Chromium (III) oxide

Toxicity to soil microorganisms

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

Test material information

1

Reference substance name:

Chromium trichloride

EC Number:

233-038-3

EC Name:

Chromium trichloride

Cas Number:

10025-73-7

Molecular formula:

Cl3Cr

IUPAC Name:

Chromium chloride

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 concentrations

Effect concentrations 1

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)

Effect concentrations 2

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)

Effect concentrations 3

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)

Effect concentrations 4

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.