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Environmental fate & pathways

Phototransformation in water

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Reference
Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
key study
Study period:
11 June - 20 November 1990
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Study type:
direct photolysis
Qualifier:
according to guideline
Guideline:
EPA Guideline Subdivision N 161-2 (Photodegradation Studies in Water)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable.
Radiolabelling:
yes
Analytical method:
high-performance liquid chromatography
other: TLC
Details on sampling:
- Sampling intervals for the parent/transformation products:
--Photolysis experiment: 1, 2, 3, 6, 8.5, 10.75, 23.5, 30.8 and 48 hours after irradiation start.
--Dark experiment: 27 and 48 hours after irradiation start.
--Sensitized photolysis experiment: 0.5, 1, 2, 3, 4, 5, 7, 9 and 24.5 hours after irradiation start.
--Sensitized dark control: 8.45 and 24 hours after irradiation start.
- Sampling methods for the volatile compounds, if any: Traps for volatiles exchanged and analysed at each sample occasion.
- Sampling intervals/times for sterility check: For last samples taken.
- Sample storage conditions before analysis: At 4°C in the dark, with CH3CN content adjusted to 25% v/v.
Buffers:
- pH: 5.36
- Type and final molarity of buffer: 9.6 mM citrate buffer at a concentration of 0.8 mg/L
Light source:
Xenon lamp
Light spectrum: wavelength in nm:
< 290
Relative light intensity:
0.63
Details on light source:
- Emission wavelength spectrum: Wavelengths less than 290 nm cut off
- Filters used and their purpose: Filters cut off wavelength at 290 nm
- Light intensity at sample and area irradiated: 72400 energy units
- Relative light intensity based on intensity of sunlight: 0.63 (based on midday midsummer at 50° N)
- Duration of light/darkness: Constant
Type of sensitiser:
other: triplet sensitiser
Details on sensitiser:
acetone
Concentration of sensitiser:
1 other: % v/v
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test apparatus/vessels: Cylindrical borosilicate glass vessels, of volume 15 mL, with lids.
- Details of traps for volatile, if any: NaOH
- Sterilization: Heat or filtration
- Air flow: 5 mL/min

TEST MEDIUM
- Volume used/treatment: 15 mL
- Identity and concentration of co-solvent: CH3CN at 1% v/v

REPLICATION
- No. of replicates (dark): 1
- No. of replicates (irradiated): 1

OTHER
A senstized control was also run in parallel with 1% acetone
Duration:
48 h
Temp.:
25 °C
Initial conc. measured:
0.8 mg/L
Reference substance:
no
Dark controls:
yes
Computational methods:
- Experimental photolysis reaction rate (direct and/or indirect photolysis): Calculated
- Quantum yield calculations (quantum yield should be expressed as a fraction and not as a percent): Not calculated
- GCSOLAR or ABIWAS calculation of reaction rates at different latitudes, seasons, time of the day, water bodies: Yes (calculation method not specified)
- Half-lives or DT50, DT75, and DT90 values and appropriate associated confidence intervals: Calculated
Parameter:
max lambda
Value:
244 nm
% Degr.:
99.37
Sampling time:
48 h
Test condition:
Non-sensitized
% Degr.:
4.46
Sampling time:
48 h
Test condition:
Non-sensitized, Dark control
% Degr.:
100
Sampling time:
24.5 h
Test condition:
Sensitized
% Degr.:
0
Sampling time:
24.5 h
Test condition:
Sensitized, dark control
DT50:
9.3 h
Test condition:
Non-sensitized
DT50:
4.3 h
Test condition:
Sensitized
Predicted environmental photolytic half-life:
0.62 days at 30°N
Transformation products:
yes
Details on results:
Transformation products detected but could not be identified.

HALF-LIFE
Non-sensitized: 9.3 hours
Sensitized: 4.3 hours

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

Table 1. Measurements of CGA185072 as % of initial level

Irradiation time [hours] CGA185072 [%]
Non-sensitized Sensitized
Photolysis Dark Control Photolysis Dark Control
0 100 100
0.5 95.86
1 97.08 92.97
2 94.9 83.16
3 92.43 70.56
4 57.32
5 32.06
6 82.5
7 13.72 100
8.5 59.06
9 0
10.75 34.43
23.5 11.92 98.4
24.5 0 100
30.8 5.98
48 0.63 95.54
Validity criteria fulfilled:
not applicable
Conclusions:
Based on the experimental result with artifical light, the half life of the test substance in summer sunlight at 30° N is 0.62 days.
Executive summary:

The photodegradation of the test substance in water was evaluated in a GLP-compliant, guideline test. Based on the experimental result with artifical light, the half life of the test substance in summer sunlight at 30° N is 0.62 days.

Description of key information

The photodegradation of the substance in water was investigated in two studies. The key study determined a half-life of the substance in summer sunlight (assuming 12 hours a day) at 30° N of 0.62 days.

A further study was performed with Acetic acid, 2-[(5-chloro-8-quinolinyl)oxy]- (i.e. the main transformation product in soil and water/sediment systems).

Key value for chemical safety assessment

Half-life in water:
0.62 d

Additional information

The key study (Schäffer, 1991) is a GLP-compliant test conducted according to EPA guideline subdivision N 161-2 (photodegradation studies in water). The photodegradation of the test substance in water was evaluated under artificial light (wavelength <290 nm, relative light intensity based on intensity of sunlight: 0.63 based on midday midsummer at 50° N)) and the half-life of the substance in summer sunlight at 30° N was determined to be 0.62 days (assuming 12 hours of sunlight). A GLP compliant, guideline (UBA Test Guideline "Phototransformation of Chemicals in Water, Part A, Direct Phototransformation", Berlin, FRG, January 1990) supporting study (Phaff, 1996) also found that the photochemical half-life of the substance in surface waters is likely to be short.

A GLP compliant, guideline (UBA Test Guideline "Phototransformation of Chemicals in Water, Part A, Direct Phototransformation", Berlin, FRG, January 1990) supporting study (Abildt, 1995) found that the photochemical half-life of Acetic acid, 2-[(5-chloro-8-quinolinyl)oxy]- in surface waters is likely to be short.