 g: 22.2
- % Moisture at 1/3 bar: 47.7
- % Organic Carbon: 4.0
- pH in 1:1 sediment: water ratio: 8.2

Duration of test (contact time):

100 d

Initial conc.:

0.3 other: µg/g

Based on:

act. ingr.

Remarks:

Sediment

Initial conc.:

0.1 other: µg/mL

Based on:

act. ingr.

Remarks:

Water layer

Parameter followed for biodegradation estimation:

radiochem. meas.

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: 25 μL
- Test temperature: 20 ± 2°C
- CEC (meq/100 g):
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 8-oz. (ca. 250 mL) wide-mouth glass bottles.
- Number of culture flasks/concentration: 2 replicates
- Method used to create aerobic conditions: By drawing humidified air over the aqueous phase
- Method used to control oxygen conditions: A vacuum pump was placed after the water trap to ensure a steady flow, as witnessed by bubbling, of humidified air through the systems.

- Details of trap for CO2 and volatile organics if used: Each set of sediments was equipped with a trapping system consisting of a trap to collect organic volatiles (ethylene glycol) followed by two traps to collect carbon dioxide [1 N sodium hydroxide (NaOH)] (sampling “train”).

SAMPLING
- Sampling frequency: Duplicate samples on Days 0, 7, 21, 46, 74, 100

Compartment:

entire system

Remarks on result:

other: The overall mass balance for both the phenyl and 2-quinoline labeled [14C] test substance test systems ranged from 89.1% to 99.6% AR for all sampling points.

Remarks:

Golden lake sediment

Compartment:

entire system

Remarks on result:

other: The overall mass balance for both the phenyl and 2-quinoline [14C] test substance test systems ranged from 89.4% to 100.1% AR for all sampling points.

Remarks:

Goose river

Key result

% Degr.:

39.2

Parameter:

radiochem. meas.

Remarks:

Applied radioactivity (AR)

Sampling time:

100 d

Remarks on result:

other: Degradation was exclusively to 2-oxo-quinoxyfen (maximum 39.2% AR at 100 DAT).

Remarks:

Golden lake

Key result

Parameter:

radiochem. meas.

Remarks:

Applied radioactivity (AR)

Sampling time:

100 d

Remarks on result:

other: Degradation was to 2-oxo-quinoxyfen (maximum 35.7% AR at 74 DAT), 6-hydroxy-quinoxyfen (maximum 7.6% AR at 21 DAT) only in 2-Q-label, and DCHQ (maximum 1.8% AR at 100 DAT only in 2-Q-label).

Key result

Compartment:

natural water

DT50:

3.545 d

Type:

other: Single first order

Temp.:

20 °C

Remarks on result:

other: Golden lake

Key result

Compartment:

natural sediment

DT50:

62.06 d

Type:

other: Single first order

Temp.:

20 °C

Remarks on result:

other: Golden lake

Key result

Compartment:

entire system

DT50:

47.16 d

Type:

other: Single first order

Temp.:

20 °C

Remarks on result:

other: Golden lake

Key result

Compartment:

natural sediment

DT50:

25.71 d

Type:

other: Single first order

Temp.:

20 °C

Remarks on result:

other: Goose river

Key result

Compartment:

entire system

DT50:

15.13 d

Type:

other: Single first order

Temp.:

20 °C

Remarks on result:

other: Goose river

Transformation products:

yes

Remarks:

2-oxo-quinoxyfen, 6-hydroxy-quinoxyfen, 5,7-dichloro-4-hydroxyquinoline (DCHQ)

No.:

#1

No.:

#2

No.:

#3

Details on transformation products:

- Formation and decline of each transformation product during test: Golden lake water: In the aqueous layer the maximum amount of radioactivity as quinoxyfen was 82.3 % (phenyl) and 85.4 % (2-quinoline). The maximum amount of radioactivity in the aqueous layer as 2-oxo-quinoxyfen was 12.4 % (phenyl, 21 DAT) and, no degradation products were detected for the 2-quinoline labeled aqueous samples.
Golden lake sediment: The presence of extractable 2-oxo-quinoxyfen generally increased over the course of the study for both the phenyl and 2-quinoline labels and was detected at a maximum level of 39.2% and 30.3% AR at 100 DAT, respectively.
Goose river water: The maximum amount of radioactivity as test substance in the aqueous layer was 86.7% (phenyl) and 81.0% (2-quinoline). No degradation products were detected during the analysis of the aqueous water samples.
Goose river sediment: The presence of 2-oxo-quinoxyfen generally increased over the course of the study for both the phenyl and 2-quinoline labels and was detected at a maximum level of 35.7% AR and 32.9% AR at 74 DAT, respectively. Due to the position of the radiolabel, the presence of radioactive DCHQ was only detected for the 2-quinoline labeled test substance, and was observed only in one sample at 1.8% AR at 100 DAT. Likewise, the presence of radioactive 6-hydroxy-quinoxyfen was only detected for the 2-quinoline labeled test substance, reaching a maximum level of 7.6% AR at 21 DAT.
- Pathways for transformation: Under aerobic sediment conditions, test substance rapidly degraded. The test substance primarily metabolized into 2-oxo-quinoxyfen. Further degradation of 2-oxo-quinoxyfen to minor metabolites, and through mineralization to carbon dioxide and immobilization as sedimentbound residue occurred.

Volatile metabolites:

yes

Remarks:

14 CO2

Residues:

yes

Details on results:

MAJOR TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: Golden lake water: The maximum amount of radioactivity in the aqueous layer as 2-oxo quinoxyfen was 12.4 % (phenyl, 21 DAT) and, no degradation products were detected for the 2-quinoline labeled aqueous samples.
Goose river water: No degradation products were detected during the analysis of the aqueous water samples.
Golden lake sediment: The presence of extractable 2-oxo-quinoxyfen generally increased over the course of the study for both the phenyl and 2-quinoline labels and was detected at a maximum level of 39.2% and 30.3% AR at 100 DAT, respectively. No other degradation products were detected during the study.
Goose river sediment: The presence of 2-oxo-quinoxyfen generally increased over the course of the study for both the phenyl and 2-quinoline labels and was detected at a maximum level of 35.7% AR and 32.9% AR at 74 DAT, respectively. Due to the position of the radiolabel, the presence of radioactive DCHQ was only detected for the 2-quinoline labeled test substance, and was observed only in one sample at 1.8% AR at 100 DAT. Likewise, the presence of radioactive 6-hydroxy-quinoxyfen was only detected for the 2-quinoline labeled test substance reaching a maximum level of 7.6% AR at 21 DAT. Similarly, the presence of radioactive 4-fluorophenol was initially detected for the phenyl labeled test substance, and only observed at 46 DAT; however, due to the poor HPLC chromatography generated from the 46 DAT extracts, the data was not considered accurate or representative. In order to confirm this inaccuracy, the 46 DAT extracts were prepared for HPLC again. The second HPLC results were not consistent, confirming the initial analyses were not representative of the 46 DAT extracts. Therefore 4-fluorphenol was considered not detected.

VOLATILIZATION
- Golden lake: Throughout the course of the study the radioactivity in the volatile traps increased accumulating an average of 13.7% AR at day 100 in the phenyl label and 0.4% AR in the 2-quinoline label.
- Goose river: Throughout the course of the study the radioactivity in the volatile traps increased accumulating an average of 11.8% AR at 100 DAT in the phenyl label and 0.4% AR in the 2-quinoline label.

POST EXTRACTED SOLIDS (PES)
- Golden lake: The overall average amount of bound residue generally increased over the course of the study for both phenyl and 2-quinoline labeled test substance systems, reaching maximum levels of 36.0%, and 29.0% AR at 100 DAT, respectively. Following soxhlet extraction, the amount of phenyl and 2-quinoline labeled radioactivity removed was 16.3%, and 7.6% AR, leaving 19.7%, and 17.6% AR, respectively, as bound residues. The total recovery of AR for the phenyl and 2-quinoline in the PES samples following soxhlet extraction was 27.2% AR, and 25.2% AR, which agrees within 10 % of the original PES values of 36.0% AR, and 28.3% AR, respectively.
- Goose river: The overall amount of bound residue generally increased over the course of the study for both the phenyl and 2-quinoline labeled test substance systems, reaching maximum levels of 52.7%, and 52.9% AR at 100 DAT, respectively. Following soxhlet extraction, the amount of phenyl and 2-quinoline labeled radioactivity removed was 11.2%, and 11.9% AR, leaving 39.6% and 40.2% AR respectively as bound residue. The total recovery of AR for phenyl and 2-quinoline labeled test substance in the PES samples following soxhlet extraction was 50.8%, and 52.1 % AR, which agrees within 2% of the original PES values of 52.7%, and 52.6% AR, respectively.

Validity criteria fulfilled:

yes

Conclusions:

DT50 value under aerobic condition was 47.16 days (total system) for Golden Lake and 15.13 days (total system) for Goose River.

Executive summary:

The study was conducted according to guideline OECD 308 to evaluate aerobic sediment metabolism study for test substance, radiolabeled in both the phenyl and 2-test substance labeled positions, in a sediment system under laboratory conditions. The study was conducted to understand the overall fate of test substance in the environment. The ¹⁴C test substances were applied to two different sediment systems.

The first sediment system, Golden Lake (EFS 406) was sampled in two feet of water to a depth of five centimeters, from Steele County, North Dakota, consisted of loamy sand sediment. The microbial activity of the sediment following the final time point was 348.7 μg/g on a dry basis. The second sediment system, Goose River (EFS 407) was sampled in two feet of water to a depth of five centimeters, from Grand Forks County, North Dakota, consisted of clay loam sediment. The microbial activity of the sediment following the final time point was 537.4 μg/g on a dry basis. The sediments (50.00 g dry weight) were weighed into separate 250 mL glass jars, flooded with the appropriate sediment water to a 3:1 ratio, and maintained under aerobic conditions in flow-through test systems to determine the rate and route of degradation of test substance in the dark at 20 ± 2°C.

Each test sample’s water layer was treated with either 15.0 μg of phenyl- or 15.5 μg of 2-test substance-labeled [14C]test substance. The [14C]test substance was applied based on the maximum single label application rate of 300 g ai/ha. equivalent to 0.1μg/mL assuming a 30 cm pond depth. The incubation of treated test systems continued under aerobic conditions by continuously flowing air over the sediment for 100 days. Each set of sediments was equipped with a trapping system consisting of a trap to collect organic volatiles (ethylene glycol) followed by two traps to collect carbon dioxide [1 N sodium hydroxide (NaOH)].

Duplicate sediment samples of each radiolabel were assayed at 0, 7, 21, 46, 74 and 100 DAT of the test substance. At each sampling interval, the aqueous layer of the sediment system was gently stirred, aliquots analyzed by LSC then decanted into an acid-washed graduated cylinder. The sediment was transferred to a 250 mL centrifuge bottle and extracted with acetonitrile: 0.1N HCl (90:10, v:v). The aqueous layers and sediment extracts were analyzed by HPLC to determine the amount of test substance and degradates present. Radioactivity in the post extracted solids (PES) was quantified by combustion analysis. The 1 N NaOH and volatile organic traps for each time point were radioassayed by LSC typically on the day of their collection. In addition, all traps were radioassayed by LSC and replenished with fresh sodium hydroxide and ethylene glycol following each time point.

For sediment Golden Lake, the mass balance of the applied radioactivity (based on the sum of the aqueous layer, sediment extracts, volatiles, and bound radioactivity) ranged between an average of 90.1% applied radioactivity (AR) and 97.5% AR at all sampling points. The amount of radioactivity present in the aqueous layer of the test samples decreased throughout the study from an average of 80.6% AR at 0 DAT to 3.7% AR at 100 DAT. The amount of extractable radioactivity generally slowly declined throughout the study after 7 DAT, ranging from of 73.1% AR to 42.8% AR. Throughout the course of the study the radioactivity in the volatile traps increased accumulating an average of 13.7% AR at day 100 in the phenyl label and 0.4% AR in the 2-test substance label. Degradation was exclusively to 2-oxo-quinoxyfen (maximum 39.2% AR at 100 DAT).

For sediment Goose River, the mass balance of the applied radioactivity (based on the sum of the aqueous layer, sediment extracts, volatiles, and bound radioactivity) ranged between an average of 89.5% AR and 99.0% AR at all sampling points. The amount of radioactivity present in the aqueous layer of the test samples decreased throughout the study from an average of 82.1% AR at 0 DAT to 1.9% AR at 100 DAT. The amount of extractable radioactivity generally slowly declined throughout the study after 7 DAT ranging from of 54.0% AR to 31.6% AR. Throughout the course of the study the radioactivity in the volatile traps increased accumulating an average of 11.8% AR at 100 DAT in the phenyl label and 0.4% AR in the 2-test substance label. Degradation was to 2-oxo-quinoxyfen (maximum 35.7% AR at 74 DAT), 6-hydroxy-quinoxyfen (maximum 7.6% AR at 21 DAT) only in 2-Q-label, and DCHQ (maximum 1.8% AR at 100 DAT only in 2-Q-label).

Water fractions and sediment extracts were typically analyzed by HPLC within 24 hours of sampling. Whenever immediate analysis was not possible, samples were placed in storage at -5°C. All samples were analyzed within 14 days of sampling. As a result, no storage stability testing was required.

The DT₅₀, and DT₉₀ of test substance under aerobic aquatic conditions were estimated by fitting the data to a single first-order linear regression analysis using the data through 100 DAT.

At Golden lake, single first order, DT50 values of test substance under aerobic aquatic conditions were 3.545, 62.06 and 47.16 days in water layer, sediment layer (excluding 0 DAT data) and total system, respectively. DT90 values of test substance under aerobic aquatic conditions were 11.78, 206.1 and 156.7 days in water layer, sediment layer(excluding 0 DAT data) and total system, respectively.

At Goose river, single first order, DT50 values of test substance under aerobic aquatic conditions were 25.71 and 15.13 days in sediment layer (excluding 0 DAT data) and total system, respectively. DT90 values of test substance under aerobic aquatic conditions were 85.40 and 50.25 days in sediment layer (excluding 0 DAT data) and total system, respectively.

Degradation occurred over the course of the study under the aerobic aquatic conditions of this study.

Reference 4

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: BBA Guidelines, Part IV, Section 5-1 (1990)

Deviations:

no

GLP compliance:

yes

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

Radiolabelled test substance name: Carbon-14 labelled XDE-795
Batch No: GHD-3058-19
Radiochemical purity: 99%

Non-radiolabelled test substance: XDE-795
Batch No: TSNl0004
Purity: 99.7%

Duration of test (contact time):

100 d

Initial conc.:

250 other: g a.i/ha

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

radiochem. meas.

Compartment:

entire system

% Recovery:

93

Remarks on result:

other: Overall mean recovery of applied radioactivity

Remarks:

Sandy loam

Compartment:

entire system

% Recovery:

91

Remarks on result:

other: Overall mean recovery of applied radioactivity

Remarks:

Clay loam

Key result

Parameter:

radiochem. meas.

Remarks:

Sandy loam

Sampling time:

100 d

Remarks on result:

other: The levels of [14C]-labelled test substance declined from ca 83% of applied in zero time samples of sandy loam to ca 11% of applied after 100 days.

Key result

Parameter:

radiochem. meas.

Remarks:

Clay loam

Sampling time:

100 d

Remarks on result:

other: The levels of [14C]-XDE-795 declined from ca 85% of applied in zero time samples of sandy loam to ca 51 of applied after 100 days

Key result

Parameter:

radiochem. meas.

Sampling time:

100 d

Remarks on result:

other: The major degradation product in the sandy loam was 3-OH-XDE-795 which was first detected at levels of ca 9% of applied after 7 days and increased to ca 41% of applied after 100 days.

Remarks:

This was principally found in the sediment.

Key result

Compartment:

sediment

DT50:

150 d

Temp.:

18 °C

Remarks on result:

other: Temperature: 18 to 21°C

Remarks:

Clay loam

Key result

Compartment:

sediment

DT50:

35 d

Temp.:

18 °C

Remarks on result:

other: Temperature: 18 to 21°C

Remarks:

Sandy loam

Key result

Compartment:

water

DT50:

3 d

Temp.:

18 °C

Remarks on result:

other: Temperature: 18 to 21°C

Remarks:

Surface water alone in sandy loam

Key result

Compartment:

water

DT50:

7 d

Temp.:

18 °C

Remarks on result:

other: Temperature: 18 to 21°C.

Remarks:

Surface water alone in clay loam

Transformation products:

yes

Remarks:

3-OH-XDE-795 (sandy loam system); 6-OH-XDE-795 (clay loam system)

Volatile metabolites:

yes

Remarks:

Less than I% of the applied radioactivity was recovered as 14C-volatiles.

Residues:

yes

Remarks:

Nonextractable residues reached maximum levels of ca 16% of applied in the sandy loam after 60 days and ca 14% of applied in the clay loam after 30 days.

Validity criteria fulfilled:

yes

Conclusions:

The overall DT50 value for [14C]-labelled test substance in the sandy loam was 35 days and in the clay loam 150 days. In surface water alone, the DT50 was estimated to be 3 days in the sandy loam (data to 2 days) and 7 days in the clay loam (data to 7 days).

Executive summary:

The study was conducted to investigate the fate of [14C]-labelled test substance, labelled in position 2 of the quinoline ring, in sandy loam and clay loam sediment/water systems, (under an aerobic/anaerobic gradient) according to BBA Guidelines, Part IV, Section 5-1 (1990).

Samples of each sediment and its associated surface water were treated with [14C]-labelled test substance at a nominal rate equivalent to 250 g ai/ha, by application to the water layer. Treated samples were incubated in the dark under an aerobic/anaerobic gradient at a temperature of 18-21°C for up to 100 days. 14CO2 was collected in ethanolamine traps and non-specific [14C]-organic volatiles in ethanediol traps. At intervals throughout the incubation period, surface waters were separated from sediments and each analyzed separately for total radioactivity. The nature of the radioactivity extracted from each was investigated by HPLC and TLC.

The overall mean recovery of applied radioactivity ranged from ca. 80-98% (mean =ca. 93%) in the sandy loam system and ca. 77-96% (mean = ca. 91%) in the clay loam system. Less than 1% of the applied radioactivity was recovered as either 14CO2 or non-specific organic volatiles. The proportion of applied radioactivity associated with the surface waters declined from ca. 34% and ca. 41% in zero time samples to levels of <10% after 7 days in the sandy loam and 14 days in the clay loam, respectively. Maximum levels of ca 72% and ca 66% of applied radioactivity were extracted from the sandy loam and clay loam sediments after 7 days and 14 days, respectively. Nonextractable residues reached maximum levels of ca. 16% of applied in the sandy loam after 60 days and ca. 14% of applied in the clay loam after 30 days. Apparatus washings generally accounted for <10% of applied. In the case of 3 sandy loam samples and 2 clay loam samples, this level was exceeded with a maximum of ca 16% of applied being recorded for one sample. Preliminary testing showed significant adsorption of the test compound to silanised glass with ca 36% adsorption from aqueous solution over ca. 24 h.

It is suggested that the lower mass balance values observed for some samples may be due to further adsorption of radioactivity to the silanised glass units without recovery of this radioactivity in apparatus washings.

Sediment extracts and surface waters (containing >10% of applied) were analyzed by reverse phase HPLC. Sediment extracts and a number of surface waters were also analyzed by TLC. A single 100 day sandy loam apparatus wash was analyzed by HPLC and TLC. HPLC data was used for identification and quantification and TLC data for confirmation where this was possible. The levels of [14C]-labelled test substance declined from ca. 83% of applied in zero time samples of sandy loam to ca. 11% of applied after 100 days. The corresponding values were ca. 85% and ca. 51% in the clay loam. The major degradation product in the sandy loam was 3 -OH-XDE-795 which was first detected at levels of ca. 9% of applied after 7 days and increased to ca. 41% of applied after 100 days. This was principally found in the sediment. This component was not observed in the clay loam system. However, an unidentified component (Unknown A) was detected after 60 days and reached levels of ca. 10% after 100 days. A second unidentified minor degradation product was also observed in a single 100 day sample at a level of ca. 1% of applied. Unknown A was found to have similar chromatographic properties to 6 -OH-XDE-795 during HPLC analysis but not to 2-oxo-XDE-795 or N-oxide-XDE-795.

Analysis of the sandy loam apparatus wash indicated the presence of test substance (12.81%) and 3-OH-XDE-795 (1.28%).

The overall DT50 value for [14C]-labelled test substance in the sandy loam was 35 days and in the clay loam 150 days. Corresponding DT90 values were 117 days and 498 days. In the surface water alone, the DT50 was estimated to be 3 days in the sandy loam (data to 2 days) and 7 days in the clay loam (data to 7 days).

In the sterilized samples at 30 days only [14C]-labelled test substance was observed in either system indicating the absence of any chemical degradation. This was also suggested to be true at 100 days, although it could not be confirmed for the water layers which, since they contained <10% of applied, were not characterized.

Description of key information

DT50 values were calculated in several different studies using different soil/sediments. In neutral pond water, the DT50 values for the test substance under aerobic conditions in surface water were calculated to be 128.6 days for the high dose, 318.6 days for the high dose sterile, and 115.0 days for the low dose experiment. In a second study, DT50 value under aerobic condition was 47.16 days (total system) for Golden Lake and 15.13 days (total system) for Goose River. In yet another study, the overall DT50 value for the test substance in the sandy loam was 35 days and in the clay loam 150 days. In surface water alone, the DT50 was estimated to be 3 days in the sandy loam (data to 2 days) and 7 days in the clay loam (data to 7 days). Another study noted that the test substance will reside mostly sorbed to the sediment phase if accidentally introduced to surface waters