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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Reference
Endpoint:
biodegradation in water and sediment: simulation testing, other
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)
Deviations:
yes
Remarks:
guideline not cited, no in depth reporting, results comparable to guideline test
Principles of method if other than guideline:
Surface water samples were incubated with 5 different guanidinium concentrations (added as 64% guanidinium chloride) and 1µCi carbon-14 guanidinium. Percentaged of guanidinium carbon converted to carbon dioxide were determined from levels of trapped radioactivity in each sample during up to 90 days.
GLP compliance:
not specified
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on source and properties of surface water:
surface water samples obtained from two streams in the vicinity of a nitroguanidine pilot production facility (Hansen and Kill Creek) and several stream (Carroll Creek) and river (Monocacy) sites in the vicinity of Frederick, USA
Duration of test (contact time):
< 90 d
Initial conc.:
0.001 mg/L
Based on:
other: Guanidinium
Initial conc.:
0.01 mg/L
Based on:
other: Guanidinium
Initial conc.:
0.1 mg/L
Based on:
other: Guanidinium
Initial conc.:
1 mg/L
Based on:
other: Guanidinium
Initial conc.:
10 mg/L
Based on:
other: Guanidiniumø
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Volume of test solution/treatment: 250ml water
- Composition of medium: 0.2% potassium phosphate, pH7
- Additional substrate: 17mg/L arginine
- Test temperature: 25°C
- Aeration of dilution water: agitation
- Suspended solids concentration: 20mg/L guanidine nitrate
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: flask
- Method used to create aerobic conditions: agitation


CONTROL
- Abiotic sterile control: autoclaved water

Key result
% Degr.:
9.9
Parameter:
radiochem. meas.
Sampling time:
93 d
Remarks on result:
other: 0.0005 mg/l
Key result
% Degr.:
5.3
Parameter:
radiochem. meas.
Sampling time:
93 d
Remarks on result:
other: 0.01 mg/l
Key result
% Degr.:
77
Parameter:
radiochem. meas.
Sampling time:
93 d
Remarks on result:
other: 0.10 mg/l
Key result
% Degr.:
80
Parameter:
radiochem. meas.
Sampling time:
75 d
Remarks on result:
other: 1.0 mg/l
Key result
% Degr.:
85
Parameter:
radiochem. meas.
Sampling time:
75 d
Remarks on result:
other: 10 mg/l
Key result
Compartment:
water
DT50:
8 d
Remarks on result:
other: Winter Carroll Creek (west) after 52 d lag
Key result
Compartment:
water
DT50:
3 d
Remarks on result:
other: Winter Carroll Cree (central) after 28 d lag
Key result
Compartment:
water
DT50:
3 d
Remarks on result:
other: Winter Monocacy (north) after 22 d lag
Key result
Compartment:
water
DT50:
4 d
Remarks on result:
other: Winter Monocacy (south) after 20 d lag
Key result
Compartment:
water
DT50:
7.5 d
Remarks on result:
other: Summer Carroll Creek (central) after 50 d lag
Key result
Compartment:
water
DT50:
3 d
Remarks on result:
other: Summer Monocacy River (south) after 40 d lag
Key result
Compartment:
water
DT50:
4.5 d
Remarks on result:
other: Winter Hansen Creek after 11 d lag
Key result
Compartment:
water
DT50:
5 d
Remarks on result:
other: Winter Kill Creek after 16 d lag
Transformation products:
yes
No.:
#1
Evaporation of parent compound:
no
Validity criteria fulfilled:
not applicable
Conclusions:
Guanidine chloride is shown to be biodegraded in environmental water.
Executive summary:

Guanidine chloride is shown to be biodegraded in environmental water.

For Guanidine chloride, levels of carbon dioxide production after 1 and 10 days were less than 1 and 5% respectively for all of the concentrations tested and did not exceed their initial rates during that period. At the three highest concentrations (0.1 - 10 mg Guanidinium/l), inflections in carbon dioxide production occurred with continued incubation such that by the end of the experiment 85, 80, and 77% respectively of the guanidinium carbon was converted to carbon dioxide. Similar extensive mineralization did not occur at or below 0.01 mg/L and developed more slowly at 0.1 mg/L than at the two higher concentrations. Mineralization patterns for guanidinium carbon were reproducible in surface water from a second site (Carroll Creek), Thus, the development of the microbial populations capable of enhanced guanidinium mineralization is related to the concentration of the cation. At higher concentrations, a biodegrading population could well develop that would ultimately effect the persistence of the cation. However, both from direct observations in surface water samples (other experiments in the publication) and from the evaluation of an enriched laboratory population, the development of such a population as well as its degradation of guanidinium would likely be slow.

Degradation tests with 8 river water samples from different locations showed a mean degradation half life for guanidine of 5.25 d at 25°C after a mean lag phase of 30 d.

Description of key information

Guanidine chloride is shown to be biodegraded in environmental water.

Key value for chemical safety assessment

Half-life in freshwater:
5.25 d
at the temperature of:
25 °C

Additional information

The development of the microbial populations capable of enhanced guanidinium mineralization is related to the concentration of the cation. At the three highest concentrations (0.1 - 10 mg/l), a biodegrading population developed that ultimately effected the persistence of the cation. Mineralization occurred also at 3 guanidinium concentrations tested from 0.0005 - 0.01 mg/l but not with a similar extensive mineralization rate as at 0.1 - 10 mg/ Guanidinium /L and mineralization rate developed more slowly as at 0.1 mg/L.

Both from direct observations in surface water samples (other experiments in the publication) and from the evaluation of an enriched laboratory population, the development of such a population as well as its degradation of guanidinium would likely be slow.

Degradation tests with 8 river water samples from different locations showed a mean degradation half life for guanidine of 5.25 d at 25°C after a mean lag phase of 30 d.