Chlorpyrifos

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

BBA Part VI, 1-1

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Substance ID: Dursban 4
Batch#: EK 890712542
Purity: 480 g/L of chlorpyrifos active isubstance

Analytical monitoring:

yes

Details on sampling:

The soils were sampled on January 16th, 1990 (soil 1) and February 2nd 1990 (soil 2) at a depth up to 20 cm. The soils were predried before sieving (≤ 4 mm) (soil 1: January 16th - January 22nd, 1990; 10°C; water content after predrying: 8.0 %; soil 2: February 5th - February 8th; 1990; 16°C; water content after predrying: 13.5%) and stored at room temperature (soil 1: February 8th, 1990; water content: 12.8%; soil 2: February 8th - February 13th 1990; water content: 13.5%). The soils arrived at the Fraunhofer-Institute on March 8th, 1990. They were sieved (≤ 2 mm), adjusted to 45% of the water holding capacity and stored at 20 ± 2°C until March 23rd. Weekly the water content was controlled and adjusted. Subsequently the soils were stored at 2 - 4°C and then at 20 ± 2°C for 2 - 4 days prior to use.

Vehicle:

yes

Remarks:

water

Details on preparation and application of test substrate:

AMENDMENT OF SOIL
- Type of organic substrate: For each sample a test vessel containing soil amended wlth glucose was prepared.

APPLICATION OF TEST SUBSTANCE TO SOIL
- Method: The test mixture was sprayed over the soil wlth a syringe and thoroughly mixed. The syringe was rinsed with distilled water, which was then spread over the soil surface and thoroughly mixed.

Test organisms (inoculum):

soil

Total exposure duration:

90 d

Test temperature:

20 ± 2°C

Moisture:

The water content of the soils was adjusted with distilled water to 50% of the maximum water holding capacity.

Details on test conditions:

TEST SYSTEM
- Testing facility: Fraunhofer institute for environmental chemistry and ecotoxicology
- Test container (type, material, size): The vessel were closed type and placed in a respirometer.
- Amount of soil: 2000g for measurement of short-term respiration and 900 g for nitrogen mineralization.
- No. of replicates per concentration: 3
- No. of replicates per control: 3
- No. of replicates per vehicle control: 3

SOIL INCUBATION
- Method: For measurement of short-term respiration: For each set-up test substance stock solution and distilled water were added to 2000 g soil, dry weight. The water content was adjusted to 50% of the maximum water holding capaclty. For Nitrogen mineralization: For each set-up 4.5 ml test substance stock solution and 4.5 g lucerne meal were added to 900 g soil, dry weight. With dlstilled water the water content was adjusted to 50% of the maximum water holding capaclty.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- History of site: Soil 1: 1988-1990: Fallow; Soil 2: 1988: cultivation of cabbage, 1989: Cultivation of sunflowers, 1990: No culture at the date of sampling.
- Treatments with pesticides or fertilizers: No fertilizer and no plant protection products were treated in both soils
- Depth of sampling: Soil 1 & 2: Upto 20 cm.
- Soil classification system: VDLUFA
- Code of the soil: Soil 1: Sp 120 (2.1); Soil 2: F 220 (2.2)
- pH (0.01M Calcium chloride): Soil 1: 5.9; Soil 2: 6.8
- Content of min nitrogen mg/100g soil: Soil 1: 7.26; Soil 2: 5.45
- Particle size distribution (%): Given under 'Any other information on materials and methods incl. tables"

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Measurement of short-term respiration: 14, 28, 56 and 90 days after treatment with test substance, samples (300 g fresh weight) was taken from soils for measurement of short-term repiration. After the addition of glucose (50% stock Solution; concentration in the test: 1 g glucose/100g SoiI, dry weight) the oxygen uptake was measured at 20°C, over a measuring period of about 20 hours. Additionally, at day 0 the activity of the controls was determined. The amount of oxygen consumed was calculated from the first 8 hours (soil 2) and from the first 10 hours (soil 1) of the measuring period.
Nitrogen mineralization: 0 (= 3 hours), 7, 14, 21, 28, 56 and 90 days after treatment with the plant protection product, samples were taken and frozen until the determination. Before the product and lucerne meal was applied, samples were taken for the determination of the initial mineral nitrogen content.

VEHICLE CONTROL PERFORMED: yes

Nominal and measured concentrations:

Nominal: 2 L/ha and 10L/ha

Reference substance (positive control):

yes

Remarks:

Aretit (6 L/ha and 15 L/ha)

Key result

Duration:

90 d

Remarks on result:

other: Test substance showed no significant deviations from untreated control in both soils neither for determination of short-term respiration nor for nitrogen mineralization.

Details on results:

Short term respiration:
Soil 1: In contrast to the reference substance which caused a decreased microbial respiration activity the test substance indicated no significant deviation as compared to the control.
Soil 2: Both concentrations of the test substance caused no significant effect on the microbial respiration activity. The reference substance decreased the respiration activity according to the applied concentration.
Nitrification mineralization:
Soil 1: In contrast to the reference substance which caused an inhibition of the transformation from ammonium to nitrate the test substance had no effect on the nitrogen mineralization. At all sampling times the content of soluble ammonium and nitrate in the soil with test substance and ln the control soils were nearly the same.
Soil 2: In contrast to the reference substance which caused a small inhibition of the transformation from ammonium to nitrate during the first 7 days of the incubation period the test substance had no significant effect on the nitrogen mineralization.

Conclusions:

Test substance did not affect short-term respiration and nitrogen mineralization in both soils tested at a concentration of 2L/ha and 10L/ha.

Executive summary:

The study was conducted according to BBA guidelines VI, 1-1 to determine the effect of test substance of soil microflora in two soils using the short-term respiration and nitrogen mineralization tests. Two concentrations of test substance were tested, maximum application rate 21/Ha and 5 x maximum application rate for 3 months.

Test substance was not found to significantly decrease microbial respiration activity in both soils and at both concentrations. The reference substance was found to decrease respiration activity.

In contrast to the reference substance, test substance did not cause a inhibition of the transformation from ammonium to nitrate. At all sampling times the content of soluble ammonium and nitrate in the soil with test substance and in the control soils were nearly the same.

It can thus be concluded that both short term respiration and nitrogen mineralization’s are not affected by test substance in both soils tested and at both test substance concentrations.

Description of key information

no adverse effect on soil respiration and nitrogen turnover; BBA Part VI, 1 -1; Reliability = 1