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Toxicity to soil microorganisms

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Endpoint:
toxicity to soil microorganisms
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
The available identification data for the Target and the Source substance support the read-across hypothesis. Adequate, reliable and available scientific information indicate that the Target and Source substance have, or are very likely to have, similar (eco)toxicological properties. There are no indications that constituents other than those identified for the substances or impurities may influence the validity of the read-across. There is no evidence that additional toxicological mechanisms, other than those identified in the read-across hypothesis, may be acting or have an adverse effect on the validity of the read-across.
Reason / purpose for cross-reference:
read-across source
Vehicle:
no
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
10 g/kg soil dw
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
respiration rate
Remarks on result:
other: respiration was slightly activated by ABS
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
10 g/kg soil dw
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Remarks on result:
other: nitrate formation was slightly activated by ABS
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
see the following Tables
Validity criteria fulfilled:
yes
Conclusions:
Slags, ferrous metal, blast furnace (air-cooled – ABS) had no relevant on the activity of the soil microflora even in the highest concentration tested (10 g/kg) for 28 d. The activity of the soil microflora was negatively influenced temporarily (only respiration rates at time t0) by the test item but was slightly higher after 28 days. Concerning the nitrogen metabolism the test item served as a fertilizer.
Executive summary:

To test the effects of slags, ferrous metal, blast furnace (air-cooled – ABS) on the soil microflora as an indicator for conservation of soil fertility, the metabolic activity of microbial biomass and its nitrogen conversion potential were determined. The tests were performed according to C.22 (Soil Microorganisms: Carbon Transformation Test)(identical to OECD-Guideline No. 217) andC.21 (Soil Microorganisms: Nitrogen Transformation Test) of the EU-Regulation 440/2008 (identical to OECD-Guideline No. 216).The metabolic activity of the microbial biomass was influenced only temporarily by the slag in the acclimatisation phase. The respiratory activity (carbon transformation test) in the soil mixtures treated with 10 g test item / kg of soil (dry matter) was negatively affected only at the start of the incubation period t0 (28% reduction). At the later time points, the differences between slag-incubated and control soils were less than ± 25 %. After 28 d, the microbial respirationof the soil was slightly increased in the treatment with 10 g/kg soil dry matter in comparison to the controls.

The nitrogen conversion (ammonification and nitrification) of lucerne meal (alfalfa) which was added to the soil was not negatively influenced by the test item applied at a dose of 10 g / kg (dry matter). In general, the deviations of the NO3-- and NO2--nitrogen values of the treated samples from the untreated ones were <25%. In regard to nitrogen metabolism, ABS served as a fertilizer.

Slags, ferrous metal, blast furnace (air-cooled – ABS) had no relevant on the activity of the soil microflora even in the highest concentration tested (10 g/kg) for 28 d.

Endpoint:
toxicity to soil microorganisms
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
The available identification data for the Target and the Source substance support the read-across hypothesis. Adequate, reliable and available scientific information indicate that the Target and Source substance have, or are very likely to have, similar (eco)toxicological properties. There are no indications that constituents other than those identified for the substances or impurities may influence the validity of the read-across. There is no evidence that additional toxicological mechanisms, other than those identified in the read-across hypothesis, may be acting or have an adverse effect on the validity of the read-across.
Reason / purpose for cross-reference:
read-across source
GLP compliance:
not specified
Key result
Duration:
780 wk
Dose descriptor:
NOEC
Effect conc.:
> 1 300 kg/ha
Nominal / measured:
estimated
Conc. based on:
test mat.
Remarks:
CaO calculated from the CaCO3 applied (e.g. pH control)
Basis for effect:
respiration rate
Remarks on result:
other: Respiration rate was increased at a fertilization rate of 1300 kg CaO/ha x year by approximately 40 % in comparison to control fields.
Key result
Duration:
780 wk
Dose descriptor:
NOEC
Effect conc.:
> 13 000 kg/ha
Nominal / measured:
estimated
Conc. based on:
test mat.
Remarks:
ABS
Basis for effect:
respiration rate
Remarks on result:
other: CaO assumed to be 10 % for effect level estimate. Respiration rate was increased by a fertilization rate of 1300 kg CaO/ha x year by approximately 17 % in comparison to control fields without fertilization.
Validity criteria fulfilled:
not applicable
Remarks:
review on field study
Conclusions:
Fertilization with slags improves the yield of agricultural crops. Although the Cr levels in the soil may increase due to application of slags, the ferrous slags ABS (slags, ferrous metal, blast furnace, air-cooled) did not affect the microbial respiration and the cellulose degradation potential of soils.
Executive summary:

To assess the applicability of slags as agricultural fertilizers in regard to soil microorganisms, agricultural research done at the Sommerland Agricultural Research Station was reviewed. The metabolic potential of soil microorganisms had been measured as respiration rate and cellulose degradation. The chromium accumulation in soils in dependence of different fertilization regimes (control, lime, ABS other slags) was monitored for 15 years. Soil contained approximately 50 mg Cr(total)/kg soil in controls and fields fertilized with lime or ABS.

The agricultural yields was highest in slag treated fields (approximately 5 % above controls), The soil respiration in controls was 420 mg CO2/kg soil. It was highest in lime-treated fields (580 mg CO2/kg soil), and 490 mg CO2/kg soil in ABS-treated fields. Microbial cellulose degradation was lowest in control soils (1.4 mg/cm2) and highest in the slags: ABS 2 mg/cm2.

The ferrous slags ABS (slags, ferrous metal, blast furnace, air-cooled) did not inhibit the microbial respiration and cellulose degradation potential of soils.

Description of key information

Slags, ferrous metal, blast furnace (air-cooled – ABS) had no relevant on the activity of the soil microflora even in the highest concentration tested (10 g/kg) for 28 d. The activity of the soil microflora was negatively influenced temporarily (only respiration rates at time t0) by the test item but was slightly higher after 28 days. Concerning the nitrogen metabolism the test item served as a fertilizer.

Fertilization with slags improves the yield of agricultural crops. Although the Cr levels in the soil may increase due to application of slags, the ferrous slags ABS (slags, ferrous metal, blast furnace, air-cooled) did not affect the microbial respiration and the cellulose degradation potential of soils.

Ferrous slags are not inhibitory to key metabolic activities of soil microorganisms.

Key value for chemical safety assessment

Long-term EC10 or NOEC for soil microorganisms:
10 000 mg/kg soil dw

Additional information

It was shown by laboratory and field studies that ferrous slags are not inhibitory to key metabolic activities of soil microorganisms i.e. respiration. Nitrogen metabolism and cellulose degradation were also shown not to be inhibited, but even slightly activated.

Laboratory guideline study

To test the effects of slags, ferrous metal, blast furnace (air-cooled – ABS) on the soil microflora as an indicator for conservation of soil fertility, the metabolic activity of microbial biomass and its nitrogen conversion potential were determined. The tests were performed according to C.22 (Soil Microorganisms: Carbon Transformation Test)(identical to OECD-Guideline No. 217) and C.21 (Soil Microorganisms: Nitrogen Transformation Test) of the EU-Regulation440/2008 (identical to OECD-Guideline 216). The metabolic activity of the microbial biomass was influenced only temporarily by the slag in the acclimatisation phase. The respiratory activity (carbon transformation test) in the soil mixtures treated with 10 g test item / kg of soil (dry matter) was negatively affected only at the start of the incubation period t0 (28% reduction). At the later time points, the differences between slag-incubated and control soils were less than ± 25 %. After 28 d, the microbial respiration of the soil was slightly increased in the treatment with 10 g/kg soil dry matter in comparison to the controls.

The nitrogen conversion (ammonification and nitrification) of lucerne meal (alfalfa) which was added to the soil, was not negatively influenced by the slags applied at a dose of 10 g / kg (dry matter). In general, the deviations of the NO3-- and NO2--nitrogen values of the treated samples from the untreated ones were <25%. In regard to nitrogen metabolism, ABS served as a fertilizer.

Slags, ferrous metal, blast furnace (air-cooled – ABS) had no relevant effect on the activity of the soil microflora even in the highest concentration tested (10 g/kg) for 28 d (SGS 2010).

Extended laboratory study

To evaluate the effects of steelmaking slags (SMS) on soil microorganisms, in laboratory experiments SMS was added to oxisol soil at concentrations of up to 21.2 t/ha. The pH varied between 4.8 (controls) and 7.4 (SMS, 21.2 t/ha, no pH controls done). Dry matter production, pH and metal uptake into Sorghum bicolor plants raised in parallel experiments in pot were plotted against each other and a correlation analysis was performed.

The dry matter production of Sorghum bicolor was highest when the concentration of SMS added to oxisol was approximately 9.6 t/ha. Uptake of Ca, Mg, Fe, Mn and Zn shows a flat maximum at 7 -10 t/ha in regard to the concentration of slag in the oxisol (controls not reported). The uptake of Cu was independent of the slag concentration whereas the Ni content was low but increased with increasing concentration of slag in the range tested, and in parallel to the pH.

Minimum of microbial respiration occured at a SMS concentration of approximately 10 t/ha. This minimum is explained by the authors by pH controlled availability of metal ions. Although this hypothesis cannot be verified, it is apparent that the inhibition of microbial respiration is not caused by high slag concentration in the soil, as the microbial respiration recovered at the highest slag concentration tested (Costa et al. 1992).

Field studies

To assess the applicability of slags as agricultural fertilizers in regard to soil microorganims, agricultural research done at the Sommerland Agricultural Research Station was reviewed. The metabolic potential of soil microorganisms had been measured as respiration rate and cellulose degradation with the ferrous slags ABS

(slags, ferrous metal, blast furnace, air-cooled) and BOS (slags, steelmaking, converter).

The chromium accumulation in soils in dependence of different fertilization regimes (controls, lime, ABS, BOS) was monitored for 15 years. Soil contained approximately 50 mg Cr(total)/kg soil in controls and fields fertilized with lime or ABS, and approximately 65 mg/kg soil in fields fertilized with BOS.

The agricultural yields was highest in slag treated fields (approximately 5 % above controls), The soil respiration in controls was 420 mg CO2/kg soil. It was highest in lime-treated fields (580 mg CO2/kg soil), and 490 and 550 mg CO2/kg soil in ABS- and BOS-treated fields, respectively. Microbial cellulose degradation was lowest in control soils (1.4 mg/cm2) and highest in the slags: ABS 2 mg/cm2, and BOS 2.3 mg/cm2.

The ferrous slags ABS (slags, ferrous metal, blast furnace, air-cooled) and BOS (slags, steelmaking, converter) did not inhibit the microbial respiration and cellulose degradation potential of soils.