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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1973
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Principles of method if other than guideline:
Similar to Kempe 1973
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on inoculum:
Sediment was collected by scraping the upper 2-3 cm from the bottom of the Milwaukee River, Ozaukee County and sived through a 595-µm mesh screen (U.S. Standard Sieve no. 30) before being added to the incubation vessels. Twelve hundred grams of mud were placed in each of two 20-liter carboys.
Duration of test (contact time):
2.5 mo
Initial conc.:
700 000 other: dpm/5 mg TFM
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: optical density at 395 nm
Details on study design:
Mud was placed in each of two 20-liter carboys. Fifty-gram amounts were added as an inoculum to two other 20-liter carboys and all four bottles were filied with river water. A mixture of unlabelled and 14C (ring UL) TFM was added to one of the bottles with sediment and to one of the bottles with the bacterial inoculum, so that the initial concentration and radioactivity in each was about 7 x 10^ dpm/5 mg TFM per liter. The remaining two carboys served as controls for optical density readings. Magnetic stirrers kept the solution slowly mixing during the entire experimental period. Incubations were carried out at 15 °C. Oxygen concentrations were never allowed to drop below 3 mg/liter during the initial phase of this experiment and were maintained by bubbling with compressed air at 2 week intervals.
Key result
Parameter:
other: Optical density (395 nm)
Sampling time:
2.5 mo
Remarks on result:
other: see "Attached background material"
Details on results:
For the graphes see "Attached background material". Under aerobic conditions, there was no significant decrease in optical density at 395 nm in either of the TFM containing bottles for a 2.5-month period (Fig. IB). Similarly, there was no change in the radioactivity of the supenatant water (Fig. lA).Thin-layer chromatography of the XAD-2 methanol fraction obtained from these flasks also indicated that there had been no alteration of the TFM molecule. Essentially all of the 14C was retained by the XAD-2 resin and the only labelled organic compound in the methanol eluate had Rf values identical to those of TFM when chromatographed on silica gel plates in two solvent systems.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
In this aerobic biodegradation test over 2.5 month no degradation of the test item could be determined. The test item is regarded as not biodegradable.
Executive summary:

The stability of the test item was determined in an aerobic test system with sediment form a natural stream in US. The optical density measured at 395 nm showed no significant decline after the test duration of 2.5 months. The test item is regarded as not biodegradable.

Description of key information

In this aerobic biodegradation test over 2.5 month no degradation of the test item could be determined. The test item is regarded as not biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The stability of the test item was determined in an aerobic test system with sediment from a natural stream in US. The optical density measured at 395 nm showed no significant decline after the test duration of 2.5 months. The test item is regarded as not biodegradable.