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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication which meets basic scientific priinciples. Test procedure not in accordance with defined methods, but data are comprehensible and scientifically acceptable.
Study type:
indirect photolysis
Principles of method if other than guideline:
Indirect photolysis (sensitiser: OH-radicals) was examined in an experimental study with natural lake water.
GLP compliance:
not specified
Radiolabelling:
not specified
Analytical method:
not specified
Light source:
other: mercury lamp
Relative light intensity:
ca. 10
Details on light source:
merry-go-round reactor (MGRR) equipped with a Hanau TQ 718 high pressure mercury lamp and a solidex borosilicate glass filter tube (10 % transmission at 282 nm).
Type of sensitiser:
OH radical
Details on sensitiser:
n-butyl chloride as the OH-radical probe
Reference substance:
no
Dark controls:
not specified
% Degr.:
50
Sampling time:
50 d
Test condition:
Indirect photolysis
Rate constant (for indirect photolysis):
0 cm³/(molecule*sec)
Transformation products:
not measured

Conc. of Sensitizer: 1*10E-16 mol/L; DT50 = 50 days.

Rate Constant reported as (1.7 +/- 0.3)*10E9 L/mol*sec and recalculated to 3*10E-12 cm³/molecules*s

Validity criteria fulfilled:
yes
Conclusions:
DT50 = 50 days;
Rate Constant reported as 1.7 (+/- 0.3)*10E9 L/mol*sec and recalculated to 3*10E-12 cm³/molecules*s
Executive summary:

Indirect photolysis (sensitiser: OH-radicals) was examined in an experimental study with natural lake water. DT50 = 50 days; Rate Constant reported as (1.7 +/- 0.3)*10E9 L/mol*sec and recalculated to 3*10E-12 cm³/molecules*s

Description of key information

Indirect photolysis, no guideline followed, non-GLP; result: DT50 = 50 days; rate constant reported as (1.7 +/- 0.3)*10E9 L/mol*sec and recalculated to 3*10E-12 cm³/molecules*s.

Key value for chemical safety assessment

Half-life in water:
50 d

Additional information

There is one valid study in context of phototransformation in water available from Haag et.al. (1985). Indirect photolysis was examined in natural lake water with OH - radicals used as sensitiser. Water lake samples from Greifensee lake were spiked with 1 -2 µM n-butyl chloride as OH - radical probe. The samples were placed into quartz tubes without headspace and irradiated in a merry-go-round reactor (MGRR), equipped with a Hanau TQ 718 high pressure mercury lamp and a solidex borosilicate glass filter tube (10 % transmission at 282 nm). The temperature was held at 26 +/- 2 °C. Irradiations in sunlight were performed in the same quartz tubes held on a rack at a 30° angle from the horizon. Based on the rate of O2 formation sensitized by humics, the irradiation intensity in the MGRR was about 10 times that in the natural sunlight experiment. The OH - radical concentration was 1 E-16 mol/L. As result the half-life was determined to be 50 days.