S1
Supporting Information for:
Deposition vs. Photochemical Removal of PBDEs from Lake Superior Air
Jonathan D. Raff and Ronald A. Hites*
School of Public and Environmental Affairs
Indiana University
Bloomington, Indiana 47405
*Author to whom correspondence should be addressed at HitesR@Indiana.edu
Contents: 19 pages that include 5 tables, 4 figures, and 20 references.
S2
TABLE S1: Polybrominated diphenyl ether congeners studied in this work.
O 2' 3'
4'
5'
6'
2
6
5
4
3
Compound IUPAC ab-
breviation
Compound IUPAC ab-
breviation
2-bromodiphenyl ether BDE-1 2,3,4,5,6-pentabromodiphenyl
ether
BDE-116
3-bromodiphenyl ether BDE-2 3,3',4,4',5-pentabromodiphenyl
ether
BDE-126
4-bromodiphenyl ether BDE-3 2,2'4,4',5,5'-
hexabromodiphenyl ether
BDE-153
2,2'-dibromodiphenyl
ether
BDE-4 2,2'4,4',5,6'-
hexabromodiphenyl ether
BDE-154
2,4-dibromodiphenyl
ether
BDE-7 2,3,3',4,5,6-
hexabromodiphenyl ether
BDE-160
3,3'-dibromodiphenyl
ether
BDE-11 2,2',3,4,4',5,5'-
heptabromodiphenyl ether
BDE-180
4,4'-dibromodiphenyl
ether
BDE-15 2,2',3,4,4',5,6-
heptabromodiphenyl ether
BDE-183
2,2',4-tribromodiphenyl
ether
BDE-17 2,2',3,3',4,4',5,6'-
octabromodiphenyl ether
BDE-196
2,4,4'-tribromodiphenyl
ether
BDE-28 2,2',3,3',4,4',6,6'-
octabromodiphenyl ether
BDE-197
2,2',4,4'-
tetrabromodiphenyl
ether
BDE-47 2,2',3,3',4,4',5,5',6-
nonabromodiphenyl ether
BDE-206
3,3',4,4'-
tetrabromodiphenyl
ether
BDE-77 2,2',3,3',4,5,5',6,6'-
nonabromodiphenyl ether
BDE-208
2,2',4,4',5-
pentabromodiphenyl
ether
BDE-99 2,2',3,3',4,4',5,5',6,6'-
decabromodiphenyl ether
BDE-209
2,2',4,4',6-
pentabromodiphenyl
ether
BDE-100
S3
TABLE S2: Absorption cross sections, 10–18 cm2 molecule–1 (base e), as a function of
wavelength λ for selected PBDE congeners measured at 298 K in isooctane.
λ BDE-1 BDE-3 BDE-4 BDE-7 BDE-11 BDE-15 BDE-17 BDE-28
280 4.057 5.939 6.946 5.572 7.187 7.624 7.468 7.728
281 3.842 5.751 7.707 5.412 8.004 7.713 7.737 7.478
282 3.867 5.488 7.250 5.430 8.703 7.645 7.735 7.256
283 3.747 5.113 5.819 5.644 8.466 7.272 7.607 7.174
284 3.306 4.616 4.277 5.938 7.393 6.797 7.415 7.208
285 2.706 4.125 3.052 6.097 5.936 6.299 7.073 7.276
286 2.019 3.749 2.136 6.033 4.361 5.946 6.520 7.307
287 1.398 3.572 1.465 5.787 2.994 5.852 5.889 7.262
288 0.912 3.583 0.967 5.413 1.959 5.984 5.289 6.993
289 0.597 3.627 0.637 5.001 1.279 6.156 4.851 6.385
290 0.394 3.455 0.419 4.614 0.862 6.013 4.623 5.590
291 0.276 2.953 0.286 4.347 0.605 5.402 4.627 4.874
292 0.194 2.234 0.196 4.201 0.441 4.476 4.743 4.325
293 0.144 1.546 0.142 4.212 0.341 3.477 4.694 3.983
294 0.108 0.996 0.100 4.251 0.270 2.515 4.225 3.737
295 0.074 0.617 0.075 4.117 0.217 1.726 3.461 3.435
296 0.058 0.379 0.051 3.691 0.179 1.129 2.659 3.033
297 0.044 0.241 0.034 3.064 0.146 0.734 1.978 2.530
298 0.036 0.160 0.029 2.359 0.126 0.476 1.425 1.992
299 0.028 0.108 0.020 1.723 0.100 0.315 1.011 1.481
300 0.023 0.070 0.021 1.201 0.091 0.217 0.732 1.062
301 0.021 0.058 0.025 0.826 0.082 0.164 0.528 0.739
302 0.013 0.037 0.020 0.586 0.063 0.127 0.394 0.523
303 0.020 0.026 0.021 0.404 0.044 0.099 0.285 0.366
304 0.014 0.026 0.017 0.283 0.029 0.075 0.231 0.265
305 0.004 0.010 0.011 0.218 0.022 0.065 0.172 0.185
306 0.007 0.018 0.010 0.151 0.019 0.052 0.138 0.141
307 0.009 0.121 0.009 0.046 0.112 0.101
308 0.003 0.084 0.028 0.096 0.072
309 0.070 0.026 0.079 0.036
310 0.061 0.022 0.070 0.020
311 0.028 0.007 0.053
312 0.027 0.009 0.052
313 0.029 0.060
314 0.015 0.050
315 0.018 0.043
316 0.016 0.036
317 0.012 0.037
318 0.017 0.021
319 0.012 0.022
320 0.006
S4
TABLE S2 (cont.): Absorption cross sections, 10–18 cm2 molecule–1 (base e), as a func-
tion of wavelength λ for selected PBDE congeners measured at 298 K in isooctane.
λ BDE-47 BDE-49 BDE-77 BDE-99 BDE-100 BDE-116 BDE-126 BDE-153
280 8.684 10.325 9.256 8.570 7.539 7.109 8.383 8.586
281 8.799 10.300 9.379 8.960 8.090 6.638 8.466 9.167
282 9.151 10.286 9.685 9.514 8.444 6.265 8.564 9.925
283 9.620 10.366 10.061 10.049 8.453 5.921 8.729 10.694
284 9.889 10.254 10.228 10.317 8.111 5.635 8.895 11.273
285 9.711 9.868 10.075 10.230 7.580 5.415 8.933 11.566
286 9.143 9.454 9.644 9.943 7.036 5.274 8.841 11.761
287 8.430 9.332 9.100 9.695 6.698 5.155 8.684 11.997
288 7.735 9.229 8.598 9.554 6.679 5.065 8.446 12.223
289 7.233 8.720 8.238 9.536 6.967 4.996 8.195 12.364
290 7.030 7.792 8.185 9.590 7.421 4.880 7.930 12.493
291 7.152 6.885 8.492 9.717 7.742 4.768 7.768 12.723
292 7.365 6.124 8.901 9.775 7.394 4.629 7.746 12.855
293 7.252 5.359 8.971 9.512 6.318 4.464 7.807 12.573
294 6.467 4.432 8.451 8.818 4.907 4.319 7.826 11.800
295 5.285 3.446 7.394 8.009 3.581 4.171 7.746 10.931
296 4.094 2.568 6.045 7.426 2.535 4.036 7.552 10.451
297 3.096 1.860 4.631 7.202 1.767 3.936 7.121 10.481
298 2.290 1.308 3.355 7.027 1.224 3.875 6.503 10.600
299 1.667 0.895 2.346 6.597 0.846 3.799 5.640 10.157
300 1.223 0.609 1.600 5.762 0.579 3.757 4.641 8.961
301 0.861 0.395 1.094 4.685 0.387 3.685 3.686 7.321
302 0.622 0.266 0.759 3.687 0.274 3.605 2.793 5.753
303 0.432 0.165 0.555 2.790 0.182 3.468 2.089 4.381
304 0.317 0.117 0.410 2.076 0.122 3.295 1.520 3.312
305 0.231 0.067 0.328 1.494 0.072 3.112 1.095 2.455
306 0.181 0.049 0.246 1.048 0.050 2.899 0.815 1.791
307 0.146 0.024 0.211 0.712 0.039 2.680 0.584 1.263
308 0.115 0.025 0.189 0.470 0.024 2.468 0.435 0.866
309 0.101 0.022 0.160 0.312 0.026 2.255 0.319 0.603
310 0.081 0.025 0.135 0.206 0.029 2.027 0.255 0.396
311 0.084 0.018 0.116 0.138 0.017 1.864 0.183 0.267
312 0.065 0.012 0.095 0.093 1.673 0.133 0.179
313 0.057 0.081 0.065 1.465 0.100 0.133
314 0.050 0.091 0.057 1.322 0.072 0.098
315 0.046 0.082 0.032 1.190 0.056 0.072
316 0.046 0.063 0.017 1.036 0.052 0.053
317 0.047 0.042 0.018 0.888 0.028 0.047
318 0.032 0.039 0.008 0.773 0.015 0.025
319 0.031 0.042 0.655 0.027
320 0.021 0.028 0.559 0.013
321 0.028 0.474
322 0.022 0.408
323 0.019 0.377
S5
324 0.005 0.313
325 0.011 0.276
326 0.241
327 0.200
328 0.167
329 0.133
330 0.136
331 0.126
332 0.105
333 0.087
334 0.066
335 0.069
336 0.057
337 0.046
338 0.046
339 0.034
340 0.032
341 0.021
342 0.016
343 0.010
344 0.014
345 0.014
346 0.018
347 0.009
348 0.005
S6
TABLE S2 (cont.): Absorption cross sections, 10–18 cm2 molecule–1 (base e), as a func-
tion of wavelength λ for selected PBDE congeners measured at 298 K in isooctane.
λ BDE-154 BDE-160 BDE-180 BDE-183 BDE-196 BDE-197 BDE-206 BDE-208 BDE-209
280 6.986 10.993 6.569 8.737 8.059 12.462 10.743 18.270 43.437
281 7.234 9.450 6.475 8.764 7.810 11.998 10.346 17.589 32.943
282 7.386 7.712 6.307 8.857 7.554 11.597 9.899 16.858 26.544
283 7.479 6.368 6.103 9.028 7.424 11.340 9.520 16.189 22.164
284 7.609 5.456 5.934 9.275 7.359 11.071 9.170 15.427 19.139
285 7.881 4.869 5.878 9.665 7.448 10.828 8.970 14.674 16.924
286 8.420 4.510 6.012 10.290 7.659 10.542 8.933 13.946 15.275
287 9.167 4.270 6.313 10.939 7.915 10.131 9.006 13.238 14.057
288 9.818 4.118 6.742 11.362 8.150 9.666 9.160 12.590 13.083
289 9.997 3.983 7.102 11.323 8.359 9.225 9.328 12.047 12.312
290 9.690 3.868 7.211 10.918 8.380 8.809 9.343 11.513 11.745
291 9.169 3.721 7.042 10.415 8.238 8.593 9.271 11.151 11.333
292 8.533 3.591 6.711 9.886 8.043 8.596 9.065 10.840 11.038
293 7.870 3.433 6.349 9.415 7.920 8.779 8.830 10.523 10.789
294 7.394 3.319 6.046 9.207 7.833 8.966 8.570 10.262 10.561
295 7.455 3.200 5.935 9.562 8.021 9.041 8.484 9.990 10.310
296 8.157 3.091 5.995 10.423 8.285 8.760 8.463 9.706 10.039
297 8.982 3.016 6.255 11.173 8.588 8.226 8.610 9.414 9.752
298 9.039 2.971 6.700 11.020 8.885 7.506 8.912 9.105 9.500
299 8.007 2.900 7.110 9.756 9.152 6.836 9.260 8.791 9.244
300 6.388 2.888 7.388 7.955 9.131 6.192 9.402 8.451 9.062
301 4.714 2.833 7.288 6.173 8.765 5.671 9.257 8.123 8.976
302 3.361 2.777 6.891 4.686 8.131 5.338 8.851 7.801 8.915
303 2.331 2.649 6.204 3.519 7.287 5.058 8.204 7.594 8.927
304 1.622 2.529 5.479 2.635 6.390 4.905 7.501 7.328 9.022
305 1.105 2.384 4.716 1.984 5.484 4.762 6.731 7.065 9.080
306 0.759 2.231 4.042 1.488 4.649 4.619 6.009 6.822 9.016
307 0.500 2.045 3.414 1.119 3.954 4.469 5.359 6.599 9.004
308 0.332 1.876 2.902 0.829 3.345 4.261 4.725 6.261 8.807
309 0.214 1.728 2.433 0.616 2.776 4.071 4.147 5.940 8.525
310 0.132 1.563 2.048 0.458 2.326 3.849 3.641 5.599 8.204
311 0.079 1.422 1.742 0.327 1.935 3.600 3.154 5.238 7.833
312 0.047 1.268 1.455 0.249 1.602 3.369 2.756 4.894 7.484
313 0.037 1.105 1.199 0.200 1.359 3.152 2.412 4.533 7.023
314 0.019 0.997 1.016 0.154 1.129 2.938 2.103 4.232 6.622
315 0.015 0.909 0.862 0.126 0.913 2.739 1.810 3.930 6.263
316 0.013 0.779 0.708 0.099 0.767 2.514 1.546 3.625 5.884
317 0.015 0.676 0.564 0.083 0.634 2.308 1.336 3.351 5.481
318 0.006 0.615 0.479 0.046 0.545 2.117 1.169 3.080 5.056
319 0.523 0.380 0.028 0.447 1.942 0.991 2.837 4.660
320 0.468 0.330 0.008 0.389 1.755 0.849 2.599 4.272
321 0.403 0.264 0.017 0.310 1.580 0.698 2.352 3.948
322 0.347 0.218 0.034 0.243 1.387 0.604 2.154 3.563
323 0.308 0.182 0.191 1.240 0.519 1.957 3.217
S7
324 0.286 0.167 0.157 1.119 0.461 1.788 2.909
325 0.247 0.146 0.129 0.975 0.369 1.576 2.601
326 0.224 0.131 0.112 0.842 0.354 1.443 2.284
327 0.183 0.092 0.105 0.741 0.308 1.316 2.083
328 0.157 0.061 0.083 0.649 0.279 1.160 1.780
329 0.122 0.051 0.067 0.537 0.202 1.024 1.532
330 0.126 0.065 0.039 0.477 0.171 0.874 1.369
331 0.124 0.073 0.042 0.412 0.152 0.808 1.178
332 0.119 0.063 0.020 0.331 0.120 0.680 1.008
333 0.103 0.056 0.272 0.106 0.598 0.914
334 0.095 0.044 0.250 0.118 0.522 0.768
335 0.084 0.039 0.213 0.105 0.496 0.647
336 0.063 0.181 0.089 0.458 0.551
337 0.055 0.130 0.088 0.383 0.463
338 0.060 0.103 0.076 0.324 0.377
339 0.040 0.098 0.074 0.284 0.358
340 0.029 0.092 0.058 0.252 0.339
341 0.017 0.080 0.039 0.220 0.297
342 0.021 0.061 0.017 0.186 0.255
343 0.017 0.047 0.016 0.155 0.225
344 0.017 0.036 0.015 0.136 0.200
345 0.019 0.026 0.125 0.184
346 0.019 0.026 0.123 0.168
347 0.009 0.020 0.117 0.151
348 0.004 0.017 0.100 0.119
349 0.014 0.089 0.093
350 0.072 0.091
351 0.058 0.094
352 0.052 0.092
353 0.053 0.097
354 0.041 0.078
355 0.030 0.072
356 0.016 0.060
357 0.020 0.041
358 0.023 0.041
359 0.023 0.046
360 0.018 0.043
361 0.039
362 0.028
363 0.047
364 0.037
365 0.043
366 0.029
367 0.032
368 0.027
369 0.021
S8
FIGURE S1: UV-vis absorption spectra of PBDE congeners measured at 298 K in iso-
octane. Note that the shape and position of absorption bands are dependent on the bro-
mine substitution pattern, suggesting that the two rings of the diphenyl ether act as inde-
pendent chromophores [1].
Mono-BDEs
0
1
2
3
4
5
6
BDE-1
BDE-3
0
1
2
3
4
5
6
7
8
9
BDE-4
BDE-7
BDE-11
BDE-15
0
1
2
3
4
5
6
7
8
9
BDE-17
BDE-28
0
1
2
3
4
5
6
7
8
9
10
11
BDE-47
BDE-49
BDE-77
Wavelength (nm)
280 290 300 310 320 330 340 350 360
0
1
2
3
4
5
6
7
8
9
10
11
BDE-99
BDE-100
BDE-116
BDE-126
Ab
so
rp
tio
n
C
ro
ss
S
ec
tio
n
(x
10
18
c
m
2 m
ol
ec
ul
e-
1 ,
ba
se
e
)
Di-BDEs
Tri-BDEs
Tetra-BDEs
Penta-BDEs
S9
0
1
2
3
4
5
6
7
8
9
10
11
12
13
BDE-153
BDE-154
BDE-160
0
1
2
3
4
5
6
7
8
9
10
11
12
BDE-180
BDE-183
0
1
2
3
4
5
6
7
8
9
10
11
12
BDE-196
BDE-197
0
1
2
3
4
5
6
7
8
9
10
11
12
BDE-206
BDE-208
Wavelength (nm)
280 290 300 310 320 330 340 350 360
0
1
2
3
4
5
6
7
8
9
10
11
12
Hexa-BDEs
Hepta-BDEs
Octa-BDEs
Nona-BDEs
Deca-BDE
Ab
so
rp
tio
n
C
ro
ss
S
ec
tio
n
(x
10
18
c
m
2 m
ol
ec
ul
e-
1 ,
ba
se
e
)

S10
Quantum Yield Measurements.
Irradiations of mono- and dibromodiphenyl ethers and a chemical actinometer (Cl2) were
performed in a 160 cm3 quartz reaction chamber located in the oven of a Hewlett-Packard
5890 gas chromatograph (for temperature control) and interfaced to a Hewlett-Packard
5989A quadrupole mass spectrometer operated in the electron ionization (EI) mode [2].
Collimated light was provided by a 200 W Xe(Hg) arc lamp (Hamamatsu Corporation)
that was filtered by a dichroic mirror (Newport Corporation) to eliminate infrared radia-
tion and an interference filter (Andover Corporation) to select light of 307 ± 26 nm at
FWHM.
In a typical experiment, between 0.2–5 µg of a selected PBDE dissolved in cyclohexane
was added to the reaction chamber containing helium at 323 K; cyclohexane acted as
both a solvent and a OH radical scavenger. The instrument responses for the most in-
tense m/z values were monitored before and after irradiation of the reactor to establish the
background (dark) decay of the PBDE signal. Irradiations were carried out for 3–5
minutes and corrected for the average background decay before deriving the photolysis
rates. A few experiments with BDE-7 were performed in the presence of 1,3-butadiene
(~1 × 1014 molecules cm–3, kBr = 5.7 × 10-11 cm3 molecule–1 s-1 [3]), to scavenge Br at-
oms; no differences in photolysis rates were observed in the presence or absence of 1,3-
butadiene, indicating that reactions with Br atoms did not contribute to the observed
BDE-7 decays.
Chlorine gas (~1014 molecules cm–3) was used as an actinometer in separate experiments
at 298 K. Methanol (~2 × 1014 molecules cm–3) and oxygen (5 % in helium) were added
to the reactor during the actinometer experiments to prevent chlorine atom recombination
and scavenge alkyl radicals that would enhance Cl2 consumption [4]. The m/z values
monitored during the PBDE photolysis and actinometer experiments were as follows: di-
phenyl ether, 170 [M]+, monobromodiphenyl ethers 248 [M]+, dibromodiphenyl ethers,
328, [M + 2]+, chlorine, 70, [M]+. The reaction chamber was cleaned after each experi-
ment by heating it to 150 ºC and flushing it with helium for 60 min.
S11
Applicability of Solution-Phase Spectra for Gas-Phase Photolysis Calculations.
In deriving the absorption cross-sections of PBDEs from solution spectra and using them
to estimate gas-phase photolysis frequencies, we assume that the position and intensity of
absorption bands is independent of phase (gas vs. solution). In reality, solvent effects
will result in a shift of the PBDE spectra relative to those measured in the gas phase.
Spectra of aromatic hydrocarbons recorded in perfluorinated hydrocarbon solvents show
negligible shifts compared to gas-phase spectra [5] and provide a surrogate for gas-phase
spectra. Although PBDEs are only slightly soluble in perfluorinated solvents, the spectra
of several PBDEs in perfluorohexane (C6F14) were recorded, indicating that the lowest
energy band of the congeners studied would likely result in a 1–2 nm red shift in isooc-
tane compared to the gas-phase; see Figure S2. The intensity of absorption bands may al-
so be different in the gas- vs. solution-phase; this effect is more difficult to assess, but ar-
omatic compounds have been observed to have higher cross-sections (by up to 50%) in
hydrocarbon solutions compared to the gas-phase [6]. No corrections were applied to the
absorption spectra used to calculate the photolysis frequencies.
BDE Congener
3 7 15 28 47 49 99 100
So
lv
en
t S
hi
ft,
∆
λ
in
n
m
0
1
2
3
4
FIGURE S2: Solvent shift ∆λ = λ(C8H18) – λ(C6F14) of the lowest energy absorption
band of several PBDE congeners in two different solvents: Isooctane (C8H18) and per-
fluorohexane (C6F14) at 298 K. The average spectral shift (∆λ = +1.7 nm) is indicated by
the dashed line.
S12
Photochemical Dibenzofuran Formation.
Evidence for the formation of brominated dibenzofurans was also obtained during irra-
diation of gas-phase PBDEs in the above experiments. As shown in Figure S3, the
broad-band photolysis (λ > 260 nm) of BDE-1 for 14 min is accompanied by an increase
in the signal of m/z 168, the molecular ion of dibenzofuran. Similarly, 2-bromo-
dibenzofuran, m/z 246 [M]+, is formed during the photolysis of BDE-7 at 307 nm; see
Figure S3. The low volatility of 2-bromodibenzofuran and its tendency to undergo sub-
sequent photolysis prevents substantial amounts from accumulating in the reactor during
the experiment and explains the weak signal intensity observed. These products were
confirmed by gas chromatographic mass spectrometry (GC/MS) after they were extracted
from the reaction chamber walls with organic solvents using documented methods [2].
Dibenzofuran products were not observed when similar experiments were performed for
the photolysis of 4-bromodiphenyl ether (BDE-3) or 4,4-dibromodiphenyl ether (BDE-
15).
These results provide direct evidence that PBDEs containing bromines in an ortho-
position form brominated dibenzofurans via dehydrodebromination when photolyzed in
the gas-phase. This observation corroborates previous reports of bromodibenzofurans
formed during the photolysis of PBDEs in solution [7,8,9]. The potential toxicity of
brominated dibenzofurans is of great concern due to their similarity to polychlorinated
dibenzo-p-dioxins and furans. Our results indicated that one possible source of bromin-
ated dibenzofurans observed in atmospheric samples [10] may be from the photolytic de-
composition of PBDEs. However, bromodibenzofurans are more highly conjugated than
PBDEs due to their rigid structure, causing their absorption bands to extend further into
the solar actinic range [11,12]. Thus, the atmospheric lifetimes of gas-phase polybromin-
ated dibenzofurans due to photolysis are expected to be shorter than those for PBDEs.
The yield of dibenzofurans from PBDE photolysis appears to be sensitive to the bath-gas
composition. For example, photolysis of BDE-1 at λ > 260 nm in helium in the presence
of acetone showed enhanced production of dibenzofuran. It was also more difficult to
detect dibenzofuran from BDE-1 photolysis during experiments carried out in air com-
pared to experiments conducted in helium. However, in this case it was unclear whether
this was from the reduced sensitivity of the mass spectrometer under these conditions or
if the yield of dibenzofuran was indeed lower due to quenching of the excited state by O2.
Additional investigations into PBDE photochemistry would be useful to help understand
the nature of the excited state (singlet or triplet) that produces dibenzofurans [13] and the
effect that oxygen and photosensitizers (e.g., acetone [14]) may have on dibenzofuran
yields.
S13
Time (minutes)
0 2 4 6 8 10 12 14
Si
gn
al
In
te
ns
ity
Time (minutes)
0 1 2 3 4
Si
gn
al
In
te
ns
ity
O
O
Br
O
Br
Br
O
Br
(m/z 168)
(m/z 248)
(m/z 328)
(m/z 246)
x10
FIGURE S3. (top) Decay of 2-bromodiphenyl ether (BDE-1) and formation of dibenzo-
furan during broad-band irradiation at λ > 260 nm. (bottom) Loss of 2,4-dibromodiphenyl
ether (BDE-7) and formation of 2-bromodibenzofuran from irradiation centered at 307
nm; the signal for m/z 246 has been magnified by ×10 for clarity. Both experiments were
carried out at 325 K in a bath gas of He at ~740 Torr.
S14
TABLE S3: Estimates of gas-phase photolysis rate constants (J), photolysis lifetimes
(τphoto), hydroxy radical rate constants (kOH), and hydroxyl radical lifetimes (τOH) for
PBDEs.
Congener #Br J a kOHb τphoto τOH
10–5 s-1 10
–12 cm3
molecule-1 s-1 h h
BDE-1 1 0.024 5.1 1157 56
BDE-3 1 0.081 5.1 344 56
BDE-4 2 0.043 2.1 650 134
BDE-7 2 1.7 3.6 17 80
BDE-11 2 0.082 4.7 338 61
BDE-15 2 0.36 2.1 77 134
BDE-17 3 2.0 1.4 14 203
BDE-28 3 0.93 1.4 30 203
BDE-47 4 3.1 1.0 9 285
BDE-49 4 0.52 1.0 54 283
BDE-77 4 3.8 1.0 7 281
BDE-99 5 7.4 0.55 4 520
BDE-100 5 0.52 0.72 54 398
BDE-116 5 72 1.6 0.4 182
BDE-126 5 6.8 0.69 4 412
BDE-153 6 13 0.23 2 1236
BDE-154 6 5.8 0.37 5 773
BDE-160 6 60 0.99 0.5 288
BDE-180 7 57 0.16 0.5 1780
BDE-183 7 13 0.17 2 1722
BDE-196 8 62 0.11 0.4 2642
BDE-197 8 184 0.12 0.2 2437
BDE-206 9 118 0.066 0.2 4313
BDE-208 9 305 0.066 0.09 4313
BDE-209 10 470 0.034 0.06 8498
aCalculated using modeled actinic flux and by assuming Φphoto = 0.5; actinic flux was the sun intensity at
noon, averaged over 0–2.5 km at the solstices and equinoxes (see text). bThe values are for T = 298 K, as
calculated from structure activity relationships [15, 16].
S15
TABLE S4: The fraction (f) of PBDEs in the particle phase at 288 ± 1 K, as determined
from atmospheric samples collected with high volume air samplers at five different sites
in the east-central U.S. [17,18].
Congener #Br N f ±2σ
diphenyl ether 0 0
17 3 13 0.05 0.04
28 3 14 0.06 0.04
49 4 12 0.19 0.12
47 4 16 0.17 0.09
66 4 13 0.25 0.12
85 5 14 0.61 0.16
99 5 16 0.42 0.12
100 5 16 0.32 0.11
154 6 16 0.62 0.15
153 6 15 0.79 0.13
206–208 9 0.99999
209 10 0.99999
#Br is the number of bromine substituents; N is the number of samples; 2σ is the 95% confidence interval
of the mean. For the purposes of deriving an empirical expression to describe the partitioning of PBDEs to
the particle-phase, it is assumed that diphenyl ether is entirely in the gas-phase and that nona-BDEs and de-
ca-BDE occur 99.999% in particles.
FIGURE S4: The fraction (f) of PBDEs in the particle phase at 288 ± 1 K vs. the num-
ber of bromine substituents, as determined from atmospheric samples collected with high
volume air samplers at 5 different sites in the east-central U.S. [17,18]. The error bars are
the 95% confidence interval of the mean. The data, which also appear in Table S4 is fit to
the expression, f = 1.005 / [1 + e–(#Br – 5.207)/0.876], with R2 = 0.958.
Number of Bromines
0 1 2 3 4 5 6 7 8 9 10
Fr
ac
tio
n
in
th
e
Pa
rti
cl
e
Ph
as
e
0.0
0.2
0.4
0.6
0.8
1.0 O
Brn
S16
Uncertainties in Lifetime Estimates
The uncertainty associated with the terms used to construct the mass balance of PBDEs in
Lake Superior can be high, especially for variables derived from single measurements or
for those associated with meteorological parameters. Unfortunately, it is virtually impos-
sible to quantitatively propagate these errors and to apply them to the final fluxes as giv-
en in Table 1 and in Figure 4. Part of the problem is that many of the errors associated
with the information used in the mass balance calculation are not quantitatively known,
and the distribution functions of these errors are often non-normal. For example, most
environmental concentration measurements are log-normally distributed [19,20]. While
it is possible to guess at the errors for many (but not all) of the terms used in the mass
balance calculation, propagation of these errors leads to unrealistically high errors for the
final result [21]. In fact, it may be more appropriate to base the error propagation on log-
arithmically transformed data. At the moment, our best estimate of the errors associated
with the fluxes is about a factor of 2.
S17
TABLE S5: List of Symbols Used and Their Meaning
A surface area of Lake Superior
Φ photolysis quantum yield
Fem emission rate of a PBDE congener to the Lake Superior
airshed
F solar actinic flux
Fdry removal rate due to particle dry deposition
f fraction of a PBDE congener in the particle-phase
FOH removal rate due to reactions with OH radical
Fphoto removal rate due to photolysis
Fsed flow of a given PBDE congener to the sediment
Fvap removal rate due to vapor deposition (air-water exchange)
Fwet removal rate due to wet deposition
H' dimensionless Henry's Law constant
I light intensity
J photolysis frequency (the first order photolysis rate con-
stant)
kBDE pseudo-first order photolysis decay rates of a given BDE
congener
2Cl
k pseudo-first order photolysis decay rates of Cl2
kdry rate constant for removal by dry deposition
KL total liquid-phase mass transfer coefficient
kOH room temperature OH rate constant
OHk′ pseudo-first order removal rate constant with respect to
OH radical reactions, considering particle-partitioning
photok′ removal rate constant with respect to photolysis, consider-
ing particle-partitioning
kvap gaseous dry deposition removal rate constant
kwet rate constant for wet removal of PBDEs from the atmos-
phere
λ wavelength in nm
νp deposition velocity for the particle-bound PBDEs
[PBDE] concentration of PBDE in the specified phase
p annual precipitation rate for Lake Superior
σ absorption cross section to the base e
τphoto photolysis lifetime
τtot overall lifetime of PBDEs in the atmosphere
W washout ratio of a specified PBDE congener
Z tropospheric mixing height
S18
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