Analysis of non-extractable DDT-related compounds in riverine sediments of the Teltow Canal, Berlin, by pyrolysis and thermochemolysis

Article abstract of DOI:10.1021/es0605568

Eighteen pre-extracted samples derived from a subaquatic riverine sediment core taken from the Teltow Canal, Berlin (Germany), were treated by off-line TMAH-thermochemolysis and subsequently analyzed by GC-MS to investigate release and thermodegradation o

Full text of DOI:10.1021/es0605568

Environ. Sci. Technol. 2006, 40, 5882-5890
of anthropogenic organic compounds to particulate matter
Analysis of Non-Extractable
DDT-Related Compounds in Riverine
Sediments of the Teltow Canal,
Berlin, by Pyrolysis and
leads to the formation of an extractable fraction and a
nonextractable fraction. The latter is characterized by
interactions with geomacromolecules, e.g., humic com-
pounds, covering the range from reversible adsorptive or
van-der-Waals forces to reversible or irreversible covalent
bonds (2-6). These associations prevent the extraction of
such compounds, termed bound residues. Nonextractable
compounds can also be encapsulated in humic matrices (7,
8). Within the bound state, the compounds’ environmental
behavior change compared to the labile fraction. For example,
bound residues are principally immobile and of a limited
bioavailability. Further details concerning environmental
chemical properties of incorporated organic xenobiotics are
described elsewhere (9, 10). Bound residues have been
investigated extensively in relation to incorporation of
pesticides and other organic xenobiotics in soils (11-16).
However, corresponding investigations in aquatic sediments
are rare (10, 16). Generally, two types of approaches have
been used to obtain information on bound residues in
particulate matter. The first approach, nondestructive meth-
ods like NMR- and FTIR-spectroscopy, allow to determine
covalent interactions between macromolecular organic mat-
ter and associated bound residues. This approach is ap-
propriate when using isotope-labeled compounds (17-19).
However, the application of spectroscopy to natural samples
has limitations due to overlapping of specific and unspecific
background signals and generally low relative amounts of
xenobiotic constituents compared to natural compounds.
The second approach relies on destructive methods, which
bring about the degradation of macromolecular compounds
or specific interactions to release associated bound residues
for subsequent sensitive analysis by methods such as GC-
MS. Destructive methods can be subdivided into chemical
and thermochemical approaches. Chemical procedures target
specific chemical bonds (e.g., cleavage of ester bonds by acidic
or alkaline hydrolysis) providing information on chemical
interactions between bound residues and geomacromol-
ecules. More detailed information can be obtained by
applying different chemical degradation procedures sequen-
tially (10). Thermochemical degradation procedures, such
as pyrolysis and thermochemolysis, can provide comple-
mentary insights by cleaving bonds that are not affected by
chemical degradation techniques.
Thermochemolysis
A L E X A N D E R K R O N I M U S
Institute of Geology and Geochemistry of Petroleum and Coal,
RWTH Aachen University, Lochnerstrasse 4-20, D-52056
Aachen, Germany
J A N S C H W A R Z B A U E R *
Institute of Geology and Geochemistry of Petroleum and Coal,
RWTH Aachen University, Lochnerstrasse 4-20, D-52056
Aachen, Germany
M A T H I A S R I C K I N G
Environmental Organic Geochemistry, Department of Earth
Sciences, Free University of Berlin, Malteserstrasse 74-100,
D-12249 Berlin, Germany
Eighteen pre-extracted samples derived from a subaquatic
riverine sediment core taken from the Teltow Canal,
Berlin (Germany), were treated by off-line TMAH-
thermochemolysis and subsequently analyzed by GC-MS
to investigate release and thermodegradation of non-
extractable anthropogenic organic compounds (bound
residues). Furthermore, six selected samples from the lower
core section were additionally treated by off-line pyrolysis.
Due to former investigations of the extractable fraction
of Teltow Canal sediments, high amounts of compounds
structurally related to the pesticide DDT (1,1,1-trichloro-2,2-
bis(4-chlorophenyl)ethane) were anticipated within the
nonextractable fraction. It has been shown that DDT-related
bound residues can be gathered by pyrolysis and TMAH-
thermochemolysis. Among other compounds, the experi-
ments revealed two DDT-related degradation products (DDPU
(3,3-bis(4-chlorphenyl)-1-propene) and DDPS (1,1-bis(4-
chlorophenyl)propane)) which were detected for the first
time in the environment. The latter compounds may represent
formerly unknown metabolites or hints for the existence
of carbon-carbon incorporated DDT-metabolites. Both
methods tend to produce artifacts which complicate the
interpretation of the results. With more knowledge on
mechanisms occurring during application of pyrolysis and
thermochemolysis, both methods can serve as valuable
tools for analyzing bound residues in sediments.
Schwarzbauer et al. (10) investigated bound residues of
DDT-(1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) related
compounds in sediments of the Teltow Canal, Berlin using
both chemical and pyrolytic degradation. The chemical
degradation methods revealed numerous DDT-related com-
pounds within the bound fraction. However, on-line pyrolysis
provided poor results due to the imperfect chromatographic
separation accompanying this analytical technique. Con-
sequently, the goal of the present investigation was to
establish off-line pyrolytic methods with subsequent chro-
matographic fractionation of the solvent-extractable products
for GC-MS analysis. Further aims were to screen compre-
hensively for released DDT-related analytes and to charac-
terize interactions between macromolecular matter and
bound residues through interpretation of the structural
information obtained during the experiment. Sealed-vessel
tetramethylammonium hydroxide thermochemolysis (SV-
TMAH-thermochemolysis) and sealed-vessel pyrolysis were
considered suitable analytical techniques to reach these
objectives. Unlike conventional pyrolysis, TMAH-thermo-
chemolysis facilitates methylation of acidic groups on
degradation products generated during the experiment (20).
Introduction
Direct or indirect emission of anthropogenic organic com-
pounds into aquatic systems results in a complex network
of transport, transformation, and adsorption processes
occurring in both water and particulate phases (1). Adsorption
* Corresponding author phone: ++49 241 80-95750; fax: ++49
241 80-92152; e-mail: schwarzbauer@lek.rwth-aachen.de.
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5882 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 19, 2006
10.1021/es0605568 CCC: $33.50
2006 American Chemical Society
Published on Web 08/22/2006

This methylation facilitates analysis of acidic organic analytes
by gas chromatography. Additionally, the alkalinity of TMAH
supports thermochemical bond cleavage; consequently, this
procedure has also been termed thermally assisted chemol-
ysis (21).
sealing the tube by smelting the opening with a Bunsen
burner, it was heated for 30 min at 250 °C and, thereafter,
cooled to -18 °C. The tube was opened and 1 mL of n-hexane
was added to the degraded sample residue. The mixture was
sonicated for 3 min at 35 kHz with a 120 W Sonorex RK-52
ultrasonic device (Bandelin, Berlin, Germany). After washing
the inner vessel surface with n-hexane, the extract was
decanted into a glass flask. The sample and the vessel surface
were washed again with 1 mL of n-hexane and the organic
solutions were combined. The extraction procedure was
repeated with acetone. To the combined solutions, ap-
proximately 5 mL of n-hexane was added, and acetone was
removed by rotary evaporation, followed by drying the
resulting n-hexane phase with anhydrous Na2SO4 (>99%).
Before using, the sodium sulfate was Soxhlet-extracted for
12 h with acetone. Pyrolysis procedures were performed
similary to the TMAH-thermochemolyses (30 min, 250 °C),
but without introduction of TMAH into the glass tubes. The
extracts were separated into four fractions on silica gel
microcolumns, using mixtures of n-pentane, dichloro-
methane, and methanol as eluates according to Schwarzbauer
et al. (29). Subsequently, 50 µL of an internal standard mixture,
containing d34-hexadecane (5.0 ng/µL), d10-anthracene (5.0
ng/µL), and d12-chrysene (5.0 ng/µL) in n-hexane, was added
to each fraction. All methanol fractions derived from pyrolysis
procedures were treated with a methanolic diazomethane
solution to methylate acidic compounds (10). The procedure
is illustrated in Figure 1, Supporting Information.
TMAH-thermochemolysis was applied in this study for
several reasons. First, the method has been successfully
applied for degradation of geomacromolecules in organic
geochemistry. Second, the method facilitates gas chromato-
graphic detection of acidic compounds, such as bis(4-
chlorophenyl)acetic acid (DDA), a quantitatively important
metabolite of DDT. TMAH-thermochemolysis was formerly
applied primarily in the field of organic geochemistry for the
characterization of naturally occurring organic matter in
aquatic sediments, peat, or natural waters (22-26) and also
in biological systems (27). However, thermochemical deg-
radation with TMAH increases the potential of secondary
reactions that can result in artifact generation. Consequently,
conventional pyrolysis was also applied in this study to
evaluate the degradation characteristics of both methodolo-
gies. Heim et al. (28) previously investigated the extractable
fraction of the same sample set. Dominating DDT-related
compounds within this investigation were DDD (1,1-dichloro-
2,2-bis(4-chlorophenyl)ethane), DDMS (1-chloro-2,2-bis(4-
chlorophenyl)ethane), and DBP (4,4′-dichlorobenzophe-
none).
Experimental Section
Degradation Experiments on Reference Compounds. In
order to investigate the question of artifact generation, several
reference compounds were treated by TMAH-thermochemol-
ysis as well as pyrolysis in pure state and within a matrix of
pre-extracted riverine sediments. DDT, DDD, DDE, DDA,
DBP, and DDOH served as reference compounds (see Table
1, Supporting Information). Bis(4-chlorophenyl)methanol
(BCMeOH) was additionally considered within thermo-
chemolysis experiments as a potential precurser of bis(4-
chlorophenyl)methoxymethane (BCMM) due to methylation
by TMAH. Approximately 10 µg of each reference compound
was dissolved in n-hexane and introduced into a pyrolysis
tube. The solvent was evaporated by a nitrogen stream and
pyrolysis or thermochemolysis procedures were performed
as described above.
For experiments with sediment matrix, riverine sediment
not affected by DDT-related compounds and similar in TOC-
content and grain size distribution as compared to the Teltow
sediment, was pre-extracted as described above. Approxi-
mately 100 mg of the preextracted sediment was then
transferred into a pyrolysis tube. Thereafter, approximately
10 µg of each single reference compound dissolved in
n-hexane was spiked on the sediment, respectively. After
evaporation of the solvent under a gentle stream of nitrogen,
the spiked sediments were treated by pyrolysis or thermo-
chemolysis procedures.
For each degradation experiment, the relative abundance
of the total measured analytes of the degradation products
was determined under consideration of the compound-
specific response factors. Consequently, these values do not
represent absolute recoveries. Due to the fact that conden-
sation and rearrangement reactions by pyrolysis are known
processes, a significant portion of organic matter has not
been considered by the analyses.
Within all four experimental seriessthermochemolysis
and pyrolysis on pure compounds and spiked sedimentss
additional blank experiments were performed, which re-
vealed no relevant laboratory contamination.
Sampling. The sampling site was situated within the Teltow
Canal, Berlin, near a chemical plant which operated in the
time of the German Democratic Republic. Production of high
tonnages of the insecticide DDT took place at this plant until
1989. More details of the sediments and the sampling site
are reported by Heim et al. (28). High concentrations of DDT-
related compounds in the water and sediment phase of the
canal have been described previously (29, 30). Freeze probing
facilitated sampling of an undisturbed sediment core of 36
cm length. More details of the sampling technique are
described elsewhere (Supporting Information, 31). The frozen
core was cut vertically into 18 samples in 2 cm intervals which
were freeze-dried and, thereafter, stored in glass vessels with
PTFE seals at +4 °C until extraction.
Chemicals, Reagents, and Syntheses. All chemicals used
as reference materials and for synthesis were purchased from
Sigma Aldrich (Taufkirchen, Germany) and Merck (Darm-
stadt, Germany). Before using, solvents were distilled and
purity was checked by reducing an aliquot of 50 mL of each
solvent to 50 µL and subsequent analysis by GC. Distillation
was achieved with a reflective coated 80 cm Vigreux column.
The reflux condensor was tempered with a coolstar SC-500
cooling device (resona technics, Gossau, Switzerland) at 10
°C. The reflux ratio was 10:1 (reflux/distillate).
Three reference compounds (bis(4-chlorophenyl)meth-
oxymethane, 3,3-bis(4-chlorophenyl)propene, and 1,1-bis-
(4-chlorophenyl)propane) had to be synthesized. Details are
given in the Supporting Information.
TMAH-Thermochemolysis, Pyrolysis, Extraction, and
Fractionation. Prior to TMAH-thermochemolysis, the samples
were extensively preextracted by a 5-step dispersion extrac-
tion with different solution mixtures of acetone and n-hexane,
performed with an Ultra Turrax T25 dispersion device (IKA,
Staufen, Germany) at 19 000 rpm. Details of the extraction
procedure are described elsewhere (35, 36). An aliquot of
approximately 100 mg of each pre-extracted sample was
transferred into a DURAN glass tube (8 mm i.d. × 200 mm
length). Additionally, 200 µL of a 20% methanolic tetra-
methylammonium hydroxide (TMAH) solution was added,
and the mixture was suspended by shaking the tube gently.
Methanol and oxygen were removed by a gentle stream of
nitrogen (Westfalengas, Mu¨nster, Germany, 99.999%). After
Gas Chromatography-Mass Spectrometry (GC-MS).
Qualitative and quantitative GC-MS analyses were per-
formed on a Finnigan Trace MS single quadrupole mass
spectrometer (ThermoElectron, Egelsbach, Germany), op-
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VOL. 40, NO. 19, 2006 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 5883

erating in impact ionization mode (EI+, 70 eV) and linked to
a HRGC 5160 gas chromatograph (Carlo Erba, Milano, Italy),
which was equipped with a 30 m × 0.25 mm i.d. × 0.25 µm
film BPX-5 fused silica capillary column (SGE, Australia).
Chromatographic conditions were 1-3 µL splitless injection
at 60 °C, 3 min hold, then programmed at 3 K/min to 310
°C. The limit of quantification (LOQ) was 0.05 µg/g while the
limit of detection (LOD) was 0.01 µg/g. The limits are
influenced by compound-specific response factors as well
as by sample-specific matrix and noise effects, meaning that
the limits differ from sample to sample and from analyte to
analyte. For LOQ and LOD, signal-to-noise ratios of 10:1 and
2.5:1 were used, respectively. More details on the GC-MS
analyses are given in the Supporting Information.
ones in a sediment sample. These data demonstrate the
accordance of sample analytes and reference compounds.
Mass spectra of both compounds show the molecular ions
(DDPS, M+/z ) 264; DDPU, M+/z ) 262) and the fluorenyl
cation (m/z)165) which is characteristic for most chlorinated
diphenylmethane derivates. Additionally, the mass spectrum
of DDPS shows a fragmentation leading to the bis(4-
chlorophenyl)methyl cation (m/z ) 235) by loss of an ethyl
group followed by loss of two chlorine radicals.
The mass spectra of 2,4′-DDPU and 4,4′-DDPU show no
significant differences. They are characterized by sequential
abstraction of two chlorine radicals from the molecular ion
(m/z ) 227, 192) and the subsequent loss of a vinyl radical
(∆m/z ) 27) resulting in the generation of a flourenyl ion.
A distinct structural feature of DDPS and DDPU is the fact
that those propane-based compounds contain one carbon
atom more than the ethane-based structure of DDT. Possible
reasons will be discussed below.
Artifact Generation During TMAH-Thermochemolysis.
Synthetic reference compounds of DDT and the most
important metabolites, namely 1,1-dichloro-2,2-bis(4-chlo-
rophenyl)ethane (DDD), 1,1-dichloro-2,2-bis-(4-chlorophe-
nyl)ethene (DDE), 2,2-bis(4-chlorophenyl)ethanol (DDOH),
DDA, DBP, and additionally bis(4-chlorophenyl)methanol
(BCMeOH), were treated by TMAH-thermochemolysis under
the same conditions as the sediment samples in order to
investigate artifact generation. A first experimental series was
performed on pure reference compounds and a second series
was performed on pre-extracted spiked sediments to inves-
tigate the influence of naturally occurring inorganic and
organic matrices on the degradation behavior of the com-
pounds. Results are listed in Table 2.
When using heated injectors for gas chromatography, a
possible breakdown of DDT to DDD (1,1-dichloro-2,2-bis-
(4-chlorophenyl)ethane) and DDE has been reported (37,
38). In our calibration experiments we quantified the
breakdown of DDT below 1%.
Results and Discussion
The experiments revealed several DDT-related compounds
which will be presented and discussed. Identified structures
are listed in Table 1, Supporting Information.
Degradation Products Obtained by TMAH-Thermo-
chemolysis. Nine DDT-related degradation products were
identified, of which some occurred as different structure
isomers, mostly 2,4′- and 4,4′-substituted, resulting in
detection of 17 different isomers. DDT was not detected. All
quantitative data obtained from thermochemolysis experi-
ments are given in Table 1.
The quantitatively most important degradation products
were DDM and DDNU. DDM was present at concentrations
up to almost 79 µg/g and DDNU was present up to about 20
µg/g. The amounts of DDM and DDNU relative to the total
amount of quantified compounds were quite constant (81-
93%), in spite of the large range of the total amount of
degradation products. These results differ significantly from
those of Schwarzbauer et al. (10). Within this investigation
of subaquatic sediments, also taken from Teltow Canal, DDA
(bis(4-chlorophenyl)acetic acid) and DBP were identified as
major degradation products in the non-extractable fraction,
whereas DDM and DDNU were quantitatively less important.
Other identified compounds were DDEt, DBP, and DDMU,
which are all well-known metabolites of DDT. The monochlo-
rinated 4-chlorodiphenylmethane (4-CDM) clearly also shows
a structural relation to the DDT metabolites. BCMM, DDPU,
and DDPS have not been previously described as DDT-related
transformation products. It is reasonable to consider BCMM
as a methylated artifact of oxygen-containing degradation
products like DBP or bis(4-chlorophenyl)methanol (BC-
MeOH) due to the presence of TMAH during thermo-
chemolysis. The methoxy group of BCMM indicates a former
incorporation by an ether functionality. Generally, the overall
distribution patterns of detected degradation products were
similar in all 18 samples.
The concentration ranges of the extractable fraction of
the samples, investigated by Heim et al. (28), are given in
Table 2, Supporting Information. Apart from DBP and DDMU,
the quantities of all other compounds in post-thermo-
chemolysis extracts were within the same magnitude or
higher than the corresponding concentrations in the ex-
tractable fraction. Hence, the detected amounts of DBP and
DDMU might represent extractable residues.
Structure Elucidation of DDPU and DDPS. Due to the
fact that mass spectra of DDPU and DDPS were not available
within the digital libraries, structures for these compounds
had to be elucidated from their mass spectra. Figure 1 shows
the EI+-spectra as well as the retention behavior of the
synthesized reference compounds and the corresponding
In order to check the degradation products with extended
carbon chains that were found following thermochemolysis
of the Teltow sediments, samples 17 and 18 were treated by
thermochemolysis in the presence of tetraethlyammonium
hydroxide (TEAH), instead of tetramethylammonium hy-
droxide (TMAH). Within those experiments, DDPS and DDPU
were also generated, indicating that these compounds are
not the result of transalkylation by TMAH.
With respect to experiments considering thermochemol-
ysis of reference compounds without matrix, degradation
products of the majority of compounds were dominated by
DDM and DDNU. During thermochemolysis of DDT, DDD
and DDE, DDM was generated as the major degradation
product with relative contents of more than 70%, respectively.
Degradation products of DDOH were dominated by DDNU
with a relative content of 55%. Generation of DDNU is
possibly preferred as it is a dehydration product of DDOH.
DDA was almost quantitatively decarboxylated to DDM;
negligible amounts of DDNU were found as a by product.
Decarboxylation of several benzoic acid derivates with
specific non-halogen ortho- and para-substituents during
TMAH-thermochemolysis has been described by Joll et al.
(39).
Significant amounts of DBP survived thermochemolysis.
The main degradation product was BCMM, which was
probably generated by electrophilic attack of TMAH on the
carbonyl function of the substrate. Bis(4-chlorophenyl)-
methanol (BCMeOH) was methylated to bis(4-chlorophenyl)-
methoxymethane by transalkylation. BCMeOH has been
described as a photodegradation product of DDT in labora-
tory experiments (40). Therefore, DBP as well as BCMeOH
are possible precursors of BCMM in the Teltow sediments.
Because there was a general trend of DDT-related
compounds (DBP and BCMeOH excepted) to degrade to
DDM and DDNU during TMAH-thermochemolysis, the
dominance of those compounds within the Teltow sediment
thermochemolysis analyses is explainable. Because of their
high relative amounts, quantities of the two main degradation
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5884 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 19, 2006

TABLE 1. Quantitative Results of Thermochemolysis Experiments in µg/g Based on Dry Weight (n.d. Means Not Detected)
sample (depth [cm])
1(2)
0.1
n.d.
3
0.2
13
2(4)
0.1
0.1
4
0.3
15
3(6)
0.1
n.d.
3
0.2
16
4(8)
0.1
0.1
4
0.3
20
5(10)
0.1
0.1
4
0.3
20
6(12)
7(14)
0.1
0.1
4
0.4
22
8(16)
9(18)
10(20)
11(22)
12(24)
13(26)
14(28)
15(30)
16(32)
17(34)
18(36)
2,2′-DDM
DDM isomer 2a
2,4′-DDM
DDM isomer 4a
4,4′-DDM
Σ(DDM)
0.2
n.d.
6
0.3
28
0.2
0.1
7
0.5
35
0.1
0.1
3
3.0
18
0.5
0.2
13
1
57
0.4
0.2
12
1
51
0.2
0.1
5
0.2
15
0.1
0.1
4
0.2
12
0.6
0.2
16
1
61
0.4
0.2
12
1
63
0.4
0.2
14
1
58
0.2
0.1
8
1
51
0.4
0.2
11
1
42
16.3
19.5
19.3
24.5
24.5
34.5
26.6
42.8
24.3
71.7
64.6
20.5
16.4
78.8
76.6
73.6
60.3
54.6
2,4′-DDNU
4,4′-DDNU
Σ(DDNU)
4,4′-DDEt
2,4′-DBP
4,4′-DBP
Σ(DBP)
2,4′-BCMM
4,4′-BCMM
Σ(BCMM)
4,4′-DDMU
4-CDM
4,4-DDPS
2,4′-DDPU
4,4′-DDPU
Σ(DDPU)
1
1
2
1.2
0.1
1
1.1
n.d.
0.3
0.3
0.1
0.1
0.3
0.2
1
1
1
2
1
1
2
1
2
3
1
1
2
2
1
3
1
1
2
2
4
6
1
1
2
1.3
n.d.
3
3.0
n.d.
0.3
0.3
0.3
0.2
0.3
0.2
0.2
0.4
32.2
3
7
10
4
11
15
1.7
0.1
3
3.1
0.1
0.7
0.8
0.2
0.2
1.2
0.6
2
2
2
4
1
2
3
4
13
17
5.3
0.2
2
2.2
0.3
2
2.3
n.d.
0.2
<0.05
0.6
3
3.6
109.2
88%
4
4
8
5
10
15
3
2
5
2.9
0.2
2
2.2
0.1
1
5
15
20
1.1
<0.05
0.5
0.5
0.1
0.3
0.4
<0.05
0.1
0.4
0.2
0.2
0.4
24.3
1.2
0.3
0.5
0.8
n.d.
0.2
0.2
0.2
0.1
0.3
n.d.
0.4
0.4
24.3
1.5
0.1
0.5
0.6
0.1
0.4
0.5
0.2
0.1
0.4
0.2
0.4
0.6
31.5
0.7
0.2
0.7
0.9
0.1
1
1.1
0.1
0.2
0.1
0.2
0.1
0.3
29.9
3.0
0.1
0.1
0.2
0.1
0.5
0.6
0.5
0.1
0.5
0.3
n.d.
0.3
42.6
1.3
0.2
3
3.2
0.1
1
1.1
0.1
0.1
0.3
0.2
0.3
0.5
35.2
1.0
0.2
2.0
2.2
0.2
1
1.2
<0.05
0.2
0.8
0.3
0.7
1.0
55.1
1.8
0.2
3
3.2
0.3
2
2.3
<0.05
0.3
1.3
0.5
1
0.8
0.1
0.4
0.5
0.2
1
1.2
n.d.
0.1
<0.05
0.2
0.5
0.7
27.3
0.7
0.1
0.6
0.7
0.1
1
1.1
n.d.
0.1
<0.05
0.2
0.3
0.5
22.9
2.8
n.d.
0.2
0.2
0.1
1
1.1
n.d.
0.3
<0.05
0.5
1
2.8
0.1
0.4
0.5
0.4
2
2.4
0.3
0.2
<0.05
0.5
1
1.9
0.1
2
2.1
0.1
1
1.1
0.2
0.2
1
0.4
2
1.1
0.2
0.3
0.6
0.3
0.2
0.5
73.2
89%
1.2
22.3
81%
1.5
92.1
89%
2.6
89.5
89%
1.5
90.0
93%
1.5
95.9
92%
2.4
83.5
89%
total
Σ(DDM+DDNU)
88%
87%
88%
89%
88%
81%
88%
82%
88%
86%
/Total
a Structure unidentified.

FIGURE 1. Mass spectra of reference compounds and corresponding analytes detected in sample 18 of (a) DDPS and (b) DDPU. (c) GC-MS
chromatograms (m/z ) 264) of the compounds.
TABLE 2. Degradation Products Generated by TMAH-Thermochemolysis of DDT and Important Metabolites (Relative Contributions
of the Generated Degradation Products Are Given in Parentheses)
substrate
TMAH-thermochemolysis without matrix
TMAH-thermochemolysis with matrix
DDT
DDM (92%), CDM (3%), BCMM (5%)
DDM (72%), DDNU (24%), CDM (4%)
DDM (80%), DDNU (15%), CDM (4%)
DDM (98%), DDNU (2%)
DDM (100%)
DDD
DDM (100%)
DDE
DDM (100%)
DDM (100%)
DDM (10%), BCMM (95%)
DDM (5%), BCMM (95%)
DDM (90%), DDNU (10%)
DDA
DBP
DBP (15%), BCMM (85%)
BCMeOH
DDOH
BCMM (100%)
DDM (34%), DDNU (55%), DDEt (9%), CDM (2%)
products represent an estimation of the total quantity of
DDT-related bound residues. However, detailed structural
information is lost. In summary, TMAH-thermochemolysis
on pure reference compounds induces artifact generation
by abstraction, elimination, etherification, and addition
reactions. DDPS and DDPU were not detected within any
degradation experiment and, thus, would appear not to be
artifacts.
ments on pure compounds (Table 2). DDT, DDD, DDE, and
DDA were completely degraded to DDM. Matrix-associated
degradation of BCMeOH resulted in products similar to those
generated in experiments on pure compounds.
Degradation of DBP revealed no substrate residues.
Regarding degradation of DDOH, loss of methanol to DDM
dominates over dehydration. As in experiments on pure
compounds, DDPS and DDPU were not detected as artifacts
(Table 2).
Experiments with spiked sediments, representing an
inorganic and organic matrix, revealed similar but more
distinct trends concerning artifact generation than experi-
Degradation patterns derived from matrix-associated
experiments are characterized by a more intensive degrada-
9
5886 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 19, 2006

TABLE 3. Quantitative Results of Pyrolysis Applied on Teltow Canal Sediments in µg/g Based on Dry Weight (n.d. Means Not
Detected)
sample (depth [cm])
13(26)
14(28)
15(30)
16(32)
17(34)
18(36)
2,2′-DDM
0.1
<0.05
3
0.1
8
2
1
52
3
150
208
0.4
5
10
8
3
1
50
2
133
188
0.3
4
3
1
63
3
170
239
0.4
7
n.d.
0.3
6
n.d.
16
22.3
n.d.
1
0.5
120
1
2
0.5
42
1
130
175.5
n.d.
5
DDM isomer 2a
2,4′-DDM
DDM isomer 4a
4,4′-DDM
Σ(DDM)
11.2
0.1
1
2,2′-DDNU
DDNU isomer 2a
2,4′-DDNU
DDNU isomer 4a
4,4′-DDNU
Σ(DDNU)
2
6
11
9
10
23
21
61.4
61
29
150
179
4
4
145
9
2
3
16
39.4
40
20
106
126
5
8.1
7
30.3
33
20
36
56
2
122.5
9
163
42
24
178
202
1
4,4′-DDEt
2,4′-DBP
10
74
84
1
8
4,4′-DBP
25
Σ(DBP)
33
2,4′-DDMU
4,4′-DDMU
Σ(DDMU)
n.d.
7
7
1
5
2
4
8
2
10
2
4
8
9
2,2′-DDPU
2,4′-DDPU
4,4′-DDPU
Σ(DDPU)
1
2
2
n.d.
0.3
18
1
1
3
2
2
2
2
2
5
4
25
28
7
4
7
9
8
18.3
2
2,2′-DDE
0.5
n.d.
3
1
1
3
2,4′-DDE
n.d.
4
n.d.
6
2
1
1
4,4′-DDE
22
27
0.5
0.1
12
0.3
28
40.9
624.3
4
34
42
n.d.
n.d.
6
Σ(DDE)
3.5
n.d.
n.d.
1
n.d.
2
3
5
7
7
2,2′-DDCN
DDCN isomer 2a
2,4′-DDCN
DDCN isomer 4a
4,4′-DDCN
Σ(DDCN)
0.5
n.d.
10
0.2
20
30.7
466.1
0.4
n.d.
10
0.2
23
33.6
360.9
n.d.
n.d.
4
n.d.
8
12
n.d.
9
15
676.5
total
122.8
231.1
a Structure unidentified.
tion. However, those patterns are not consistent with respect
to the results of thermochemolysis experiments of the Teltow
Canal sediments. These field sediment data, indicating
relative contents of [DDM] + [DDNU] around 85%, are more
similar to results derived from the experiments on pure
compounds. Even those results are characterized by much
higher contents of DDM and DDNU than the analytical results
of Teltow Canal sediments.
Degradation Products Obtained by Pyrolysis. Pyrolysis
was applied on the lower section of the sediment core
(samples 13-18). The experimental results are listed in Table
3. Eight different DDT-related compound groups were
detected, some including different isomers; 26 compounds
were identified. Quantitatively most important were DDM
(11-240 µg/g), DDNU (8-160 µg/g), and DBP (33-200 µg/
g). DDEt, DDMU, DDPU, DDE, and DDCN occurred at
concentrations between 2 and 41 µg/g. The total of all
quantified compounds ranged between 120 and 670 µg/g.
Similar to the thermochemolysis experiments, the overall
distribution pattern was similar in all six samples. All
quantities are higher than or in the same magnitude as the
corresponding concentrations in the extractable fraction (see
Table 2, Supporting Information) investigated by Heim et al.
(28).
ments, there is no single dominating compound following
pyrolysis. The three main degradation products DDM, DDNU,
and DBP are quantitatively within the same range. Further-
more, the specific compounds generated by the two meth-
odologies differ. Whereas DDM, DDNU, DDEt, DBP, DDMU,
and DDPU were revealed by both techniques, DDE and
DDCN were found only after pyrolysis, and BCMM, CDM,
and DDPS were generated only by TMAH-thermochemolysis.
As production of BCMM is attributed to reaction of TMAH
with oxygen-containing DDT-related structures, the absence
of BCMM after pyrolysis is expected. The observation of
DDPU in the post-pyrolysis extracts is further confirmation
that this compound is not produced by transalkylation of
TMAH.
Artifact Generation During Pyrolysis. Analogous to the
thermochemolysis artifact generation experiments, degrada-
tion of DDT, DDD, DDE, DDA, DBP, and DDOH during
pyrolysis was investigated, both as pure compounds and in
association with sediment matrix. BCMeOH was not inves-
tigated because potential methylation reactions of alcohols
are of no relevance when applying pyrolysis. The results are
listed in Table 4. Regarding pyrolysis experiments on pure
compounds, DDT, DDD, DDE, and DBP remained completely
or largely stable. DDA and DDOH were completely degraded
to DBP.
There are several differences between the results obtained
by TMAH-thermochemolysis and pyrolysis. First, the con-
centrations of DDT-related compounds are significantly
higher after pyrolysis, indicating a more effective release of
incorporated compounds or less destruction of degradation
products compared to the thermochemolysis experiments.
Unlike the pattern found in the thermochemolysis experi-
The degradation pattern of matrix-associated pyrolysis
experiments was different. Whereas DDT, DDE, and DBP
also remained largely or entirely unaltered, DDD was
completely degraded to DDNU, DDMU, and DBP, and DDA
was transformed to DBP. DDPU was not detected within any
degradation experiment. As in the thermochemolysis experi-
9
VOL. 40, NO. 19, 2006 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 5887

TABLE 4. Degradation Products Generated by Prolysis of DDT and Important Metabolites (Relative Contributions of the Generated
Degradation Products Are Given in Parentheses)
substrate
pyrolysis without matrix
pyrolysis with matrix
DDT
DDD
DDE
DDA
DBP
DDT (80%), DDE (20%)
DDD (80%), DDMU (20%)
DDE (100%)
DDT (93%), DBP (7%)
DDNU (37%), DDMU (55%), DBP (8%)
DDE (100%)
DBP (100%)
DBP (100%)
DDNU (22%), DBP (78%)
DBP (100%)
DBP (100%)
DBP (100%)
DDOH
FIGURE 2. Proposed scheme of DDPS and DDPU generation during thermochemical degradation of carbon-carbon incorporated DDT-
related metabolites.
ments, matrix-associated pyrolysis experiments are char-
acterized by a more intensive degradation of the substrates.
Apart from the high amounts of DBP, the analytical results
for pyrolysis treatments of Teltow Canal sediments (Table 3)
are not congruent with the degradation experiments on
reference compounds. For example, DDM and DDNU, both
quantitatively important compounds in the Teltow sediment
pyrolysis extracts did not occur as dominating artifacts within
degradation experiments of the reference compounds. At
the same time, DDT and DDE were reasonably stable in the
reference compound pyrolysis experiments regardless of the
presence or absence of the matrix. Therefore, those com-
pounds could be regarded as unaltered bound residues when
found in environmental samples. Taken together, the ob-
tained facts indicate that analytical results derived from offline
pyrolysis of Teltow Canal sediments are more realistic than
those of TMAH-thermochemolysis.
Former investigations of Teltow sediments by Curie-point
pyrolysis (10, 41) revealed only two DDT-related compounds
(2,4′- and 4,4′-DDM), superimposed by a huge amount of
natural pyrolysis products. Other DDT-related compounds
were supposably also yielded but not detected because of
the complex pyrolysate. Because this pyrolytic approach
differed signifficantly from the off-line sealed-vessel pyrolysis,
different degradation reactions of DDT-related compounds
have to be expected.
thermochemolysis, the pyrolysis results of Teltow Canal
sediments allow some interpretation. The above-mentioned
absence of DDM as an artifact within degradation experi-
ments indicates that the analyzed amounts are probably
authentic. Similary, DDNU, a possible byproduct of DDOH-
degradation, is considered to be dominately authentic. If
DDNU was derived from degradation of DDOH in the Teltow
sediment, the amount of DBP would be expected to be much
higher than it is (Table 3). DDEt was not detected as an artifact
and therefore can represent a genuine compound. Due to
the artifact generation of DBP from DDA, DBP, and DDOH,
DBP would appear to represent the sum of the oxygen-
containing metabolites of DDT. DDMU is a potential
byproduct of DDD. Due to the relatively low amounts of
DDMU detected (Table 3), the authenticity of DDMU
generated during pyrolysis cannot be assumed. DDPU,
DDCN, and DDE were not recognized as potential artifacts,
and can therefore represent authentic compounds. However,
the experiments revealed no specific information regarding
former modes of incorporation of these compounds.
Potential Origins of DDPU and DDPS. DDPU and DDPS
were described for the first time as environmental contami-
nants within this study. By degradation experiments on
reference compounds and by thermochemolysis experiments
with TEAH the compounds were proven not to be artifacts.
Regarding the structures of the compounds characterized
by an additional carbon atom compared to the structure of
DDT, two potential origins are conceivable. First, the
Interpretation of Pyrolysis Results. Because fewer ar-
tifacts were generated by pyrolysis compared to TMAH-
9
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Acknowledgments
We greatfully acknowledge the financial support by the
German Research Foundation (DFG). We also thank the four
reviewers of this article for their gainful comments.
Supporting Information Available
Sampling, synthesis, and GC-MS details, schematic workflow
diagram of the applied analytical procedure, table of
quantitative data of extractable DDT-related contaminants,
and table of names, structures, and ions used for quaniti-
fication of the detected compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
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