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Toxicity to soil microorganisms

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Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not specified
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Tests performed in accordance with recognised testing guidelines (although detailed methodology is not given). Results presented in summary only. No GLP, but peer reviewed. No purity reported.
Qualifier:
according to
Guideline:
other: Microbial basal respiration and substrate induced respiration (SIR) according to ISO 17155, potential nitrification (ammonium oxidation: ISO/DIS 15685)
Deviations:
not specified
GLP compliance:
not specified
Analytical monitoring:
yes
Vehicle:
yes
Test organisms (inoculum):
soil
Remarks:
No data
Moisture:
No data
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
respiration rate
Duration:
6 h
Dose descriptor:
EC50
Effect conc.:
2.2 - 17 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate

The results for the terrestrial tests based on nominal concentrations are presented in Table 6.

Validity criteria fulfilled:
not specified
Conclusions:
The EC50 values for respiration in Sandy, Silty & Loamy soils are > 1000 mg/kg.
The EC50 values for potential nitrification in Sandy, Silty & Loamy soils are 11, 64 (57–72) and 156 (77–316) mg/kg respectively.
Executive summary:

In a Microbial basal respiration and substrate induced respiration (SIR) according to ISO 17155 and potential nitrification (ammonium oxidation: ISO/DIS 15685 the EC50 values were determined.

The EC50 values for respiration in Sandy, Silty & Loamy soils are > 1000 mg/kg.

The EC50 values for potential nitrification in Sandy, Silty & Loamy soils are 11, 64 (57–72) and 156 (77–316) mg/kg respectively.

Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not specified
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Not GLP, but peer reviewed. No purity reported. Test appears to have been well conducted and details of the methodology used have been well reported.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The influence of the test material on transformations in anoxic sediment cultures, during approximately 14 d incubations, was studied using acetylene inhibition and acetylene reduction techniques as measures of microbially mediated denitrification and dinitrogen fixation, respectively.
GLP compliance:
not specified
Analytical monitoring:
not specified
Vehicle:
yes
Test organisms (inoculum):
soil
Total exposure duration:
14 d
Moisture:
No data
Details on results:
The presence of the test material had no appreciable effect on microbially mediated fermentation, denitrification or on N fixation in sediment slurry. However, concentration dependent effects of the test material, either stimulatory or antagonistic, were observed in porewater. It seems likely that the bioavailability of Bu3Sn+ to the microorganisms which mediate N transformations is attenuated by paniculate matter and by microbial growth. Both of these processes concentrate the toxicant within the solid fraction of sediments and natural waters. There was no evidence from these trials to suggest that exposure of this diverse microbial population (in a sediment) to levels of the test material which have been reported for field contaminated sites would present any appreciable hazard to fermentation, denitrification or to N2 fixation. Moreover, denitrifiers rapidly developed resistance to the presence of high concentrations of the test material.
Validity criteria fulfilled:
not specified
Conclusions:
The test material had no appreciable effect on microbially mediated fermentation, denitrification or on N fixation in sediment slurry.
Executive summary:

The influence of the test material on transformations in anoxic sediment cultures, during approximately 14 d incubations, was studied using acetylene inhibition and acetylene reduction techniques as measures of microbially mediated denitrification and dinitrogen fixation, respectively. The accumulation of N2O, CO2 and C2H4 with time was modelled with a best-fit polynomial to detect statistically significant differences between treatments and with a three-segment continuous line model to assess lag times, rates of accumulation and rates of subsequent loss of these gases from the headspace. In sediment cultures, the presence of up to 100 mg/L of test material had a barely detectable influence on these transformations. However the analogous processes in porewater, prepared by centrifuging sediment slurry at 3000 × g for 30 min, were appreciably modified by the presence of > 1 mg/L of this toxicant. Although the two media were different in terms of their denitrifying potential and their fermenting capacity, dose related responses in the porewater were evident for both processes.

Description of key information

Key value for chemical safety assessment

Additional information

Supporting information is available for this endpoint:

- In the Hund-Rinke & Simon (2005) paper, a Microbial basal respiration and substrate induced respiration (SIR) was conducted according to ISO 17155 and potential nitrification (ammonium oxidation: ISO/DIS 15685 the EC50 values were determined.

The EC50 values for respiration in Sandy, Silty & Loamy soils are > 1000 mg/kg. The EC50 values for potential nitrification in Sandy, Silty & Loamy soils are 11, 64 (57–72) and 156 (77–316) mg/kg respectively. A reliability rating of 2 was assigned to this study, according to the criteria of Klimisch, 1997.

- In the Bergeron et al (1993) paper, the influence of the test material on transformations in anoxic sediment cultures, during approximately 14 d incubations, was studied using acetylene inhibition and acetylene reduction techniques as measures of microbially mediated denitrification and dinitrogen fixation, respectively. The test material had no appreciable effect on microbially mediated fermentation, denitrification or on N fixation in sediment slurry. A reliability rating of 2 was assigned to this study, according to the criteria of Klimisch, 1997.