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EC number: 202-607-8
CAS number: 97-77-8
14C-Thiram is very rapidly degraded, mainly to 14CS2, 14CO2 and to at
least 20 minor metabolites, which were further degraded to CO2, other
small fractions and disappeared by adsorption to sediment. The
continuous formation of 14CO2 and the decrease of the amount of the
bound residues in sediment, show that the non-extractable radioactivity
is slowly released and further degraded and mineralised. The half-life
of Thiram in the river as well as in the pond system was 1.9 days and
the DT90 was 6.2 and 6.3 days for river and pond system, respectively.
The rapid conversion to 14CS2 and 14CO2 indicated that Thiram will not
persist in aquatic environments.
Materials and methods:The
objective of the study was to provide information on the distribution
and metabolism of14C-THIRAM in two different water/sediment
systems under aerobic conditions according to BBA (Biologische
Bundesanstalt /Federal Biological Research Centre/) Guidelines, Part IV,
Section 5-1 (December 1990): Abbaubarkeit und Verbleib von
Pflanzenschutzmitteln im Wasser/Sediment-System.
A water-sediment test systems was sampled from the
river Rhine (Mumpf Zeltplatz, Aargau/Switzerland) and from the pond
Judenweiher (Rheinfelden near Görbelhof, Aargau/Switzerland).
The study was performed in 0,5 L all-glass metabolism flasks. The water
was filtered through a 0.2 mm sieve and the sediment was sieved through
a 2.0 mm screen. The study was run in duplicate. The treated samples as
well as the controls were prepared and incubated at 20 ± 2°C in the dark
under aerobic conditions.
Each river and pond
water-sediment system prepared for sampling on days 0.25, 1, 2, 7, 14,
30 and 57 was treated with14C-THIRAM in concentration of
1.195 mg/L water. The test systems prepared for sampling on days 0, 4
and 101 were treated with 1.378 mg14C-THIRAM/L water.
The results obtained for the samples of the second application were
normalised to achieve the first application rate.
sediment and volatile substances were worked up and analysed by High
Performance Liquid Chromatography (HPLC).
Results and discussion:
Radioactivity (RA) in the river and pond test system:
After treatment, the radioactivity (RA) in the
river water as well as in the pond water decreased steadily from 107.5%
of the applied RA on day 0 to 6.5% and 6.1% on day 101, respectively.
In the sediment the RA first increased up to a
maximum of 29.6% (river) and 34.7% of the applied RA (pond) on day 14
and on day 30, respectively, then slowly decreased to 15.6% in the river
system and to 23.9% of the applied RA in the pond system at the end of
the incubation period.
The sediments were extracted with chloroform and
with methanol. The extractable RA from sediments was low and increased
continuously reaching maximum values of 3.9% for river and 7.5% for pond
at days 14 and 30, respectively. Thereafter the extractable RA decreased
to values of 1.8% at day 101 of incubation for both systems.
The degradation of14C-THIRAM to volatile
which were trapped in the volatile traps, was very high and reached
65.8% and 60.8% of the applied RA for river and pond system,
respectively, at study termination. In the river system the highest
volatilisation rate was observed between days 7 and 30. The highest
volatilisation rate for pond system was between days 7 and 14.
In the river system 56.1% of the RA applied was
detected as14CO2and 9.6% as14CS2in
the river at the study termination. Concurrently in the pond system
36.6% and 24.2% of the applied RA were detected as14CO2and14CS2,
The amount of14CO2in the NaOH
trap was determined after precipitation with aqueous Ba(OH)2solution.
The amount of14CO2increased with the incubation
time and ranged from about 18% to 56% of the RA in the volatile traps of
the river system, between days 4 and 14. At the study termination the
value of 96% RA was reached. The corresponding values for the pond
system ranged from 9% to 23%, respectively. On the last incubation day
97% of the RA was detected. The remaining volatile RA in the NaOH traps
was considered to be 14CO2.
Also in the water phase as well as in sediment
extracts from both systems volatiles compounds were observed. After
precipitation with Ba(OH)2up to 57.5% (river) and 43.9%
(pond) of the initial RA was detected in water as14CO2.
Total volatiles (in volatile traps and dissolved in water and sediment
extracts) amounted to 70.6% and 67.3% of the RA applied at the study
termination in the river and pond systems, respectively.
total mean recoveries of radioactivity obtained during the whole
incubation time were 95.6 ± 6.2% and 99.1% ± 6.1% of RA applied for the
river and pond systems, respectively.
Thiram degraded fast from 96.7% or 15.7 ug/L on day 0 to 0.5% or 0.08
ug/L on day 10 which was just above the determination limit in this
study. The degradation rate of Thiram was calculated using a first order
kinetic model and the Optimum fit found. The degradation time (50%
degradation of Thiram, DT-50 value) was 0.7 days and the DT-90 (90%
degradation) value was 2.5 days. The calculted level of Thiram was 0.01%
er 0.0016 ug/L on day 10.
Materials and methods:The objective of the
study was to provide information on the distribution and metabolism of14C-THIRAM
in water/sediment systems according to BBA (Biologische Bundesanstalt
/Federal Biological Research Centre/) Guidelines, Part IV, Section 5-1
(December 1990): Abbaubarkeit und Verbleib von Pflanzenschutzmitteln im
A water-sediment test system was sampled from the
river Rhine (Sisseln, AG /Switzerland).
The study was performed in an open gas-flow-system in 1.0 L all-glass
metabolism flasks. The water was filtered through a 0.2 mm sieve and the
sediment was sieved through a 2.0 mm screen. The study was run in
duplicate. 14 flasks with treated samples, 14 untreated flasks as
reserves and 2 controls were prepared and incubated at 20 ± 2°C in the
dark. Each water/sediment test system was treated with 460 µL of the
radiolabelled14C-THIRAM in acetone. The actual radioactivity
of the application solution was 5454844 dpm per flask. The test item was
applicated at actual concentration of 16.26 µg a.i./L water or 8.62 µg
a.i. per flask. Water, sediment and volatile substances were worked up
and analysed by HPLC and TLC.
Results and discussion:14C-THIRAM
was detected with 96.7% of the radioactivity applied (15.7 µg a.i./L) in
the river water directly after treatment on day 0. This amount rapidly
decreased to 51.6% (8.4 µg/L) on day 0.75 and was just slightly above
the determination limit of 0.3% on day 10. Only 0.5% of applied RA (0.08
µg/L) was detected at the study termination.
The rate of degradation was calculated according to
1st-order kinetic model. 0.7 and 2.5 days were obtained for DT50and
DT90, respectively. In water phase the level of radioactivity
decreased very fast from 99.7% of applied radioactivity (16.2 µg parent
equivalents per litre water) on day 0 to 25.2% (5.7 µg/L) on day 10. In
sediment samples the radioactivity first increased from 0.6% (0.1 µg/L)
on day 0 to 33.4% (5.4 µg/L) on day 7. Afterwards a slight decrease of
RA up to 32.6% (5.3 µg/L) on day 10 was observed. The water phase was
partitioned twice with dichloromethane. The RA in the dichloromethane
phase decreased steadily to 5% at the end of the study. The
radioactivity remaining in the water phase increased until day 2 to >
40% of the RA applied, but decreased thereafter until day 10 to about
30%. Volatile RA, including the14CO2dissolved in
the water phase increased continuously during the incubation time.
Within the first day the RA increased to 13.1% (2.1 µg parent
equivalents per litre). Afterwards 23.6% of applied RA (correspond to
3.8 µg/L) were detected on day 2 and at the study termination 25.7% (4.2
No RA was found in the ethylene glycol traps. The radioactivity was
retained in the 1M KOH in methanol and consisted mainly of14CO2.
The amount of14CO2in the test system at the end of
the study was 21.0% of the RA applied. At the same time other volatile
substances reached only 4.7% (due to information of a former study
probably14CS2). The mean recovery of radioactivity
was 94.9 ± 2.9% of RA applied (15.4 ± 0.5 µg parent equivalents per L
water). The individual recoveries were all between 92.0 and 101.5%.
Disulfiram is not expected to be persistent in aquatic environments
(DT50 < 2 days).
No data on the biodegradation of disulfiram
(CAS No. 97-77-8) in water and sediment were available. Therefore, a
conclusion based on data from an analogue substance had to be drawn.
Biodegradation in water/sediment systems of tetramethylthiuram disulfide
(CAS No.137-26-8), substance structurally and composition related to
tetraethylthiuram disulfide, was investigated in two studies.
These tests were
conducted according to the German BBA Guidelines, Part IV, Section 5-1
(1990): “Degradability and metabolism of Plant Protection Products in
Water/Sediment Systems”, under GLP conditions. A concentration of 1.195
mg14C-thiram/L water of the radiolabelled compound was
incubated in the first study (1992) for 101 days.14C-thiram
was very rapidly degraded, mainly to14CS2,14CO2and
at least 20 minor metabolites, which were further degraded to CO2,
other small fractions and disappeared by adsorption to sediment. The
half life of the compound was 1.9 days. The non-extractable
radioactivity was there further degraded and mineralised. In the second
study (1995), 16.26 ug/L a.i. were incubated for 10 days under similar
conditions, resulting in a rapid degradation (half life= 0.7 days)
leading to several minor metabolites that further mineralised, being CO2the
main degradation product.
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