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chlorinated dibenzodioxins and dibenzofurans
C h e m o s p h e r e , Vol.17, No.5, P r i n t e d in Great Britain
RAPID
pp 889-903,
PHOTOLYTIC
1988
DECOMPOSITION
BROMINATED/CHLORINATED
Federal
CH-8820
OF B R O M I N A T E D
DIBENZODIOXINS
Hans-Rudolf Swiss
0 0 4 5 - 6 5 3 5 / 8 8 $3.00 + .OO P e r a a m o n Press plc
AND
AND D I B E N Z O F U R A N S
Buser
Research
W~denswil,
Station
Switzerland
ABSTRACT
Rapid
photolytic
dibenzofurans sunli g h t ing
compounds.
chemi c a l the
with
laboratory ted
that
cautions
(PCDDs)
and
light
are
major
and of
in
compounds order
solution
showed
exposure.
compounds
likely
has
be
In
are
environmental
full
and
summer
that of c o r r e s p o n d -
this
was
way, from
Solid
phase
surfaces
under
of
the
consequences
was
compounds
some d e c o m p o s i t i o n
photochemical
photo-
photolysis
sunlight
the
provided
reductive
polychloro-
formed
Exposure
obtained
The
under
observed
analogues.
hours.
to m i n i m i z e
so far unknown.
congeners.
on quartz
can
than
pathway
(PCDFs)
dibenzodioxins
solution
faster
of
data
cations
much
bromo/chloro
analytical
halogenated are
I min,
brominated
the
bromo/chloro
photochemical
in h y d r o c a r b o n
taken
and
hydrocarbon
dibenzofurans the
bromo/chloro
half-lives
reliable
bromo
dilute
to lower
decomposition
bromo
of
in
as low as
The
leading
dibenzodioxins
slower
observed
with h a l f - l i v e s
chloro
debromination
of
decomposition
was
but
indica-
suitable
behaviour but
to
of
actual
prethese impli-
INTRODUCTION
Polychlorinated much
scientific
mental these rial
dibenzodioxins and
contaminants compounds chemicals
are they
public and
some
varied. are
(PCDDs)
and d i b e n z o f u r a n s
attention. of
them
Apart
also
These are
from
formed
precursors.
889
extremely
being in
compounds
(PCDFs) are
toxic
contaminants
combustion
have attained
known (I). in
processes
The
as
environ-
sources
certain from
of
industsuitable
890
Bromo
and b r o m o / c h l o r o
ty as the chloro as
thermolysis
an
accidental
tional
products fire
PCDDs
PCDFs.
chlorinated
halogen
compounds
are
brominated
thought
compounds
mixed
of leaded
to
entering
flame
be
retardants
such
a
one
of
the
both
scavenger
compounds
(dichloro-
and d i b r om o e t h a n e )
and
PCDFs
have
been
associated
and
some
other
bromo
compounds
have
been
identified
(10-12),
bromo
and
and d i b e n z o f u r a n s
have not yet been a c t u al l y
However,
bromo/chloro
dibenzodioxins
ash
incinerators
(13-15);
from
(pyrenes)
were
identified
PCDDs
and
PCDFs
about
the
1940-50s
with
the
use
of
and
other
could
and
would
from
the
dation
of
by sunlight
and
PCDFs
bromo
(19,20).
obtained
We
bromo
halogenated pounds
were
pected
and
behaviour
found. later
of
Photolysis
of
so
far
the
Photochemical
bromo
a
and
In
on
paper
bromo/chloro
since
correlate increased
Switzerland
increase
analysis
of
halogenated
route
also
environcompounds
sources.
of these
of
aromatic
less
the
loss
The
compounds,
now
high
a
year
with
The
although
rapid
artificial
light
only
instability
and
different
chloro
compounds
exceptional
dibenzodioxins
including
containing and
chemicals
photodegra-
photolytic
of the bromo the
of
compounds
attention
solution
over
decomposition this
compounds
the in
similar
fly
(14,16).
and present
reported
standard after
and
dehalogenation.
was
indication
when
reanalyzed
confirmed.
via
attained
(PBBs)
aromatic
in
used.
chlorinated
has
a The
stability
potential
to proceed
first
was
one
emissions.
environment
of additional
and p r e c a u t i o n s
is known
compounds
compounds
However, gasoline.
PCDDs
aromatic
detected
processes
of such previous
represents
the
of
or absence
polybromobiphenyls
aromatic
time.
use
in
from
dibenzodioxins
samples
compounds
on the e n v i r o n m e n t a l
compounds
of
that and
found
concentrations
in the
combustion
is
in a u t o m o b i l e were
of
halogenated
Whereas
bromo/chloro
aromatic
presence
bromo/chloro
measureable
levels
other
importance
techniques
degradation
of
about
depend
environment.
PCDDs
chloro
and
traffic
the r e l a t i v e
finding
Decomposition
of
for the p r e s e n c e
the a n a l y t i c a l
PCBs,
since
in
stable
and bromine
involved.
in e n v i r o n m e n t a l
increased
to
other
bromo and b r o m o / c h l o r o
environment The
production
countries
samples
the
incineration
in a u t o m o b i l e
reveal
actual
in
other
from addi-
environmental lead
situation
and
reported
these
The
to
dibenzofurans
in fly ash and
(17,18).
increased
municipal
occurred mental
are
and
of
chlorine
are
samples
investigated.
PCDFs.
a
toxici-
identified
of
can
lead
Such
usually
in
sources
and may
products.
where
and
processes
PCDDs
were
occurrence
systematically
process
halogenated gasoline
the
combustion
including
in
are of similar
such c o m p o u n d s
however,
has not yet been
elements
including
the c o m b u s t i o n
and d i b e n z o f u r a n s
Very r e c e n t l y
Otherwise,
Chlorine
aromatic
additional
from
congeners
processes
and
(2-6).
(7-9).
halogenated
Combustion
dibenzodioxins
analogues
was
comsus-
photochemical
dibenzofurans
is
891
pointed and
out.
Emphasis
elucidation
environmental
listed from
investigated.
in
Table
a previous
because
tions
A,
The
and
and
halogenated
prepared
of r e a c t i o n
Potential
C
products
analytical
toxicity
which
Compounds
to yield
of
these
their
and
sources
dibenzofurans
were
light.
(1,2,3,4-tetra-BDD)
All
these
with
compounds.
ng/~L
and
Soluof
the
the residues
range
(see
contained
as a p h o t o c h e m i c a l
very
to m i n i m i z e
solutions
to d r y n e s s
solutions
available
out
combined
stock
in the
were
(2,3,7,8-
were
carried
were
from
were brought
concentrations from
were
between
made
are
2,3,7,8-tetrachlorodi-
compounds
compounds
c o m p ar i s o n s
or nonane,
protected
and
and of
the e x p e r i m e n t s Several
each)
were
bromination
amounts
~L
in i-octane
used
2,3,7,8-tetrachlorodibenzofuran
small
solutions.
(500-1000
tetrabromodibenzodioxin
I:
and
compounds
dibenzodioxins
via
and to a l l o w direct
solutions
Table
pathways.
out.
halogenated
only
high
of dilute
in toluene
redissolved I).
The
Mixed
Because
work B
compounds
I.
study
of their
volumes
analytical
are pointed
(2,3,7,8-tetra-CDD)
tetra-CDF)(21).
small
study was on i d e n t i f i c a t i o n degradation
SECTION
benzodioxin
and
in this possible
consequences
EXPERIMENTAL
Compounds
of
Table
1,2,3,4-
standard.
investigated Solution, A
conc. B
1,2,3,4-tetra-BDD 2,3,7,8-tetra-BDD 2,3,7,8-tetra-BDD
5
2 I I
1,2,3,4-tetra-CDD 2,3,7,8-tetra-CDD
2.5 2.5
1,2,3,4-tetra-CDF 2,3,7,8-tetra-CDF 1,2,7,8-tetra-CDF
2 3 0.3
Compound
1-bromo-2,3,7,8-tetra-CDD dibromo" " " 1-/4-bromo-2,3,7,8-tetra-CDF dibromo-tetra-CDF
in ng/pl C
5
I
Source
a b b c d
I
e c f
5
g
10
g
a) O. Hutzinger, U n i v e r s i t y of Bayreuth, Bayreuth, FRG; b) R a d i a n Corp., Austin, Texas; c o u r t e s y W. Rotard, B u n d e s g e s u n d h e i t s a m t , Berlin, FRG; c) C. Rappe, U n i v e r s i t y of Umea, Umea, Sweden; d) G i v a u d a n Ltd., D~bendorf, Switzerland; e) Y. Masuda, Daiichii College of P h a r m a c e u t i c a l Sciences, Fukuoka, Japan; f) impurity from 2 , 3 , 7 , 8 - t e t r a - C D F ; g) see r e f e r e n c e 21.
892
S unli g h t
exposure
small
quartz
about
40 mm
a volume
sunlight
of
as
zero
toluene), aliquot
zero
the
with
solvent error
and
than
were
for 72 hr. addition
This
inside
for
a
weather
period
possible.
B
left than
initial
small
All
the
were
a n a l y z ed
with
(more
the
surface Traces
with
as
98%
vacuum.
for
of
vials
recovered)
the
during
at W a d e n s w i l 10-20
hrs
solution
tip
vials.
Aliquots volume)
removed
of 25 ~ L with
to u n e x p o s e d
controls
of 2-~L were
of
of
solvent
500
ng)
by
eva-
by hand. a
thin
of the tip the
from
vials
light
flame-sealed.
operations.
photolyses.
quartz
as
keeping
these
similar
each
was
of the vials
vials
of J u l y - e a r l y though
Unexposed
not
vials
as
Pre-
photolytic The
6
used
25 ~ L
individual
The
negligible
under
screw-
2 m dis-
then
end
of
in
covers)
were p r o t e c t e d
the
of
from
showed
at
simul-
light
(about
were
at
sea-
in May.
50 mm 2) on the walls
were
The vials the
exposed
Aliquots
rotation
covered
],2,3,4-tetra-BDD
of
the
sky)
above
Evaporation
artificial
films.
in
m
out
Aliquots
material
solvent
(area
a concentration
protective
and axial
area
2-~L
analysis.
carried
(I mL
to
separate
solid
of
necks
to sunlight time
to
A
in
causing
comparatively
placed
heating of
narrow
than
and
450
were
light.
vials
as d i s p e r s e d
added
(30 s) under The
exposure
conditions
mixed
C was
gentle
vials.
horizontally total
were
glass
(I ng/~L
analyzed.
exposure.
were
laboratory PVC
imme-
small
(cloudless
solutions
laboratory
with
removed in
(GC-MS)
47o;
thereby
soft-glass
in
sunlight
during
I mg/hr
after
reproducibility
(latitude
open
and and
I%.
experiments
40 Watt,
deposition
experiments
composition exposed
midday
28-30°C.
compounds
(estimated
quartz
for a short
the
solution
in
film
the
liminary
into
samples
of
and
by v a c u u m
as
full
to a r t i f i c i a l
(Osram-L, The
of
resulted
dispersed
much
A
25 ~ L
porated
Some
(vertically)
exposure
solutions
vials;
of
until
analyzed;
i.d.)
standard
spectrometric
than
to
were
light
were
in were
in a vial syringe
placed
internal
better
Switzerland
(0.5 mm
Hamilton
were
exposed
The vials
was placed
subsamples
of 10 ng of 13C I 2 -2 ' 3 , 7 , 8 - t e t r a - C D D analysis.
for GC-MS
Sunli g h t
neck
from
separately was
to be less
I-2%.
lamps
after
narrow
a 25-~L
Two
were
tubing.
subsamples
protected
vertically
vials
placed
tance
with
60 min. All
were
temperatures quartz
exposed
fluorescent
and
W~denswil,
of the compounds
solution
caps
in
air
long
Solutions
quartz
of a s o l u t i o n
chromatographic-mass
standard)
was d e t e r m i n e d
Expos u r e
15 and
controls.
controls
exposed
The
of less
5,
for gas
July
tip,
250 ~ L
periodically
refrigerated
were of
taneously.
of
2,
solution.
10 ng 1 3 C 1 2 - 2 , 3 , 7 , 8 - t e t r a - C D D
exposure
end
level)
a
for
used
in
5x3 mm d i a m e t e r
About
removed
analyte/internal
The vials
from
a flame-sealed
exposure
with
kept
was
compounds
300 ~ L .
25 ~ L
spiked
ratio
with
exposure
diately
Two
long,
the
prepared
of around
subsamples
vials,
of
vials
dewere
August
identical were
kept
893
as
zero
exposure
controls.
2,3,7,8-tetra-CDD pL)
of
was
used
i-octane
GC-MS
and
for G C - M S
analysis.
Finnigan
4000 50
25-m
SE54
fused
was
to
160°C,
All
eV),
used. was
were
compound
50-750,
Table
and 1.5
2:
Table
2).
The
were
large as
Some
samples
spectrometric
used
for m o n i t o r i n g GC-MS
A
13C12of
2-~L
an
i.d.)
Incos
with
100
aliquot
out
with
a
ionization
datasystem. 1.5-m
A
retention
made.
The
isothermal,
HRGC
20°C/min
300°C.
with
while
were
a
were
2 min
(MID).
two
chosen
for
compound
to 24-
monitor
sufficient
full-scan
(m/z
identification.
dibenzodioxins
(quantitation
to
retaining
concentrated
halogenated
18-
(M + or s a t e l l i t e )
were
still
and
Three
ions
descriptors
analyses
carried
electron-impact
detection
analysis
ions
and di-
underlined)
Ions m o n i t o r e d (m/z Dibenzodioxins Dibenzofurans
498, 418, 340, 262, 320, 286, 398, 478,
500 420 342 264 322 288 400 480
were
calculated compared
percent
were
made
lute
quantitative
first-order
was
i-octane)
used
MID
tetra-BDDs/BDFs tri" " di" " mono" " tetra-CDD/CDF tri" " bromo-tetra-CDD/CDF dibromo-tetra-CDD/CDF
as
10 ng (total
30 ~ L .
and
80°C,
at
possible
mass
in M I D
mm
in
multiple-ion time)
334
pressed
about
the
(0.32
isothermal
332,
were
opened,
4 portions
analysis
follows:
13C12-2,3,7,8-tetra-CDD
values
were
with to
in
(2-pl
as
compounds
sensitivity.
(m/z)
column
then
using
Compound
Results
vials
chromatograph
injections
s cycling
benzofurans
operating
programmed
as m a n y
GC-MS
Mega
capillary
analyzed (0.6
s/scan)
Ions
(HR)
Erba
to 300°C,
(see
simultaneously precision
Carlo
On-column
5°C/min
the
extracted
concentrated
instrument
a
temperature
samples
extract
silica
ion d e s c r i p t o r s per
the
exposure
residues
analysis.
GC-MS
(EI,
column
After
the
High-resolution
mode
gap
added,
via
to
analyte
for d i f f e r e n t data
area
those
of
ratios the
remaining
MID
response
is r e p o r t e d .
482 402 324 246 304 270 382 462
484 404 326 248 306 272 384 464
analyte/13C]2-2,3,7,8-tetra-CDD;
zero versus
exposure time
of d i f f e r e n t Half-lives
of
controls exposure.
congeners
(tl/2)
were
kinetics -in
(Cl/C0)=
kt
tl/2
= in 2/ k
and
(100%) No
and
the ex-
corrections
hence
no abso-
estimated
assuming
894
where
cl/c o
time
is
t, and
the
k the
tion p h o t o l y s i s
RESULTS
rate
and
under
sunlight
as thin
bromo/chloro
solid
films.
in all
creased
was
light
intensity
(23,24;
geners.
see
shown
for
exposure the
solu-
tetrabromo around
I-2 min).
single
peak
a
analogy
to
are
expected
not
estimated longer
the
to be
at around
than
that
(2,7- and/or
Reductive
the
a
(23,24).
debromination
In
this
less The
brominated
way
data
the
and
strong
to
be
major
indicates
high
if
final
dibenzodioxin
not
products
of
formed
pre-
for
exclusive
(DF).
expected and
the
these
in
2,3,8-tri-BDF
again
and
a
were
rather
experiments
formation
(DD) and d i b e n z o f u r a n
con-
tri-BDFs
9 min,
higher
under
estimated
were
and
congeners
observed
chloro
decomposition
with
2:2
type
observed.
pathway
carbon-ring
from
the
was
these
decomposition
2,3,7,8-substituted likely
indicating
were observed.
C6H3 +) were
observed
formafurther
brominated
expected)
brominated
previously
2,3,7-
in-
with
fast
preliminary
the
higher
The
considerations
at around
75 ion,
to
eluting)
two tri-BDFs time
m/z
very
The
In
lower
rather
(2,3,7-tri-BDD
due
with
l-isomer)
half-lives
the di-BDFs
compound.
toxic
the
compounds
The
analogy
com-
Accelerated
subsequently
(earlier
C as a
this
experiment.
of
B showed
chloro
3).
1,2,4-tri-BDD
half-life (likely
(25). of
was
of
B and
possibly
the
nonane) dispersed
for
eluting)
in
retention
not
species.
unsubstituted
same
half-life
From
Table
are
(later
positions
longer
tri-BDD
the
the
2,3,7,8-tetra-BDF
the
appears
(see
which
A,
observed
1,2,4-isomer
in solution
parent
from The
stable
a
2,8-isomer;
predominantly
lateral-positions.
The
those
single
is the
and m o n o - B D D
with
min
of
compounds
solutions
was
photolysis
part
1,2,3-tri-BDD
separated
2 min,
of
2,3,7,8-tetra-BDD
latter
observed.
situation
2-3
was o b s e r v e d
From
to
of
(i-octane,
the same
added
of
lateral
I).
compounds
(half-lives only
of
indicating di-BDD
was
solution
decomposition
solution
with
proceeding
the
the
in h y d r o c a r b o n
decomposition
formed
at
but
geners.
after
(22).
photochemical
decomposition
congeners
Scheme
min,
Furthermore,
three
be
was
et al.
hydrocarbon
half-lives
amounts
compounds
11
fast
in
during
tri-BDD
smaller
around
very
during
brominated
debromination
to
remaining
kinetics
and PBDFs
significant with
ferential
be
slower
apparent
The major
concommitant
occur
compound
by N e s t r i c k
1,2,3,4-Tetra-BDD
solutions
tion of lower degraded.
showed
standard;
decomposition
of PBDDs
compounds
but much
photochemical
di-BDD
the
First-order
tetra-CDDs
photolysis
experiments
bromo
All
of
AND D I S C U S S I O N
Preliminary
to
amount
constant.
of several
Sunlight-induced
pound
relative
and
chloro can
be
and
from
compounds expected
substituted of
to the
these
conditions
conlower were
895
Scheme
I:
Br Br~O~ fasy ~r O"~///m slOW~Br Br O
Br Br
Br
di-BDDs I ono BDD(s)
:
DD
I
further degradation Sunlight-induced
p h o t o l y s i s of PCDDs and PCDFs
The p h o t o l y t i c h a l f - l i v e s to
that
of
Tetra-CDD
first-order
1,2,3,4-Tetra-CDD in the order
of
appears
380
by
Nestrick
et
in the
decomposition
two b r o m o a n a l o g u e s .
case
of
half-lives CDDs,
no
the of
the
much
same
(22).
rates Very
and
more.
of
solution
an
more
stable
these
two
rather
slow
the
half-life was
re-
variation
between
the
observed
with
with
the
tetra-
was
found.
of b r o m o / c h l o r o d i b e n z o d i o x i n s
with
was
situation
Sunlight-induced
Solution
than
min.
2,3,7,8-tetra-CDF
amounts
in h y d r o c a r b o n
14
isomers
greater
isomers
2,3,7,8-
of
estimated two
decomposition
and
3).
f o r m a t i o n was observed.
The f o r m a t i o n of only small
photolysis
(about
an
these
chloro
from
1,2,3,4-
(Table
half-life
is a much
tri-CDD
Different
between
with
with
there
(about I%)
A
estimated
observation
between little
difference
data
solution
-CDFs can be d i r e c t l y c o m p a r e d
with
Apparently
tetra-CDFs
180 min
large
The
al.
three
from
kinetics
to be
min.
ported
In
of the t e t r a - C D D s and
1,2,3,4-tetra-BDD shows
in h y d r o c a r b o n
3%) of tri-CDFs was observed.
and d i b e n z o f u r a n s
solution
C contained
mixtures
2,3,7,8-tetra-CDD
showed a h a l f - l i f e
around
and
of mono-CDF
2.5 min
Apparently
the
(21).
and d i b r o m o - t e t r a - C D D s I ,2,3,4-Tetra-BDD
(see Table
previous
values.
profound
i n f l u e n c e on the d e c o m p o s i t i o n
additional
3) w h i c h
and
in
-CDFs
this
is in a g r e e m e n t
compounds
present
rate of this compound.
here
along
solution with the have
no
896
Table
3:
Sunlight-induced
photolysis
dibenzofurans
i-octane
in
of
Rel.
halogenated
amounts a
dibenzodioxins
(% r e m a i n i n g )
exposure Compound
Sol.
Control
2
5
A "
100 <0.05
64 27
"
" " "
<0.05 <0.05 <0.05
1,2,3,4-tetra-CDD 2,3,7,8" "
" "
100 100
101 92
1,2,3,4-tetra-CDF 2,3,7,8" " 1,2,7,8" "
" " "
100 100 100
101 101 100
1,2,3,4-tetra-BDD 2,3,7,8" " tri-BDDs di" mono-"
B " " " "
100 100 ~0.4 < 0.4 <0.2
56 30 29 20 < 0.2
2,3,7,8-tetra-BDF tri-BDF di"
" " "
100 0.5 0.5
"
0.5
1,2,3,4-tetra-BDD 1,2,4-tri" 1,2,3-tridi-BDDs mono-BDD
mono-" 1,2,3,4-tetra-BDD
C
100
2,3,7,8-tetra-CDD I -bromo" dibromo" bromo-tri-CDD tri-CDD
" " " " "
2,3,7,8-tetra-CDF I-bromo" 4-bromo" dibromo" bromo-tri-CDF tri-CDF
" " " " " "
a)
peak
control
area
bromo-PCDDs, tetra-CDD and
accuracy,
not
-CDF and
estimated
33 53
0.8 40
<0.05 2
11
9 12 0.8
3 52 17
<0.1 33 76
104 82
95 44
91 5
380 14
102 104 103
92 95 95
80 84 94
180 220 600
3
18 1.6 44 25 I
0.2 <0.4 25 73 27
<0.2 <0.4 < 0.4 10 53
2 0.8 8 16
<0.5 15 116 1
<0.5 <0.5 129 31
<0.5 <0.5 4 71
0.7 2 9
<0.1
2.5
139 1 35 10 4 3
180 82 3 2 6
178 15 <0.1 0.5 17
151 <0. I <0.I <0.I 3
100 203 118 140 2 <0.1
514 48 55 16 10 2
691 I 2 <0.I 9 7
629 <0.1 ~0.I <0.1 3 18
444 <0.1 <0.1 <0.1 <0.1 22
to
to
accuracy
of
-CDF
reported
total
derived
2
90 0.5 0.5 0.5
standard
relative values
amounts
from
half-lives
4
MID-response;
respectively; the
(200)
internal
different
and
values
I
13C-tetra-CDD
for
compounds,
relative b)
Half-life(min)
100 1 67 18 3 0.5
tri-CDD
parent
respectively;
0.5
60
27
corrected
-BDFs
15 38 29
Estimated b
(min) 15
63
relative
bromo-PCDFs,
and
tri-BDDs
tetra-BDFs, ted
ratios
samples,
4 0.8 <0.1
and
few
±50%.
of
data
of
and
values to
mono-,
tetra-BDDs points
of
2,3,7,8-
of
diand limi-
897
In
case of the b r o m o / c h l o r o d i b e n z o f u r a n s
than
I min)
of
the mono-
f o r m a t i o n of a d d i t i o n a l and f i n a l l y CDF.
of
the
predominant
loss of c h l o r i n e
bromo-tri-CDF
This
and d i b r o m o - t e t r a - C D F s
formed
decomposition
to
compounds
this
mixture
have
BDF.
The p h o t o l y t i c
be
into
about
less
than
results
in
PCDFs.
the
same
is
half-life
3% the
The
(half-lives
observed
less
resulting
in the
to be m u c h more
stable
t o g e t h e r w i t h a small a m o u n t of tri-
reaction
the
is a very m i n o r p a t h w a y
pathway
bromo/chloro
was
2,3,7,8-tetra-CDF which appears
is the m a j o r p r o d u c t o b s e r v e d
Apparently
tuents;
fast d e c o m p o s i t i o n
of
relative
to
the
the
preferential
I-
half-life
loss
and e s t i m a t e d
and
bromo-substi-
from the amount loss
of
conversion
bromine. of
these
4-bromo-2,3,7,8-tetra-CDF
(about
0.5
of 2 , 3 , 7 , 8 - t e t r a - C D F
min)
in this
as
in
2,3,7,8-tetra-
s o l u t i o n was around
90 min.
The
same
The
small
posed
II).
behaviour
amounts
fast
further
be
general
(half-life
decomposed
reaction
200 with
compounds Figure their
Scheme
min, the
with
the
I document conversion
about
observed
2 min)
(half-life
The p h o t o l y t i c
around
was
of d i b r o m o - t e t r a - C D D s
half-life somehow
bromo
into
bromo/chloro
was
longer again
photolysis
dibenzodioxins.
not separated)
1-bromo-2,3,7,8-tetra-CDD,
4 min)
substituents
rapid
the
to
2,3,7,8-tetra-CDD
of 2 , 3 , 7 , 8 - t e t r a - C D D much
bromo-PCDDs
the
to
around
for
(3 isomers,
than
in
in this solution
debromination
at
in
peri-position.
of
the
2 , 3 , 7 , 8 - t e t r a - C D D and
bromo-PCDDs
were decomwhich (see
solution A.
The
high
The
then
Scheme
appears
to
predominant
rate
even
for
chromatograms
and
2,3,7,8-tetra-CDF,
bromo-PCDFs
in and
respectively.
II:
Br Br cIIf(~"T'°~(~'~lcIA __ fast cIr~------'~o-v~cI fast cI
c
c,
Br slow
I
-CI
o
cI
o©c,
I
slow I-CI
slow ~ - CI T
slow 1 further degradation
898
Photolysis s olut i o n
This
o__ff h a l o g e n a t e d
with a r t i f i c i a l
experiment
bromo tory
was
carried
and b r o m o / c h l o r o light
reason
as
the
it
(5 hours
tions
A,
and
These
conditions
sample
B
All
C
of
the
were
than
those
precautions
were
days).
The
of these
under
to m i n i m i z e
quartz the
the
and
teristics
are more
here
to
sunlight expected
(5-8%)
p rodu c t s
around
normally
encountered
during
are
taken
(prevention
indicates
compounds,
was
however,
(half-lives in the
low decomposhowed
~8
same
The results
order
as
The
in case
and
indicate
conditions
more
days).
-CDFs
sufficient
provided
suitable
exposure.
dibenzodioxins
A
the
the
compounds
are
given
from
and d i b e n z o f u r a n s
probably
of
of
for
26-35
hrs.
Only
tribromo pathways
so far have
rates
as
films
in
4. More
variation
in
because
film
hrs. of
10
or
2,3,7,8-
was
20
Compared
hrs with
and
reported
previously
tetrabromo
compounds
very
small
be
amounts were
involved.
not been detected.
(1%)
of
observed, However,
charac-
observed. exposure the
Also All with
situation
1,2,3,4-tetra-CDD
3
compounds)
thin
to reproduce.
controls
was
the
may
vial
as
are d i f f i c u l t
after
35-300
finding
found
to
the u n e x p o s e d
relative
similar
dispersed
in Table
vial
decomposition range
was
degradation
products
some
in the
(predominantly
additional chemical
showed
reversed.
uniformity)
in the data
photolysis
decomposition
half-lives
with
was
half-lives
so l u t i o n
Solulamps.
e.t.c).
analytical
rates
compounds
estimated
decomposition.
dibromo-2,3,7,8-tetra-CDDs
of h a l o g e n a t e d
experiments
(area covered,
variation
chloro
this
Preliminary
fluorescent
79-93%
days).
light
exposed
decomposition
more
in
photolysis
normal
vials.
laboraFor
films
of
vials
and
(half-lives~9
are taken
results
only
compounds
Bromo-
stability
The
tetrabromo at
ordinary
of
from
at 93% or more which
recovered
at 80-86%
light
use of amber vials,
recovered
were
to
if any
some
precautions
solid
little
hrs
behaviour
procedures.
in quartz
severe
photolytic
diffuse
very
72
not
provided
exposures.
Sunlight-induced
and
be more
susceptibility
recovered
in glass
under
preparation
should
and
sunlight
and d i b e n z o f u r a n s sample
showed
procedures
i__n h y d r o c a r b o n
photochemical
for
(half-lives ~ 2 8
photolytic
the
exposed
tetra-CDDs/CDFs
sition
investigate
during
exposure)
sun- or daylight,
decomposition
to
exposed
dibenzofurans
were
preparation
of direct
occur
were
experiments
out
and
light
dibenzodioxins
might
samples
dibenzodioxins
laboratory
(22). with some
Somewhat estimated
photolysis
indicating additional
that photo-
899
r-, I-I
p,.
C::I C~
¢q I¢,,1~,
I-I
I~ C~
_i~i
..
0.4+,
C4 ,,,.,+
I'-I
,~ m
~0 p--
l cO " t~
2 P..+ E
' <~ B +...i
m
~
O
m
m
£',,I I
0 N
!
2\ ~'
~
-,'-,
0
.+5+ -H
Y
~
p-!
I-" I CO
I
,
¢¢
J i
-,-~
~
~
0
r~
E
-,-t
3
,./
m
i
c'-q r~
O
I-I
Y
~4
-~--
~
~ ~
C3
C)
0
~
p-
0
LI_ '+-'
I--
¢_)
I
p,,.. +.'+O
b~
m
¢0
~
I-I
'-~ {1}
0
C~
o~2 I.I_ I-I O~ reo
O
-\
+,,,
+/
r-,
'7
I
p,_ I
r~ I
+~
-H
"0
0
0
0
O
~
•
i
8 Y
-\
0
.~ ~ •.,.-.+ ..-i
I
O
~q
I-.I p~ O}
/
,,-+
0
-,~
i
i.-+
8
e~ i-i
O
~
~
-~
0
i
~
0
q3 >~
4-} <1}
0 ,z~
0 -,-+
900
Table
4:
Sunlight-induced dibenzofurans
photolysis
dispersed
o_~f h a l o g e n a t e d
as
solid
Rel.
dibenzodioxins
films
amounts a
(% r e m a i n i n g )
exposure Compound
Sol.
1,2,3,4-tetra-CDD
and
Control
(hrs)
10
20a
Estimated
20b
half-life c
A+B
100
85
76
84
65
"
100
98
91
101
300
1,2,3,4-tetra-CDF
"
100
90
82
90
95
1,2,7,8-
"
"
"
100
86
64
73
35
2,3,7,8-
"
"
"
100
93
84
94
120
"
100
60
51
63
26
100
67
52
77
32
77
35
2,3,7,8-
"
"
I ,2,3,4-tetra-BDD 2,3,7,8-
"
.
.
.
.
2,3,7,8-tetra-BDF
"
100
60
53
1,2,3,4-tetra-BDD
C
100
12
13
2,3,7,8-tetra-CDD
"
100
117
100
1-bromo-
"
"
167
113
105
30
dibromo-
"
"
9
I
3
12
"
2
0.5
2
bromo-tri-CDDs
7 b)
2,3,7,8-tetra-CDF
"
100
290
212
b)
1-bromo-
"
"
227
105
115
b)
4-bromo-
"
"
134
23
35
dibromo-
"
"
139
25
35
bromo-tri-CDF a)
peak
"
area
control
bromo-PCDDs, tetra-CDD of
The
and
solution
C)
indicating
the
was the
of
deposition tion
tri-CDD
accuracy,
of
10-
and
techniques
with
pathway
1,2,3,4-tetra-BDD with
phase and
the
photolysis 20-hr
homogenity will
solid
of
the
respectively;
b)
values
in
-CDFs;
c)
accuracy
is m o r e
of
7
compounds this
This on
of
derived
(solid
the
of
2,3,7,8because from
half-lives
few
±50%.
films
from
and
-CDF
Similarly,
somehow
larger
the than
A+B.
to v a r i a t i o n may
to
2,3,7,8-tetra-CDD
was
and
values
estimated
photolysis.
hrs)
solution
subject
data.
not
compounds
solution
from
standard
relative
and
(half-life
improve
internal MID-response;
reported
formation as
films
exposure
hopefully
-CDF
bromo/chloro
concurrent
reaction
0.8
different
estimated
the
b) 10
13C-tetra-CDD and
compounds,
of
0.5
for
bromo-tetra-CDDs
larger
solid
the
parent
limited
same
experiment
Apparently some
of
to
corrected
decomposition
decomposition in
CDF from
points
photolytic
relative
not
bromo-PCDFs,
formation
data
ratios
samples,
0.7
(hrs)
be
due
surface.
situation.
The
as to
indicated variations
by in
Different
deposi-
difference
between
901
the
estimated
half-life
tions A+B and C (7 and ce of
non-volatile
solution
C.
Such
pronounced more
not
1,2,3,4-tetra-BDD
26 hours,
sensitizing
compounds
influence
sample
leads
of
handling
respectively) compounds
or
remain
the
may
here
than
in
to
fully
account
in
solution
(evaporation,
to g r e a t e r data v a r i a t i o n
expected
in
for
may be due
solid
film
photolysis. from
in s o l u t i o n
the
solid
films
as
and
the
solu-
influen-
impurities
may
have
Additionally vials)
photolysis.
differences
from
to a larger
hydrogen-donors
extraction
than
the
a more
there
involved
is
which
This,
however,
with
the
observed
in
is
exposed
samples.
CONCLUSIONS
The m a j o r
photochemical
dibenzodioxins
dibenzodioxin
Additional
these c o m p o u n d s . position much
rates
under
rates
indications
that
carbon-rings
are
furans
A
lateral-halogens
loose
e x p e r i m e n t s was
like
bromine
significantly
brominated
consequences
losses of these analytes.
due
dures
be
to
brominated
compound
extraction,
There
are
chemicals
as
a
halogenated
phase
photolysis
detect, and
some
in
a
sample.
the
The use
photochemical
our
for the bromo
too
low values
during
conversion
added
to
from
should m i n i m i z e
of
to decom-
these
proce-
some
bromo/
of a p h o t o c h e m i c a l l y
standard
Because
Protection
-BDF were most prone congeners
especially
PCDFs.
aro-
in
behaviour.
a n a l y s e s may p r e t e n d
present
of
(PCDDs
in the range of 7-35 hrs.
2 , 3 , 7 , 8 - T e t r a - B D D and decomposition
dibenzo-
compounds
mixed
are
halogenated and
chlorinated
sample p r e p a r a t i o n and a n a l y s i s
Photochemical
into PCDDs
higher
There
other Solid
of
a few minutes,
compounds.
to this p h o t o c h e m i c a l
originally
position.
difficult
the
further
show high decom-
slower but still a p p r e c i a b l e
so r a p i d l y d e c o m p o s e d , compounds
from
to lower
are
film p h o t o l y s i s
of only
chloro
halogenated
leading
dibenzodioxins
with
pyrenes.
with h a l f - l i v e s
sun- or d a y l i g h t d u r i n g
congeners
to
exist
solid
those
all
likely
compounds
half-lives
and
leading may
then
in the
Bromo/chloro
bromo/chloro
compounds
these c o m p o u n d s are
may
which
corresponding
lost.
situation the
There are a n a l y t i c a l
chloro
with
the
model
direct
involved
sunlight of the
preferably
compounds
the
be
those
matic
for
natural
similar
and b r o m o / c h l o r o
may
with
reductive dehalogenation
and d i b e n z o f u r a n
than
preferably
PCDFs).
pathways
was
solution
In s o l u t i o n bromo and b r o m o / c h l o r o
higher
and
in h y d r o c a r b o n
and d i b e n z o f u r a n s
or u n s u b s t i t u t e d degraded.
reaction
samples
sensitive prior
to
c l e a n - u p and a n a l y s i s w o u l d be advisable.
also
potential
by s u n l i g h t
environment.
environmental
represents
The bromo and b r o m o / c h l o r o
photochemically
less
stable
in
consequences.
an i m p o r t a n t
the
route
compounds
environment
Decomposition
for their r e m o v a l
investigated
than
the
of
here are
chloro
some
from the likely
compounds
and
902
thus
may
be
atmospheric after
preferentially transport
deposition
surfaces vents
together
and
genated pounds
on
quired
light
a situation
analysis
for
bromo
bromo/chloro
and
be
samples
in
a
thought
grave
compounds
are e s p e c i a l l y
which
can
may
then
experiments
realistic
during or
even
be a d s o r b e d
photolysis
Additional
as
site
act of
as
the
with
environment
solhalo-
the
experiments
with
will
on
be
comthe re-
situation.
that
identification
especially
compounds
in our model
more
such
a deposition
situation
in
are
way
stable
samples may
in the
prone
this
more
of e n v i r o n m e n t a l
source
may
The
surface.
into this
is the
situation
mental
than
quartz
situations
to
compounds this
into the p h o t o c h e m i c a l l y
the
compounds
soil).
in
faster
surfaces
intriguing
may be c o n v e r t e d
be
that
certain source
additional
so
clean
on
to shed more
Especially
ted
a
adsorbed
(plants,
many
could on
in
combustion
surfaces
with
compounds
compounds
a
hydrogen-donors
adsorbed
degraded
from
for
lead
case
of
expected
bromo/chloro
PCDDs the
to
and
different
false
leaded
congeners
and PCDFs.
In such
halogena-
conclusions.
fuel
combustion
in situations
were
The were
environ-
to photolysis.
ACKNOWLEDGMENT
I
thank
several tute
O.
Hutzinger,
of the bromo
C.
Rappe,
and chloro
W.
Rotard,
compounds,
for W a t e r
Resources
and Water
for c r i t i c a l l y
reviewing
this manuscript.
Y.
Masuda
and
and J. Hoigne
Pollution
Control,
Givaudan
(Swiss
Ltd.
Federal
D~bendorf,
Insti-
Switzerland)
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I.
W.J.
Nicholson,
2.
J.A.
Moore,
Acad.
J.A.
E.E.
Moore,
Ann.
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McConnell,
D.W.
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320,
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W.F.
Greenlee,
3.
A.
4.
A.
5.
A.S.
Kende,
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T.O.
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M.W.
320,
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(1979). N.Y.
(1979). A.S.
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320,
214
251,
4936
(1976).
(1979). Poland,
E. Glover, J.J.
Wade,
Malloy,
M.L.
Compounds,
H.R.
Buser,
8.
H. Thoma,
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EHP,
B. Ramalingam,
Related 7.
A.S.
Taylor,
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Environ. J.H.
5th Intern.
Sept.
16-19,
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G. Hauschulz,
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H.R.
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C.M.
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D.J.
on C h l o r i n a t e d Bayreuth
(1987). 9.
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Chemosphere
for
16,
277
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10.
K. Ballschmiter, sphere 15, 901
11.
S. Marklund,
H. Buchert,
R. Niemczyk,
A. Munder,
M. Swerev,
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(1986).
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M. Tysklind,
K.E. Egeb~ck,
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16, 29
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G.W.
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R.L. Harless,
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D.D. McDaniel,
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(Received in Germany 9 January 1988; accepted 18 February
1988)
RAPID
pp 889-903,
PHOTOLYTIC
1988
DECOMPOSITION
BROMINATED/CHLORINATED
Federal
CH-8820
OF B R O M I N A T E D
DIBENZODIOXINS
Hans-Rudolf Swiss
0 0 4 5 - 6 5 3 5 / 8 8 $3.00 + .OO P e r a a m o n Press plc
AND
AND D I B E N Z O F U R A N S
Buser
Research
W~denswil,
Station
Switzerland
ABSTRACT
Rapid
photolytic
dibenzofurans sunli g h t ing
compounds.
chemi c a l the
with
laboratory ted
that
cautions
(PCDDs)
and
light
are
major
and of
in
compounds order
solution
showed
exposure.
compounds
likely
has
be
In
are
environmental
full
and
summer
that of c o r r e s p o n d -
this
was
way, from
Solid
phase
surfaces
under
of
the
consequences
was
compounds
some d e c o m p o s i t i o n
photochemical
photo-
photolysis
sunlight
the
provided
reductive
polychloro-
formed
Exposure
obtained
The
under
observed
analogues.
hours.
to m i n i m i z e
so far unknown.
congeners.
on quartz
can
than
pathway
(PCDFs)
dibenzodioxins
solution
faster
of
data
cations
much
bromo/chloro
analytical
halogenated are
I min,
brominated
the
bromo/chloro
photochemical
in h y d r o c a r b o n
taken
and
hydrocarbon
dibenzofurans the
bromo/chloro
half-lives
reliable
bromo
dilute
to lower
decomposition
bromo
of
in
as low as
The
leading
dibenzodioxins
slower
observed
with h a l f - l i v e s
chloro
debromination
of
decomposition
was
but
indica-
suitable
behaviour but
to
of
actual
prethese impli-
INTRODUCTION
Polychlorinated much
scientific
mental these rial
dibenzodioxins and
contaminants compounds chemicals
are they
public and
some
varied. are
(PCDDs)
and d i b e n z o f u r a n s
attention. of
them
Apart
also
These are
from
formed
precursors.
889
extremely
being in
compounds
(PCDFs) are
toxic
contaminants
combustion
have attained
known (I). in
processes
The
as
environ-
sources
certain from
of
industsuitable
890
Bromo
and b r o m o / c h l o r o
ty as the chloro as
thermolysis
an
accidental
tional
products fire
PCDDs
PCDFs.
chlorinated
halogen
compounds
are
brominated
thought
compounds
mixed
of leaded
to
entering
flame
be
retardants
such
a
one
of
the
both
scavenger
compounds
(dichloro-
and d i b r om o e t h a n e )
and
PCDFs
have
been
associated
and
some
other
bromo
compounds
have
been
identified
(10-12),
bromo
and
and d i b e n z o f u r a n s
have not yet been a c t u al l y
However,
bromo/chloro
dibenzodioxins
ash
incinerators
(13-15);
from
(pyrenes)
were
identified
PCDDs
and
PCDFs
about
the
1940-50s
with
the
use
of
and
other
could
and
would
from
the
dation
of
by sunlight
and
PCDFs
bromo
(19,20).
obtained
We
bromo
halogenated pounds
were
pected
and
behaviour
found. later
of
Photolysis
of
so
far
the
Photochemical
bromo
a
and
In
on
paper
bromo/chloro
since
correlate increased
Switzerland
increase
analysis
of
halogenated
route
also
environcompounds
sources.
of these
of
aromatic
less
the
loss
The
compounds,
now
high
a
year
with
The
although
rapid
artificial
light
only
instability
and
different
chloro
compounds
exceptional
dibenzodioxins
including
containing and
chemicals
photodegra-
photolytic
of the bromo the
of
compounds
attention
solution
over
decomposition this
compounds
the in
similar
fly
(14,16).
and present
reported
standard after
and
dehalogenation.
was
indication
when
reanalyzed
confirmed.
via
attained
(PBBs)
aromatic
in
used.
chlorinated
has
a The
stability
potential
to proceed
first
was
one
emissions.
environment
of additional
and p r e c a u t i o n s
is known
compounds
compounds
However, gasoline.
PCDDs
aromatic
detected
processes
of such previous
represents
the
of
or absence
polybromobiphenyls
aromatic
time.
use
in
from
dibenzodioxins
samples
compounds
on the e n v i r o n m e n t a l
compounds
of
that and
found
concentrations
in the
combustion
is
in a u t o m o b i l e were
of
halogenated
Whereas
bromo/chloro
aromatic
presence
bromo/chloro
measureable
levels
other
importance
techniques
degradation
of
about
depend
environment.
PCDDs
chloro
and
traffic
the r e l a t i v e
finding
Decomposition
of
for the p r e s e n c e
the a n a l y t i c a l
PCBs,
since
in
stable
and bromine
involved.
in e n v i r o n m e n t a l
increased
to
other
bromo and b r o m o / c h l o r o
environment The
production
countries
samples
the
incineration
in a u t o m o b i l e
reveal
actual
in
other
from addi-
environmental lead
situation
and
reported
these
The
to
dibenzofurans
in fly ash and
(17,18).
increased
municipal
occurred mental
are
and
of
chlorine
are
samples
investigated.
PCDFs.
a
toxici-
identified
of
can
lead
Such
usually
in
sources
and may
products.
where
and
processes
PCDDs
were
occurrence
systematically
process
halogenated gasoline
the
combustion
including
in
are of similar
such c o m p o u n d s
however,
has not yet been
elements
including
the c o m b u s t i o n
and d i b e n z o f u r a n s
Very r e c e n t l y
Otherwise,
Chlorine
aromatic
additional
from
congeners
processes
and
(2-6).
(7-9).
halogenated
Combustion
dibenzodioxins
analogues
was
comsus-
photochemical
dibenzofurans
is
891
pointed and
out.
Emphasis
elucidation
environmental
listed from
investigated.
in
Table
a previous
because
tions
A,
The
and
and
halogenated
prepared
of r e a c t i o n
Potential
C
products
analytical
toxicity
which
Compounds
to yield
of
these
their
and
sources
dibenzofurans
were
light.
(1,2,3,4-tetra-BDD)
All
these
with
compounds.
ng/~L
and
Soluof
the
the residues
range
(see
contained
as a p h o t o c h e m i c a l
very
to m i n i m i z e
solutions
to d r y n e s s
solutions
available
out
combined
stock
in the
were
(2,3,7,8-
were
carried
were
from
were brought
concentrations from
were
between
made
are
2,3,7,8-tetrachlorodi-
compounds
compounds
c o m p ar i s o n s
or nonane,
protected
and
and of
the e x p e r i m e n t s Several
each)
were
bromination
amounts
~L
in i-octane
used
2,3,7,8-tetrachlorodibenzofuran
small
solutions.
(500-1000
tetrabromodibenzodioxin
I:
and
compounds
dibenzodioxins
via
and to a l l o w direct
solutions
Table
pathways.
out.
halogenated
only
high
of dilute
in toluene
redissolved I).
The
Mixed
Because
work B
compounds
I.
study
of their
volumes
analytical
are pointed
(2,3,7,8-tetra-CDD)
tetra-CDF)(21).
small
study was on i d e n t i f i c a t i o n degradation
SECTION
benzodioxin
and
in this possible
consequences
EXPERIMENTAL
Compounds
of
Table
1,2,3,4-
standard.
investigated Solution, A
conc. B
1,2,3,4-tetra-BDD 2,3,7,8-tetra-BDD 2,3,7,8-tetra-BDD
5
2 I I
1,2,3,4-tetra-CDD 2,3,7,8-tetra-CDD
2.5 2.5
1,2,3,4-tetra-CDF 2,3,7,8-tetra-CDF 1,2,7,8-tetra-CDF
2 3 0.3
Compound
1-bromo-2,3,7,8-tetra-CDD dibromo" " " 1-/4-bromo-2,3,7,8-tetra-CDF dibromo-tetra-CDF
in ng/pl C
5
I
Source
a b b c d
I
e c f
5
g
10
g
a) O. Hutzinger, U n i v e r s i t y of Bayreuth, Bayreuth, FRG; b) R a d i a n Corp., Austin, Texas; c o u r t e s y W. Rotard, B u n d e s g e s u n d h e i t s a m t , Berlin, FRG; c) C. Rappe, U n i v e r s i t y of Umea, Umea, Sweden; d) G i v a u d a n Ltd., D~bendorf, Switzerland; e) Y. Masuda, Daiichii College of P h a r m a c e u t i c a l Sciences, Fukuoka, Japan; f) impurity from 2 , 3 , 7 , 8 - t e t r a - C D F ; g) see r e f e r e n c e 21.
892
S unli g h t
exposure
small
quartz
about
40 mm
a volume
sunlight
of
as
zero
toluene), aliquot
zero
the
with
solvent error
and
than
were
for 72 hr. addition
This
inside
for
a
weather
period
possible.
B
left than
initial
small
All
the
were
a n a l y z ed
with
(more
the
surface Traces
with
as
98%
vacuum.
for
of
vials
recovered)
the
during
at W a d e n s w i l 10-20
hrs
solution
tip
vials.
Aliquots volume)
removed
of 25 ~ L with
to u n e x p o s e d
controls
of 2-~L were
of
of
solvent
500
ng)
by
eva-
by hand. a
thin
of the tip the
from
vials
light
flame-sealed.
operations.
photolyses.
quartz
as
keeping
these
similar
each
was
of the vials
vials
of J u l y - e a r l y though
Unexposed
not
vials
as
Pre-
photolytic The
6
used
25 ~ L
individual
The
negligible
under
screw-
2 m dis-
then
end
of
in
covers)
were p r o t e c t e d
the
of
from
showed
at
simul-
light
(about
were
at
sea-
in May.
50 mm 2) on the walls
were
The vials the
exposed
Aliquots
rotation
covered
],2,3,4-tetra-BDD
of
the
sky)
above
Evaporation
artificial
films.
in
m
out
Aliquots
material
solvent
(area
a concentration
protective
and axial
area
2-~L
analysis.
carried
(I mL
to
separate
solid
of
necks
to sunlight time
to
A
in
causing
comparatively
placed
heating of
narrow
than
and
450
were
light.
vials
as d i s p e r s e d
added
(30 s) under The
exposure
conditions
mixed
C was
gentle
vials.
horizontally total
were
glass
(I ng/~L
analyzed.
exposure.
were
laboratory PVC
imme-
small
(cloudless
solutions
laboratory
with
removed in
(GC-MS)
47o;
thereby
soft-glass
in
sunlight
during
I mg/hr
after
reproducibility
(latitude
open
and and
I%.
experiments
40 Watt,
deposition
experiments
composition exposed
midday
28-30°C.
compounds
(estimated
quartz
for a short
the
solution
in
film
the
liminary
into
samples
of
and
by v a c u u m
as
full
to a r t i f i c i a l
(Osram-L, The
of
resulted
dispersed
much
A
25 ~ L
porated
Some
(vertically)
exposure
solutions
vials;
of
until
analyzed;
i.d.)
standard
spectrometric
than
to
were
light
were
in were
in a vial syringe
placed
internal
better
Switzerland
(0.5 mm
Hamilton
were
exposed
The vials
was placed
subsamples
of 10 ng of 13C I 2 -2 ' 3 , 7 , 8 - t e t r a - C D D analysis.
for GC-MS
Sunli g h t
neck
from
separately was
to be less
I-2%.
lamps
after
narrow
a 25-~L
Two
were
tubing.
subsamples
protected
vertically
vials
placed
tance
with
60 min. All
were
temperatures quartz
exposed
fluorescent
and
W~denswil,
of the compounds
solution
caps
in
air
long
Solutions
quartz
of a s o l u t i o n
chromatographic-mass
standard)
was d e t e r m i n e d
Expos u r e
15 and
controls.
controls
exposed
The
of less
5,
for gas
July
tip,
250 ~ L
periodically
refrigerated
were of
taneously.
of
2,
solution.
10 ng 1 3 C 1 2 - 2 , 3 , 7 , 8 - t e t r a - C D D
exposure
end
level)
a
for
used
in
5x3 mm d i a m e t e r
About
removed
analyte/internal
The vials
from
a flame-sealed
exposure
with
kept
was
compounds
300 ~ L .
25 ~ L
spiked
ratio
with
exposure
diately
Two
long,
the
prepared
of around
subsamples
vials,
of
vials
dewere
August
identical were
kept
893
as
zero
exposure
controls.
2,3,7,8-tetra-CDD pL)
of
was
used
i-octane
GC-MS
and
for G C - M S
analysis.
Finnigan
4000 50
25-m
SE54
fused
was
to
160°C,
All
eV),
used. was
were
compound
50-750,
Table
and 1.5
2:
Table
2).
The
were
large as
Some
samples
spectrometric
used
for m o n i t o r i n g GC-MS
A
13C12of
2-~L
an
i.d.)
Incos
with
100
aliquot
out
with
a
ionization
datasystem. 1.5-m
A
retention
made.
The
isothermal,
HRGC
20°C/min
300°C.
with
while
were
a
were
2 min
(MID).
two
chosen
for
compound
to 24-
monitor
sufficient
full-scan
(m/z
identification.
dibenzodioxins
(quantitation
to
retaining
concentrated
halogenated
18-
(M + or s a t e l l i t e )
were
still
and
Three
ions
descriptors
analyses
carried
electron-impact
detection
analysis
ions
and di-
underlined)
Ions m o n i t o r e d (m/z Dibenzodioxins Dibenzofurans
498, 418, 340, 262, 320, 286, 398, 478,
500 420 342 264 322 288 400 480
were
calculated compared
percent
were
made
lute
quantitative
first-order
was
i-octane)
used
MID
tetra-BDDs/BDFs tri" " di" " mono" " tetra-CDD/CDF tri" " bromo-tetra-CDD/CDF dibromo-tetra-CDD/CDF
as
10 ng (total
30 ~ L .
and
80°C,
at
possible
mass
in M I D
mm
in
multiple-ion time)
334
pressed
about
the
(0.32
isothermal
332,
were
opened,
4 portions
analysis
follows:
13C12-2,3,7,8-tetra-CDD
values
were
with to
in
(2-pl
as
compounds
sensitivity.
(m/z)
column
then
using
Compound
Results
vials
chromatograph
injections
s cycling
benzofurans
operating
programmed
as m a n y
GC-MS
Mega
capillary
analyzed (0.6
s/scan)
Ions
(HR)
Erba
to 300°C,
(see
simultaneously precision
Carlo
On-column
5°C/min
the
extracted
concentrated
instrument
a
temperature
samples
extract
silica
ion d e s c r i p t o r s per
the
exposure
residues
analysis.
GC-MS
(EI,
column
After
the
High-resolution
mode
gap
added,
via
to
analyte
for d i f f e r e n t data
area
those
of
ratios the
remaining
MID
response
is r e p o r t e d .
482 402 324 246 304 270 382 462
484 404 326 248 306 272 384 464
analyte/13C]2-2,3,7,8-tetra-CDD;
zero versus
exposure time
of d i f f e r e n t Half-lives
of
controls exposure.
congeners
(tl/2)
were
kinetics -in
(Cl/C0)=
kt
tl/2
= in 2/ k
and
(100%) No
and
the ex-
corrections
hence
no abso-
estimated
assuming
894
where
cl/c o
time
is
t, and
the
k the
tion p h o t o l y s i s
RESULTS
rate
and
under
sunlight
as thin
bromo/chloro
solid
films.
in all
creased
was
light
intensity
(23,24;
geners.
see
shown
for
exposure the
solu-
tetrabromo around
I-2 min).
single
peak
a
analogy
to
are
expected
not
estimated longer
the
to be
at around
than
that
(2,7- and/or
Reductive
the
a
(23,24).
debromination
In
this
less The
brominated
way
data
the
and
strong
to
be
major
indicates
high
if
final
dibenzodioxin
not
products
of
formed
pre-
for
exclusive
(DF).
expected and
the
these
in
2,3,8-tri-BDF
again
and
a
were
rather
experiments
formation
(DD) and d i b e n z o f u r a n
con-
tri-BDFs
9 min,
higher
under
estimated
were
and
congeners
observed
chloro
decomposition
with
2:2
type
observed.
pathway
carbon-ring
from
the
was
these
decomposition
2,3,7,8-substituted likely
indicating
were observed.
C6H3 +) were
observed
formafurther
brominated
expected)
brominated
previously
2,3,7-
in-
with
fast
preliminary
the
higher
The
considerations
at around
75 ion,
to
eluting)
two tri-BDFs time
m/z
very
The
In
lower
rather
(2,3,7-tri-BDD
due
with
l-isomer)
half-lives
the di-BDFs
compound.
toxic
the
compounds
The
analogy
com-
Accelerated
subsequently
(earlier
C as a
this
experiment.
of
B showed
chloro
3).
1,2,4-tri-BDD
half-life (likely
(25). of
was
of
B and
possibly
the
nonane) dispersed
for
eluting)
in
retention
not
species.
unsubstituted
same
half-life
From
Table
are
(later
positions
longer
tri-BDD
the
the
2,3,7,8-tetra-BDF
the
appears
(see
which
A,
observed
1,2,4-isomer
in solution
parent
from The
stable
a
2,8-isomer;
predominantly
lateral-positions.
The
those
single
is the
and m o n o - B D D
with
min
of
compounds
solutions
was
photolysis
part
1,2,3-tri-BDD
separated
2 min,
of
2,3,7,8-tetra-BDD
latter
observed.
situation
2-3
was o b s e r v e d
From
to
of
(i-octane,
the same
added
of
lateral
I).
compounds
(half-lives only
of
indicating di-BDD
was
solution
decomposition
solution
with
proceeding
the
the
in h y d r o c a r b o n
decomposition
formed
at
but
geners.
after
(22).
photochemical
decomposition
congeners
Scheme
min,
Furthermore,
three
be
was
et al.
hydrocarbon
half-lives
amounts
compounds
11
fast
in
during
tri-BDD
smaller
around
very
during
brominated
debromination
to
remaining
kinetics
and PBDFs
significant with
ferential
be
slower
apparent
The major
concommitant
occur
compound
by N e s t r i c k
1,2,3,4-Tetra-BDD
solutions
tion of lower degraded.
showed
standard;
decomposition
of PBDDs
compounds
but much
photochemical
di-BDD
the
First-order
tetra-CDDs
photolysis
experiments
bromo
All
of
AND D I S C U S S I O N
Preliminary
to
amount
constant.
of several
Sunlight-induced
pound
relative
and
chloro can
be
and
from
compounds expected
substituted of
to the
these
conditions
conlower were
895
Scheme
I:
Br Br~O~ fasy ~r O"~///m slOW~Br Br O
Br Br
Br
di-BDDs I ono BDD(s)
:
DD
I
further degradation Sunlight-induced
p h o t o l y s i s of PCDDs and PCDFs
The p h o t o l y t i c h a l f - l i v e s to
that
of
Tetra-CDD
first-order
1,2,3,4-Tetra-CDD in the order
of
appears
380
by
Nestrick
et
in the
decomposition
two b r o m o a n a l o g u e s .
case
of
half-lives CDDs,
no
the of
the
much
same
(22).
rates Very
and
more.
of
solution
an
more
stable
these
two
rather
slow
the
half-life was
re-
variation
between
the
observed
with
with
the
tetra-
was
found.
of b r o m o / c h l o r o d i b e n z o d i o x i n s
with
was
situation
Sunlight-induced
Solution
than
min.
2,3,7,8-tetra-CDF
amounts
in h y d r o c a r b o n
14
isomers
greater
isomers
2,3,7,8-
of
estimated two
decomposition
and
3).
f o r m a t i o n was observed.
The f o r m a t i o n of only small
photolysis
(about
an
these
chloro
from
1,2,3,4-
(Table
half-life
is a much
tri-CDD
Different
between
with
with
there
(about I%)
A
estimated
observation
between little
difference
data
solution
-CDFs can be d i r e c t l y c o m p a r e d
with
Apparently
tetra-CDFs
180 min
large
The
al.
three
from
kinetics
to be
min.
ported
In
of the t e t r a - C D D s and
1,2,3,4-tetra-BDD shows
in h y d r o c a r b o n
3%) of tri-CDFs was observed.
and d i b e n z o f u r a n s
solution
C contained
mixtures
2,3,7,8-tetra-CDD
showed a h a l f - l i f e
around
and
of mono-CDF
2.5 min
Apparently
the
(21).
and d i b r o m o - t e t r a - C D D s I ,2,3,4-Tetra-BDD
(see Table
previous
values.
profound
i n f l u e n c e on the d e c o m p o s i t i o n
additional
3) w h i c h
and
in
-CDFs
this
is in a g r e e m e n t
compounds
present
rate of this compound.
here
along
solution with the have
no
896
Table
3:
Sunlight-induced
photolysis
dibenzofurans
i-octane
in
of
Rel.
halogenated
amounts a
dibenzodioxins
(% r e m a i n i n g )
exposure Compound
Sol.
Control
2
5
A "
100 <0.05
64 27
"
" " "
<0.05 <0.05 <0.05
1,2,3,4-tetra-CDD 2,3,7,8" "
" "
100 100
101 92
1,2,3,4-tetra-CDF 2,3,7,8" " 1,2,7,8" "
" " "
100 100 100
101 101 100
1,2,3,4-tetra-BDD 2,3,7,8" " tri-BDDs di" mono-"
B " " " "
100 100 ~0.4 < 0.4 <0.2
56 30 29 20 < 0.2
2,3,7,8-tetra-BDF tri-BDF di"
" " "
100 0.5 0.5
"
0.5
1,2,3,4-tetra-BDD 1,2,4-tri" 1,2,3-tridi-BDDs mono-BDD
mono-" 1,2,3,4-tetra-BDD
C
100
2,3,7,8-tetra-CDD I -bromo" dibromo" bromo-tri-CDD tri-CDD
" " " " "
2,3,7,8-tetra-CDF I-bromo" 4-bromo" dibromo" bromo-tri-CDF tri-CDF
" " " " " "
a)
peak
control
area
bromo-PCDDs, tetra-CDD and
accuracy,
not
-CDF and
estimated
33 53
0.8 40
<0.05 2
11
9 12 0.8
3 52 17
<0.1 33 76
104 82
95 44
91 5
380 14
102 104 103
92 95 95
80 84 94
180 220 600
3
18 1.6 44 25 I
0.2 <0.4 25 73 27
<0.2 <0.4 < 0.4 10 53
2 0.8 8 16
<0.5 15 116 1
<0.5 <0.5 129 31
<0.5 <0.5 4 71
0.7 2 9
<0.1
2.5
139 1 35 10 4 3
180 82 3 2 6
178 15 <0.1 0.5 17
151 <0. I <0.I <0.I 3
100 203 118 140 2 <0.1
514 48 55 16 10 2
691 I 2 <0.I 9 7
629 <0.1 ~0.I <0.1 3 18
444 <0.1 <0.1 <0.1 <0.1 22
to
to
accuracy
of
-CDF
reported
total
derived
2
90 0.5 0.5 0.5
standard
relative values
amounts
from
half-lives
4
MID-response;
respectively; the
(200)
internal
different
and
values
I
13C-tetra-CDD
for
compounds,
relative b)
Half-life(min)
100 1 67 18 3 0.5
tri-CDD
parent
respectively;
0.5
60
27
corrected
-BDFs
15 38 29
Estimated b
(min) 15
63
relative
bromo-PCDFs,
and
tri-BDDs
tetra-BDFs, ted
ratios
samples,
4 0.8 <0.1
and
few
±50%.
of
data
of
and
values to
mono-,
tetra-BDDs points
of
2,3,7,8-
of
diand limi-
897
In
case of the b r o m o / c h l o r o d i b e n z o f u r a n s
than
I min)
of
the mono-
f o r m a t i o n of a d d i t i o n a l and f i n a l l y CDF.
of
the
predominant
loss of c h l o r i n e
bromo-tri-CDF
This
and d i b r o m o - t e t r a - C D F s
formed
decomposition
to
compounds
this
mixture
have
BDF.
The p h o t o l y t i c
be
into
about
less
than
results
in
PCDFs.
the
same
is
half-life
3% the
The
(half-lives
observed
less
resulting
in the
to be m u c h more
stable
t o g e t h e r w i t h a small a m o u n t of tri-
reaction
the
is a very m i n o r p a t h w a y
pathway
bromo/chloro
was
2,3,7,8-tetra-CDF which appears
is the m a j o r p r o d u c t o b s e r v e d
Apparently
tuents;
fast d e c o m p o s i t i o n
of
relative
to
the
the
preferential
I-
half-life
loss
and e s t i m a t e d
and
bromo-substi-
from the amount loss
of
conversion
bromine. of
these
4-bromo-2,3,7,8-tetra-CDF
(about
0.5
of 2 , 3 , 7 , 8 - t e t r a - C D F
min)
in this
as
in
2,3,7,8-tetra-
s o l u t i o n was around
90 min.
The
same
The
small
posed
II).
behaviour
amounts
fast
further
be
general
(half-life
decomposed
reaction
200 with
compounds Figure their
Scheme
min, the
with
the
I document conversion
about
observed
2 min)
(half-life
The p h o t o l y t i c
around
was
of d i b r o m o - t e t r a - C D D s
half-life somehow
bromo
into
bromo/chloro
was
longer again
photolysis
dibenzodioxins.
not separated)
1-bromo-2,3,7,8-tetra-CDD,
4 min)
substituents
rapid
the
to
2,3,7,8-tetra-CDD
of 2 , 3 , 7 , 8 - t e t r a - C D D much
bromo-PCDDs
the
to
around
for
(3 isomers,
than
in
in this solution
debromination
at
in
peri-position.
of
the
2 , 3 , 7 , 8 - t e t r a - C D D and
bromo-PCDDs
were decomwhich (see
solution A.
The
high
The
then
Scheme
appears
to
predominant
rate
even
for
chromatograms
and
2,3,7,8-tetra-CDF,
bromo-PCDFs
in and
respectively.
II:
Br Br cIIf(~"T'°~(~'~lcIA __ fast cIr~------'~o-v~cI fast cI
c
c,
Br slow
I
-CI
o
cI
o©c,
I
slow I-CI
slow ~ - CI T
slow 1 further degradation
898
Photolysis s olut i o n
This
o__ff h a l o g e n a t e d
with a r t i f i c i a l
experiment
bromo tory
was
carried
and b r o m o / c h l o r o light
reason
as
the
it
(5 hours
tions
A,
and
These
conditions
sample
B
All
C
of
the
were
than
those
precautions
were
days).
The
of these
under
to m i n i m i z e
quartz the
the
and
teristics
are more
here
to
sunlight expected
(5-8%)
p rodu c t s
around
normally
encountered
during
are
taken
(prevention
indicates
compounds,
was
however,
(half-lives in the
low decomposhowed
~8
same
The results
order
as
The
in case
and
indicate
conditions
more
days).
-CDFs
sufficient
provided
suitable
exposure.
dibenzodioxins
A
the
the
compounds
are
given
from
and d i b e n z o f u r a n s
probably
of
of
for
26-35
hrs.
Only
tribromo pathways
so far have
rates
as
films
in
4. More
variation
in
because
film
hrs. of
10
or
2,3,7,8-
was
20
Compared
hrs with
and
reported
previously
tetrabromo
compounds
very
small
be
amounts were
involved.
not been detected.
(1%)
of
observed, However,
charac-
observed. exposure the
Also All with
situation
1,2,3,4-tetra-CDD
3
compounds)
thin
to reproduce.
controls
was
the
may
vial
as
are d i f f i c u l t
after
35-300
finding
found
to
the u n e x p o s e d
relative
similar
dispersed
in Table
vial
decomposition range
was
degradation
products
some
in the
(predominantly
additional chemical
showed
reversed.
uniformity)
in the data
photolysis
decomposition
half-lives
with
was
half-lives
so l u t i o n
Solulamps.
e.t.c).
analytical
rates
compounds
estimated
decomposition.
dibromo-2,3,7,8-tetra-CDDs
of h a l o g e n a t e d
experiments
(area covered,
variation
chloro
this
Preliminary
fluorescent
79-93%
days).
light
exposed
decomposition
more
in
photolysis
normal
vials.
laboraFor
films
of
vials
and
(half-lives~9
are taken
results
only
compounds
Bromo-
stability
The
tetrabromo at
ordinary
of
from
at 93% or more which
recovered
at 80-86%
light
use of amber vials,
recovered
were
to
if any
some
precautions
solid
little
hrs
behaviour
procedures.
in quartz
severe
photolytic
diffuse
very
72
not
provided
exposures.
Sunlight-induced
and
be more
susceptibility
recovered
in glass
under
preparation
should
and
sunlight
and d i b e n z o f u r a n s sample
showed
procedures
i__n h y d r o c a r b o n
photochemical
for
(half-lives ~ 2 8
photolytic
the
exposed
tetra-CDDs/CDFs
sition
investigate
during
exposure)
sun- or daylight,
decomposition
to
exposed
dibenzofurans
were
preparation
of direct
occur
were
experiments
out
and
light
dibenzodioxins
might
samples
dibenzodioxins
laboratory
(22). with some
Somewhat estimated
photolysis
indicating additional
that photo-
899
r-, I-I
p,.
C::I C~
¢q I¢,,1~,
I-I
I~ C~
_i~i
..
0.4+,
C4 ,,,.,+
I'-I
,~ m
~0 p--
l cO " t~
2 P..+ E
' <~ B +...i
m
~
O
m
m
£',,I I
0 N
!
2\ ~'
~
-,'-,
0
.+5+ -H
Y
~
p-!
I-" I CO
I
,
¢¢
J i
-,-~
~
~
0
r~
E
-,-t
3
,./
m
i
c'-q r~
O
I-I
Y
~4
-~--
~
~ ~
C3
C)
0
~
p-
0
LI_ '+-'
I--
¢_)
I
p,,.. +.'+O
b~
m
¢0
~
I-I
'-~ {1}
0
C~
o~2 I.I_ I-I O~ reo
O
-\
+,,,
+/
r-,
'7
I
p,_ I
r~ I
+~
-H
"0
0
0
0
O
~
•
i
8 Y
-\
0
.~ ~ •.,.-.+ ..-i
I
O
~q
I-.I p~ O}
/
,,-+
0
-,~
i
i.-+
8
e~ i-i
O
~
~
-~
0
i
~
0
q3 >~
4-} <1}
0 ,z~
0 -,-+
900
Table
4:
Sunlight-induced dibenzofurans
photolysis
dispersed
o_~f h a l o g e n a t e d
as
solid
Rel.
dibenzodioxins
films
amounts a
(% r e m a i n i n g )
exposure Compound
Sol.
1,2,3,4-tetra-CDD
and
Control
(hrs)
10
20a
Estimated
20b
half-life c
A+B
100
85
76
84
65
"
100
98
91
101
300
1,2,3,4-tetra-CDF
"
100
90
82
90
95
1,2,7,8-
"
"
"
100
86
64
73
35
2,3,7,8-
"
"
"
100
93
84
94
120
"
100
60
51
63
26
100
67
52
77
32
77
35
2,3,7,8-
"
"
I ,2,3,4-tetra-BDD 2,3,7,8-
"
.
.
.
.
2,3,7,8-tetra-BDF
"
100
60
53
1,2,3,4-tetra-BDD
C
100
12
13
2,3,7,8-tetra-CDD
"
100
117
100
1-bromo-
"
"
167
113
105
30
dibromo-
"
"
9
I
3
12
"
2
0.5
2
bromo-tri-CDDs
7 b)
2,3,7,8-tetra-CDF
"
100
290
212
b)
1-bromo-
"
"
227
105
115
b)
4-bromo-
"
"
134
23
35
dibromo-
"
"
139
25
35
bromo-tri-CDF a)
peak
"
area
control
bromo-PCDDs, tetra-CDD of
The
and
solution
C)
indicating
the
was the
of
deposition tion
tri-CDD
accuracy,
of
10-
and
techniques
with
pathway
1,2,3,4-tetra-BDD with
phase and
the
photolysis 20-hr
homogenity will
solid
of
the
respectively;
b)
values
in
-CDFs;
c)
accuracy
is m o r e
of
7
compounds this
This on
of
derived
(solid
the
of
2,3,7,8because from
half-lives
few
±50%.
films
from
and
-CDF
Similarly,
somehow
larger
the than
A+B.
to v a r i a t i o n may
to
2,3,7,8-tetra-CDD
was
and
values
estimated
photolysis.
hrs)
solution
subject
data.
not
compounds
solution
from
standard
relative
and
(half-life
improve
internal MID-response;
reported
formation as
films
exposure
hopefully
-CDF
bromo/chloro
concurrent
reaction
0.8
different
estimated
the
b) 10
13C-tetra-CDD and
compounds,
of
0.5
for
bromo-tetra-CDDs
larger
solid
the
parent
limited
same
experiment
Apparently some
of
to
corrected
decomposition
decomposition in
CDF from
points
photolytic
relative
not
bromo-PCDFs,
formation
data
ratios
samples,
0.7
(hrs)
be
due
surface.
situation.
The
as to
indicated variations
by in
Different
deposi-
difference
between
901
the
estimated
half-life
tions A+B and C (7 and ce of
non-volatile
solution
C.
Such
pronounced more
not
1,2,3,4-tetra-BDD
26 hours,
sensitizing
compounds
influence
sample
leads
of
handling
respectively) compounds
or
remain
the
may
here
than
in
to
fully
account
in
solution
(evaporation,
to g r e a t e r data v a r i a t i o n
expected
in
for
may be due
solid
film
photolysis. from
in s o l u t i o n
the
solid
films
as
and
the
solu-
influen-
impurities
may
have
Additionally vials)
photolysis.
differences
from
to a larger
hydrogen-donors
extraction
than
the
a more
there
involved
is
which
This,
however,
with
the
observed
in
is
exposed
samples.
CONCLUSIONS
The m a j o r
photochemical
dibenzodioxins
dibenzodioxin
Additional
these c o m p o u n d s . position much
rates
under
rates
indications
that
carbon-rings
are
furans
A
lateral-halogens
loose
e x p e r i m e n t s was
like
bromine
significantly
brominated
consequences
losses of these analytes.
due
dures
be
to
brominated
compound
extraction,
There
are
chemicals
as
a
halogenated
phase
photolysis
detect, and
some
in
a
sample.
the
The use
photochemical
our
for the bromo
too
low values
during
conversion
added
to
from
should m i n i m i z e
of
to decom-
these
proce-
some
bromo/
of a p h o t o c h e m i c a l l y
standard
Because
Protection
-BDF were most prone congeners
especially
PCDFs.
aro-
in
behaviour.
a n a l y s e s may p r e t e n d
present
of
(PCDDs
in the range of 7-35 hrs.
2 , 3 , 7 , 8 - T e t r a - B D D and decomposition
dibenzo-
compounds
mixed
are
halogenated and
chlorinated
sample p r e p a r a t i o n and a n a l y s i s
Photochemical
into PCDDs
higher
There
other Solid
of
a few minutes,
compounds.
to this p h o t o c h e m i c a l
originally
position.
difficult
the
further
show high decom-
slower but still a p p r e c i a b l e
so r a p i d l y d e c o m p o s e d , compounds
from
to lower
are
film p h o t o l y s i s
of only
chloro
halogenated
leading
dibenzodioxins
with
pyrenes.
with h a l f - l i v e s
sun- or d a y l i g h t d u r i n g
congeners
to
exist
solid
those
all
likely
compounds
half-lives
and
leading may
then
in the
Bromo/chloro
bromo/chloro
compounds
these c o m p o u n d s are
may
which
corresponding
lost.
situation the
There are a n a l y t i c a l
chloro
with
the
model
direct
involved
sunlight of the
preferably
compounds
the
be
those
matic
for
natural
similar
and b r o m o / c h l o r o
may
with
reductive dehalogenation
and d i b e n z o f u r a n
than
preferably
PCDFs).
pathways
was
solution
In s o l u t i o n bromo and b r o m o / c h l o r o
higher
and
in h y d r o c a r b o n
and d i b e n z o f u r a n s
or u n s u b s t i t u t e d degraded.
reaction
samples
sensitive prior
to
c l e a n - u p and a n a l y s i s w o u l d be advisable.
also
potential
by s u n l i g h t
environment.
environmental
represents
The bromo and b r o m o / c h l o r o
photochemically
less
stable
in
consequences.
an i m p o r t a n t
the
route
compounds
environment
Decomposition
for their r e m o v a l
investigated
than
the
of
here are
chloro
some
from the likely
compounds
and
902
thus
may
be
atmospheric after
preferentially transport
deposition
surfaces vents
together
and
genated pounds
on
quired
light
a situation
analysis
for
bromo
bromo/chloro
and
be
samples
in
a
thought
grave
compounds
are e s p e c i a l l y
which
can
may
then
experiments
realistic
during or
even
be a d s o r b e d
photolysis
Additional
as
site
act of
as
the
with
environment
solhalo-
the
experiments
with
will
on
be
comthe re-
situation.
that
identification
especially
compounds
in our model
more
such
a deposition
situation
in
are
way
stable
samples may
in the
prone
this
more
of e n v i r o n m e n t a l
source
may
The
surface.
into this
is the
situation
mental
than
quartz
situations
to
compounds this
into the p h o t o c h e m i c a l l y
the
compounds
soil).
in
faster
surfaces
intriguing
may be c o n v e r t e d
be
that
certain source
additional
so
clean
on
to shed more
Especially
ted
a
adsorbed
(plants,
many
could on
in
combustion
surfaces
with
compounds
compounds
a
hydrogen-donors
adsorbed
degraded
from
for
lead
case
of
expected
bromo/chloro
PCDDs the
to
and
different
false
leaded
congeners
and PCDFs.
In such
halogena-
conclusions.
fuel
combustion
in situations
were
The were
environ-
to photolysis.
ACKNOWLEDGMENT
I
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Rotard,
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Resources
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(Received in Germany 9 January 1988; accepted 18 February
1988)