Registration Dossier

Ecotoxicological information

Toxicity to soil microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
toxicity to soil microorganisms
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well documented publication which meets basic scientific principles.
Principles of method if other than guideline:
Microbial biomass, measured as induced CO2 production from glucose ( (Anderson & Domsch 1978)), was measured in natural forest soils of different aluminum ion content (plant available aluminium extracted with 1M KCl, soil:solution=1:10), but otherwise similar chemical characteristics (pH approx. 3.2); samples of 8 sites were used.
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (inoculum):
soil
Total exposure duration:
6 d
Details on test conditions:
TEST SYSTEM
- Testing facility: Natural soils

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Tyrol, Austria
- History of site:
- Vegetation cover: spruce, pine and beech (forest soils)
- Depth of sampling: Samples taken from Ah horizon
- Soil taxonomic classification: podzol, semipodzol, podzolic brecksie
- Soil classification system: Tyrolean Soil Condition database
- pH (in water): 2.9 to 3.5
- Pretreatment of soil: sieved through 2 mm
- Storage (condition, duration): stored frozen at -20°C

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Microbial biomass, microbial respiration, CM-cellulase activity, N-mineralization
Reference substance (positive control):
no
Reported statistics and error estimates:
Mean results of three to six replicates were used (depending on particular experiment). According to the presence or absence of a normal distribution (Kolmogoroff-Smirnoff Test), regression analysis or rank of correlation (three levels of significance p<0.05, p<0.01 and p<0.001) were applied.
Partical correlations were used to clarify complex (triangle) connections. Stepwise variable selection procedure (using F-ratios) was applied as entry of variables into multiple regression models

Microbial biomass decreased with increasing available aluminum (KCl) concentration (regression analysis of 24 values - 3 replicates of 8 sites: r2=0.635, p<0.001), independent of pH (2.9 to 3.5). From about 3 mg C biomass/g DM/h at 0 µmol/g DM Al, the microbial biomass decreased to approximately 1 mg C biomass/g DM/h at 87 µmol/g DM Al. Illusory correlation between microbial biomass and aluminium concentration via pH and Mg concentration were excluded via partial correlation analysis. A multivariate model established that the Al concentration is alone responsible for 70% of the changes in microbial biomass.

Microbial respiration showed a slight, non-significant tendency to decrease with increasing available Al (KCl) concentration.

CM-Cellulase activity (representative of the C-Cycle) did not significantly correspond to an increased available Al (KCl) concentration.

The N-mineralization (representative of the N-Cycle) was negatively influenced by an increased available Al (KCl) concentration (p<0.01).

Endpoint:
toxicity to soil microorganisms
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well documented publication which meets basic scientific principles.
Principles of method if other than guideline:
Rhizobium leguminosarum bv. trifolii strains were streaked on agar plates. Colonies were streaked with and without 48h incubation at 25°C and colonies counted 72 hours after the respective streaking. The ratio between number of colonies streaked after 48 hours incubation and the number of colonies streaked without incubation is referred to as growth in terms of fold increase. A value of 1 means mere survival, a value >1 a colony increase.
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (inoculum):
other: Rhizobium leguminosarum bv. trifolii72
Total exposure duration:
72 h
Details on test conditions:
TEST SYSTEM
- Test container (type, material, size): 12 culture flasks
- No. of replicates per concentration: 3


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Colony growth inhibition
Reference substance (positive control):
no

Inhibition of cell growth (increase in cell number) by AlCl3 in solutions of pH 4.4. Little or no cell increases occcured at 2 µM AlCl3 with die-off of the inoculum at higher concentrations.

The toxicity of 1 µM AlCl3 increased with increasing pH (range 4.0 to 6.0) (an effect of pH on the cationic dye - methylene blue - was excluded). As explanation for the pH effect, increasing bacterial cell surface negativity with increasing pH or simplified agar plate conditions versus complex soil systems were discussed.

Endpoint:
toxicity to soil microorganisms
Data waiving:
other justification
Justification for data waiving:
other:

Description of key information

Key value for chemical safety assessment

Additional information

There are no studies available on soil microorganisms for the registered substance reaction mass of aluminium hydroxide and aluminium nitrate and aluminium sulphate.

Nevertheless, aluminium is the most abundant metallic element in the Earth's crust. Based on its ubiquitous occurrence the present natural background concentration far outweighs anthropogenic contributions of aluminium to the terrestrial environment. As detailed in the endpoint summary on terrestrial toxicity in general further toxicity testing on terrestrial organisms is considered unjustified and waiving based on exposure consideration is applied.

However, for reasons of completeness existing data on the terrestrial toxicity of aluminium are provided in addition and summerised here.

Illmer et al. (1995) studied the toxicity of aluminium to soil microorganisms, using an undefined microbial biomass, by following biomass, microbial respiration, CM-cellulase activity and N-mineralisation. Microbial biomass decreased with increasing available aluminum concentration, independent of pH (2.9 to 3.5). From about 3 mg C biomass/g DM/h at 0 µmol/g DM Al, the microbial biomass decreased to approximately 1 mg C biomass/g DM/h at 87 µmol/g DM Al. Microbial respiration showed a slight, non-significant tendency to decrease with increasing available Al concentration. CM-Cellulase activity (representative of the C-Cycle) did not significantly correspond to an increased available Al concentration. The N-mineralization (representative of the N-Cycle) was negatively influenced by an increased available Al concentration. Kinraide & Sweeney (2003) investigated Rhizobium leguminosarum bv. trifolii strains streaked on agar plates after addition of AlCl3. Colonies were streaked with and without 48h incubation at 25 °C and colonies counted 72 hours after the respective streaking. The ratio between number of colonies streaked after 48 hours incubation and the number of colonies streaked without incubation is referred to as growth in terms of fold increase. Inhibition of cell growth (increase in cell number) by AlCl3 in solutions was observed at pH 4.4. Little or no cell increases occurred at 2 µM AlCl3 with die-off of the inoculum at higher concentrations. The toxicity of 1 µM AlCl3 increased with increasing pH (range 4.0 to 6.0).