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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Reference
Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: data is from peer reviewed journal
Justification for type of information:
data is from peer reviewed journal
Qualifier:
according to guideline
Guideline:
other: refer principle below
Principles of method if other than guideline:
Test filter experiment was performed for the test chemical 2, 4, 6 trichloroaniline to study the biodegradation rate and half life in water and sediments.
GLP compliance:
not specified
Specific details on test material used for the study:
-Name of the test material: 2,4,6-trichloroaniline
- Molecular formula: C6H4Cl3N
- Molecular weight: 196.464 g/mol
- Smiles notation: Nc1c(Cl)cc(Cl)cc1Cl
- InChl : 1/C6H4Cl3N/c7-3-1-4(8)6(10)5(9)2-3/h1-2H,10H2
-Substance type: Organic
- Physical state: solid
Radiolabelling:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): River Elbe water was taken at Dresden, 55km downstream of the Czech border, between March 1995 and December 1998.
- Laboratory culture:
- Method of cultivation:
- Storage conditions:
- Storage length:
- Preparation of inoculum for exposure:
- Pretreatment:
- Concentration of sludge:
- Initial cell/biomass concentration:
- Water filtered: Yes
- Type and size of filter used, if any: Glass column filled with pumice
Duration of test (contact time):
11 wk
Initial conc.:
>= 3 - <= 24 µg/L
Based on:
DOC
Details on study design:
Details on study design
TEST CONDITIONS
- Test temperature: 20 OC
- Aeration of dilution water: Yes
- Continuous darkness: Yes

TEST SYSTEM
- Method used to create aerobic conditions: No data available
- Test performed in open system: Yes

CONTROL AND BLANK SYSTEM
- Inoculum blank: For each testfilter, experiments were conducted on a control sample which was unpumped and maintained in an open bottle under the same conditions.

STATISTICAL METHODS: No data available
Reference substance:
not specified
Test performance:
No data available
Compartment:
natural water / sediment: freshwater
% Recovery:
78
St. dev.:
4.3
Remarks on result:
other: other details not available
Compartment:
natural water / sediment: freshwater
DT50:
19 h
St. dev.:
0.02
Type:
not specified
Temp.:
20 °C
Remarks on result:
other: other details not available
Other kinetic parameters:
first order rate constant
Transformation products:
not specified
Evaporation of parent compound:
not specified
Volatile metabolites:
not specified
Residues:
not specified
Results with reference substance:
The concentration of 2, 4, 6 trichloroaniline in the control samples decreased, but the rates of degradation were significantly lower

The biodegradation rate increased by a factor of 20 within 6 weeks. From this it is concluded that this compound, which was found to be hardly biodegradable in the first experiment (t ½:0:76 d),experiences greater microbial degradation following adaptation (t ½:0:03 d). After the 11-week period with out amines in the circulated water, a small decrease in the degradation rate of 2, 4, 6-trichloraniline was observed, although it was still much higher than the result from the first week.

Validity criteria fulfilled:
yes
Remarks:
Not readily biodegradable
Conclusions:
The half life of test compound 2, 4, 6 trichloroaniline is observed to be 19 hrs and the mean biodegradation rate constant was 0.036/h. On the basis of this half life value it can be concluded that test chemical is not persistent in river water with sediments.

Executive summary:

Test filter experiments were carried out by circulating water through a glass column (diameter: 42mm, height:90 mm) filled with pumice .The experiments were carried out in darkness at a temperature of 20oC in aerobic conditions. After filling of columns with pumice, unfiltered water from the river Elbe was circulated for a minimum of one month, and replaced by fresh river water every week. During the following experiments the water was replaced with filtered river water (glass fibre filter of 0.5mm) every 6 to 8 days. The decrease in the volume of water due to sampling was corrected for by calculating relative contact times in the filter. For each test filter, experiments were conducted on a control sample which was un-pumped and maintained in an open bottle under the same conditions. The samples were analysed by using HPLC/DAD (DAD L- 4500, Merck) using a C-18-column (ABZ+Plus, Supelco). The half life test compound 2, 4, 6 trichloroaniline is observed to be 19 hrs and the mean biodegradation rate constant was 0.036/h. On the basis of this half life value it can be concluded that test chemical is not persistent in river water with sediments.

Description of key information

Test filter experiments were carried out by circulating water through a glass column (diameter: 42mm, height:90 mm) filled with pumice .The experiments were carried out in darkness at a temperature of 20oC in aerobic conditions. After filling of columns with pumice, unfiltered water from the river Elbe was circulated for a minimum of one month, and replaced by fresh river water every week. During the following experiments the water was replaced with filtered river water (glass fibre filter of 0.5mm) every 6 to 8 days. The decrease in the volume of water due to sampling was corrected for by calculating relative contact times in the filter. For each test filter, experiments were conducted on a control sample which was un-pumped and maintained in an open bottle under the same conditions. The samples were analysed by using HPLC/DAD (DAD L- 4500, Merck) using a C-18-column (ABZ+Plus, Supelco). The half life test compound 2, 4, 6 trichloroaniline is observed to be 19 hrs and the mean biodegradation rate constant was 0.036/h. On the basis of this half life value it can be concluded that test chemical is not persistent in river water with sediments.

Key value for chemical safety assessment

Additional information

Two different experimental studies were reviewed from different journals to determine half life of degradation of test chemical in water as well as sediments results of both the studies are summarized below.

 

The first study was reviewed from Water Research Journal (2001)in this study the Test filter experiments were carried out by circulating water through a glass column (diameter: 42mm, height:90 mm) filled with pumice .The experiments were carried out in darkness at a temperature of 20oC in aerobic conditions. After filling of columns with pumice, unfiltered water from the river Elbe was circulated for a minimum of one month, and replaced by fresh river water every week. During the following experiments the water was replaced with filtered river water (glass fibre filter of 0.5mm) every 6 to 8 days. The decrease in the volume of water due to sampling was corrected for by calculating relative contact times in the filter. For each test filter, experiments were conducted on a control sample which was un-pumped and maintained in an open bottle under the same conditions. The samples were analysed by using HPLC/DAD (DAD L- 4500, Merck) using a C-18-column (ABZ+Plus, Supelco). The half life test compound 2, 4, 6 trichloroaniline is observed to be 19 hrs and the mean biodegradation rate constant was 0.036/h. On the basis of this half life value it can be concluded that test chemical is not persistent in river water with sediments.

 

Next experimental study was reviewed from journal Environmental Toxicology and Chemistry (1992) in this study an experiment was performed to determine half life of degradation of test chemical 2,4,6-trichloroaniline in anaerobic condition in this experiment the Sediment-water slurries were collected from Loosdrechtse Plassen eutrophic pond and slow-moving streams in The Netherlands in this organic carbon content was 33% and pH was 6.5 . The characteristic parameters of the sediment-water systems are given below. Samples were taken by scraping off the top 5 to 10 cm of the sediment and collecting it in glass jars. The jars were completely filled with a mixture of sediment and water and closed below the water surface with an aluminum screw-cap containing a rubber stopper. The jars were incubated for at least one week before substrate addition to ensure anaerobic conditions.

The rate constant of the initial transformation process obtained was -5.47 per minutes. The half life of test substance 2, 4, 6-trichloroaniline observed was 143 days under water-sediment system in anaerobic condition, indicating that the substance is persistent in water-sediment system.

On the basis of result of first study the half life of degradation of test chemical 2, 4, 6 trichloroaniline is observed to be 19 hrs in aerobic condition and in another study it was 143 days this higher number of days is may be because study was performed in anaerobic condition. By considering half life value in aerobic condition it can be concluded that test chemical is not persistent.