Propargite

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16th October 1999 to 26th September 2000

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)

Version / remarks:

(draft version)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

- Details on collection: Rheinsulz AG, Switzerland (river); Ormalingen BL, Switzerland (pond); sampled 11th October 1999; sample depth 10-30 cm
- Storage conditions: 4 ºC for one week
- Temperature (°C) at time of collection: 14.4-14.5 (river); 10.9-11.1 (pond)
- pH at time of collection: 8.22-8.28 (river); 7.46-7.55 (pond)
- Redox potential (mv) initial/final: 195-198/184 (river); 190-194/199 (pond)
- Oxygen concentration (mg/l) initial/final: 9.0-9.2 (river); 3.3-6.4 (pond)
- Hardness (dH): 16 (river); 24 (pond)
- Dissolved organic carbon: 4 mg/L (river); 6.1 mg/L (pond)
- Water filtered: yes
- Type and size of filter used, if any: 0.2 mm sieve

Details on source and properties of sediment:

- Details on collection: Rheinsulz AG, Switzerland (river); Ormalingen BL, Switzerland (pond); sampled 11th October 1999; sample depth top 5 cm
- Storage conditions: 4 ºC for one week
- Textural classification (i.e. % sand/silt/clay): 6.3/18.1/75.7 - loamy sand (river); 3.3/46.9/49.8 (sandy loam)
- pH at time of collection: 7.54 (river); 7.33 (pond)
- Organic carbon (%): 0.77 (river); 5.38 (pond)
- Redox potential (mv) initial: -8 (river); -136 (pond)
- CEC (meq/kg): 53 (river); 326.1 (pond)
- Biomass (g microbial C/kg dry sediment): 0.3 (river); 0.8 (pond)
- Sediment samples sieved: yes (2 mm sieve)

Duration of test (contact time):

106 d

Initial conc.:

229 µg/L

Based on:

test mat.

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: 240 and 220 g wet weight of river and pond sediment, respectively, was added to the flasks to a depth of 2.6-3.0 cm. 550 mL of the appropriate water was added to the sediment to reach a water column of approximately 6 cm. The sediment (dry weight)/total water ratio was approximately 0.25 and 0.08 for the river and pond systems, respectively.
- Test temperature: 20 ± 2 ºC
- Continuous darkness: yes
- Any indication of the test material adsorbing to the walls of the test apparatus: no

TEST SYSTEM
- Culturing apparatus: 1000 mL glass metabolism flasks
- Number of culture flasks/concentration: 16 (duplicates at eight sampling intervals)
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: the flasks were connected to two traps, the first containing 50 mL ethylene glycol and the second containing 50 mL 2N sodium hydroxide.

SAMPLING
- Sampling frequency: 0, 1, 2, 8, 16, 30, 63, 71 (pond only) and 106 days of incubation.
- Sampling method: supernatant water was separated from the sediment by removal of water using a pipette without disturbing the underlying sediment. Practically the total amount of water was removed; the small quantity of residual water was treated as sediment.

CONTROL AND BLANK SYSTEM
- Other: four untreated samples to determine microbial biomass at the beginning and end of the study; four untreated samples to determine physico-chemical characteristics/for pre-tests/for additional sampling interval purposes.

Key result

Compartment:

water

DT50:

1.7 d

Type:

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

Remarks on result:

other: river system; r = 0.9965

Key result

Compartment:

water

DT50:

2.5 d

Type:

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

Remarks on result:

other: pond system; r = 0.9941

Key result

Compartment:

sediment

DT50:

31.4 d

Type:

other: sequential first-order kinetics

Remarks on result:

other: river system; r = 0.9969

Key result

Compartment:

sediment

DT50:

19.9 d

Type:

other: sequential first-order kinetics

Remarks on result:

other: pond system; r = 0.9703

Key result

Compartment:

entire system

DT50:

22.5 d

Type:

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

Remarks on result:

other: river system; r = 0.9944

Key result

Compartment:

entire system

DT50:

18.3 d

Type:

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

Remarks on result:

other: pond system; r = 0.9942

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

yes

Physico-chemical parameters

River system

The redox potential of the water and sediment of treated samples during incubation averaged 219 ± 22 and -135 ± 36 mV, respectively. The oxygen concentration averaged 6.4 ± 1.9 mg/L. These values were indicative of aerobic conditions in the water phase throughout the study. The average pH was 8.2 ± 0.2. The microbial mass was 306 mg microbial C/kg at the end of incubation.

Pond system

The redox potential of the water and sediment of treated samples during incubation averaged 210 ± 27 and -115 ± 26 mV, respectively. The oxygen concentration averaged 5.7 ± 1.6 mg/L. These values were indicative of aerobic conditions in the water phase throughout the study. The average pH was 8.1 ± 0.2. The microbial mass was 819 mg microbial C/kg at the end of incubation.

 

Mass balances

Mass balances were 91.6-102.1 % for the river system and 92.3-103.7 % for the pond system.

Table 1: Distribution of radioactivity in the river system (percentage of applied radioactivity)

	Water phase				Sediment phase
Time (day)	Propargite	Trans-TBPC	M2	Cis-TBPC	Propargite	Trans-TBPC	M2	Cis-TBPC	Sediment unextractable	CO2
0	56.0	3.3	n.d.	n.d.	41.7	n.d.	n.d.	n.d.	0.3	n.p.
1	62.4	4.1	n.d.	n.d.	31.0	0.5	n.d.	n.d.	0.7	<0.1
2	40.8	8.5	n.d.	n.d.	45.5	1.7	n.d.	n.d.	0.9	<0.1
8	10.7	16.7	0.2	n.d.	57.8	8.3	n.d.	1.2	2.7	<0.1
16	3.2	14.8	6.5	1.3	49.1	11.6	0.8	1.8	5.7	0.3
30	0.9	1.4	11.3*	2.1	41.2	5.9	n.d.	2.5	18.5	5.7
63	<0.1	n.d.	6.6	n.d.	16.1	5.7	0.4	1.7	29.8	31.9
106	n.d.	n.d.	3.3	n.d.	4.9	3.4	n.d.	n.d.	29.3	51.8

n.d. = not detected

*consists of five peaks each <7 %

Table 2: Distribution of radioactivity in the pond system (percentage of applied radioactivity)

	Water phase				Sediment phase
Time (day)	Propargite	Trans-TBPC	M2	Cis-TBPC	Propargite	Trans-TBPC	M2	Cis-TBPC	Sediment unextractable	CO2
0	47.3	n.d.	n.d.	n.d.	52.9	<LOD	n.d.	n.d.	1.0	n.p.
1	63.7	2.2	n.d.	n.d.	28.0	0.7	n.d.	n.d.	0.7	<0.1
2	58.3	6.9	n.d.	n.d.	27.9	1.8	n.d.	n.d.	0.5	<0.1
8	12.7	15.8	n.d.	0.9	55.8	11.3	n.d.	0.5	2.3	<0.1
16	3.7	14.2	3.7	1.7	47.0	19.9	n.d.	2.3	3.5	0.1
30	1.4	5.5	8.9*	3.3	36.5	21.2	n.d.	8.5	7.6	0.9
63	n.d.	0.3	7.7	n.d.	2.9	20.2	0.8	4.6	30.7	21.4
106	n.d.	n.d.	3.1	n.d.	1.4	15.1	n.d.	n.d.	28.9	39.9

n.d. = not detected

*consists of seven fractions each ≤2.5 %

The sediment non-extractable fraction at day 106 was found to contain 7.3 % fulvic acid, 12.4 % humic acid and 13.8 % humin in the river sample with the same results being 8.9, 7.8 and 13.5 % in the pond sample.

Half-life values

Table 3: DT90 values for propargite

	River system		Pond system
Compartment	DT90	r	DT90	r
Water	5.6	0.9965	8.2	0.9941
Sediment	104.2	0.9969	66.0	0.9703
Entire system	74.7	0.9944	60.7	0.9942

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of the test, propargite partitions rapidly into sediment (approximately 58 % after 8 days) and subsequently degrades. Dissipation DT50 values for the water phase are 1.7-2.5 days and DT50 values for degradation in the sediment are 19.9-31.4 days. The overall DT50 for propargite degradation in the system was 18.3-22.5 days. The major metabolite in the water and sediment phases was trans-TBPC (maximum 16.7 % in water after 8 days; 21.2 % in sediment after 30 days; 34.1 % in the entire system after 16 days). cis-TBPC was also found at levels <10 % as was an unknown compound, M2. DT50 values for trans-TBPC were 11-15.5 days in the water phase and 8.5-74.5 days in the entire system.

Executive summary:

The route and rate of degradation of ¹⁴C-propargite was investigated in two equilibrated water/sediment systems. Two systems (Rheinsulz river and Ormalingen Pond) were established containing natural sediment (approximately 28 cm) and associated water (approximately 6 cm). The water was gently stirred and the flasks were allowed to equilibrate for approximately two weeks. [¹⁴C]-propargite was added to the water phase, appropriate traps were connected and the flasks were incubated in the dark at 20 ºC for up to 106 days. Duplicate samples were taken at each timepoint. Sediment was extracted with acetonitrile/water (8:2 v/v) and at later times acetone/water (9:1 v/v) by Soxhlet. After clean-up procedures, water samples and sediment extracts were analysed by HPLC and TLC.

Mass balances were 91.6-102.1 % for the river system and 92.3-103.7 % for the pond system. Propargite partitioned rapidly into sediment (approximately 58 % after 8 days). In addition, five other compounds were found at various timepoints but these did not exceed 2.6 % in any systems at any time. The sediment non-extractable fraction at day 106 was further analysed and found to contain 7.3 % fulvic acid, 12.4 % humic acid and 13.8 % humin in the river sample and 8.9 % fulvic acid, 7.8 % humic acid and 13.5 % humin in the pond sample. DT50 values for the water phase are 1.7-2.5 days and for the sediment are 19.9-31.4 days. The overall DT50 for propargite degradation in the system was 18.3-22.5 days.

Reference 2

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27th May 1992 to 23rd December 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA Subdivision N Pesticide Guideline 162-4 (Aerobic Aquatic Metabolism)

Deviations:

no

GLP compliance:

yes

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Details on source and properties of surface water:

- Details on collection: location - Lake Van, Polk County, Florida; sampling depth - 15-18 inches
- Temperature at time of collection: 78 ºF
- pH at time of collection: 8.5-8.7
- Electrical conductivity: 269 µmhos/cm
- Redox potential (mv): 600
- Oxygen concentration: 2.2 ppm
- Total organic carbon: 17 mg/L

Details on source and properties of sediment:

- Details on collection: location - Lake Van, Polk County, Florida; sampling depth - 6 inches
- Textural classification (i.e. % sand/silt/clay): 37.6/37.9/24.5 (classification - sand)
- pH: 5.5
- Organic matter (%): 1.97
- CEC (meq/100 g): 8.31
- Biomass (CFU): 937,500 (day 0); 925,000 (day 30)

Duration of test (contact time):

30 d

Initial conc.:

5.18 other: ppm

Based on:

test mat.

Initial conc.:

ca. 20 other: ppm

Based on:

test mat.

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: 5.56 g sediment and 9.4 mL water per tube
- Test temperature: 25 ± 1 ºC

TEST SYSTEM
- Culturing apparatus: 50 mL glass centrifuge tubes
- Number of culture flasks/concentration: 16 tubes at 5.18 ppm, 4 tubes at 20 ppm
- Method used to create aerobic conditions: air supply
- Details of trap for CO2 and volatile organics if used: a series of traps consisting of 1 N potassium hydroxide for 14CO2 and acidic volatiles, ethylene glycol for neutral volatiles and 0.1 N sulphuric acid for basic volatiles. The traps were changed at each sampling interval.

SAMPLING
- Sampling frequency: days 0, 3, 7, 14, 21 and 30 post-treatment (duplicate tubes)

Key result

Compartment:

entire system

DT50:

38.41 d

Type:

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

Remarks on result:

other: DT50; r2 = 0.987

Key result

Compartment:

entire system

DT50:

127.8 d

Type:

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

Remarks on result:

other: DT90; r2 = 0.987

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

No.:

#5

Details on transformation products:

- Proposed metabolic pathway: see Figure 1.

Evaporation of parent compound:

not specified

Volatile metabolites:

not specified

Residues:

yes

Mass balances

Mass balances were 94.66-105.51 %.

Table 1: Distribution of radioactivity

	Water phase		Sediment phase
Time (day)	Propargite	TBPC	Propargite	TBPC	Sediment unextractable	Volatiles
0	6.28	n.d.	98.30	n.d.	0.18	n.a.
3	7.31	1.16	86.89	2.18	4.13	0.05
7	5.47	1.75	80.27	4.49	5.33	0.11
14	5.90	5.03	75.46	6.50	6.53	0.22
21	3.48	7.21	63.06	9.32	6.41	0.38
30	3.96	12.32	56.08	13.25	4.79	0.68

Seven other compounds including PMTP were found at various timepoints but these did not exceed 1.2 % in the system at any time.

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of the test, propargite degraded under aerobic aquatic conditions with a DT50 of 38.41 days. The major metabolite was TBPC which reached 25.6 % in the system at the end of the 30 day experiment.

Executive summary:

Under laboratory conditions at approximately 25 ºC in the dark, ¹⁴C-labelled Omite^® degraded moderately in an aerobic aquatic system following treatment at approximately 5 µg/g. A pond water sample and a sand sediment from Lake Van, Florida were used in the study. Samples were taken for assay at 0, 3, 7, 14, 21 and 30 days post-treatment. Duplicate harvested samples were centrifuged and the solid and supernatant fractions extracted with ethyl acetate. Organic, aqueous and solid fractions were analysed by LSC and TLC with radiochromatography. Organosoluble samples from the day 30 sampling interval were also analysed by HPLC using a flow-through radiometric detector.

In addition to the parent compounds, at least eight metabolites were detected in the extractable fractions by day 30. M1, M2, M3, M4, M5 and M7 were formed by day 3 with their amounts increasing as the incubation time increased. M6 was only detected on day 21 whereas metabolite M8 was only first detected on day 21. M2, M3, M4, M6, M7 and M8 did not exceed 1 % of the applied dose. M1 was the major metabolite in the organic extracts and found to consist of two components which showed identical mass spectra indicating that they are possibly stereoisomers; GC/MS confirmed that this metabolite was Omite glycol ether. HPLC and TLC analysis of M2 showed that it consisted of at least three major components, the major component was p-tertiary-butyl-phenol (PTBP). M3 was shown to be a derivative of OGE hydroxylated at the p-tertiary-butyl group of the phenyl ring. M5 was shown to be OGE oxidised in the form of carboxylic acid at a methyl moiety of the p-tertiary-butyl group.

Less than 1 % of the total applied radioactivity was recovered as volatiles and virtually all was in the potassium hydroxide traps. The average total percent recovery of radioactivity for all the test systems was >95.82 % during the study.

Sediment-bound residues increased slowly from days 0 to 3 (0.18 to 4.13 %); however as the study progressed the amount of sediment-bound residues remained at around 4-6 %. Extraction of the day 21 post-extraction solids (PES) from the soil with acetonitrile/water/acetic acid released 5.59 % into the aqueous medium. Ethyl acetate extracted 5.53 % into the organic phase. Radioactivity remaining in the solids amounted to 1.6 %. TLC analysis of the EtOAc fraction from PES extraction indicated the presence of Omite^®, OGE and PTBP.

The half-life of Omite^® in the hydrosoil under aerobic aquatic conditions was calculated to be 38.41 days. The rate constant was determined to be 0.018/day.

Description of key information

The overall DT50 was determined to be 18.3-22.5 days; study conducted in accordance with OECD 308; Völkel (2001)

The DT50 of the entire system was determined to be 38.41 days; study conducted in accordance with EPA Guidelines, Subdivision N, Section 162-4; Comezoglu (1993)

Additional information

See 'Environmental fate and pathways'. Both studies were considered acceptable, performed in line with standardised guidelines and in line with GLP and so both studies are considered to be key studies.