6-Amino-5-chloro-2-cyclopyrimidine-4-carboxylic acid

Biodegradation in soil

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19 Jul 2007 - 07 Feb 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)

Version / remarks:

2002

GLP compliance:

yes (incl. QA statement)

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

2007

Soil no.:

#1

Soil type:

sandy loam

% Clay:

7

% Silt:

34

% Sand:

59

% Org. C:

1.3

pH:

7.48

CEC:

6.4 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Soil no.:

#2

Soil type:

silty clay

% Clay:

43

% Silt:

52

% Sand:

5

% Org. C:

2.7

pH:

6.13

CEC:

24.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1

Soil no.:

#3

Soil type:

clay loam

% Clay:

31

% Silt:

48

% Sand:

21

% Org. C:

3.8

pH:

5.79

CEC:

34.5 meq/100 g soil d.w.

Bulk density (g/cm³):

1.1

Details on soil characteristics:

SOIL COLLECTION AND STORAGE
- Geographic location: soil 1: Nambsheim, Europe, soil 2: Tama, USA, soil 3: Drummer, USA
- Pesticide use history at the collection site: None
- Collection procedures:
- Sampling depth (cm): ≤ 20 cm
- Storage conditions: ca. 3 to 5°C, Aerobic
- Storage length: soil 1: 44 d, soil 2: 77 d, soil 3: 62 d
- Soil preparation: Sieved through 2 mm

Soil No.:

#1

Duration:

120 d

Soil No.:

#2

Duration:

120 d

Soil No.:

#3

Duration:

120 d

Soil No.:

#1

Initial conc.:

0.448 mg/kg soil d.w.

Based on:

act. ingr.

Soil No.:

#2

Initial conc.:

0.448 mg/kg soil d.w.

Based on:

act. ingr.

Soil No.:

#3

Initial conc.:

0.448 mg/kg soil d.w.

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

radiochem. meas.

Soil No.:

#1

Temp.:

20 ± 2°C

Humidity:

40-60% WHC

Microbial biomass:

4796.40 mg/g soil

Soil No.:

#2

Temp.:

20 ± 2°C

Humidity:

40-60% WHC

Microbial biomass:

4234.01 mg/g soil

Soil No.:

#3

Temp.:

20 ± 2°C

Humidity:

40-60% WHC

Microbial biomass:

4181.11 mg/g soil

Details on experimental conditions:

1. PRELIMINARY EXPERIMENTS: None

2. EXPERIMENTAL DESIGN
- Soil preincubation conditions (duration, temperature if applicable): 10 days at 20 ± 2 °C
- Soil condition: fresh
- Soil (g/replicate): 50 g (dry weight equivalent)
- Control conditions: There were no control conditions
- No. of replication treatments: 20
- Test apparatus (Type/material/volume): glass Erlenmeyer flask
- Details of traps for CO2 and organic volatile, if any: One ethanediol (organic volatiles) then up to two 1 M KOH (CO2)
- Identity and concentration of co-solvent: Acetonitrile:Milli-Q(R) Water, 18:82, (v/v)

Test material application
- Volume of test solution used/treatment: 0.32 mL
- Application method: applied drop-wise to soil surface using a Micropipette
- Is the co-solvent evaporated: no

Any indication of the test material adsorbing to the walls of the test apparatus: no

Experimental conditions (in addition to defined fields)
- Moisture maintenance method: Gravimetric adjustment
- Continuous darkness: Yes

3. OXYGEN CONDITIONS (delete elements as appropriate)
- Methods used to create the an/aerobic conditions: Moist air flowthrough system

4. SUPPLEMENTARY EXPERIMENTS: none

5. SAMPLING DETAILS
- Sampling intervals: 0, 3, 7, 15, 30, 60, 90 and 120 days post application
- Sampling method for soil samples:
at day 0 soils 1 and 2: extracted by shaking twice with acetonitrile : 0.2% (v/v) formic acid in water followed by acetonitrile : 0.15M ammonium acetate, 70 : 30, v/v. The samples were additionally extracted with phosphate buffer pH 7.4 overnight. The next day acetonitrile was added to the same vessels followed by continued extraction. Finally the samples were extracted by skaking with acetonitrile : phosphate
buffer pH 7.4 (70 : 30, v/v).
at day o, soil 3: extracted first by shaking with phosphate buffer pH 7.4 overnight. The next day acetonitrile was added to the same vessels followed by continued extraction. The soils were then extracted by shaking twice more with acetonitrile : phosphate buffer pH 7.4 (70 : 30, v/v). Finally the soils were extracted with acetonitrile alone.
Soil samples from Day 7, 15, 30, 60, 90 and 120 were extracted first by shaking with phosphate buffer pH 7.4 overnight. The next day acetonitrile was added to the same vessels followed by continued extraction. The soils were then extracted by shaking twice more with acetonitrile : phosphate buffer pH 7.4 (70 : 30, v/v) and once with acetonitrile : 0.15M ammonium acetate, 70 : 30, v/v. Finally the soils were extracted with acetonitrile alone.
- Method of collection of CO2 and volatile organic compounds: LSC

- Sampling intervals/times for:
- Moisture content: at least once in 15 days

Soil No.:

#1

% Recovery:

94.3

Soil No.:

#2

% Recovery:

92.4

Soil No.:

#3

% Recovery:

90.4

Soil No.:

#1

DT50:

433 d

Type:

(pseudo-)first order (= half-life)

Temp.:

ca. 20 °C

Remarks on result:

other: K: 0.0016 (day-1)

Soil No.:

#2

DT50:

120 d

Type:

(pseudo-)first order (= half-life)

Temp.:

ca. 20 °C

Remarks on result:

other: K: 0.0058 (day-1)

Soil No.:

#3

DT50:

126 d

Type:

(pseudo-)first order (= half-life)

Temp.:

ca. 20 °C

Remarks on result:

other: K: 0.0055 (day-1)

Soil No.:

#1

DT50:

919.3 d

Type:

(pseudo-)first order (= half-life)

Temp.:

ca. 20 °C

Remarks on result:

other: Re-calculated using Arrhenius equation

Soil No.:

#2

DT50:

254.8 d

Type:

(pseudo-)first order (= half-life)

Temp.:

ca. 20 °C

Remarks on result:

other: Re-calculated using Arrhenius equation

Soil No.:

#3

DT50:

254.8 d

Type:

(pseudo-)first order (= half-life)

Temp.:

ca. 20 °C

Remarks on result:

other: Re-calculated using Arrhenius equation

Transformation products:

no

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

no

Details on results:

TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: Yes

MINOR TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: soil 1: 4.0, soil 2: 0.019, soil 3: 4.2
- Range of maximum concentrations in % of the applied amount at end of study period: soil 1: 0.2, soil 2: 0.001, soil 3: 0.3

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT:

EXTRACTABLE RESIDUES
- % of applied amount at day 0: soil 1: 110.1, soil 2: 0.513, soil 3: 98.4
- % of applied amount at end of study period: soil 1: 80.7, soil 2: 0.377, soil 3: 49.1

NON-EXTRACTABLE RESIDUES
- % of applied amount at day 0: soil 1: 0.6, soil 2:0.003 , soil 3: 4.3
- % of applied amount at end of study period: soil 1: 13.0, soil 2: 0.061, soil 3: 43.2

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: soil 1: 0.6, soil2: 0.003, soil 3: 0.1

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: none

Description of key information

DT50 (120 d) = 120 - 433 d (OECD 307, aerobic conditions, 20°C)

DT50 (120 d) = 245.8 - 913.3 d (OECD 307, aerobic conditions, recalculated to 12 °C)

Additional information

The rate of degradation of the carbon-14 labelled test item was investigated in a GLP study conducted according to OECD 307. The study was performed in three soils of varying physiochemical characteristics (sandy loam, silty clay, clay loam) in the dark under aerobic conditions at a temperature of 20°C for 120 days. The test system consisted of a flow-through metabolism apparatus where the soils were incubated in vessels connected to traps for the collection of non-specific 14C-volatile organic compounds and 14CO2, respectively. Soil samples were subjected to total radioactivity analysis as determined by LSC. Extracts from each sample were analyzed for the amount of the test substance using HPLC with radiochemical detection and fraction collection.

Material balances were generally quantitative for all samples (overall mean 98.5 ± 5.7%). HPLC analysis of soil extracts from each soil type demonstrated quantitative recovery of the test substance. The amount of test substance in extracts declined from 105.2, 93.1 and 94.0% applied radioactivity at zero time to 76.5, 42.3 and 44.7% applied radioactivity after 120 days in the the three different soils, respectively.
Non-extractable residues accounted for 0.6 to 43.2% of applied radioactivity for the soils studied throughout the incubation period. The DT50 values for the test substance calculated using simple first order kinetics are 433, 120 and 126 days.