mecoprop-P (ISO); (R)-2-(4-chloro-2-methylphenoxy)propionic acid

Field studies

Administrative data

Endpoint:

field studies

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

May 1989 to November 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The fate of the test material in undisturbed soil monoliths and its uptake by plants was investigated using two outdoor lysimeters filled with a sandy soil. The lysimeters were of 1 m^2 surface and 1.2 m depth. 120 mg a.i./m^2 were applied in May 1989 to both lysimeters. Both lysimeters were planted with summer wheat in April 1989. Winter wheat and winter rape were used as rotational crops. In May 1991 the soil monoliths were analysed in detail. The cultivation and fate related data for the active ingredient and metabolites were monitored and measured.

GLP compliance:

yes (incl. QA statement)

Type of measurement:

To elucidate the fate and leaching behaviour of the test material in soil under outdoor conditions after single application in spring.

Media:

Undisturbed soil monoliths of a sandy soil were used for the study.

Test material

Test material information

Constituent 1

Reference substance name:

(R)-2-(4-chloro-2-methylphenoxy)propionic acid

EC Number:

240-539-0

EC Name:

(R)-2-(4-chloro-2-methylphenoxy)propionic acid

Cas Number:

16484-77-8

Molecular formula:

C10H11ClO3

IUPAC Name:

(R)-2-(4-chloro-2-methylphenoxy)propionic acid

Test material form:

not specified

Results and discussion

Any other information on results incl. tables

Leachate

Amount and Concentrations of the Active Ingredient (Each Sample)

At the beginning of the study (till 03/90) selected leachate samples were filtered, measured before and after purging of CO2 and the wash flask were measured for radioactive material. No significant amounts of 14CO2 in the respective samples could be detected. Both lysimeters were comparable. Therefore, no other samples were investigated for 14CO2 in the further course of the study.

From the tables it can be seen that in none of the samples of lysimeter 13 and 14 in the two years period the concentration of the test material exceeded the detection limit of a value of 0.03 μg/L. For the calculation of the amounts of a.i. the values of 0.00 μg/L(lower limit) and 0.03 μg/L(upper limit) were used.

 

Amount and Concentrations of Metabolites (Each Sample)

The metabolite could not be observed in any of the samples of both lysimeters during the whole test period. Analogously to the active ingredient values of 0.00 μg/L(lower limit) and 0.03 μg/L(upper limit) were used for calculating the amount of the metabolite.

 

Amount and Concentrations of Unidentified Radioactive Material (Each Sample)

The respective values are calculated by subtraction of the amount of a.i. plus the metabolite from the total radioactivity.

As expected most of the unidentified material occurred during and at the end of the first winter period. For lysimeter 13 a concentration maximum between 0.78 and 0.84μg/L was observed in January 1990. A modest decrease could be detected for the following months. Lower concentrations of unidentified material could be observed for lysimeter 14 (maximum: 0.54 - 0.60μg/L in February 1990), but the leaching behaviour for both lysimeters was comparable.

The unidentified material could be characterised as being volatile and polar indicating the formation of short-chain carboxylic acids as final degradation products. The GC/MS-analyses of both the leachate and a reference sample of an untreated lysimeter showed formic acid, propionic acid, 2- methylpropionic acid, butyric acid and 3-methylbutyric acid in comparable amounts. In the second winter period, again an increase of leached unidentified material was monitored. However, the values of the first winter were not reached. Concentration maxima between 0.22 and 0.28 μg/L for lysimeter 13 (January 1991) and 0.36 to 0.42 μg/L for lysimeter 14 (March 1991) were detected.

 

Amount and Concentration of the Active Ingredient (One Year aAfter Application)

Concentrations of less than 0.03 μg/L (detection limit) for lysimeter 13 and 14 were observed. Amounts up to 13.25 μg for lysimeter 13 and 13.66 μg for lysimeter 14 showed the good conformity of both lysimeters.

 

Amount and Concentration of Metabolites (One Year After Application)

The investigated concentrations are below the detection limit (0.03 μg/L). The calculated amount in the leachate was in the range of 0.00 μg (best case) - 13.25 μg (worst case) for lysimeter 13 and 0.00 μg- 12.14 μg for lysimeter 14.

 

Amount and Concentration of Unidentified Radioactive Material (One Year After Application)

The average concentration of unidentified material during the first year after application was 0.49 - 0.54 μg/L (lysimeter 13) and 0.38 - 0.44 μg/L (lysimeter 14), respectively. The total amount in the leachate was between 227.22 - 253.72 μg (lysimeter 13) and 183.25 - 210.58 μg (lysimeter 14).

 

Amount and Concentration of the Active Ingredient (Two Years Period)

During the whole study the test material could not be observed in one of the samples above the detection limit of 0.03 μg/L. That means an average concentration of less than 0.03 μg/L. Amounts were calculated in the range of 0.00 - 25. 79 μg (lysimeter 13) and 0.00 - 25.80 μg (lysimeter 14).

 

Amount and Concentration of the Metabolites (Two Years Period)

There is no difference in the concentrations of the metabolite 4-chloro-2-methylphenol between the one-year and the two-year period. Concentrations above the detection limit could not be observed for both lysimeters. The total amount of the metabolite in the leachate was in the range of 0.00 - 25.79 μg (lysimeter 13) and 0.00 - 25.80 μg (lysimeter 14).

 

Amount and Concentration of Unidentified Radioactive Material (Two-Year Period)

Formation of polar degradation products resulted in an input into the leachate in the range of 283.68 - 335.25 μg (lysimeter 13) and 229.81 - 281.41 μg (lysimeter 14). The average concentration for the two-year period was between 0.32 - 0.38 μg/L(lysimeter 13) and 0.26 - 0.32 μg/L (lysimeter 14).

 

Soil

The lysimeters were removed from the test site. According to the BBA guideline IV, 4-3 the monolith was divided into 10 cm layers using a specially developed equipment. (This procedure contains a slight modification of the GLP-protocol, however, it results in a more detailed investigation of the soil). In order to avoid contaminations disassembly started with the 110 – 120 cm layer. The layers were investigated for inhomogeneities (e.g. stones, cracks) and respective samples were taken for analyses, combined and dried.

Disassembly of the monoliths indicated the following facts:

- the selected soil was fairly homogeneous (no bigger stones or cracks);

- the soil contained a usual amount of earthworms;

- no favoured growth of roots could be observed at the edges of the lysimeter;

- favoured growth of roots could be observed in canals caused by earthworms;

- roots grew down to a depth of 90 cm;

- both lysimeter were identical by means of macroscopic observations;

- some little bones could be observed in the deeper soil layer (50 - 60 cm) of the lysimeter 14.

 

Date of Sampling

The studies were terminated two years after application. Data for disassembly of the soil monoliths were:

Lysimeter 13: 16/05/91 (disassembly)

Lysimeter 14: 17/05/91 (disassembly)

 

Procedures for Extraction

100 g soil of the respective layers were extracted twice using 100 mL of an acetonitrile solution (containing 20 % water and 2 % acetic acid) and twice using 100 mL 1 n NaOH in order to extract the humic fraction. The extracts were counted for radioactive material. The residual soil was dried, combusted and radioassayed for evolving 14CO2. To the acetonitrile solution 200 mL of a sodium chloride solution (5 per cent; containing 4 mL l n hydrochloric acid) and 50 mL dichloromethane were added. The organic extracts were dried, concentrated under a stream of nitrogen to a volume of approx. 2 mL, counted for radioactive material and used for TLC analyses (system described in chapter 9). The clean-up procedure was carried out in duplicate in order to confirm reproducibility.

Quantification of the active ingredient and metabolites under investigation was carried out upon peak integration, characterisation was carried out upon comparison with reference substances. Due to low amounts of the respective compounds samples were not subjected to GC/MS-analyses. The detection limit for the analytical procedure was approximately 0.3 μg/kg soil.

 

Total Amount of Radioactive Material

12.09 % (lysimeter 13) and 5.50 % (lysimeter 14) of originally applied radioactive material (i. TRR) could be detected in the 0 - 10 and 10 - 20 cm layer. Below 60 cm amounts less 0.1 % i.TRR (lysimeter 13) and 0.9 % i.TRR (lysimeter 14) could be observed. In total, 12.51 % i. TRR (lysimeter 13) and 6.89 % i. TRR (lysimeter 14) were present at termination of the study.

 

Extractable RadioactiveResidues

Minor amounts of radioactive material (< 1 % i.TRR) could be extracted from the soil using dichloromethane. The total amount of radioactive material corresponding to equivalents of the active ingredient was in the range of 0.03 ng/g - 1.91 ng/g (lysimeter 13) and 0.01 - 1.21 ng/g (lysimeter 14).

For the two upper soil layers the active ingredient could be quantified upon TLC analysis to be:

1.76 ng/g (0 - 10 cm, lysimeter 13)

0.88 ng/g (0 - 10 cm, lysimeter 14)

0.77 ng/g (10 - 20 cm, lysimeter 13)

0.35 ng/g (10 - 20 cm, lysimeter 14).

The major amount of radioactive material remaining in soil at termination of the study could be extracted using NaOH. This fact indicated the incorporation of active ingredient derived radioactive material into the soil organic matter. Its amount ranged between 3.08 % i. TRR for the upper soil layer and 0.02 % i.TRR for the 110 - 120 cm layer (lysimeter 13) and 1.79 % i. TRR for the upper soil layer and 0.03 % i. TRR for the 70 - 80 cm layer (lysimeter 24).

 

Non-Extractable Residues

At termination of the study 6.75 % i. TRR (lysimeter 13) and 3.74 % i. TRR (lysimeter 14) were non-extractable.

 

Plants

Total Amount of Radioactive Material

The uptake of radioactive material by plants was quantified by combustion of plant material. Due to an application of the active ingredient to the young culture in spring followed by an uptake of the growing plants the concentration of radioactive material in summer wheat is higher compared to first rotational crop (winter wheat).

Harvest of summer wheat:

- total amount of harvested plants is known

- the proportional relation of straw/grains is approximately 84/16

- consequently, the total weight of the respective harvested parts could be calculated and plant uptake (in % of initially applied radioactive material) determined.

 

Harvest of winter wheat:

- total amount of harvested plants is known

- the proportional relation of straw/seeds/chaff is approximately 51/36/13

- consequently, the total weight of the respective harvested parts could be calculated and plant uptake (in % of initially applied radioactive material) determined.

 

Radioactivity Balance

Upon the above demonstrated results the following radioactivity balance (% of the initially applied radioactive material, % i. TRR) can be established:

 

Compartment	Lysimeter 13	Lysimeter 14
Soil	12.51 % i.TRR	6.90 % i.TRR
Leachate	0.28 % i.TRR	0.23 % i.TRR
Plants*	0.10% i.TRR	0.15% i.TRR
Loss**	87.11% i.TRR	92.72 % i.TRR

* Approximate values, calculated according to the above assumptions

** Due to e.g. volatilisation and mineralisation, calculated by difference

 

For the active ingredient the following distribution can be established:

 

Compartment	Lysimeter 13	Lysimeter 14
Soil	0.28 % i.TRR	0.14 % i.TRR
Leachate	0.00 – 0.02 % i.TRR	0.00 – 0.02 % i.TRR
Plants	No identification in plants performed

 

As can be seen from the results 0.28 % (lysimeter 13) and 0.23 % (lysimeter 14) of the applied amount of radioactive material reached the leachate containing varying amounts of the active ingredient. Up to 0.02 % (both lysimeters) of the active ingredient occurred in the leachate. Only minor amounts of the test material could be detected in the two upper soil layers at termination of the study. These results indicated that the test material did not tend to accumulate in soil.

 

Analytical Procedures

TLC Analyses

Eluates of the RP 18 columns (eluent: 1 x 2 mL acetone) were subjected to one-dimensional respective two-dimensional TLC analyses. 500 μLwere applied to the TLC-plates.

 

Conditions for TLC analyses:

TLC plates: silicagel F 254, 20 x 20 cm, 0.25 mm thickness

Solvent systems (1):

1) Chloroform (one-dimensional chromatography)

2) Diisopropylether/n-hexane/acetic acid (80/16/4; VNN) (two-dimensional chromatography, 2. dimension)

Rf-values of active ingredient and reference substances:

 

System 1:

Test material: Rf-value 0.09

4-chloro-2-methylphenol: Rf-value 0.05

 

System 2:

Test material: Rf-value 0.37

 

The recovery for the TLC method was between 80 and 100 % for the active ingredient and the metabolite.

The detection limit was 0.03μga.i./L leachate.

 

GC/MS Analyses:

Some representative samples were subjected to GC/MS analyses in order to identify the active ingredient as well as the metabolite under investigation.

Since the active ingredient as well as the metabolite could not be detected in the leachate, no representative MS-chromatograms can be shown.

Applicant's summary and conclusion

Conclusions:

Under the conditions of the study the test material can be characterised as being easily degradable in soil and having no leaching potential when applied in spring.

Executive summary:

The fate of the test material in undisturbed soil monoliths and its uptake by plants was investigated using two outdoor lysimeters filled with a sandy soil. The lysimeters were of 1 m^2 surface and 1.2 m depth. 120 mg a.i./m^2 were applied in May 1989 to both lysimeters. Both lysimeters were planted with summer wheat in April 1989. Winter wheat and winter rape were used as rotational crops. In May 1991 the soil monoliths were analysed in detail. The following cultivation and fate related data for the active ingredient and metabolites were monitored and measured:

 

Total amount of intact test material in the leachate

Lysimeter 13:

1. Year after application: 0.00 - 0.01 % of initial total radioactive residues

2. Year after application: 0.00 - 0.01 % of initial total radioactive residues

Sum, two years period: 0.00 - 0.02 % of initial total radioactive residues

Lysimeter 14

1. Year after application: 0.00 - 0.01 % of initial total radioactive residues

2. Year after application: 0.00 - 0.01 % of initial total radioactive residues

Sum, two years period: 0.00 - 0.02 % of initial total radioactive residues

 

Test material concentration in the leachate

Lysimeter 13:

1. Year after application: Mean value 0.00 - 0.03 μg/L

2. Year after application: Mean value 0.00 - 0.03 μg/L

Sum, two years period: Mean value 0.00 - 0.03 μg/L

Lysimeter 14:

1. Year after application: Mean value 0.00 - 0.03 μg/L

2. Year after application: Mean value 0.00 - 0.03 μg/L

Sum, two years period: Mean value 0.00 - 0.03 μg/L

 

Amount of intact test material in soil after two years

Lysimeter 13: 0.29 % of initial total radioactive residues

Lysimeter 14: 0.14 % of initial total radioactive residues

 

Data for the metabolites

Total amount of 4-chloro-2-methylphenol in the leachate

Lysimeter 13:

1. Year after application: 0.00 - 0.01 % of initial total radioactive residues

2. Year after application: 0.00 - 0.01 % of initial total radioactive residues

Sum, two years period: 0.00 - 0.02 % of initial total radioactive residues

Lysimeter 14:

1. Year after application: 0.00 - 0.01 % of initial total radioactive residues

2. Year after application: 0.00 - 0.01 % of initial total radioactive residues

Sum, two years period: 0.00 - 0.02 % of initial total radioactive residues

 

Concentration of 4-chloro-2-methylphenolinthe leachate

Lysimeter 13:

1. Year after application: Mean value 0.00 - 0.03 μg/L

2. Year after application: Mean value 0.00 - 0.03 μg/L

Sum, two years period: Mean value 0.00 - 0.03 μg/L

Lysimeter 14:

1. Year after application: Mean value 0.00 - 0.03 μg/L

2. Year after application: Mean value 0.00 - 0.03 μg/L

Sum, two years period: Mean value 0.00 - 0.03 μg/L

 

Amount of 4-cbloro-2-methylphenolinsoil after two years

Lysimeter 13: 0.00 % of initial total radioactive residues

Lysimeter 14: 0.00 % of initial total radioactive residues

 

Data for unidentified material

Amount in the leachate

Lysimeter 13:

1. Year after application: 0.19 - 0.21 % of initial total radioactive residues

2. Year after application: 0.05 - 0.07 % of initial total radioactive residues

Sum, two years period: 0.24 - 0.28 % of initial total radioactive residues

Lysimeter 14:

1. Year after application: 0.15 - 0.18 % of initial total radioactive residues

2. Year after application: 0.04 - 0.06 % of initial total radioactive residues

Sum, two years period: 0.19 - 0.23 % of initial total radioactive residues

 

Concentrationinthe leachate

Lysimeter 13:

1. Year after application: Mean value 0.49 - 0.54 μg/L

2. Year after application: Mean value 0.14 - 0.20 μg/L

Sum, two years period: Mean value 0.32 - 0.38 μg/L

Lysimeter 14:

1. Year after application: Mean value 0.38 - 0.44 μg/L

2. Year after application: Mean value 0.12 - 0.18 μg/L

Sum, two years period: Mean value 0.26 - 0.32 μg/L

 

Relative amountinsoil after two years (sum: Extractable and unextractable)

Lysimeter 13: 12.21 % of initial total radioactive residues)

Lysimeter 14: 6.69 % of initial total radioactive residues)

 

After spring application neither the active ingredient nor the metabolite 4-chloro-2-methylphenol could be detected in any leachate sample in concentrations exceeding the detection limit of 0.03 μg/L. The mean concentration of unidentified material only amounted to 0.4 - 0.5 μg/L during the first year after application and further decreased to 0.1 - 0.2 μg/L during the second year after application. In summary the lysimeter study showed no leaching potential of the active ingredient and its main metabolite. Also, polar degradation products occurred in the leachate in very low amounts only.

At termination of the study the soil only contained 12.5 % (lysimeter 13) and 6.9 % (lysimeter 14) of the originally applied radioactive material. These relative amounts consisted of 0.29 % i.TRR (lysimeter 13) and 0. 14 % i.TRR(lysimeter 14) test material. The formation of non-extractable residues was modest and resulted in the amount of 6.74 % (lysimeter 13) and 3.72 % (lysimeter 14) of the originally applied material.

The plant material only contained negligible amounts of radioactive material (approximately 0.1 % of the applied material in total for all rotational crops).

In summary, upon this study the test material can be characterised as being easily degradable in soil and having no leaching potential when applied in spring.