mancozeb (ISO); manganese ethylenebis(dithiocarbamate) (polymeric) complex with zinc salt  

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:

August 2000 - Januar 2001

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)

Version / remarks:

1999

Deviations:

no

GLP compliance:

yes

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

2001

Soil no.:

#3

Soil type:

silt loam

% Clay:

23.56

% Silt:

56.12

% Sand:

20.32

% Org. C:

0.99

pH:

5.8

CEC:

15.49 meq/100 g soil d.w.

% Moisture content:

55.35

Soil no.:

#2

Soil type:

loamy sand

% Clay:

7.5

% Silt:

15.4

% Sand:

77.1

% Org. C:

2.17

pH:

5.7

CEC:

11 meq/100 g soil d.w.

Bulk density (g/cm³):

1 156

% Moisture content:

50

Soil no.:

#1

Soil type:

sandy loam

% Clay:

7.4

% Silt:

26.5

% Sand:

66.2

% Org. C:

0.71

pH:

6.5

CEC:

11 meq/100 g soil d.w.

Bulk density (g/cm³):

1 328

% Moisture content:

37

Details on soil characteristics:

pH measured in CaCl2

soil 1 = Speyer 2.3/Germany
soil 2 = Speyer 2.2/Germany
soil 3 = Senozan/France

The soils have not been subfected to any pesticide and organic fertiliser treatment for the last five years.

Soil 1 and 2 were sieved through a 2 mm sieve by LUFA and stored ar RCC Ltd. at 4°C for about 6 weeks.

Soil 3 was freshly sampled by RCC Ltd. from the top 0 to 20 cm soil layer and sieved through a 2 mm sieve by RCC Ltd. prior to use. Sampling was performed according to the ISO/DIS 10381-6 guidelines.

Each soil was conditioned at room temperature for about 10 days prior to the start of the study.

Soil No.:

#3

Duration:

120 d

Soil No.:

#2

Duration:

120 d

Soil No.:

#1

Duration:

120 d

Soil No.:

#1

Initial conc.:

3.61 mg/kg soil d.w.

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

radiochem. meas.

Soil No.:

#3

Temp.:

20°C

Microbial biomass:

Start = 587 mg OC/kg soil End = 393mg OC/kg soil (20°C); 487 mg OC/kg soil (10°C)

Soil No.:

#2

Temp.:

20°C

Microbial biomass:

Start = 401 mg OC/kg soil End = 406 mg OC/kg soil

Soil No.:

#1

Temp.:

20°C

Microbial biomass:

Start = 142 mg OC/kg soil End = 93 mg OC/kg soil

Details on experimental conditions:

The test item was applied to the soils at a concentration of 3.61 mg Mancozeb/kg soil dry weight (corresponding to a field rate of about 2.7 kg a.s./ha Mancozeb; assuming a uniform distribution in the 5 cm top soil and a bulk density of 1.5 g/cm3. The soil samples were incubated at 20 ± 2 °C and for one soil at 10 ± 2 °C. All soils were maintained at a moisture content of about 40 % of the soils maximum water holding capacity (MWC).
Samples from all three soils were taken for analysis immediately after treatment and after 1, 7, 14, 28 (duplicates), 63 and 120 (duplicates) days of incubation. Volatiles and 14CO2 were collected. All samples were subjected to exhaustive solvent extractions, and the extracts were analysed by HPLC and TLC. The total radioactivity balance and the distribution of radioactivity in each incubation sample were established on each sampling day.

Soil No.:

#3

% Recovery:

95.9

St. dev.:

4

Remarks on result:

other: incubation at 10°C

Soil No.:

#3

% Recovery:

95.3

St. dev.:

2.6

Remarks on result:

other: incubation at 20°C

Soil No.:

#2

% Recovery:

99.2

St. dev.:

3.1

Remarks on result:

other: incubation at 20°C

Soil No.:

#1

% Recovery:

100.2

St. dev.:

3.4

Remarks on result:

other: incubation at 20°C

Parent/product:

parent

Key result

Soil No.:

#3

% Degr.:

58.4

Sampling time:

120 d

Remarks on result:

other: degradation at 10 °C

Parent/product:

parent

Key result

Soil No.:

#3

% Degr.:

61.6

Sampling time:

120 d

Remarks on result:

other: parent degrades on DAT 0 with a value of 63.6 % to 2.0 % on DAT 120; degradation at 20°C

Parent/product:

parent

Key result

Soil No.:

#2

% Degr.:

67.5

Sampling time:

120 d

Remarks on result:

other: parent degrades on DAT 0 with a value of 69.7 % to 2.2 % on DAT 120; degradation at 20°C

Parent/product:

parent

Key result

Soil No.:

#1

% Degr.:

80.8

Parameter:

radiochem. meas.

Sampling time:

120 d

Remarks on result:

other: parent degrades on DAT 0 with a value of 85.2 % to 4.3 % on DAT 120; degradation at 20°C

Key result

Soil No.:

#3

DT50:

0.027 d

Type:

other: Single First Order (SFO)

Temp.:

10 °C

Remarks on result:

other: re-analysis of the degradation kinetics according to FOCUS degradation kinetics (Hardy, 2015)

Key result

Soil No.:

#3

DT50:

0.027 d

Type:

other: Single First Order (SFO)

Temp.:

20 °C

Remarks on result:

other: re-analysis of the degradation kinetics according to FOCUS degradation kinetics (Hardy, 2015)

Key result

Soil No.:

#2

DT50:

0.027 d

Type:

other: Single First Order (SFO)

Temp.:

20 °C

Remarks on result:

other: re-analysis of the degradation kinetics according to FOCUS degradation kinetics (Hardy, 2015)

Key result

Soil No.:

#1

DT50:

0.043 d

Type:

other: Single First Order (SFO)

Temp.:

20 °C

Remarks on result:

other: re-analysis of the degradation kinetics according to FOCUS degradation kinetics (Hardy, 2015)

Transformation products:

yes

No.:

#3

No.:

#2

No.:

#1

Details on transformation products:

Metabolite EBIS was detected at maximum amounts, 1.5 hours after application, of 29.1 %, 29.1 %, 24.8 % and 24.8 % of the applied radioactivity in soil extracts from soils I, II, III incubated at 20 °C and soil III incubated at 10 °C, respectively. Thereafter EBIS disappeared with a DT50 value of 0.6 days or less in all soils at 20 °C and 1.3 days at 10 °C.

Metabolite ETU was detected in all three soils. Maximum amounts of 22.0 %, 24.8 % and 14.7 % of the applied radioactivity were present at incubation day 1 in soils I, II and III, respectively incubated at 20 °C. For soil III incubated at 10 °C the maximum amount of ETU was detected on day 7 with 11.9 %. The DT50 values for ETU were 18.2 days, 4.4 days, and 10.7 days for soils I to III incubated at 20 °C and 23.1 days for soil III incubated at 10 °C.

Metabolite EU was detected at maximum amounts of 18.5 % (soil I, day 7), 11.8 % (soil II, day 1), 11.7 % (soil III at 20 °C, day 1) and 11.6 % (soil III at 10 °C, day 7). Thereafter, EU disappeared with a DT50 value of 2.7 days or less in all soils. Kinetic analysis indicates that EU is formed mainly from EBIS (via other transient metabolites) in this study, as well as potentially directly from ETU.

Evaporation of parent compound:

yes

Details on results:

The total mean recoveries were 100.2 % ± 3.4 %, 99.2 % ± 3.1 %, 95.3 % ± 2.6 % and 95.9 % ± 4.0 % of the applied radioactivity for soils I, II, III incubated at 20 °C and soil III incubated at 10 °C, respectively. Individual recoveries ranged from 90.3 % to 106.1 % for soils I to III.

Immediately after treatment (DAT 0), 85.2 %, 69.7 % and 63.6 % of the applied radioactivity could be extracted from soils I, II and III, respectively. With increasing incubation time, the amount of extractable radioactivity decreased continuously amounting to 10.6 %, 5.2 %, 4.5 % and 10.3 % on DAT 28 in soils I, II, III incubated at 20 °C and soil III incubated at 10 °C, respectively. At the end of incubation (DAT 120) the corresponding extracted radioactivity amounted to 4.3 %, 2.2 %, 2.0 % and 5.2 % of the applied radioactivity, respectively.

The amount of non-extractable radioactivity increased for all soils to a maximum value and thereafter decreased until the end of incubation. The following maximum amounts were attained: 59.1 % (soil l/20 °C/DAT 28), 69.8 % (soil II/20 °C/DAT 28), 70.7 % (soil III/20 °C/DAT 7) and 66.7 % (soil III/10 °C/DAT 63). The maximum of bound residues in soil III was observed later for the incubation at 10 °C than at 20 °C. Therefore, the amounts of bound residues decreased on incubation DAT 120 to 49.0 %, 58.0 %, 52.0 % and 62.0 % for the four parts, respectively. The incubation at 10 °C ended at a higher amount of bound residue than the corresponding incubation at 20 °C.

Additional organic matter fractionation was performed with selected samples of soil non-extractables from DAT 120. The results show that 38.1 %, 45.9 %, 40.8 % and 38.5 % the applied radioactivity in the soils I to III incubated at 20 °C and in soil III incubated at 10 °C, respectively, were bound to the immobile humic acids and humin fractions. Similarly, the radioactivity associated with the fulvic acids fraction amounted to 14.0 %, 15.2 %, 11.9 % and 23.3 % of the applied radioactivity in the four parts, respectively.

The mineralization of [14C]-Mancozeb was high in all soils. The amount of 14CO2 evolved increased continuously with incubation time. Maximum mean values of 49.6 %, 41.8 %, 44 % and 33 % of the applied radioactivity were evolved as 14CO2 from soils I to III incubated at 20 °C and from soil III incubated at 10 °C, respectively, at the end of incubation. Volatile radioactivity other than 14CO2 did not exceed 0.1 % of the radioactivity applied.

Metabolite EBIS was detected at maximum amounts, 1.5 hours after application, of 29.1 %, 29.1 %, 24.8 % and 24.8 % of the applied radioactivity in soil extracts from soils I, II, III incubated at 20 °C and soil III incubated at 10 °C, respectively. Thereafter EBIS disappeared with a DT50 value of 0.6 days or less in all soils at 20 °C and 1.3 DAT at 10 °C.

Metabolite ETU was detected in all three soils. Maximum amounts of 22.0 %, 24.8 % and 14.7 % of the applied radioactivity were present at incubation DAT 1 in soils I, II and III, respectively incubated at 20 °C. For soil III incubated at 10 °C the maximum amount of ETU was detected on DAT 7 with 11.9 %. The DT50 values for ETU were 18.2 DAT , 4.4 DAT , and 10.7 days for soils I to III incubated at 20 °C and 23.1 DAT for soil III incubated at 10 °C.

Metabolite EU was detected at maximum amounts of 18.5 % (soil I, DAT 7), 11.8 % (soil II, DAT 1), 11.7 % (soil III at 20 °C, DAT 1) and 11.6 % (soil III at 10 °C, DAT 7). Thereafter, EU disappeared with a DT50 value of 2.7 DAT or less in all soils. Kinetic analysis indicates that EU is formed mainly from EBIS (via other transient metabolites) in this study, as well as potentially directly from ETU.

Highly transient metabolite M11 was detected at maximum amounts of 20.3 % (soil I, DAT 0.06), 16.6 % (soil II, DAT 0.06), 20.3 % (soil III at 20 °C, DAT 0.06) and 20.3 % (soil III at 10 °C, DAT 0.06). Thereafter, M11 rapidly disappeared with a DT50 value of 2-6 hours in all soils; with no residues >LOD remaining on DAT 1 in soils I and III (20°C). Evaluation of the time series data indicates that M11 rapidly forms significant levels of NER. Chromatographically, M11 appears less polar than EBIS [longer retention time by reverse phase HPLC].
New chromatographic evaluations have been made with standards not available during study conduct [TDIT and TCIT], comparing them to historical HPLC data within the study report (in relation to the renewal). TCIT and TDIT have previously been postulated as transient intermediates in the degradation pathway for metiram, but these did not correspond chromatographically with M11. M11 corresponds to the same metabolite in the hydrolysis study at pH4, but this could not be ionised by LC/MS or GC/MS by Völkel, W. (2001b). The highly transient nature of M11 (DT50 <6 hours) and non-polar nature indicate that M11 will not be a risk to groundwater or surface water. Consideration of M11 in the soil risk assessment is taken into account using a conservative DT50 for mancozeb of 0.6 days based on CS2 formation, which adequately covers the decline in total mancozeb + M11 residues of 0.04 - 0.08 days [ Hardy, IAJ (2015)].

Additionally, at least twelve unknown radioactive fractions were detected in all three soils. None of these metabolites exceeded 7.4 % of the applied radioactivity and none >5 % at two consecutive timepoints.

Characterisation of the extractable radioactivity from soil I (Speyer 2.3)

	%Applied radioactivity
Time (d)	0	0.06	1	7	14	28	28	63	120	120
Mancozeb	92.0	33.2	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD
EBIS	4.6	29.1	4.9	1.2	1.2	0.6	<LOD	0.1	0.2	<LOD
ETU	1.3	<LOD	22.0	13.0	14.9	6.1	5.3	3.9	2.5	2.0
EU	1.3	<LOD	14.2	18.5	1.1	1.2	0.7	1.0	0.5	0.4
M11	0.8	20.3	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD
NER	np	18.0	41.3	55.3	56.9	59.2	58.9	53.8	48.4	49.5
CO2	np	np	<0.1	2.8	22.5	28.0	28.4	39.3	46.8	52.4
Total	103.2	np	95.0	103.1	98.8	97.7	97.8	100.1	99.6	106.1

np not performed     LOD 0.1%

 

Characterisation of the extractable radioactivity from soil II (Speyer 2.2)

	%Applied radioactivity
Time (d)	0	0.06	1	7	14	28	28	63	120	120
Mancozeb	92.0	18.0	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD
EBIS	4.6	29.1	2.8	1.6	0.7		0.2	0.2	<LOD	0.1
ETU	1.3	6.0	24.8	8.6	4.0	2.7	2.4	2.0	1.3	1.3
EU	1.3	<LOD	11.8	1.4	1.2	0.4	0.2	0.1	0.6	0.6
M11	0.8	16.6	1.7	<LOD	0.3	<LOD	<LOD	<LOD	<LOD	<LOD
NER	np	31.8	50.6	69.7	67.9	67.3	72.2	61.7	56.4	59.5
CO2	np	np	<0.1	12.1	18.5	24.9	25.4	33.5	41.1	42.4
Total	101.5	np	96.6	95.6	96.4	97.3	103.0	98.7	99.6	104.1

np not performed     LOD 0.1%

 

Characterisation of the extractable radioactivity from soil III (Senozan) – 20^oC

	%Applied radioactivity
Time (d)	0	0.06	1	7	14	28	28	63	120	120
Mancozeb	92.0	18.4	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD
EBIS	4.6	24.8	7.6	2.8	0.7	0.2	0.2	0.3	<LOD	<LOD
ETU	1.3	<LOD	14.7	10.4	5.8	2.9	2.7	1.1	0.9	0.7
EU	1.3	<LOD	11.7	2.4	0.7	0.7	0.6	0.6	0.8	0.9
M11	0.8	20.3	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD
M19	<LOD	<LOD	7.4	3.1	0.3	0.2	<LOD	<LOD	<LOD	<LOD
NER	np	30.7	48.6	70.7	59.0	58.7	60.4	57.6	51.9	52.1
CO2	np	np	<0.1	3.5	22.4	29.5	28.7	37.1	44.9	43.0
Total	94.3	np	97.0	95.8	91.0	93.0	93.3	97.6	98.8	97.1

np not performed     LOD 0.1%

 

Characterisation of the extractable radioactivity from soil III (Senozan) – 10^oC

	%Applied radioactivity
Time (d)	0	0.06	1	7	14	28	28	63	120	120
Mancozeb	92.0	18.4	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD	<LOD
EBIS	4.6	24.8	14.5	0.8	1.7	0.8	1.3	0.8	<LOD	<LOD
ETU	1.3	<LOD	3.3	11.9	6.3	5.5	5.7	2.6	1.6	1.5
EU	1.3	<LOD	8.0	11.6	1.7	1.1	0.6	0.7	0.8	0.9
M11	0.8	20.3	<LOD	2.0	<LOD	<LOD	0.6	<LOD	<LOD	<LOD
M19	<LOD	<LOD	<LOD	5.9	3.2	<LOD	<LOD	<LOD	<LOD	<LOD
M23	<LOD	<LOD	6.9	<LOD	<LOD	<LOD	<LOD	1.5	1.2	1.4
NER	30.7	np	52.2	61.1	65.1	64.3	64.6	66.7	62.0	61.9
CO2	np	np	<0.1	<0.1	7.9	15.7	16.1	25.5	31.7	34.2
Total	94.3	np	97.9	97.7	92.6	90.3	90.9	99.6	98.7	101.4

np not performed     LOD 0.1%

 

DT₅₀ values of Mancozeb and its metabolites EBIS, ETU and EU according to Hardy, 2015

	DT50 [days]
	Soil I – 20°C	Soil II – 20°C	Soil III – 20°C	Soil III – 10°C
Mancozeb	0.043	0.027	0.027	0.027
EBIS	0.29	0.24	0.42	0.95
ETU	15.3	4.6	8.8	34.1
EU	8.0	2.1	2.3	5.8

Conclusions:

The degradation of [14C]-Mancozeb was investigated in three typical use soils, incubated at 20 °C under aerobic conditions for a period of up to 120 days. Additionally one soil (soil III) was also incubated at 10 °C. [14C]-Mancozeb was rapidly eliminated initially by hydrolysis to the degradates EBIS, ETU and EU with a half-life of less than 0.1 days. Kinetic re-evaluation according to FOCUS Kinetics requirements results in calculated DT50 values of up to 0.043 days for mancozeb, 0.42 days for EBIS, 15.3 days for ETU and 8.0 days for EU at 20°C (at 10°C, the corresponding DT50 values were 0.027, 0.95, 34.1 and 5.8 days).

Executive summary:

The summary below taken from the updated RAR Volume 3 CA B8 version December 2018.

 

Mancozeb disappeared rapidly from the soils I, II and III. Its half llfe in any of these soils was less than 1 hour.

 

The metabolic pathway of Mancozeb in the soils used was similiar in all three soils. [14C]-Mancozeb was rapidly degraded to the major metabolites EBIS (M1), ETU (M2) and EU (M3) and finally to carbon dioxide. An intermediate degradation product M11 was detected, however, it disappeared rapidly in less than 1 day.
The amount of radioactive carbon dioxide evolved from soils I to III incubated at 20°C and soil III incubated at 10°C accounted for up to 49.6%, 41.8%, 44.0% and 33.0% of the applied radioactivity, respectively.

 

Metabolite EBIS (M1) was detected at maximum amounts, 1.5 hours after application, of 29.1%, 29.1%, 24.8% and 24.8% of the applied radioactivity in soil extracts from soils I, II, III incubated at 20°C and soil III incubated at 10°C, respectively. Thereafter EBIS disappeared with a DT-50 value of 0.6 days or less in all soils at 20°C and 1.3 days at 10°C.

 

Metabolite ETU (M2) was detected in all three soils. Maximum amounts of 22.0%, 24.8% and 14.7% of the applied radioactivity were présent at incubation day 1 in soils I, II and III, respectively incubated at 20°C. For soil III incubated at 10°C the maximum amount of ETU was detected on day 7 11.9%. The DT-50 values for ETU were 18.2 days, 4.4 days, and 10.7 days for soils I to III incubated at 20°C and 23.1 days for soil III incubated at 10°C.

 

Metabolite EU (M3) was detected at maximum amounts of 18.5% (soil I, day 7), 11.8% (soil II, day 1), 11.7% (soil III at 20°C, day 1) and 11.6% (soil III at 10°C, day 7). Thereafter, EU disappeared with a DT-50 value of 2.7 days or less in all soils.

 

M11, an unknown intermediate, appeared only immediately after application at concentrations above 10%. It reached values of 20.3% (soils I, III at 20°C and at 10°C) and 16.6% (soil II) of the radioactivity applied 1.5 hours after application. Thereafter, it degraded rapidly, and it can therefore be concluded that its half-life is below 1 day.

 

Additionally, at least twelve unknown radioactive fractions were detected in ail three soils. None of these metabolites exceeded 7.4% of the applied radioactivity. Additionally, at least twelve unknown radioactive fractions were detected in all three soils. None of these metabolites exceeded 7.4% of the applied radioactivity and none >5% at two consecutive timepoints.

 

The non-extractable radioactivity amounted to a maximum of 59.1% (day 28), 69.8% (day 28) and 70.7% (day 7) in soils I, Il and III, respectively, incubated at 20°C and to 66.7% (day 63) in soil III incubated at 10°C. Thereafter, the mineralisation to 14C02 continued and the non-extractable radioactivity decreased to 49.0% (soil I), 58.0% (soil II), 52.0% (soil lll/20°C) and 62.0% (soil lll/10°C) after 120 days of incubation. The organic matter fractionation of the bound residues showed that the major part was bound to immobile humic acids and humin fractions amounting to 38.1%, 45.9%, 40.8% and 38.5% the applied radioactivity in the soils I to III incubated at 20°C and in soil III incubated at 10°C, respectively. The corresponding radioactivity associated with the fulvic acid fraction accounted for 14.0%, 15.2%, 11.9% and 23.3% of the applied radioactivity, respectively.

 

The results show that [14C]-Mancozeb was very rapidly eliminated from the test soils at both 20°C and 10°C. This rapid degradation implies that Mancozeb is initially degraded by hydrolysis. The major degradates, EBIS, ETU and EU, are themselves eliminated by subsequent biotransformation to carbon dioxide.
Incorporation into the organic matter of soil also played a significant role.

Description of key information

The degradation of [14C]-Mancozeb was investigated in three typical use soils, incubated at 20 °C under aerobic conditions for a period of up to 120 days. Additionally one soil (soil III) was also incubated at 10 °C. [14C]-Mancozeb was rapidly eliminated initially by hydrolysis to the degradates EBIS, ETU and EU with a half-life of less than 0.1 days. Kinetic re-evaluation according to FOCUS Kinetics requirements results in calculated DT50 values of up to 0.043 days for mancozeb, 0.42 days for EBIS, 15.3 days for ETU and 8.0 days for EU at 20°C (at 10°C, the corresponding DT50 values were 0.027, 0.95, 34.1 and 5.8 days).

Key value for chemical safety assessment

Half-life in soil:

0.043 d

at the temperature of:

20 °C

Additional information

The degradation of [14C]-Mancozeb was first investigated within the soil degradation study by Völkel (2001) in three typical use soils (sandy loam, loamy sand, silt loam), incubated at 20 °C under aerobic conditions for a period of up to 120 days. Additionally one soil (soil III) was also incubated at 10 °C. [14C]-Mancozeb was rapidly eliminated initially by hydrolysis to the degradates EBIS, ETU and EU with a half-life of less than 0.1 days.

 

The data by the study of Völkel, 2001 were re-assessed according to to FOCUS Kinetics guidance to derive DT50 values and formation fractions for mancozeb and its metabolites EBIS, ETU and EU by Hardy, 2015.

The results of the kinetic modelling evaluations indicate a modified degradation pathway for mancozeb and its metabolites in these soils. Initial evaluations with the linear pathway mancozeb-EBIS-ETU-EU were not successful and were not able to adequately fit the data, as the apparent slow decline of ETU in these soils is not consistent with the rapid formation/decline of EU (assuming a direct pathway only from ETU). An additional pathway from EBIS-EU significantly improved the fits but indicated minimal transfer from ETU-EU, thus the pathway was simplified with formation of EU only from EBIS.

                  Trigger endpoints
                  DegT50 (days)  DegT90 (days)

Soil 1          0.043                 0.141

Soil 2          0.027                 0.088

20°C

Soil 3          0.027                 0.090

10°C

Soil 3          0.027                 0.090

 

                  Modelling endpoints
                  DegT50 (days)  DegT90 (days)

Soil 1          0.043                 0.036

Soil 2          0.027                 0.027

Soil 3          0.027                 0.024

 

The behaviour of mancozeb has been investigated in eight soils under laboratory conditions at 20-23^oC [Randazzo (1986); Bieber and Kröhn (1989); Todt and Conradt (1989), summarised in the original Monograph (Annex I Inclusion) and Völkel (2001). In the Bieber and Kröhn (1989) study, ¹⁴C-mancozeb was used to follow the degradation of mancozeb in a silt loam soil.  The CS₂ evolution method was used in the Randazzo (1986) and Todt and Conradt (1989) studies, thus the calculated DT₅₀ values represent the sum of CS₂ liberating components as conservative over-estimates for mancozeb. 

 

Soil characteristics

Randazzo, 1986:

Classification	Silt loam
Sand content	16.0 %
Silt content	58.0 %
Clay content	26.0 %
Organic matter content	2.0 %
Moisture capacity	27.4 %
pH	6.1
Cation exchange capacity	11.9 meq/100 g

 

Bieber and Kröhn, 1989:

Classification	silt loam
Vegetation	pasture, sheep grazing
Organic carbon	1.7 %
pH	6.8
Water capacity	48.3 g/100 g soil
Soil particles < 0.002 mm	21.4 %
0.002-0.006 mm	4.6 %
0.006-0.02 mm	9.5 %
0.02-0.063 mm	54.2 %
0.063-0.2 mm	10.3 %
Microbial biomass	27.5 mgC/100 g soil

 

Todt and Conradt, 1989:

	Soil N° 1	Soil N° 2	Soil N° 3
Origin	Offenbach-Queich Südpfalz	Neustadt-Lachen Pfalz	Neustadt-Lachen Pfalz
Characteristics	Sand	Sand	Loamy sand
Current culture	Potato	Stone-fruit	Wine
Organic carbon (%)	1.1	1.34	0.83
% particles < 0.002 mm	10.6	5.5	12.9
0.002-0.006	4.3	4.7	5.2
0.006-0.02	9.4	11.7	13.7
0.02-0.063	19.0	20.0	23.5
0.063-0.2	20.9	24.2	11.7
0.2-0.63	33.1	31.2	30.1
0.63-2	2.7	2.7	2.9
pH	6.3	6.8	7.2
Microbial biomass (mg micro-C/100 g soil) at start of experiment	38	46	27
Microbial biomass (mg micro-C/100 g soil) at end of experiment	24	26	18

 

Völkel, 2001:

	Soil I	Soil II	Soil III
	Speyer 2.3	Speyer 2.2	Senozan
Texture (USDA)	Sandy loam	Loamy sand	Silt loam
Sand (%)	66.2	77.1	20.32
Silt (%)	26.5	15.4	56.12
Clay (%)	7.4	7.5	23.56
Organic carbon (%)	0.71	2.17	0.99
pH [CaCl2]	6.5	5.7	5.8
CEC (meq/100g soil)	11	11	15.49
MWHC (%w/w)	37	50	55.35
pF 2.5 (%w/w)	-	-	24.19
Biomass (mg OC/kg soil)
Start	142	401	587
End	93	406	393 (20^oC) 487 (10^oC)

Materials and methods

Bieber and Kröhn, 1989:

Radio labelled [¹⁴C]-Mancozeb (specific radioactivity: 1.029 MBq/mg, ETU content < 0.1%) was used together with un-labelled Mancozeb technical (purity: 87.7 %).

[¹⁴C]Mancozeb was applied in solution in acetone at ca. 4 mg a.i./kg soil (ca. 3kg a.i./ha) in the degradation experiment - up to 30 mg [¹⁴C]Mancozeb in the experiments for metabolite identification. The temperature was 20-21°C.

Sampling was performed at 0, 1, 3, 16, 24, 40, and 48 hours and 1, 2, 4 and 8 week. The analysis of CS₂ was determined according to the DFG-method S15 (xanthogenate, 302 nm, 2 cm cuvettes, S15-5).

Metabolites were identified by Thin Layer Chromatography with reference chemicals (ETU, DIDT, EMI, EU, TCIT, Sulphur, Jaffe's base) using 2 different solvents mixtures: acetonitrile: water = 85: 15 (v/v) and methanol: toluene = 1: 1(v/v). Compounds (metabolites) are identified by GC/MS and radioactivity was determined by Liquid Scintillation Spectrometry.

 

Todt and Conradt, 1989:

Technical Mancozeb (Purity:87.7%) has been used with BBA standards soils provided by Lufa Speyer.

Mancozeb was applied at a rate of 3.0 - 5.3 mg a.i./kg soil (applied in solution in acetone). Sampling was performed at 0, 1, 2, 6, 24, 48 hours and 1, 2, 4 and 8 weeks. Mancozeb was analysed by CS₂ according to the DFG-method S15 (xanthogenate, 302 nm, 2 cm cuvettes, S15-5).

 

Völkel, 2001:

For details please refer to the key study under point 5.2.3 Biodegradation in soil - aerobic.

Kinetic evaluation:

Kinetic modelling following the appropriate FOCUS Kinetics (2006) flowchart was carried out using CAKE v3.1 by Hardy, 2015.

 

Results and discussion

The geometric mean normalised DegT₅₀ is rounded up to 0.1 days for model input.

For PECsoil calculations, a conservative DT₅₀ is selected as 0.6 days - mean un-normalised SFO DT₅₀ of the 20 and 10ppm silt loam soils based on CS₂ liberation.  This DT₅₀ value is highly conservative for mancozeb and ensures that the soil exposure/risk assessment covers any transient unidentified components in soil.

 

Degradation parameters and trigger endpoints for mancozeb

Soil	Best-fit model	Chi^2 (%)	Model parameters	Trigger endpoints
				DegT50 (days)	DegT90 (days)
Silt loam (20ppm)	DFOP	3.1	k1 [d^-1]: 7.818 k2 [d^-1]: 0.06045	0.105*	1.35*
Silt loam (10ppm)	FOMC	7.0	α 0.6848 β 0.09077	0.159*	2.53*
Marsh	FOMC	8.8	α 0.5977 β 0.1829	0.017	0.35
Silty sand 1	DFOP	11.3	k1 [d^-1]: 46.42 k2 [d^-1]: 0.03743	0.027*	29.6*
Silty sand 2	DFOP	10.3	k1 [d^-1]: 24.82 k2 [d^-1]: 0.01913	0.039*	33.3*
Humic loamy sand	FOMC	11.5	α 0.3084 β 0.006505	0.055*	11.4*
Speyer 2.3	SFO	1.01	k [d^-1]: 16.3080	0.043	0.141
Speyer 2.2	SFO	1.01	k [d^-1]: 26.1120	0.027	0.088
Senozan	SFO	1.01	k [d^-1]: 25.7520	0.027	0.090

* Total of CS₂ liberating components, thus conservative for mancozeb

 

Degradation parameters and modelling endpoints for mancozeb – ¹⁴C studies

Soil	Best-fit model	Chi^2 (%)	t-test (-)	Modelling endpoints
				DegT50 (days)	Normalised DegT50 (days)^a
Marsh	FOMC	8.8	N/A FOMC DT90/3.32	0.106	0.082
Speyer 2.3	SFO	1.01	5.00E-04	0.043	0.036
Speyer 2.2	SFO	1.01	5.52E-04	0.027	0.027
Senozan	SFO	1.01	5.48E-04	0.027	0.024
Geometric mean					0.037

^a Reference conditions: 20^oC, pF2

 

Degradation parameters and modelling endpoints for mancozeb - CS₂ liberation studies

Soil	Best-fit model	Chi^2 (%)	t-test (-)	Modelling endpoints
				DegT50 (days)	Normalised DegT50 (days)^a
Silt loam (20ppm)	SFO	13.7	1.03E-04	0.595^c	0.69^c,d*
Silt loam (10ppm)	SFO	11.5	2.66E-04	0.638^c	0.74^c,d*
Silty sand 1	DFOP^b	11.3	0.008107	0.015	0.015*
Silty sand 2	DFOP^b	10.3	1.78E-04	0.028	0.028*
Humic loamy sand	DFOP^b	13.3	0.001329	0.048	0.048*

^a Reference conditions: 20^oC, pF2            
^b DFOP k₁ degradation rate selected as representing mancozeb degradation in the CS₂ liberation study.
^c Conservative SFO fit that includes other CS₂ liberating components
^d geometric mean of the two silt loam soils = 0.70 days       
* CS₂ liberation studies

 

Degradation parameters and modelling endpoints for mancozeb

Soil	Best-fit model	Chi^2 (%)	t-test (-)	Modelling endpoints
				DegT50 (days)	Normalised DegT50 (days)^a
Silt loam (20ppm)	SFO	13.7	1.03E-04	0.595^c	0.69^c,d*
Silt loam (10ppm)	SFO	11.5	2.66E-04	0.638^c	0.74^c,d*
Silty sand 1	DFOP^b	11.3	0.008107	0.015	0.015*
Silty sand 2	DFOP^b	10.3	1.78E-04	0.028	0.028*
Humic loamy sand	DFOP^b	13.3	0.001329	0.048	0.048*
Marsh	FOMC	8.8	-	0.106	0.082
Speyer 2.3	SFO	1.01	5.00E-04	0.043	0.036
Speyer 2.2	SFO	1.01	5.52E-04	0.027	0.027
Senozan	SFO	1.01	5.48E-04	0.027	0.024
Geometric mean					0.05^d,e

^a Reference conditions: 20^oC, pF2            
^b DFOP k₁ degradation rate selected as representing mancozeb degradation in the CS₂ liberation study.
^c Conservative SFO fit that includes other CS₂ liberating components
^d geometric mean of the two silt loam soils (0.7 days) calculated first
^e rounded to 0.1 days for model input      
* CS₂ liberation studies

 

Degradation parameters for total mancozeb + M11 residues

Soil	DT50 (days)	DT50 (hours)	Chi^2 (%)	t-test (-)	Visual
Speyer 2.3	0.076	1.8	0.1	0.001128	Good
Speyer 2.2	0.042	1.0	2.7	1.78E-06	Good
Senozan	0.048	1.1	0.1	0.001018	Good

 

Formation/decline degradation parameters for M11 residues

Soil	DT50 (days)	DT50 (hours)	t-test (-)	ffm (-)	Visual
Speyer 2.3	0.095	2.3	1.07E-04	0.44	Good
Speyer 2.2	0.257	6.2	6.22E-05	0.24	Good
Senozan	0.102	2.5	6.19E-05	0.35	Good