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EC number: 217-615-7 | CAS number: 1910-42-5
Phototransformation in soil
Administrative data
Link to relevant study record(s)
- Endpoint:
- phototransformation in soil
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Study period:
- 5 Mar 1979 to 2 Feb 1980
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- test procedure in accordance with generally accepted scientific standards and described in sufficient detail
- Qualifier:
- no guideline followed
- GLP compliance:
- no
- Radiolabelling:
- yes
- Remarks:
- 2,2',6,6' - 14C Labelling in the rings
- Key result
- % Degr.:
- >= 10.5
- Sampling time:
- 85 wk
- Test condition:
- sandy soil surface and stored in dry, sterile conditions was degraded in sunlight
- % Degr.:
- >= 13.4
- Sampling time:
- 85 wk
- Test condition:
- When soil samples were mixed regularly
- Transformation products:
- yes
- Validity criteria fulfilled:
- not specified
- Conclusions:
- 14C - test material applied to a sandy soil surface and stored in dry, sterile conditions was degraded in sunlight, so that at least 10.5% degradation occurred after 85 weeks irradiation. When soil samples were mixed regularly, the extent of degradation was at least 13.4% in this period. Two of the photoproducts formed were accounted for 2.4% and 1.2% respectively of the activity in the mixed irradiated soil samples. A third degradation product accounted for 2.4% of the radioactivity found in the 85 week mixed samples. These results indicate that photodegradation may be a pathway of degradation where paraquat is present in very sandy soils of low strong adsorption capacity at a level approximating to the SAC.
- Executive summary:
[14C]-test material was applied to the surface of a sterile, very sandy soil and exposed to natural sunlight for periods of up to 85 weeks. Some samples were mixed at regular intervals, while others were not mixed. Dark controls were stored at -12°C and analyzed with irradiated samples at each sampling interval.
The proportion of radioactivity in samples which were accounted for as the test item declined throughout the study until at 85 weeks it represented no more than 89.5% of the activity in the non-mixed soil and 86.6% in the mixed soil. Test item accounted for 95.0% of the activity in the dark control analyzed with the 85 week samples.Two photoproducts were found in mixed and non-mixed soil extracts and were characterized by thin layer co-chromatography. The compounds accounted for 1.4% and 1.3% respectively of radioactivity found in the non-mixed sample and 2.4% and 1.2% respectively in the mixed samples at 85 weeks. A third, uncharacterized compound accounted for 1.8% of the radioactivity in the non-mixed sample and 2.4% in the mixed samples.
14C - test material applied to a sandy soil surface and stored in dry, sterile conditions was degraded in sunlight, so that at least 10.5% degradation occurred after 85 weeks irradiation. When soil samples were mixed regularly, the extent of degradation was at least 13.4% in this period. Two of the photoproducts formed were accounted for 2.4% and 1.2% respectively of the activity in the mixed irradiated soil samples. A third degradation product accounted for 2.4% of the radioactivity found in the 85 week mixed samples. These results indicate that photodegradation may be a pathway of degradation where paraquat is present in very sandy soils of low strong adsorption capacity at a level approximating to the SAC.
- Endpoint:
- phototransformation in soil
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Study period:
- 28 Jul 1980 to 23 Oct 1982
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Qualifier:
- no guideline followed
- GLP compliance:
- no
- Radiolabelling:
- yes
- Remarks:
- [2,3,5,6,2',3',5',6' - 14C] on the rings
- Remarks on result:
- not determinable
- Remarks:
- In sandy soil and 2 years of natural sunlight exposure had no photodegrading effect on the test item in soil.
- Validity criteria fulfilled:
- not specified
- Executive summary:
Florida sandy soil was treated with 7 ppm [ring-14C] test item, which is 80% of the "tightly bound" capacity. Samples were exposed outdoors under quartz to sunlight in Richmond, California. Controls were stored in the dark. At intervals up to 2 years, samples were extracted and analyzed for the test item and degradation products by TLC and autoradiography. None of the known photodegradation products were detected at any interval. Thus, in this sandy soil 2 years of natural sunlight exposure had no effect on the test item.
Interval Months
Sample
% of Recovered Radioactivity in Spot Number:
1 (test item)*
2
3
0
1
93.9
5.5
0.6
2
91.7
6.3
2
3
90.6
6.2
3.1
6
Dark Control
-1
88.4
7.2
4.4
-2
92.5
5.6
1.9
Light - Shaken
-1
90.1
6.1
3.8
-2
86.1
4.5
9.4
Light - Not Shaken
91.1
6.7
2.2
12
Dark Control
-1
94.9
3.4
1.8
-2
95.1
3.4
1.4
Light - Shaken
-1
94.7
2.4
2.8
-2
95.0
2.7
2.4
Light - Not Shaken
94.6
3.3
2
18
Dark Control
-1
96.0
2.9
1.1
-2
94.7
4.3
1.0
Light - Shaken
-1
93.6
3.0
3.3
-2
93.7
3.1
3.1
Light - Not Shaken
94.6
4.3
1.9
24
Dark Control
-1
96.7
1.6
1.3
-2
97.0
2.3
0.7
Light - Shaken
-1
94.6
3.6
1.8
-2
94.4
3.8
1.8
Light - Not Shaken
96.8
1.9
1.3
* Test item values include unextractable14C which is assumed to be only very tightly bound the test item .
Referenceopen allclose all
The proportion of radioactivity in samples which were accounted for as the test item declined throughout the study until at 85 weeks it represented no more than 89.5% of the activity in the non-mixed soil and 86.6% in the mixed soil. Test item accounted for 95.0% of the activity in the dark control analyzed with the 85 week samples. Two photoproducts were found in mixed and non-mixed soil extracts and were characterized by thin layer co-chromatography. The compounds accounted for 1.4% and 1.3% respectively of radioactivity found in the non-mixed sample and 2.4% and 1.2% respectively in the mixed samples at 85 weeks. A third, uncharacterized compound accounted for 1.8% of the radioactivity in the non-mixed sample and 2.4% in the mixed samples.
The results of these analyses showed that after exposure to the equivalent of 36 days Florida Summer sunlight no detectable photodegradation had occurred.
Description of key information
These results indicate that photodegradation may be a pathway of degradation where the test item is present in very sandy soils of low strong adsorption capacity at a level approximating to the SAC. None of the known photodegradation products was detected at any interval. Thus, in this sandy soil 2 years of natural sunlight exposure had no effect on the test item on soil, Day & Hemingway 1981 and Pack 1983
Key value for chemical safety assessment
Additional information
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