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Administrative data

Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
This GLP study generally follows the guideline. There are several deviations in the preparation and aging of the synthetic humic water, including no information on the measurement of DOC and the pre-aging time was seven days not three. These guideline differences and potential impacts were not discussed.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report date:
1990

Materials and methods

Study type:
indirect photolysis
Test guideline
Qualifier:
according to guideline
Guideline:
EPA OTS 795.70 (Indirect Photolysis Screening Test: Sunlight Photolysis in Waters Containing Dissolved Humic Substances)
Deviations:
yes
Remarks:
The study generally follows the guideline. There are several deviations in the preparation synthetic humic water. These guideline differences and potential impacts were not discussed.
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
m-phenylenediamine
EC Number:
203-584-7
EC Name:
m-phenylenediamine
Cas Number:
108-45-2
Molecular formula:
C6H8N2
IUPAC Name:
m-phenylenediamine
Details on test material:
Purity: 99.76%

Study design

Radiolabelling:
not specified
Analytical method:
high-performance liquid chromatography
Light source:
sunlight
Details on light source:
Location: roof, 38ºN, facing south and angled at ~30º to the horizon
Time of year/month: summer/June
Other: Skies were clear during the whole exposure
Sensitiser (for indirect photolysis)
Type of sensitiser:
other: humic acid
Details on sensitiser:
synthetic humic water, pH 7
Concentration of sensitiser:
other: Absorbance (1cm cell @ 290 nm) = 0.05
Dark controls:
yes
Remarks:
No significant losses were observed with the dark controls.

Results and discussion

Preliminary study:
Because the loss of the test substance in synthetic humic acid water was considerably faster than in distilled water, a definitive study was conducted.

Screening test:
Indirect photolysis rate constant = 0.68 d-1
Direct photolysis rate constant = 0.18 d-1
Overall photolysis rate constant = 0.86 d-1
Half-life = 0.81 d
Quantum yield (for direct photolysis):
0.07
Rate constant (for indirect photolysis):
0.86 other: d-1 (Indirect photolysis)
Dissipation half-life of parent compoundopen allclose all
DT50:
0.51 d
Test condition:
Overall photolysis half-life. These results demonstrate that the substance is readily degraded by sunlight.
DT50:
0.81 d
Test condition:
Indirect photolysis half-life.
Transformation products:
not measured

Any other information on results incl. tables

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Screening Study Results: Distilled Water (DW) and Synthetic Humic Water (SHW)

Water Type

Light Conditions

Sample

Time (PDT)

Peak Area (millions), Injection #1

Peak Area (millions), Injection #2

Peak Area (millions), Injection #3

Average Area (millions)

Test Substance (µM)

Test Substance % Reacted

DW

Start (Time 0)

A

16:30

0.712

0.721

0.782

0.738

10.5

0

DW

Start (Time 0)

B

16:30

0.709

0.727

0.777

DW

Dark

1A

17:00

0.711

0.718

N/A

0.713

10.2

3

DW

Dark

1B

17:00

0.710

0.712

N/A

DW

Dark

2A

20:15

0.758

0.746

N/A

0.744

10.6

-1

DW

Dark

2B

20:15

0.742

0.742

N/A

DW

Light

1A

17:00

0.690

0.682

N/A

0.703

10.0

5

DW

Light

1B

17:00

0.722

0.718

N/A

DW

Light

2A

20:15

0.691

0.679

N/A

0.688

9.8

7

DW

Light

2B

20:15

0.686

0.695

N/A

SHW

Start (Time 0)

A

16:30

0.722

0.723

0.773

0.736

10.5

0

SHW

Start (Time 0)

B

16:30

0.714

0.725

0.759

SHW

Dark

1A

17:00

0.722

0.719

N/A

0.716

10.2

3

SHW

Dark

1B

17:00

0.724

0.698

N/A

SHW

Dark

2A

20:15

0.750

0.748

N/A

0.743

10.6

-1

SHW

Dark

2B

20:15

0.752

0.721

N/A

SHW

Light

1A

17:00

0.664

0.662

N/A

0.665

9.5

10

SHW

Light

1B

17:00

0.678

0.654

N/A

SHW

Light

2A

20:15

0.540

0.537

N/A

0.545

7.8

26

SHW

Light

2B

20:15

0.569

0.532

N/A

--

--

Definitive Study Results: Distilled Water (DW) and Synthetic Humic Water (SHW)

Water Type

Sample

Time (PDT)

Peak Area (millions), Injection #1

Peak Area (millions), Injection #2

Average Area, C (millions)

ln(C0/Ct)

Test Substance (µM)

DW

Start (Time 0)

11:00

0.843

0.834

0.839

0.000

9.8

DW

Dark 1

12:15

0.773

0.841

0.807

-0.030

10.1

DW

Dark 2

13:15

0.831

0.850

0.841

-0.049

10.3

DW

Dark 3

14:15

0.864

0.838

0.851

-0.036

10.2

DW

Dark 4

15:35

0.859

0.833

0.846

-0.056

10.4

DW

Dark 5

18:00

0.843

0.846

0.845

-0.071

10.6

DW

Light 1

12:15

0.774

0.779

0.777

0.180

8.2

DW

Light 2

13:15

0.752

0.720

0.736

0.390

6.7

DW

Light 3

14:15

0.650

0.638

0.644

0.612

5.3

DW

Light 4

15:35

0.633

0.652

0.643

0.819

4.3

DW

Light 5

18:00

0.548

0.574

0.561

1.119

3.2

SHW

Start (Time 0)

11:00

0.832

0.831

0.832

0.000

9.9

SHW

Dark 1

12:15

0.838

0.807

0.823

0.011

9.8

SHW

Dark 2

13:15

0.838

0.824

0.831

0.001

9.9

SHW

Dark 3

14:15

0.826

0.848

0.837

-0.006

10.0

SHW

Dark 4

15:35

0.854

0.832

0.843

-0.013

10.1

SHW

Dark 5

18:00

0.836

0.827

0.832

0.000

9.9

SHW

Light 1

12:15

0.670

0.693

0.682

0.199

8.1

SHW

Light 2

13:15

0.606

0.590

0.598

0.330

7.1

SHW

Light 3

14:15

0.511

0.532

0.522

0.466

6.2

SHW

Light 4

15:35

0.481

0.466

0.474

0.563

5.7

SHW

Light 5

18:00

0.380

0.383

0.382

0.778

4.6

--

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The test substance has photochemical properties very similar to those of other anilines. It is very photolabile, and direct and indirect photolysis each contribute significantly to the overall photolysis. These results demonstrate that the substance is readily degraded by sunlight.
Executive summary:

Tests were conducted to determine whether natural humic acid significantly enhances the aqueous photolysis of the test substance. In the preliminary screening test, quartz tubes containing test substance and synthetic humic acid were exposed to sunlight. Because the loss of the test substance in synthetic humic acid water was considerably faster than in distilled water, a definitive study was conducted.

 

The results demonstrate that the test substance is readily degraded by sunlight. It is very photolabile, and direct and indirect photolysis each contribute significantly to the overall photolysis. Because the indirect photolysis rate constant will vary from water to water, and direct photolysis is a significant fraction of the overall photolysis, the direct photolysis rate constant is a useful estimate of the minimum photolysis rate constant. The direct photolysis quantum yield has been estimated and can be used to calculate direct photolysis constants as a function of the latitude and time of year. Such calculations for 40ºN yield minimum rate constants of 0.34, 0.5, 0.18, and 0.068 d-1 in spring, summer, fall, and winter, respectively, and maximum half lives of 2.0, 1.4, 3.8, and 10 d for the same seasons.

 

Definitive Study Results:

Indirect photolysis rate constant: 0.86 d-1

Indirect photolysis half-life: 0.81 d

Direct photolysis rate constant: 0.50 d-1

Quantum yield (for direct photolysis): 0.07

Overall photolysis rate constant: 1.36 d-1

Overall photolysis half-life: 0.51 d

 

Screening Test Results:

Indirect photolysis rate constant = 0.68 d-1

Direct photolysis rate constant = 0.18 d-1

Overall photolysis rate constant = 0.86 d-1

Overall photolysis half-life: 0.81 d

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