Naturwissenschaften 78,219-221 (1991) © Springer-Verlag 1991
002810429100156G
Organotins in Lake Sediment
K. Fent*, J. Hunn and M. Sturm
Swiss Federal Institute for Water Resources and Water Pollution Control
(EAWAG), CH-6047 Kastanienbaum, Switzerland
Organotin compounds are entering the
aquatic environment due to their use in
antifouling paints on boats and from
municipal and industrial wastewaters
[1]. Tributyltin (TBT) is highly toxic to
aquatic life, particularly to marine mol-
luscs (oysters) [2] and gastropods, lead-
ing to observed declines of dog-whelk
populations on various coasts [3].
Chronic toxic effects on these
organisms occur at aqueous concentra-
tions of a few ng/1. TBT, dibutyltin
(DBT), and monobutyltin (MBT) have
been detected in the aquatic environ-
ment. Increased concentrations of TBT
in water, sediment, and biota have been
linked primarily to pleasure boating ac-
tivities. In the water column, TBT con-
centrations were reported to lie in the
high ng/1 range for marinas, and in the
low to medium ng/1 range for open
waters [4, 5]. TBT residues in sediments
were found to be considerably higher,
typically in the high /~g/kg range
[4 - 6], and total butyltin concentration
was shown to decrease with depth in
sediment cores [7]. In the water
column, TBT is biodegraded by succes-
sive dealkylation reactions leading to
DBT as the principal degradation prod-
uct with lesser amounts of MBT [6, 8].
In sediments, degradation was reported
to be much slower with half-lives of 4
to 5.5 months [6- 8].
To date, little is known about the oc-
currence and persistence of organotin
compounds in sediments. Here, we re-
port on the vertical distribution of a
series of butyltins and phenyltins in
the sediment of freshwater marinas of
Lake Lucerne, Switzerland. The
occurrence of phenyltin residues has
not been previously reported. By using
radiocesium isotopes in the sediment,
we derive geochronological data. Con-
* Present address during sabbatical leave:
Woods Hole Oceanographic Institution, De-
partment of Biology, Woods Hole, MA,
02543, USA
siderable concentrations of TBT in the
upper part of the dated sediment core
in conjunction with the low occurrence
of DBT and MBT suggest that TBT is
conserved in this sediment over a time
period of years.
Several sediment cores up to 60 cm in
length were taken on July 12, 1989, in
the 2.5 to 3 m deep marina Lucerne.
This marina was constructed in 1978,
has berths for 456 pleasure boats, and
is well flushed. The sediment was an-
oxic. The cores were taken with a grav-
ity corer using Plexiglas tubes of 12 cm
diameter for chemical and nuclide anal-
yses, and PVC tubes of 6.3 cm diameter
for sedimentological description and
photography. Immediately after collec-
tion, a core of 12 cm diameter and 29
cm in length was extruded in 0.5 cm or
1 cm slices, split vertically into two sub-
samples, and stored in cleaned glass
jars at -30°C. One portion of wet
sediment was used for sediment orga-
notin analysis. The other wet sub-
sample was freeze-dried and used for
porosity measurement, determination
of organic and inorganic carbon (by
Carlo Erba CNS-analyzer and Cou-
lometer inorganic carbon analyzer),
134Cs
and
137Cs
by -y-counting using a
Canberra well-type detector and multi-
channel analyzer.
Details of the organotin trace analysis
of water and sediment employing inter-
nal standards (IS) are given in [5, 9].
Briefly, the procedure consisted of the
following steps: (a) acidification of the
500 ml water or sediment sample (5 - 15
g); (b) solid-phase extraction of the
water sample, or diethyl-ether (con-
taining 0.25 070 tropolone) extraction of
sediment sample; (c) derivatization
(ethylation by a Grignard reaction); (d)
cleanup; (e) analysis by high-per-
formance gas chromatography with
flame photometric detection on a 30-m
fused silica capillary column. For quan-
tification, IS tripropyltin chloride, and
mono-, di-, tri-, and tetrapentyltin
© Springer-Verlag 1991
chloride in acetone were added to the
samples prior to extraction. The detec-
tion limit for the butyl-and phenyltins
was 2-20 ng/1 of water and 0.05-2
#g/kg (dry weight) of sediment. All the
results are reported as mean values of
duplicate or triplicate determinations
and refer to the butyltin and phenyltin
species as the ion. The concentrations
were corrected for recovery by IS
(60-95 07o for different species), and
sediment data are given on a dry-weight
basis.
First measurements in marina waters of
Lake Lucerne during 1988 showed that
TBT concentrations were remarkably
high [10]. Considerable organotin con-
centrations were also measured on July
12, 1989. The concentration of TBT
was 252 ng/1, DBT was 12 ng/1, and
MBT was 13 ng/1 in unfiltered water
collected at a depth of 1 m. Addition-
ally, triphenyltin (TPT), a biocide also
employed in some (older) antifouling
paints in addition to TBT, occurred in
concentrations of 38 ng/1. TBT occurs
in marina waters in the dissolved and
particulate phase. In seawater, virtually
all the TBT occurs in a dissolved form,
however, there is also capacity for sorp-
tion to particulates as indicated by the
reported distribution coefficients K d
between particulate and dissolved
phases in the range of 3000 [8]. Our
measurements indicate similar distribu-
tion ratios in the water of the marina
investigated [11] In addition, our study
with municipal wastewater showed that
the concentration of suspended par-
ticles was an important parameter con-
trolling partitioning between dissolved
and particulate phases [9]. In raw waste-
water containing high concentrations
of suspended solids, about 90 °70 of the
organotins were associated with the
particulate phase, whereas in the sec-
ondary effluent containing a lower sus-
pended solids concentration, it was
only 53 %. Thus, scavenging of TBT
from the lake water column to sediment
is assumed to occur on the basis of
these observations.
In the sediment of this marina, con-
siderable concentrations of a series of
butyltins and phenyltins occurred. The
organotins were only present at the top
of the core, which points to a recent
source. As in the water column, the
major compound detected was TBT.
Figure 1 shows the butyltin profiles
down to a depth of 12 cm. Concentra-
Naturwissenschaften 78 (1991) 219
~g
£3
¢-
0-
O)
E3
10'
Butyltin concentrotion [#g/kg]
0 100 200
~MBT DBT
£9
[-
O-
r~
10 ¸
137Cs activity [Bq/kg]
100
I i
Chernoby[-137Cs
Nucleor-weopons-137Cs
200
Fig. 1. Butyltin and 137Cs profiles in sediment core of marina Lucerne. TBT tributyltin,
DBT dibutyltin, MBT monobutyltin. Zero values occurred below 12 cm
10
Concentration [tag/kg]
0 100
TPT
200
E
c-
o_
Co
t'~
10
Concentrotion [I.tg/kg]
100
MPT
DPT
200
~g
O
e-
0)
C3
Fig. 2. Phenyltin profiles in sediment core of marina Lucerne. TPT triphenyltin, DPT
diphenyltin, MPT monophenyltin. No phenyltins occurred below 6 cm
which suggests a higher degradation
rate of TPT than TBT.
Much higher butyltin residues have
been detected in the top 3 cm of a 20-
cm-long sediment core, taken with
other cores in the 2.5-m-deep marina
Stansstad, another marina in Lake
Lucerne. The sediment was anoxic.
From the surface down to 3 cm, con-
centrations of TBT were in the range of
1 158 to 1 589 k~g/kg. Similar to marina
Lucerne, proportions of MBT and
DBT relative to TBT were only low,
with concentrations in the range of 50
to 220/~g/kg. In addition, considerable
concentrations of TPT in the range of
71 to 188 /xg/kg occurred. The con-
centrations of MPT and DPT were in
the range between 9 and 33/xg/kg.
In previous studies, no vertical orga-
notin sediment profiles in conjunction
with 13VCs profiles were reported. Here,
we use the ~34Cs and 137Cs isotopes to
develop geochronological data.
134Cs
originates solely from the Chernobyl
accident (April 1986), but 13VCs derives
from both Chernobyl and prior nuclear
weapons testing in the atmosphere
peaking in 1963 - 1964. 137Cs profiles in
the sediment core of marina Lucerne
are illustrated in Fig. 1. Chernobyl-
~37Cs was calculated by using the well-
tions of TBT increased from 101 #g/kg
at the top to 215 #g/kg at a depth of 1.5
to 2.0 cm. Between 2.5 and 5.5 cm,
concentrations decreased significantly
from 96 to 5 /xg/kg, and at 6 cm and
down to 29 cm, no butyltins were de-
tected. The decrease in TBT concentra-
tions was paralleled with decreases in
DBT and MBT ranging between 1 and
26/xg/kg and 0.5 and 25/xg/kg, respec-
tively. Both the low proportion of
degradation products, DBT and MBT,
and the concentration decrease with
depth, indicate a low degradation of
TBT in this sediment.
Phenyltins have not previously been re-
ported to occur in lake sediments. Our
data in Fig. 2 show that considerable
concentrations of TPT and its likely de-
gradation products, diphenyltin (DPT)
and monophenyltin (MPT), occurred.
TPT was only present in the uppermost
3.5 cm in concentrations ranging be-
tween 12 and 174/xg/kg. DPT was only
present in the top 3 cm, and MPT was
detected to a depth of 6 cm. The
proportions of degradation products
relative to the parent compound were
different between phenyltins and
butyltins. MPT as a TPT degradation
product occurred in higher proportions
than MBT or DBT relative to TBT,
established 134Cs/137Cs
ratio of 1.9
+ 0.2 [121. All values have been cor-
rected for nuclear decay (May 1, 1986),
and the detection limit of 137Cs (half-
life 30.17 a) was 0.122 Bq/kg. The oc-
currence of 134Cs with a half-life of 2.06
a proves its origin from the Chernobyl
accident. The profile of Chernobyl-
137Cs shows maximum activities in the
top of the core, gradually decreasing to
zero values at 2.5 cm. The shape of the
profile suggests mixing of at least the
uppermost 2 to 2.5 cm of the sediment
column. Homogenization and/or an
erosion process can also be deduced
from the irregular shape of the profile
of nuclear-weaponsJ37Cs. A first peak
of nuclear-weapons-137Cs occurs at 2
cm, where Chernobyl-137Cs is still pres-
ent and a second peak occurs from 2.5
to 3.5 cm, followed by a gradual
decrease to zero. Disturbances are most
likely caused by anthropogenic process-
es such as motor propellers of boats
within the shallow marinas, but also by
bioturbation processes by benthic
biota. However, as can be deduced
from the vertical distribution of Cher-
nobyl- and nuclear-weapons-137Cs, the
depositional structures are not com-
pletely disturbed in the core. The top
layer of 2 to 2.5 cm may represent ap-
proximately 3 to 4 years prior to the
date of sampling, and it is assumed that
the sediment is built up of homogenized
sections of approximately 2 to 2.5 cm.
This leads to the conclusion that the oc-
currence of considerable concentra-
tions of TBT in the sediment pre-
sumably correlates with the construc-
tion of the marina in 1978. At this time
TBT-containing antifouling paints were
already in use, but the annual amount
used is not known. The increase in the
organic carbon content at this sediment
depth (Table 1) may also indicate the
construction of the marina in 1978 and
a subsequent change of this littoral en-
vironment by cutoff from the rest of
the lake. These observations and the
geochronology of the core provide
evidence that TBT (and TPT) are
stored in this sediment over remarkably
long periods of time. The persistence of
TBT is also indicated by the low oc-
currence of its degradation products. In
previous studies, low degradation rates
of TBT, especially in anoxic sediment,
were found in freshwater [6] and ma-
rine sediments [7]. Sediments may
therefore represent a sink, and under
220 Naturwissenschaften78 (1991) © Springer-Verlag 1991
certain circumstances, a source of TBT
and TPT through desorption for
several years after inputs cease.
The ecotoxicity of marina waters and
sediments is mainly based on their TBT
and TPT concentrations. On compa-
rison with organisms living in the water
column, little is know about the toxicity
of organotins to benthic organisms.
TBT concentrations in the sediment of
marina Stansstad may be harmful to
benthic organisms. The LDs0 (48 h) of
the oligochaete
Tubifex tubifex,
a re-
presentative organism, was reported to
lie in the range of 5 and 50 ppb [13].
However, data in this study are unclear
as to whether this value holds for sedi-
ment or water concentrations. This oli-
gochaete was not observed in the sedi-
ment cores taken from marina Stans-
stad. However, absence of this worm
may also be caused by long-term anoxic
conditions at this site. In addition, it
was shown that uptake of TBT from
contaminated sediments by oli-
gochaetes takes place [6], thus making
sediment-associated TBT available to
the benthic food chain. Further studies,
however, are required to determine the
degradation processes of TBT and TPT
in sediments, and to determine the eco-
toxicological implications of TBT- and
TPT-contaminated sediments to ben-
thic organisms.
We would like to thank J. Perlinger,
EAWAG, for reading the manuscript,
and to the anonymous reviewers for
helpful comments. The study was sup-
Table 1. Water content, porosity, and organic carbon content in sediment core of marina
Lucerne
Depth [cm] Water Porosity Organ. C
content [%] [vol. °/0] [wt %]
0- 0.5 79 0.90 4.75
0.5- 1.0 76 0.89 4.54
1.0- 1.5 75 0.89 3.66
1.5- 2.0 75 0.88 3.72
2.0- 2.5 72 0.87 3.06
2.5- 3.0 70 0.86 2.49
3.0- 3.5 69 0.85 2.41
3.5- 4.0 63 0.81 1,53
4.0- 4.5 61 0.80 1.41
4.5- 5.0 60 0.80 1.21
5.0- 5.5 60 0.79 1.37
5.5- 6.0 60 0.79 1.36
6.0- 10.0 59-56 0.79- 0.76 1.30- 1.08
10.0- 29.0 55 - 46 0.75 - 0.66 1.22- 1.12
ported in part by the Kanton Luzern,
Amt ft~r Umweltschutz (P. Stadel-
mann).
Received October 12, 1990 and February 6,
1991
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Naturwissenschaften 78,221 - 223 (1991) © Springer-Verlag 1991
002810429100152W
Sensitivity to Odors in Wistar Rats Is Reduced After
Low-Level Formaldehyde-Gas Exposure
R. Apfelbach and E. Weiler
Institut fiir Zoologie (Tierphysiologie) der Universit/~t, W-7400 Tt~bingen, FRG
Formaldehyde is an irritant, often caus-
ing eye irritation, and runny noses, as
well as chronic respiratory problems
[18]. There is also evidence for the in-
volvement of formaldehyde in cancer
[7, 8], at least in high concentrations.
Naturwissenschaften 78 (1991)
Experimentally induced long-term ex-
posure to formaldehyde at a dose of ap-
proximately 15 ppm has been asso-
ciated with the development of nasal
cancers in Sprague-Dawley and Fischer
rats [13, 16]. Even a lower concentra-
© Springer-Verlag 1991
tion of about 6 ppm formaldehyde has
been found to induce lesions in the
nasal area, the trachea, and the
bronchial bifurcation of the rhesus
monkey [10]. There is no experimental
evidence, however, for noxious effects
of low-level formaldehyde-gas ex-
posure. Therefore, a promising ap-
proach to the investigation of possible
harmful effects of low-level formal-
dehyde concentrations may be the
analysis of olfactory sensitivity.
In a psychophysical study, five male
Wistar rats (Group I) were exposed to
0.25 ppm formaldehyde gas from post-
natal day 30 until 160; exact birth dates
were available for all animals. Experi-
221