3,5-bis(difluoromethyl)-1H-pyrazole

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March 2019 - July 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test)

Version / remarks:

2000

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

3,5-bis(difluoromethyl)-1H-pyrazole

EC Number:

814-072-3

Cas Number:

77614-79-0

Molecular formula:

C5H4F4N2

IUPAC Name:

3,5-bis(difluoromethyl)-1H-pyrazole

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations:
- Sampling method: 10 g soil d.w. per replicate at 3 h, 7 d, 14 d and 28 d after application
- Sample storage conditions before analysis: Soil extracts stored deepfrozen prior to analysis at -20  5 °C

Test substrate

Vehicle:

yes

Remarks:

Quartz sand

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate: lucerne meal (C/N ration = 13.2 /1)


APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: Mixture of test substance with quartz sand. Mixture of the spiked sand and soil using a hand stirrer.

VEHICLE:
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Quartz sand
- Concentration of vehicle in test medium (stock solution and final test solution): 10 g / kg soil d.w.

Test organisms

Test organisms (inoculum):

soil

Study design

Total exposure duration:

28 d

Test conditions

Test temperature:

19.5 - 20.7 °C

Moisture:

15.94 - 16.78 g /100g soil d.w. equivalent to 45.77 - 48.17 % of WHC

Organic carbon content (% dry weight):

1.47

Nitrogen content (% dry weight):

0.14

Details on test conditions:

TEST SYSTEM
- Amount of soil: 200 soil d.w.
- No. of replicates per concentration: 3
- No. of replicates per control: 3


SOIL INCUBATION
- Method: series of individual subsamples

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Saxony, Germany ,12.694435960 degrees East, 51.403774567 degrees North
- Vegetation cover: fallow ground
- Treatments with fertilizers: not sinze 203
- Treatments with pesticides: not since 1990
- Depth of sampling: 20 cm
- Soil texture according to USDA
- % sand: 21.4
- % silt: 38.3
- % clay: 10.3
- Soil taxonomic classification: loam
- Soil classification system: USDA
- pH (in water): 6.2

- Maximum water holding capacity (in % dry weigth):34.83
- Cation exchange capacity (mmol/kg): 9.9
- Pretreatment of soil: drying and sieving (2mm) at room temperature
- Storage (condition, duration): 1.5 month at 4 °C
- Initial microbial biomass as % of total organic C: 2.44 %

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Soil samples (10 g soil d.w. 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

Nominal and measured concentrations:

0.01 and 0.1 mg test item / kg soil dry weight corresponding to 0.005 and 0.05 kg test item/ha

Reference substance (positive control):

yes

Remarks:

Dinoterb as internal standart for validation of test system (not inculded in guideline requirements)

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

28 d

Dose descriptor:

other: > 25 % Difference to control

Effect conc.:

> 0.1 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Effect concentrations 2

Duration:

28 d

Dose descriptor:

other: > 25 % Difference to control

Effect conc.:

> 0.01 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

nitrate formation rate

Details on results:

Differences from the control of +23.3 % (test concentration 0.01 mg test substance/kg soil dry weight) and +1.4 % (test concentration 0.1 mg test substance /kg soil dry weight) were measured at the end of the 28-day incubation period (time interval 14-28).

Any other information on results incl. tables

Table 1: Effects on nitrogen transformation in soil after treatment

Time interval (days)	Control	0.01 mg pure metabolite/kg soil dry weight equivalent to 0.005 kg pure metabolite/ha		0.1 mg pure metabolite/kg soil dry weight equivalent to 0.05 kg pure metabolite/ha
	Nitrate-N1)	Nitrate-N1)	% difference to control	Nitrate-N1)	% difference to control
0-7	3.66 ± 0.2	3.64 ± 0.1	-0.5n.s.	3.92 ± 0.52	+7.2n.s.
7-14	1.16 ± 0.16	0.6 ± 0.15	-47.7*s.	0.81 ± 0.15	-29.6n.s.
14-28	1.05 ± 0.21	1.3 ± 0.04	+23.3n.s.	1.07 ± 0.24	+1.4n.s.

1) Rate: Nitrate-N in mg/kg soil dry weight/time interval/day, mean of 3 replicates and standard deviation

n.s. = No statistically significant difference to the control (Student-t-test for homogeneous variances, 2-sided, p > 0.05)

*s. = statistically significantly different to control (Student-t-test for homogeneous variances, 2-sided, p ≤ 0.05)

Table 2: Validity criteria for OECD 216.

Criterion from the guideline	Outcome	Validity criterion fulfilled
The variation between replicate control samples should be less than ± 15%.	6.1 %	Yes

 

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Conclusions:

The test item caused no adverse effects (difference to control < 25 %, OECD 216) on the soil nitrogen transformation (expressed as NO3-N-production) at the end of the 28-day incubation period.