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Environmental fate & pathways

Biodegradation in soil

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Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
key study
Study period:
17/05/2002 - 18/08/2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, Guideline study
Qualifier:
according to guideline
Guideline:
other: Commission Directive 95/36/EC of 14 July 1995 amending Council Directive 91/414/EEC: Annex II: 7.1.1.2 laboratory studies – aerobic degradation.
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: SETAC Europe: Procedures for assessing the environmental fate and ecotoxicity of pesticides, March 1995, Part 1 – Aerobic degradation
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: OECD Guidelines for testing chemicals: Aerobic – Anaerobic transformation in soil (Draft proposal, August 2000)
Deviations:
no
GLP compliance:
yes
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
aerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
silt loam
% Clay:
10.3
% Silt:
52.3
% Sand:
37.4
% Org. C:
1.8
pH:
7.2
CEC:
13.1 meq/100 g soil d.w.
Soil No.:
#1
Duration:
120 d
Soil No.:
#1
Initial conc.:
0.03 other: mg/100 g
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
test mat. analysis
Soil No.:
#1
Temp.:
20 ± 2 ºC
Humidity:
40% MWC (soil moisture)
Microbial biomass:
30.3 g microbial C/kg dry sediment
Soil No.:
#1
Temp.:
10 ± 2 ºC
Humidity:
40% MWC (soil moisture)
Microbial biomass:
30.3 g microbial C/kg dry sediment
Details on experimental conditions:
See Table 1
Soil No.:
#1
% Recovery:
93.5
St. dev.:
1.8
Remarks on result:
other: 20°C system
Soil No.:
#1
% Recovery:
93.5
St. dev.:
2.4
Remarks on result:
other: 10°C system
Soil No.:
#1
DT50:
10.2 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: 20ºC system
Soil No.:
#1
DT50:
21.1 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: 10ºC system
Transformation products:
yes
No.:
#1
No.:
#2
Details on transformation products:
Dinotefuran mainly degraded to MNG reaching a maximum amount of 15.6% and 16.0% AR in the 20°C and 10°C system, respectively. Additionally NG reached 5% AR on day 120 in the 10°C system and on day 62 in the 20°C system. Up to 9 minor degradation products were. Ultimate degradation to CO2 was significant reaching a maximum amount of 52.1% and 43.7% AR in the 20°C and 10°C system, respectively. Half lives for the degradation product MNG could be calculated.
Evaporation of parent compound:
not measured
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
In the experiment, total recoveries of radioactivity (mass balances) were generally 93.5±1.8% applied radioactivity (AR) for the 20°C system and 93.5±2.4% for the 10°C system. Total extractable radioactivity declined rapidly from 94.1% on day 0 to 13.3% AR on day 120 in the 20°C system, and from 94.1% to 26.4% AR in the 10°C system. There were corresponding increases with time in non-extractable radioactivity with maxima of 25.7% AR in the 20°C system and 19.9% in the 10°C system. Organic matter fractionation indicated that the non-extractable radioactivity was mainly bound to the immobile humic acids and humic fraction. Volatile radioactivity, all associated with 14CO2, represented a maximum of 52.1% AR in the 20°C system and 43.7% AR in the 20°C system.
Results with reference substance:
No reference substance used
Conclusions:
Dinotefuran declined in aerobic soil systems with DT50 values of 10.2 and 21.1 days (20°C and 10°C system, respectively). One major degradation product was formed, MNG which accounted for up to 15.6% of the applied radioactivity at 20°C. NG was formed up to 5.4% of the applied radioactivity but only on one occasion. DT50 values of 87.7 days were calculated for MNG in 20°C system.
Endpoint:
biodegradation in soil
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03/05/2002 - 11/02/2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, Guideline study
Qualifier:
according to guideline
Guideline:
other: Commission Directive 95/36/EC of 14 July 1995 amending Council Directive 91/414/EEC: Annex I: 7.1.1.2 rate of degradation; 7.1.1.1.2 anaerobic degradation study
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: SETAC Europe: Procedures for assessing the environmental fate and ecotoxicity of pesticides, March 1995, Part 1 –2 Anaerobic degradation
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: EPA 540/9-82-021; Section 162-2 Anaerobic soil metabolism studies
Deviations:
no
GLP compliance:
yes
Test type:
laboratory
Radiolabelling:
yes
Oxygen conditions:
anaerobic
Soil classification:
USDA (US Department of Agriculture)
Soil no.:
#1
Soil type:
silt loam
% Clay:
10.3
% Silt:
53.2
% Sand:
37.4
% Org. C:
1.78
pH:
7.22
CEC:
13.11 meq/100 g soil d.w.
Details on soil characteristics:
See Table 1
Soil No.:
#1
Duration:
120 d
Soil No.:
#1
Initial conc.:
0.031 other: mg/100 g
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
test mat. analysis
Soil No.:
#1
Temp.:
20 ± 2ºC
Microbial biomass:
33.0 g microbial C/kg dry sediment
Soil No.:
#1
% Recovery:
96
St. dev.:
2.5
Remarks on result:
other: total recoveries
Soil No.:
#1
DT50:
22 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: water phase
Soil No.:
#1
DT50:
77 d
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: total system
Transformation products:
yes
No.:
#1
No.:
#2
Details on transformation products:
Dinotefuran mainly degraded to DN (1- methyl-3-(tetrahydro-3-furylmethyl)guanidine) reaching a maximum amount of 33.1% AR; harsh extractions extracted additionally 8.7% of applied radioactivity as DN. Additionally UF (1-methyl-3-(tetrahydro-3-furylmethyl)urea) reached 7.7% AR on day 120. One more minor degradation product was detected chromatographically. Ultimate degradation to CO2 was low reaching a maximum amount of 4.2%.

Characterisation by HPLC and TLC co-chromatography with reference standard.
Evaporation of parent compound:
not measured
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
The degradation of dinotefuran in soil under anaerobic conditions was studied with 14C labelled test substance in two different labels. One soil system was set up at 20°C.

In the experiment, total recoveries of radioactivity (mass balances) were 96.0±2.5% of the applied radioactivity (AR). The radioactivity in water decreased from 94.6% on day 0 to 58.8% on day 7 and 25.4% on day 120. There was a corresponding increase of the radioactivity in soil reaching a maximum of 62.6% AR at the end of the test. The majority of it was extractable, amounting to 27.8% AR at day 3 and 53.5% at day 120. The maximum non-extractable radioactivity reached was 10.7% on day 59. Organic matter fractionation indicated that the non-extractable radioactivity was mainly bound to the immobile humic acids and humic fraction. Volatile radioactivity was mostly associated with 14CO2, representing a maximum of 4.2% AR. Only 0.1% AR were associated to organic volatiles. Dinotefuran mainly degraded to DN reaching a maximum amount of 33.1% AR; harsh extractions extracted additionally 8.7% of applied radioactivity as DN. Additionally UF reached 7.7% AR on day 120. One more minor degradation product was detected chromatographically. Ultimate degradation to CO2 was low reaching a maximum amount of 4.2%.
Results with reference substance:
No reference substance used.
Conclusions:
Dinotefuran declined in anaerobic soil systems with DT50 values of 22 and 77 days in the water phase and total system, respectively. One major degradation product was formed, DN, i.e. l-methyl-3-(tetrahydro-3-furylmethyl)guanidine which accounted for up to 33.1% of the applied radioactivity. UF, i.e. l-methyl-3-(tetrahydro-3-furylmethyl)urea reached 7.7% of the applied radioactivity by the end of the test.

Description of key information

Dinotefuran declined in aerobic soil systems with DT50 values of 10.2 and 21.1 days (20°C and 10°C system, respectively)

Dinotefuran declined in anaerobic soil systems with DT50 values of 22 and 77 days in the water phase and total system, respectively.

Key value for chemical safety assessment

Half-life in soil:
19.2 d
at the temperature of:
12 °C

Additional information