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Ecotoxicological information

Toxicity to soil microorganisms

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Administrative data

Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: See 'Remarks'
Remarks:
The study is not considered reliable due to insufficient documentation and methodological deficiencies: No analytical confirmation of test concentrations, test temperature and pH in soil during test, absolute values (respiration) not reported. In addition, severe soil acidification was observed at the end of the experiment and soil respiration in control soils was unstable during long-term incubation (>70w), pointing to a depletion of the soil carbon source.

Data source

Reference
Reference Type:
publication
Title:
Short-term and long-term effects of cadmium, chromium, copper, nickel, lead and zinc on soil microbial respiration in relation to abiotic soil factors
Author:
Doelman, P. and Haanstra, L.
Year:
1984
Bibliographic source:
Plant and Soil 79, 317-327 (1984)

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study investigated the influence of heavy metals including chromium on soil microbial respiration in five different soil types. After 2, 4, 8 and 70 weeks, soil respiration was assessed.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed

Sampling and analysis

Analytical monitoring:
no

Test substrate

Details on preparation and application of test substrate:
Concentrations of 55, 150, 400, 1000, 3000 and 8000 mg chromium/kg added to the respective soils (added as finely ground chloride salt)

Results and discussion

Effect concentrationsopen allclose all
Duration:
43 wk
Dose descriptor:
NOEC
Remarks:
sandy loam soil
Effect conc.:
150 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Cr(III)
Basis for effect:
respiration rate
Remarks on result:
other:
Remarks:
Derived in ERA2008 (Environmental Risk Assessment Report Metallic Chromium and trivalent chromium compounds)
Duration:
90 wk
Dose descriptor:
EC10
Remarks:
silty loam soil
Effect conc.:
262.7 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Cr(III)
Basis for effect:
respiration rate
Remarks on result:
other:
Remarks:
Derived in ERA2008 (Environmental Risk Assessment Report Metallic Chromium and trivalent chromium compounds)
Duration:
80 wk
Dose descriptor:
EC10
Remarks:
clay
Effect conc.:
507 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Cr(III)
Basis for effect:
respiration rate
Remarks on result:
other:
Remarks:
Derived in ERA2008 (Environmental Risk Assessment Report Metallic Chromium and trivalent chromium compounds)
Duration:
82 wk
Dose descriptor:
EC10
Remarks:
sandy peat
Effect conc.:
531.4 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
Cr(III)
Basis for effect:
respiration rate
Remarks on result:
other:
Remarks:
Derived in ERA2008 (Environmental Risk Assessment Report Metallic Chromium and trivalent chromium compounds)
Details on results:
The original publication only reported the reduction in soil respiration for the individual soils and chromium concentrations. According to the Environmental Risk Assessment Report on metallic chromium and trivalent chromium compounds (2008), the abovementioned NOEC and EC10 values were calculated.

Data available are for the respective soils are presented below (please also refer to table 2-6):
Sand: No clear dose-relation. No data presented for 150-400 mg/kg treatments. Significant effects observed at the 1000 mg Cr(III)/kg treatment after 2 (-23%), 4 (-45%) and 8 weeks (-57%)
Sandy loam: Significant effects at the 150 mg Cr(III)/kg treatment after 2 (-26%), 4 (-29%) and 8 weeks (-32%).
Silty loam: Significant effects observed at the 1000 mg Cr(III)/kg treatment after 2 (-15%), 4 (-46%) and 8 weeks (-58%), however no clear dose-response at higher treatments was observed. No data presented for 150-400 mg/kg treatments
Clay: Significant effects observed at the 1000 mg Cr(III)/kg treatment after 2 (-48%), 4 (-36%) and 8 weeks (-32%), however no data presented for 150-400 mg/kg treatments.
Sandy peat: Significant effects observed at the 1000 mg Cr(III)/kg treatment after 2 (-32%), 4 (-41%) and 8 weeks (-45%), however no data presented for 150-400 mg/kg treatments.

For risk assessment, values derived from long-term incubation cannot be considered reliable due to (presumably) depletion of the carbon source as indicated by significantly reduced respiration in control soils and elevated pH at the end of the experiment. In addition, the dataset does not present data for treatments ranging from 150-400 mg Cr(III) for all soils. Data available are for the respective soils are presented below (please also refer to table 2-6).

Any other information on results incl. tables

pH measurements:

Soil pH remained within 1 unit range during the experiments except for treatments with 3000 and 8000 µg Cr/g where pH values changed significantly: sandy loam (3.4 and 2.6), clay (3.8 and 3.1), sandy peat (3.7 and 2.8) and sandy soil (5.8 to 5.5)

Respiration rates:

Respiration rates of control soils were stable within the first 8 weeks of the experiment, however showed a sharp decline after >70 weeks for all soils exept the "silty loam" soil type (see table 1). The percentage reduction of soil respiration for the five different soils is summarized in tables 2 -6.

Table 1: Respiration rates (µL CO2 * 100g-1 * 24 h-1) of the control soils

 

Weeks

 

Soiltype

2

4

8

70

Sandy

874±40

691±11

504±30

371±12

Sandyloam

1,248±118

1,187±93

1,255±146

555±22

Siltyloam

1,353±95

579±42

590±56

457±14

Clay

Sandypeat

 -

2,458±65

695±50

2,285±50

695±67

2,085±57

434±14

1,177±22

Table 2: Effects of chromium on the rate of soil respiration in the soil type "sand" (expressed as percentage of untreated soil)

Cr (mg/kg) 2w 4w 8w 70w
0 100 100 100 100
150 - - - 101a
400 - - - 83b
1000 77 55 43 107ac
3000 66 60 44 82b
8000 165 124 88 115c

Table 3: Effects of chromium on the rate of soil respiration in the soil type "sandy loam" (expressed as percentage of untreated soil)

Cr (mg/kg) 2w 4w 8w 43w
0 100 100 100 100
150 74 71 68 99a
400 49 98 79 52b
1000 36 33 24 55b
3000 38 34 37 53b
8000 22 29 18 60b

Table 4: Effects of chromium on the rate of soil respiration in the soil type "silty loam" (expressed as percentage of untreated soil)

Cr (mg/kg) 2w 4w 8w 90w
0 100 100 100 100
150 - - - 105a
400 - - - 80b
1000 85 54 42 75bc
3000 118 116 67 70c
8000 139 232 120 -

Table 5: Effects of chromium on the rate of soil respiration in the soil type "clay" (expressed as percentage of untreated soil)

Cr (mg/kg) 4w 8w 80w
0 100 100 100
150 - - -
400 - - 124
1000 52 64 68a
3000 23 31 54a
8000 18 39 60a

Table 6: Effects of chromium on the rate of soil respiration in the soil type "sandy peat" (expressed as percentage of untreated soil)

Cr (mg/kg) 2w 4w 8w 82w
0 100 100 100 100
150 - - - 84b
400 - - - 89b
1000 68 59 55 98a
3000 49 42 34 77
8000 55 55 34 65

Applicant's summary and conclusion

Validity criteria fulfilled:
no
Conclusions:
The study investigated the influence of heavy metals including chromium(III) on soil microbial respiration in five different soil types after 2, 4, 8 and 70 weeks. Significant effects on microbial respiration were observed in sandy loam at the 150 mg Cr(III)/kg treatment after 2 (-26%), 4 (-29%) and 8 weeks (-32%). However, those values need to be considered with caution due to (presumably) depletion of the carbon source as indicated by significantly reduced respiration in control soils and elevated pH at the end of the experiment. In addition, the dataset does not present data for treatments ranging from 150-400 mg Cr(III) and no clear dose-response was observed for all soils.