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Ecotoxicological information

Toxicity to soil microorganisms

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Administrative data

Endpoint:
toxicity to soil microorganisms
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Meets generally accepted scientific standards, well documented and acceptable for assessment
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
other: study report with recalculated toxicity endpoints from authors
Title:
Unnamed
Year:
2007
Report Date:
2007

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Smolders E.,Buekers J.,Olivier I. and Mc Laughlin M.J. 2004. Soil properties affecting toxicity of zinc to soil microbial properties in laboratory-spiked and field-contaminated soils. Environmental Toxicology and Chemistry 23 n°11:2633-2640.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
not reported
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
The total Co concentrations of all spiked samples are determined by boiling aqua regia extraction

Test substrate

Vehicle:
no
Details on preparation and application of test substrate:
Soil samples were pre-incubated for 1 week at 20°C and at a moisture content equivalent to 70% of that at pF 2.0. Uncontaminated soils were then spiked with CoCl2 (50 mg Co ml-1) to seven concentrations (Table 2.3). Additional deionized water was added together with the spike solution to adjust the soil moisture content to pF 2.0. All soils were thoroughly mixed after amendments. Soil moisture in control samples was also raised to pF 2.0 with deionized water. Soils were left to equilibrate for another week at 20°C before starting the microbial assays. See table 2.1 below

Test organisms

Test organisms (inoculum):
soil

Study design

Total exposure duration:
7 d
Remarks:
The incubation time varied between 3 and 28 days among soils

Test conditions

Test temperature:
20 degrees celcius
Moisture:
pF 2.0
Details on test conditions:
Potential nitrification rate

Seven days after metal spiking, duplicate 100 g subsamples of each soil at each Co treatment are amended with 100 mg NH4-N kg-1 fresh soil using a stock solution containing 47 mg (NH4)2SO4 ml-1. The Potential Nitrification Rate (PNR, mg NO3-N kg-1 fresh soil day-1) is calculated from the linear increase of soil NO3-N during the period following the substrate addition. The soil nitrate is measured colorimetrically in a centrifuged soil extract (1M KCl, 10g subsample, L/S = 2.5, 2 h end-over-end shaking, n = 2). The PNR was calculated as the slope of the regression of soil nitrate concentration against time. This test is most sensitive to Co in the initial period after NH4+ addition, i.e. as long as the substrate is still abundantly present. The nitrification rate typically increases with increasing soil pH. Therefore, the test duration must be restricted at high pH whereas the test must be long enough in acid soils to identify a significant increase in soil NO3-. The incubation time therefore varied between 3 and 28 days among soils. The incubation time was always identical for each soil sample within a dose-response study.
Glucose induced respiration

Nominal and measured concentrations:
See table 2.3 below
Reference substance (positive control):
no

Results and discussion

Effect concentrationsopen allclose all
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
33 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Athens soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 27-41
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
22 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Jyndevad soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 16-31
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
26 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Kasterlee soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 15-45
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
157 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Aluminusa soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 71-347
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
34 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Woburn soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 16-72
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
172 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Sidney soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 86-342
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
80 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Leuven soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 54-117
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
101 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Souli II soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 73-138
Duration:
7 d
Dose descriptor:
EC10
Effect conc.:
695 mg/kg soil dw
Nominal / measured:
meas. (not specified)
Conc. based on:
other: added Co on Brecy soil
Basis for effect:
other: potential nitrification rate
Remarks on result:
other: 95% CL: 451-1070
Details on results:
The PNR varied more than 10 fold among the ten unspiked soils. It can be inferred from this large variability that absolute reduction of nitrification by Co at a given threshold (e.g. EC50) is highly different among soils.
From these results, two factors affecting the PNR in the control soils can be identified : the pH (undetectable PNR in the most acid soil and the highest PNR in the less acid soil) and the land use (relatively small PNR in woodlands soils).
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
The data from the three bioassays are statistically examined through the application of a log-logistic dose-response model allowing description of hormesis effects (Schabenberger et al., 1999). In case the hormesis was not significant, the model was reduced to the classic log-logistic dose-response model (Doelman and Haanstra, 1989). The models were fitted to the data with the Marquardt method (SAS 8.02, SAS Institute Inc., Cary, NC, USA). The ‘dose’ in this model is the added Co (nominal addition for freshly spiked soils and background corrected measured concentration for leached or aged soils). The dose of the control soil is assumed to be a very small value (0.001 mg kg-1). The ED10, ED20 and ED50 values, expressed as added Co, are predicted from these curves. The EC10, EC20 and EC50 values expressed as ‘total Co’ are calculated from the sum of background and corresponding ED10, ED20 and ED50 values. The soil solution based ECx and EDx values were calculated similarly as total soil based values; the dose is the background corrected soil solution Co concentration and the dose in the control soil was attributed a very small value (1E-6 mg l-1).
No Observed Effect Concentrations (NOECs) are the largest Co concentration in the soil at which no significant adverse effects were observed compared to the control soil. Similarly, Lowest Observed Effect Concentrations (LOECs) are the lowest Co Concentration in the soil at which there is a significant adverse effect observed compared to the control soil. Both NOEC and LOEC values were determined by ANOVA (Duncan test). When the LOEC was equal to the smallest Co dose tested (= unbounded LOEC), no NOEC value is reported. No dose-response curves are fitted to the data when no statistical adverse effect is detected at the largest Co dose (= unbounded NOEC). The EDx values larger than the largest Co dose are considered as not reliable anymore and are omitted for further data analysis.
Correlations and simple linear regressions

Any other information on results incl. tables

According to REACH guidance Chapter R.10 (Table R.10 -1) EC10 values are used preferentially for PNEC derivation, therefore NOEC values are only presented as supporting information.

 Duration  Endpoint  Effect conc.  Nominal/measured  Conc. based on  Basis for effect
  7 d   NOEC  36 mg/kg soil dw  meas.   added Co on Athens soil   potential nitrification rate
  7 d   NOEC  20 mg/kg soil dw  meas.    added Co on Jyndevad soil   potential nitrification rate
  7 d  NOEC   20 mg/kg soil dw  meas.    added Co on Kasterlee soil   potential nitrification rate
  7 d   NOEC  80 mg/kg soil dw  meas.   added Co on Aluminusa soil   potential nitrification rate
  7 d  NOEC   20 mg/kg soil dw  meas.   added Co on Woburn soil   potential nitrification rate
  7 d   NOEC  320 mg/kg soil dw  meas.   added Co on Sidney soil   potential nitrification rate
  7 d   NOEC  40 mg/kg soil dw  meas.   added Co on Leuven soil  potential nitrification rate 
  7 d   NOEC  100 mg/kg soil dw  meas.   added Co on Souli II soil  potential nitrification rate 
  7 d   NOEC  800 mg/kg soil dw  meas.   added Co on Brecy soil   potential nitrification rate

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
EC10 values used for PNEC derivation range from 22-695 mg added Co/kg dw.
Executive summary:

not applicable