Determination and identification of metabolites of the fungicides Iprodione and Procymidone in compost

Article abstract of DOI:10.1016/S0045-6535(99)00555-X

The main metabolites formed from Iprodione and Procymidone during the composting process have been isolated and identified by HPLC-DAD-MSD. After addition of the fungicides to the composting pile, we monitored the reaction of the two analytes and the form

Full text of DOI:10.1016/S0045-6535(99)00555-X

Chemosphere 41 (2000) 1431±1439
Determination and identi®cation of metabolites of the
fungicides Iprodione and Procymidone in compost
a,
Adriano Vanni , Roberta Gamberini , Adelaide Calabria , Pina Nappi
a
a
b
*
a
Dipartimento di Chimica Analitica, Universit aꢀ di Torino, Via P. Giuria 5, 10125 Torino, Italy
A.R.P.A., Via della Rocca 49, 10123 Torino, Italy
b
Received 2 August 1999; accepted 18 November 1999
Abstract
The main metabolites formed from Iprodione and Procymidone during the composting process have been isolated
and identi®ed by HPLC-DAD-MSD. After addition of the fungicides to the composting pile, we monitored the reaction
of the two analytes and the formation of their degradation products for eight months. We veri®ed the nature of the
metabolites by comparison with those hypothesised in the literature and by comparison with the behaviour of an abiotic
process in aqueous acetonitrile pH 6 and at 35°C. After taking into account the di€erent kinetic behaviours of the
fungicides on degradation in compost and hydro-organic solution, breakdown pathways are proposed for biodegra-
dation. Ó 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Metabolite; Iprodione; Procymidone; Kinetic; Composting process; HPLC-DAD-MSD
1
. Introduction
been done on the presence and fate of undesirable
organic compounds.
Application of recycled municipal sludges to agri-
Since compost is used for growing plants, the fate of
any anthropogenic compounds in the compost must be
known. In particular, pesticides are used with some
regularity on turf grass, vegetables and fruit, and the
fate of most of these products during the compost pro-
cess is not well known (Racke and Frink, 1989; Lemmon
and Pylypiw, 1992).
cultural land for maintaining or increasing soil fertility
has become an argument of great interest for soil sci-
entists, agronomists and environmentalists throughout
the world. Although these organic additives can have a
positive in¯uence on the physical and biochemical
properties of soils (Tietjen, 1975; Chen and Avnimelech,
1
986), great interest arises due to the presence in the
The two dicarboximidic fungicides Iprodione (Rov-
ral) and Procymidone (Sialex 50 WDG) are frequently
used for controlling fungal diseases such as the Botrytis
Cinerea, Monilia and Sclerotinia species, and they are
especially used in fruit growing, strawberry, wine, hor-
ticulture and ¯ower and ornamental cultivations. The
relative formulas are reported in Fig. 1.
sludges of hazardously high levels of heavy metals and
organic pollutants, mainly derived from industrial ef-
¯
uent that reach the treatment plants.
While a considerable amount of literature has been
published about the negative e€ects caused by toxic
metals in plant-soil systems (Wieteska et al., 1996; Leiter
et al., 1997; Zhou and Liu, 1997), very little work has
The use of these pesticides is increasing as their cor-
rect application does not produce a residual content in
the food products that is higher than that consented by
the legal limits (Molinari et al., 1980; Cabras et al., 1982;
Flori et al., 1982a,b). Nevertheless, it is possible to ®nd
crops and environments with consistent residues of these
*
Corresponding author. Tel.: +39-11-670-7611; fax: +39-11-
70-7615.
E-mail address: vanni@ch.unito.it (A. Vanni).
6
0
045-6535/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved.
PII: S 0 0 4 5 - 6 5 3 5 ( 9 9 ) 0 0 5 5 5 - X

1
432
A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
Solvents employed included acetic acid (glacial
100%); GR, Merck), ortho-phosphoric acid 99% (extra
(
pure, Riedel-de Ha e n), di-sodium hydrogen phosphate
dihydrate 99.0% (Fluka), sodium dihydrogen phosphate
dihydrate 99.0% (Fluka), ammonium acetate (analytical
reagent, Riedel-de Ha e n), acetonitrile gradient-grade
(Chromasolv, Merk). Ultra pure water was obtained
from a water puri®cation Elgastat system.
Fig. 1. Formulas of Iprodione and Procymidone.
2
2
.2. Procedure
.2.1. Addition on composting pile for biotic degradation
Fig. 2, shows a diagram of a generic composting pile.
fungicides and/or their breakdown products, as a con-
sequence of frequent application, or because the interval
between treatments (Barbero and Gaia, 1979; Flori et al.,
The analyte additions have been made in the sketched
zones (about 10 m) of two extremes, while the central
one (about 10 m) has been considered as blank.
1
982a) is not respected. In a recent study (Vanni et al., in
press), non-toxic amounts of dicarboximidic fungicides
Iprodione, Vinclozolin and Chlozolinate) have been
The medium quantity of technical product (50%
analyte + coformulates) to be applied on crops is about
(
found with or without their common metabolite (3,5-
DCA) in commercial compost. Therefore, given the
various uses of compost, the danger of bioaccumulation
of the possible breakdown products with unknown
toxicity cannot be excluded.
1
.5±2 kg/ha, therefore 450 gproduct/10 mpile has been ap-
plied in order to obtain detectable quantities of analyte.
Taking into consideration the parameters reported in
Table 1, the added quantity is therefore 20 lg of analyte
versus g dried compost (DC).
This paper reports the isolation and structural iden-
ti®cation of the breakdown products of Iprodione and
Procymidone during the composting process. After ad-
dition of the fungicides to the composting pile, the be-
haviour of the two fungicides and their degradation
products was studied, and veri®cations were made by
comparing the kinetic behaviour of every compound in
the compost in an hydro-organic acid solution (55%
acetonitrile/45% sodium phosphate bu€er pH 6.5) where
fungicides are completely soluble. In fact, the chemical
hydrolysis of pesticides could be one of the principal
mechanisms for the decomposition of organic pesticides
in the environment, in soils, in plant tissues or in
maintained foods. Therefore, understanding the reaction
kinetics could be an important parameter for predictions
on the biological activity and the persistence of the ac-
tive ingredients.
The pile was turned regularly and sampled at com-
post initiation and at 4, 11, 18, 25, 32, 43, 60, 94, 119,
1
51, 186 and 241 days after treatment. During the
composting process, pH variations were evaluated using
the ocial method reported in DIVAPRA (1998) from
pH 5.5 at acid phase to pH 7.5 before grinding until pH
8
.7 after maturation in the farmyard (eight months).
The compost samples were frozen at )18°C and
preserved in plastic bags.
2
.2.2. Extraction from compost samples
The analytical technique using sonication disruption
and acetonitrile extraction have been reported elsewhere
Vanni et al., in press). The obtained extracts have been
(
preserved at 4°C in screw-capped vials.
Based on these data, biodegradation pathways for
these fungicides are proposed.
2
. Experimental
Fig. 2. Diagram of the composting pile: sketched areas show
sampling zones.
2
.1. Materials
Iprodione [3-[(3,5-dichlorophenyl)-N-(1-methylethyl)
2,4-dioxo-1-imidazolidinecarboxyamide] was furnished
Table 1
Characteristics of composting pile
-
by Supelco. Procymidone [N-(3,5-dichlorophenyl)-1,2-
dimethylcyclopropane-1,2-dicarboximide] and 3,5-di-
chloroaniline were supplied from Dr Ehrenstorfer
GmbH. The commercial products Rovral (Iprodione)
and Sialex 50 WDG (Procymidone) were furnished by
Pile width (m)
Pile length (m)
Pile height (m)
2
120
1.5
0.6
50
3
Compost density (t/m )
Compost humidity (%)
^
RHONE-POULENC and SIAPA, respectively.

A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
1433
Table 2
Operative conditions for the analysis of fungicides, metabolites and hydrolyses
Biotic process
Abiotic process
Hydrolyses
Fungicides
Metabolites
Column
Lichrospher, HP)
RP-C18, 5 lm,
250 mm ´ 2 mm 1 i.d.
0.3
RP-C18, 5 lm,
250 mm ´ 2 mm 1 i.d.
0.3
RP-C18, 5 lm,
250 mm ´ 3 mm 1 i.d.
1
RP-C18, 5 lm,
250 mm ´ 2 mm 1 i.d.
0.3
(
Flow (ml/min)
Eluent
H
2
O/CH
3
CN
H
2
O/CH
CH COOH 0.05 M
pH 3/CH CN
3
CN
H
2
O/CH
3
CN
H
2
O/CH
3
CN
3
Phosphate bu€er
0.05 M pH 3/CH
3
3
CN
a
a
b
a
Elution
Detector
Gradient
DAD/APCI
Gradient
DAD/API-ES
Isocratic
DAD
Gradient
DAD/API-ES
a
See the solvent programming diagram below.
7
b
0% organic solvent/30% phosphate bu€er.
2
.2.3. Abiotic hydrolysis: operative conditions
The pH (6 and 8.7) values have been chosen follow-
Table 3
Working conditions for the MS detector
ing evaluations made during the composting process.
The temperatures used (35°C and 55°C) refer to the
values of the mesophilic and thermophilic steps of the T
Operative parameters
Tdrying gas (°C)
vaporiser (°C)
Flow-ratedrying gas (ml/min)
Capillary voltage (V)
Corona current (lA)
Fragmentor (V)
APCI
350
325
7
API-ES
350
T
/
10
(
°C) curves versus time, as reported in Golueke (1977).
Aliquots of 0.2 ml of a single standard solution at 500
5000
6
5000
/
70
lg/ml in acetonitrile were mixed with 0.01 M phosphate
bu€er at two di€erent levels of pH 6 and 8.7. The ®nal
concentration of fungicide in the bu€ered solutions was
70
Positive
Polarity
Negative
20 lg/ml. Aliquots of 1 ml of the bu€ered standard so-
lutions were transferred into vials and incubated at 35°C
and 55°C in a water bath and in darkness. After incu-
bation, the samples were acidi®ed with H
to stop the reaction.
Table 4
Detection limits of tested compounds from compost samples
3 4
PO to pH 3
DAD
MSD
Compounds
LOD (lg/kg)
Æ RSD (%)
35 Æ 8:9
LOD (lg/kg)
Æ RSD (%)
50 Æ 7:1
2
.2.4. Fungicides and metabolites analysis
The analysis of the extracts was executed by HPLC,
Iprodione
Procymidone
injecting 20 ll of ®ltered solutions into a liquid chro-
matograph (HP 1100) equipped with a 1100 Binary
Pump and with UV±Vis/diode array detector (HP 1100
DAD) and a mass detector (HP 1100 MS).
35 Æ 7:4
200 Æ 6:5
The operative conditions are reported in Table 2.
Every solvent was previously ®ltered and degassed.
The solvent programming was as follows:
The quantitative determination of the degradation
products was made using external standards, if com-
mercially available, or in any case, was determined ap-
proximately with the assumptions that follow.
1
4
min
0%
5 min
70%
In Cabras et al. (1983) and Pirisi et al. (1986), 3,5-
DCA is given as the ®nal product of degradation of two
analytes. By comparing absorbance spectra (see Fig. 3),
it is evident that the absorbance at 210 nm due to the
aromatic ring is slightly in¯uenced by the chromophor
groups (C¸O) adjacent to ±N—. Therefore, supposing
that at a chosen wavelength the e (molar absorbivity) of
several formed metabolites remains practically equal to
that of 3,5-DCA and analyte, we can assume that the
Lambert±Beer equation could be applied to other
breakdown products, CMet is thereby calculated by the
following equation:
!
!
100%
!
40%
3
4 min
30 min
10 min
Changes in the percentage of organic solvent in the
mobile phase through the gradient program occurred
linearly. The absorption of analytes was monitored at
210 nm and the entire absorbance data were recorded
from 190 to 400 nm during every analysis.
The working conditions for APCI and API-ES are
reported in Table 3.
The quanti®cation of peaks was carried out by an
external standard method, using measurements of peak
areas and a calibration curve for each pesticide. The
limits of detection (LOD) are reported in Table 4.
CMet ˆ ꢀCAnalyte=3;5-DCA à AMet†=AAnalyte=3;5-DCA
;
ꢀ1†

1
434
A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
Fig. 3. Comparison with absorbance spectra: (a) Iprodione and its metabolites, and (b) Procymidone and its metabolites.
where C Met and CAnalyte=3;5-DCA are the concentrations of
metabolite and of analyte (Procymidone or Iprodione)
or 3,5-DCA, respectively.
After semi-quantitative evaluations of breakdown
products, the kinetic behaviour for each compound was
studied and the relative constants rate and pattern by
mathematical expressions was determined using the lit-
erature method based on parallel-consecutive reaction
(Rodiguin and Rodiguina, 1964), which is well suited for
this kind of kinetics.
3
. Results and discussion
3
.1. Biodegradation of analytes
Fig. 4. Degradation kinetics of Procymidone during compo-
�
4
sting process. Initial substrate concentration, C : 1.23 ´ 10
0
In the present study, we previously studied the de-
molAnalyte:/gdry
.
gradation, said ÔprimaryÕ, of two analytes during the
composting process, then our attention focused on
compounds formed during the process, in order to
identify them through MSD and to verify that no ac-
cumulation of toxic reaction products is produced in the
reaction media.
by a slower process. Vandervoort and others hypothes-
ised that the ®rst step could be related to volatilisation
and photolysis, while the second step to microbial
degradation.
In the examined time range (0±241 days), the total
conversion of Procymidone did not occur: 30%
remained unchanged in the compost.
3
.2. Procymidone
From a kinetic point of view, the results of primary
degradation point out a pseudo-®rst-order law, de-
scribed by the equation
As shown in Fig. 5, the partial primary biodegrada-
tion led up to two breakdown products which were
identi®ed with MSD, 3,5-dichloronaline and 2-(3,5-di-
chlorophenylcarbamoil)-1,2-dimethylpropane carboxy-
lic acid (metabolite I) (Pirisi et al., 1986). Their mass
spectra are reported in Fig. 6.
�
dC=dt ˆ kobsC;
ꢀ2†
where C is the substrate concentration and kobs is the
observed ®rst-order rate constant. According to Eq. (2),
linear plot of ln(C/C
in Fig. 4), from which slopes kobs can be estimated. A
0
) versus time is obtained (see insert
3.3. Iprodione
�
4
� 1
value of 0.073 ´ 10 min was determined working
under the conditions reported in Fig. 4. Each point
represented three replicate experiments.
Fig. 7 shows that a rapid transformation to only a
breakdown product happens in approximately 30 days
for this fungicide.
As shown in Fig. 4, the degradation curve of fungi-
cide seemed to present the same biphasic degradation
shown by other pesticides reported in Vandervoort et al.
Following characterising with MSD, the metabolite
formed during the composting process was identi®ed:
the parent compound was quantitatively converted to its
Isomer, 3-isopropyl-N-(3,5-dichlorophenyl)-2,4-dioxo-
(
1997). There is an initial rapid dissipation rate followed

A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
1435
In addition, for Iprodione, according to Eq. (2), slope
obs has been estimated (see insert in Fig. 7) in a value of
k
�
4
� 1
0
.83 ´ 10 min
.
3
.4. Abiotic degradation of fungicides
In the literature, several studies have reported
Cabras et al., 1984; Melkebeke et al., 1986; Pirisi et al.,
986; Newsome and Collins, 1990) on analytes hydro-
(
1
lysis with precise reference to their breakdown products.
To con®rm the nature of biotic metabolites, and to es-
tablish the kind of reactions that take part during the
composting process, abiotic degradation has been car-
ried out. Hydrolysis has been taken with standard so-
lutions at several pH and temperatures. Kinetics of
fungicides degradation and metabolites formation have
been evaluated.
Fig. 5. Formation kinetics of Procymidone metabolites during
the composting process.
In the following ®gures, degradation kinetics and the
relative metabolite formations are reported for both
analytes.
3
.5. Procymidone
In the degradation rate and time range, the hydro-
lysis conditions which approach the biotic conditions
see Fig. 4) are pH 6 and 35°C. The identi®cation of the
(
two breakdown products derived with MSD, and whose
formation kinetics are reported in Fig. 10, result to be
the same as those obtained during the composting pro-
cess (see Fig. 6).
Fig. 6. Mass spectra of 3,5-DCA (a) and metaboliteI (b).
Operative conditions are reported in Table 3.
The data plotted in Fig. 9 show that the fungicide
behaved very di€erently in several analysed conditions.
At pH 6.0 and at a 35°C temperature, Procymidone
degraded to only 15% in 40 days. With the increase of
pH it was completely degraded (100%) within 35 days,
and with the increase of temperature it was completely
degraded within 10 days.
The linear lines of the pseudo-®rst-order kinetics,
obtained at two di€erent pH values (6 and 8.7), are
�
4
shown in the insert of Fig. 9. The kobs values of 2.4 ´ 10
�
1
� 4
� 1
min and 41.5 ´ 10 min were determined for pH 6
and 55°C and for pH 8.7 and 35°C, respectively, while at
pH 6 and 35°C linearisation was not possible because
t1=2 has not been reached.
Fig. 7. Degradation kinetics of Iprodione (d) and its metabo-
lite (s) during composting process. Initial substrate concen-
3.6. Iprodione
�
4
tration, C
0
: 1.04 ´ 10 molAnalyte/gdry.
As shown in Fig. 11, the data show di€erent behav-
iour at di€erent conditions for this fungicide. The hy-
drolysis conditions which approach those of the biotic
process, such as degradation rate and time (see Fig. 7),
are again pH 6 and 35°C. Nevertheless, from the for-
mation kinetics of Iprodione metabolites reported in
Fig. 12, the identi®cation of the three formed break-
down products have con®rmed only the Isomer-like
compound also formed during the composting process.
1
-imidazolidine-carboxamide (for the formula see Fig. 8)
in accordance with the formula reported in a study on
spiked vegetables samples (Newsome and Collins, 1990).
Also shown in Fig. 7, after 70 days, 20% of the
Isomer undergoes microbial degradation to other me-
tabolites which is probably not seen due to the fact that
the metabolites are under the detection limits.

1
436
A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
Fig. 8. Mass spectrum of Isomer. Operative conditions are reported in Table 3.
Fig. 11. Degradation kinetics of Iprodione during the hydro-
Fig. 9. Degradation kinetics of Procymidone during the hy-
�
�
5
5
lysis process. Initial substrate concentration: 4.0 ´ 10
Operative conditions: (d) pH 6, 35°C; (s) pH 6, 55°C; (.) pH
.7, 35°C.
M.
drolysis process. Initial substrate concentration: 3.6 ´ 10 M.
Operative conditions: (d) pH 6, 35°C; (s) pH 6, 55°C; (.) pH
8
8
.7, 35°C.
(
(
met: II), in accordance with Newsome and Collins
1990), and metabolite III whose mass spectra are
reported in Fig. 13.
On the contrary, compared to the biotic process,
generally the isomerisation has not been quantitatively
(
a low concentration of Isomer was formed) and at the
highest temperature (55°C) the presence of 3,5-DCA has
been determined.
In the insert in Fig. 11, the linear lines of the pseudo-
®
rst-order kinetics at the three di€erent analysed pH
�
4
� 1
values are shown. The kobs values of 1.4 ´ 10 min
,
�
4
� 1
� 4
� 1
1
0.7 ´ 10 min and 268 ´ 10 min were estimated
for pH 6 at 35°C and 55°C and for pH 8.7 at 35°C,
respectively. These data show that Iprodione rate con-
stants are also in¯uenced by pH and temperature vari-
ations, but more by pH rather than by temperature.
Table 5 summarises a qualitative comparison be-
tween the biotic and abiotic processes. All metabolites
obtained are reported for both analysed fungicides.
By analysing the Procymidone results ®rst, as both
processes present the same metabolites, we could
Fig. 10. Formation of Procymidone metabolites during hy-
drolysis (pH 6, 35°C).
The relative mass spectra is reported in Fig. 8. The two
new metabolites have been identi®ed by MSD as 3-iso-
propil carbamoil-5-(3,5-dichlorophenyl)hydantoic acid

A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
1437
hypothesise that during the composting process hydro-
lytic degradation prevails. This hypothesis could be
supported by the analysis of the semi-quantitative data
reported in Table 6. During the biotic process the pre-
dominance of one of the two reaction steps is not pre-
sent: k
accordance with the more similar abiotic condition (pH
and T 35°C), the biotic degradation of Procymidone is
characterised by a slow breakdown as shown by the
higher value of t1=2
1
and k
2
values have the same order. In
6
.
In the abiotic process, the reaction rate of step 1,
determining the formation of metabolite I, the re-
sults are in¯uenced more by the increase of pH than by
the increase of temperature. For the second reaction
step, determining the formation of 3,5-DCA, the rate
Fig. 12. Formation kinetics of Iprodione metabolites during
hydrolysis (pH 6, 35°C).
2
constant (k ) is a€ected by the opposite in¯uence.
For Iprodione, chemical hydrolysis is probably of
limited importance to the fate of this chemical during
Fig. 13. Mass spectra of met: II (a) and met: III (b). Operative conditions are reported in Table 3.
Table 5
Comparison between biotic and abiotic metabolites
Fungicides, (m/z) t
r
Procymidone, (283) 21.2
Iprodione, (329) 20.5
Metabolites
Biotic process
Abiotic process
I (m/z) t
(301) 6
(301) 6
r
3,5-DCA (m/z) t
(161) 15.5
r
II (m/z) t
/
r
III (m/z) t
/
r
3,5-DCA (m/z) t
/
(161) 15.5
r
Is. (m/z) t
(329) 29
(329) 29
r
(161) 15.5
(347) 2.5
(303) 9.6
Table 6
Biotic and abiotic kinetic constants for Procymidone
Biotic process
Abiotic process
pH ˆ 6, T ˆ 35°C
pH ˆ 6, T ˆ 55°C
pH ˆ 8.7, T ˆ 35°C
4
� 1
1
0 ´ kobs min
k
k
/
1
2
ˆ 0:032
ˆ 0:041
k
k
k
1
2
3
ˆ 0:18
ˆ 1:58
ˆ 0:84
k
k
k
1
2
3
ˆ 2:26
ˆ 0:14
ˆ 0:53
k
k
/
1
ˆ 41:4
2
ˆ 0:096
a
t
1=2 (days)
39.9
/
12.06
0.43
a
t
1=2 has not been reached.

1
438
A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
Table 7
Biotic and abiotic kinetic constants for Iprodione
Biotic process
Abiotic process
pH ˆ 6, T ˆ 35°C
pH ˆ 6, T ˆ 55°C
pH ˆ 8.7, T ˆ 35°C
4
� 1
1
0 ´ kobs min
/
k
k
k
/
1
2
3
ˆ 1:08
ˆ 0:36
ˆ 1:8
k
k
k
k
1
2
3
4
ˆ 7:9
k
1
k
2
k
3
/
ˆ 252
k
/
2
ˆ 0:83
ˆ 2:78
ˆ 4:93
ˆ 1:36/
ˆ 16
ˆ 337
/
t
1=2 (days)
5.54
4.78
0.45
0.013
the composting process, while other transformations
could prevail due to enzymatic activity of a particular
micro-organism. As a matter of fact, the analyte is
completely converted to a more stable isomer compound
that has an identical ratio m/z to that of the parent
compound (Iprodione) but has a di€erent retention time
(
see Table 5).
As shown in Table 7, in the analysis of semi-quan-
Fig. 14. Biotic ( ) and(!) abiotic pathways for Procymidone.
titative data of the abiotic process, the Isomer is
formed with the rate constant (k ) in the same order to
that of the biotic process, even if halved (k
ˆ 0.36) in
2
2
accordance with the decrease of transformation percent,
from the biotic 100% to the abiotic 10% (see Fig. 12).
Nevertheless, in the abiotic conditions there is also
the contemporary formation of metabolite II (re-
action step 1) which is transformed successively into
metabolite III (reaction step 3). Moreover, at pH 6
and at the highest temperature (55°C) within 24 h, an-
other reaction (step 4), relative to the transformation of
metabolite II to the 3,5-DCA, ®nal metabolite, re-
sults to be very interesting.
Fig. 15. Biotic ( ) and(!) abiotic pathways for Iprodione.
cess, such a process could proceed only through parallel
reactions.
As shown in Fig. 15, the abiotic process for Iprodi-
one probably also proceeds through parallel-consecutive
reactions which comprise the two parallel chains, one
composed of two simple reactions (reaction steps 1 and
3) and the other composed of one simple reaction (re-
action step 2). Instead, the biotic process could be de-
scribed kinetically as a system of only one consecutive
reaction: Iprodione is completely converted to the
Isomer.
As the Procymidone data have already plotted out,
the ®rst and the third reaction steps are quite in¯uenced
by the increase of pH and temperature while the second
step, also present in the biotic process, shows a minor
e€ect.
4
. Conclusions
By also taking into consideration the various possible
detoxi®cation mechanisms (absorption, leaching, bio-
degradation, etc.) that occur in soils (Ellwardt, 1975;
Herbes, 1981; Kaufman and Horwick, 1983), these re-
sults suggest that the accumulation phenomenon cannot
be excluded in the alimentary chain. The presence of
30% residue of an intact pesticide (Procymidone) after
241 days, or of a toxic pesticide metabolite (Isomer of
Iprodione, 3,5-DCA and Met: I for Procymidone), is a
real concern because of the potential damaging e€ects.
Furthermore, the possibility of the presence of the active
product or breakdown products formation during the
composting process has an importance for public health
researchers because these substances, such as chlorinat-
ed aromatic amine, result to be highly toxic to living
From the analysis of the curve-®tting data and from
previous considerations, the degradation of Procymi-
done and Iprodione could occur in accordance with
hypothesised pathways reported in Figs. 14 and 15 for
the biotic and abiotic (pH 6 and T 35°C) processes.
On this basis, Fig. 14 shows the course of the abiotic
process for Procymidone could proceed through paral-
lel-consecutive reactions: parallel chemical reactions in
which the initial substance produces two di€erent sub-
stances simultaneously (reaction steps 1 and 2), and a
consecutive reaction in which one of the intermediate
products can react again contributing to the formation
of the other metabolite (reaction step 3). On the con-
trary, as seen in the veri®ed slowness of the biotic pro-

A. Vanni et al. / Chemosphere 41 (2000) 1431±1439
1439
organisms. Therefore, the presence of metabolites could
also be used analytically as a marker to test the hoarding
danger with the use of compost, to introduce toxic
substances into the alimentary chain.
Kaufman, D., Horwick, S.B., Proceedings of the Conference on
Risk and Decision Analysis for Hazardous Waste Disposal,
1983, Sylver Spring, Madison.
Leiter, M., Einax, J.W., Loeser, C., Vetter, A., 1997. Trace
analysis of metals in plant samples with inductively coupled
plasma mass spectrometry. Fresenius' J. Anal. Chem. 359,
423±426.
Acknowledgements
Lemmon, C.R., Pylypiw, H.M., 1992. Degradation of diazi-
non, chlorpirifos, isofenphos, and pendimenthalin in grass
and in compost. Bull. Environ. Contam. Toxicol. 48, 409±
415.
Financial support from Regione Piemonte ± Assess-
orato Ambiente is gratefully acknowledged.
Melkebeke, G., De Spielgeleer, F., Sterbaut, W., Dejonckheere,
W., 1986. A kinetic study of the chemical hydrolysis of the
fungicides Iprodione, Vinclozolin and methalaxyl. Med.
Fac. Landbouww. Rijksuniv. Gent. 51/2a.
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