2,4-dichloroaniline

Phototransformation in water

Administrative data

Endpoint:

phototransformation in water

Type of information:

other: BUA report

Adequacy of study:

other information

Reliability:

other: BUA report

Rationale for reliability incl. deficiencies:

other: No reliability is given as this is a summary entry for the BUA report.

Data source

Reference

Reference 1

Reference Type:

secondary source

Title:

2,4-Dichloranilin; 2,5-Dichloranilin; 3,4-Dichloranilin

Author:

Beratergremium für umweltrelevante Altstoffe (BUA)

Year:

1994

Bibliographic source:

Wissenschaftliche Verlagsgesellschaft, BUA report 140

Reference 2

Reference Type:

publication

Title:

Ring test of a method for assessing the phototransformation of chemicals in water.

Author:

Lemaire J, Guth J. A., Klais O., Leahey J., Merz W., Philp J., Wilmes R., Wolff C.J.M.

Year:

1985

Bibliographic source:

Chemosphere 14, 53-77

Reference 3

Title:

No information

Author:

Mill T., Mabey W. R., Bomberger D. C. Chou T.-W., Hendry D. G., Smith J. H.

Year:

1982

Bibliographic source:

Environmental Protection Agency (EPA), EPA-600/3-82-022, USA

Reference 4

Reference Type:

publication

Title:

Degradation of aniline and chloroanilines by sunlight and microbes in estuarine water.

Author:

Hwang H.-M., Hodson R. E., Lee R. F.

Year:

1987

Bibliographic source:

Water Res. 21, 309-316

Materials and methods

Principles of method if other than guideline:

BUA report

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

2,4-dichloroaniline

EC Number:

209-057-8

EC Name:

2,4-dichloroaniline

Cas Number:

554-00-7

Molecular formula:

C6H5Cl2N

IUPAC Name:

2,4-dichloroaniline

Results and discussion

Any other information on results incl. tables

conclusion

 

Photodegradation plays a significant role as an elimination path in surface waters: Half-lives (t1/2) for the phototransformation of 2,4-dichloroaniline in natural solar radiation (latitude of 30° north) range from 26 hours in summer to 68 hours in winter.

____________________________________________________________________________________________________

Due to the UV absorption properties of 2,4-dichloroaniline, interactions of the substance with sunlight (> 290/295 nm) are expected.

 

Direct phototransformation is usually the dominant reaction mechanism in water while indirect phototransformation (reaction with photochemically formed radicals like OH., HO2., ROx.) is of minor importance (Lemaire et al., 1985, Mill et al., 1982). According to the results quoted below this is also true for the dichloroanilines (presumably except waters rich in carbonate). Direct phototransformation can be determined in pure water, in natural waters however both the direct and indirect phototransformation are assessed.

 

pKa values of the corresponding acids of dichloroanilines suggest that phototransformation in water should predominantly emanate from the disproportionate form of the molecule.

 

Study by Hwang et al., 1987

The quantum yield for direct photodegradation of 2,4-dichloroaniline in buffered water (pH 7.6) was 0.044, which means that 1000 light quanta transform 44 molecules of 2,4-dichloroaniline.

 

Furthermore, the photodegradation of 2,4-dichloroaniline in field trials was studied. From the rate constant k (first order) the half-life (t1/2 = 0.693/k) was calculated in each case (=> see tables below).

Samples were treated with formaldehyde in order to kill microorganisms and suppress the biodegradation. UV absorption by formaldehyde is negligible under the experimental conditions. The elimination of 2,4-dichloroaniline in dark controls without formaldehyde was also negligible. No biodegradation of 2,4-dichloroaniline took place during 4 hours or 3 days of incubation time under the given conditions. Water samples from estuaries that were not treated with formaldehyde, and for which also biomineralization was detected, had higher biomineralization rates than samples containing formaldehyde (no microbial activity).Authors suspect this result is based on the fact that 2,4-dichloroaniline can be decomposed only photochemically under the experimental conditions while the resulting phototransformation products can be mineralized both photochemically and microbially.

 

A slower photodegradation in natural water compared to that in distilled water is generally attributed to a reduction of incident UV radiation 1) due to the presence of other dissolved organic substances and suspended particles or 2) due to quenching of the excited state of the substance under study by humic molecules. The latter is suspected by the authors to occur in the case of the investigated chloroaniline.

 

Phototransformation (1. reaction step) - half-life t_1/2

information on methodology: -         25 µg 14C-2,4-dichloroaniline / l, predissolved in acetone (acetone didn't show photosensitising effects) -         midday sun, cloudless sky, about 30° north latitude -         depth of water: 3 cm -         test duration: 4 h -         samples were mixed with formaldehyde
	t1/2 summer, 25 °C	t1/2 winter, 13 °C
distilled water (pH 7.7)	10 h	21 h
surface water from an estuarine (pH 7.7)	26 h	68 h

 

Photomineralization (=>¹⁴CO₂) - half-life t_1/2

information on methodology: -         25 µg 14C-2,4-dichloroaniline / l, predissolved in acetone (acetone didn't show photosensitising effects) -         sunny days, cloudless sky, about 30° north latitude -         depth of water: 3 cm -         test duration: 3 d
	t1/2 summer, 25 °C	t1/2 winter, 13 °C
distilled water (pH 7.7)	77 d	98 d
surface water from an estuarine (pH 7.7)	84 d (49 d)*	189 d (92 d)*

* photomineralization plus biomineralization (samples without formaldehyde)