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Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03 May - 31 May 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)
Version / remarks:
2000
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Sächsisches Staatsministerium für Umwelt und Landwirtschaft, Dresden, Germany
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: The test item was grated to a fine powder using a greater, after cooling in a freezer for 2 h at ≤ -18 °C. Since the test item was not soluble in water, an exact weighed amount of the test item was thoroughly mixed with quartz sand (= stock mixture). Subsequently the obtained stock mixture was stepwise diluted with quartz sand to prepare further test item mixtures (serial dilution) containing the amount of test item which was required to adjust the test item concentration of the respective treatment group. Afterwards, the test item mixtures were thoroughly mixed with the soil by means of a hand stirrer. For an optimum distribution of the test item in the soil, the test item quartz sand mixture was applied at a ratio of about 10 g per kilogram soil dry weight.
Test organisms (inoculum):
soil
Total exposure duration:
28 d
Test temperature:
19.9 - 21.4 °C in a climatic room
Moisture:
17.39 - 18.58 g/100 g soil dw (equivalent to 44.83 - 47.89% of WHC)
Details on test conditions:
TEST SYSTEM
- Testing facility: Laboratory
- Test container (type, material, size): wide-mouth glass flasks (500 mL) with screw caps allowing for air exchange.
- Amount of soil: 200 g dry soil
- No. of replicates per concentration: 3
- No. of replicates per control: 3

SOIL INCUBATION
- Method: The incubation of the soil samples was performed as a series of individual and equal sub-samples of each treatment group.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Wassergut Canitz, Canitz, Germany; Field name: Schlag 34/3; Land owner: Wassergut Cranitz; GPS position: 12.694435960 degrees East, 51.403774567 degrees North; Batch: 1/2016; Removed on 12 Feb 2016
- History of site: Cultivation at soil removal (2016): Fallow-ground; pre-cultivation (2015): Fallow-ground
- Treatments with pesticides or fertilizers: No organic and inorganic fertilisers were used since 2003. Pesticides were last applied in 1990.
- Soil texture
- % sand: 54.6% (USDA), 52.3% (ISO 11277)
- % silt: 35.7% (USDA), 37.1% (ISO 11277)
- % clay: 9.7% (USDA), 10.6% (ISO 11277)
- Soil taxonomic classification: sandy loam (USDA), loamy sand (DIN 4220)
- Soil classification system: USDA and ISO 11277
- pH (in water): 6.0
- Initial nitrate concentration for nitrogen transformation test (mg nitrate/kg dry weight): 2.12 mg/100 g soil dw
- Maximum water holding capacity (in % dry weigth): 38.80 g/100 g soil dw
- Cation exchange capacity: 8.0 cmol+/kg soil dw
- Pretreatment of soil: Soil was dried and sieved (at room temperature) 01 Dec - 07 Dec 2015
- Storage (condition, duration): Stored at 4 °C from 07 Dec - 29 Dec 2015; Soil conditioning (under test conditions): 29 Dec - 06 Jan 2016
- Initial microbial biomass as % of total organic C: 2.05 % of Corg

EFFECT PARAMETERS MEASURED
- Soil samples (10 g soil dw per replicate) were taken at intervals of 3 hours, 7, 14 and 28 days after application and the NH4-N-, NO3-N- and NO2-N-contents were determined.

VEHICLE CONTROL PERFORMED: no (not applicable)
Nominal and measured concentrations:
Nominal: control, 10, 32, 100, 320, 1000 mg/kg soil dw
Test concentrations related to a soil depth of 5 cm and a soil density of 1.5 g/cm³.
Reference substance (positive control):
yes
Remarks:
Dinoterb (purity: 98.0 % ± 0.5 analysed)
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
>= 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
nitrate formation rate
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: 6.80 mg/kg soil dw: 12.8% deviation from control; 16.00 mg/kg soil dw: 28.6% deviation from control; 27.00 mg/kg soil dw: 40.9% deviation from control
Reported statistics and error estimates:
Shapiro-Wilk’s test and Levene’s test were used, respectively, to test the data for normality and homogeneity of variance. As the data were normally distributed and variance homogeneous, a parametric multiple comparison test for homogenous variances (Dunnett-t-test) was performed. The Dunnett-t-test compares treatment means against a single control mean.

Table 2: NO3-N-contents – interval determination

Interval

Treatment

group

Repl.

Measured values sampling day 28 - Measured values sampling day 0

Mean

value

SD

CV [%]

mg NO3-N/kg soil dw

Deviation [%] in transformation rate from control

[mg NO3-N/100 g soil dw]

0 - 28

Control

1

2

3

5.53

 

 

 

 

 

5.46

 

 

 

 

 

5.93

5.64

0.25

4.5

56.40

 -

 

Test item

10 mg/kg

1

2

3

5.36

 

 

 

 

 

5.49

 

 

 

 

 

5.64

5.50

0.14

2.5

54.97

-2.5

 

Test item

32 mg/kg

1

2

3

5.49

 

 

 

 

 

5.83

 

 

 

 

 

5.43

5.58

0.22

3.9

55.83

-1.0

 

Test item

100 mg/kg

1

2

3

5.64

 

 

 

 

 

5.34

 

 

 

 

 

5.36

5.45

0.17

3.1

54.47

-3.4

 

Test item

320 mg/kg

1

2

3

5.60

 

 

 

 

 

5.34

 

 

 

 

 

6.09

5.68

0.38

6.7

56.77

+0.7

 

Test item

1000 mg/kg

1

2

3

5.91

 

 

 

 

 

5.89

 

 

 

 

 

6.47

6.09

0.33

5.4

60.90

+8.0

SD = Standard Deviation

CV [%] = Coefficient of Variation

Repl. = Replicate

soil d.w. = soil dry weight

Validity criteria fulfilled:
yes

Description of key information

Experimental result: NOEC (28 d) of ≥ 1000 mg/kg soil dw; EC50 (28 d) of > 1000 mg/kg soil dw (OECD 216)

Key value for chemical safety assessment

Additional information

One experimental study is available investigating the effects of UMA 121 on the nitrogen transformation rate of soil microorganisms in natural soil. The study was performed according to OECD 216 (GLP) as a dose-response study with five concentrations. Since the test substance is a solid resin it was finely ground to a very fine powder and directly mixed with the soil to obtain the desired test concentrations. The soil samples were incubated at 19.9 - 21.4 °C for 28 d. During exposure, soil samples (10 g soil dw per replicate) were taken at intervals of 3 h, 7, 14 and 28 days and the NH4-N-, NO3-N- and NO2-N-contents were determined. No effects on the nitrogen transformation of soil microorganisms was recorded after 28 d resulting in a NOEC (28 d) of ≥ 1000 mg/kg soil dw and an EC50 (28 d) of > 1000 mg/kg soil dw.