Aerostat Sampling of PCDD/PCDF Emissions from the
Gulf Oil Spill In Situ Burns
1	2 *
Johanna Aurell and Brian K. Gullett'
U.S. Environmental Protection Agency, Office of Research and Development, National Risk
Management Research Laboratory, Research Triangle Park, NC 27711, USA
Corresponding author e-mail: gullett.brian@epa.gov: phone (919) 541-1534; fax (919) 541-0554
National Research Council Post Doctoral Fellow to the U.S. Environmental Protection Agency
U.S. Environmental Protection Agency, Office of Research and Development, National Risk
Management Research Laboratory
ABSTRACT
Emissions from the in situ burning of oil in the Gulf of Mexico after the catastrophic failure of the
Deepwater Horizon drilling platform were sampled for polychlorinated dibenzodioxins and
polychlorinated dibenzofurans (PCDDs/PCDFs). A battery-operated instrument package was lofted into
the plumes of 27 surface oil fires over a period of four days via a tethered aerostat to determine and
characterize emissions of PCDD/PCDF. A single composite sample resulted in an emission factor of
2.0 ng toxic equivalency (TEQ) per kg of carbon burned, or 1.7 ng TEQ per kg of oil burned, determined
by a carbon balance method. Carbon was measured as CO2 plus particulate matter, the latter which an
1

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emission factor of 0.088 kg/kg carbon burned. The average plume concentration approximately 200-300
"3
m from the fire and about 75-200 m above sea level was < 0.0002 ng TEQ/m .
KEYWORDS
Deepwater Horizon, dioxin, emission factor, oil spill, in situ oil burns, aerial sampling.
INTRODUCTION
The Deepwater Horizon oil drilling platform located in the Gulf of Mexico and owned and managed
by Transocean for British Petroleum (BP) caught fire on April 20, 2010 and sank. Eleven lives were lost
and the ensuing oil leak resulted in an environmental disaster for the Gulf region. The U.S. Coast Guard
(USCG) and BP undertook operations to collect and burn the surface oil as one means of limiting its
environmental impact. Pairs of vessels, typically fishing trawlers, towed a collection boom through
surface oil slicks, accumulating oil. Smaller "igniter" boats placed an incendiary starter charge (gelled
diesel in a plastic container with foam flotation and a road flare) within the boom's oil pool to promote
ignition. Under appropriate conditions of the oil and the sea/wind state, the collected oil would ignite,
burning for times varying from minutes to hours. The USCG estimated that between 220,000 and
310,000 barrels of oil were consumed during 411 in situ burns between April 28, 2010 and July 19,
2010 (1).
In situ burning of oil spills has the benefit of minimizing contamination of coastal marine
environments. Probably the largest detriment is the emissions from the incomplete combustion of the
oil, as indicated by the copious volumes of black, particle-laden smoke. Various efforts have been
undertaken to quantify the emissions from in situ burns, the most comprehensive at-sea effort being the
Newfoundland offshore burn experiments (2). Particle and gas concentrations sampled by aircraft-borne
instruments were developed into emission factors (3) using a carbon balance approach (mass of
2

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pollutant per mass of fuel carbon). Other measurements were made using samplers aboard remotely
controlled marine vessels and tethered aerostats (4).
Emissions of polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/PCDFs)
from the oil burns are of interest due to their health effects (5) including immunotoxicity,
carcinogenicity, and teratogenicity. The potential for PCDD/PCDF emissions from the Gulf in situ
burns exists due to the apparent presence of the prerequisite conditions for formation: incomplete
combustion, the presence of trace metals as catalysts, and availability of chloride in the seawater. Few
measurements of PCDD/PCDF have been made from oil fires and only one (2) to our knowledge from
an at-sea burn similar to those of the Gulf in situ burns. Results from two samples at sea level were
reported as indistinguishable from background levels, leading to the conclusion that PCDD/PCDF were
not formed from oil spill burns (6, 7). Similar conclusions were reached during experimental, mesoscale
burns (4) when ground-based emission samples were compared against upwind sampling. In both of
these cases the PCDD/PCDF sampling was done at sea/ground level, apparently outside of the visible
plume, so questions remain regarding their ability to resolve whether or not PCDD/PCDF is formed.
To measure the potential emissions of PCDD/PCDF from the Gulf in situ oil burns, an aerostat-lofted
instrument package was used to sample the plume emissions to determine PCDD/PCDF concentrations
and an emission factor.
MATERIAL AND METHODS
Aerostat Operations at Sea. A 4.0 m diameter, helium-filled aerostat (Kingfisher model, Aerial
Products Inc., FL) was used to loft an instrument package (termed the "Flyer") into oil fire plumes for
sample collection. The aerostat/Flyer were launched from the deck of the MV Allison (Aries
Corporation), a 67 m long oil platform work boat. The aerostat was secured to an electric winch by a
609 m long, 2.5 mm diameter Spectra tether. Tethered aerostat flight operations were conducted in
3

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accordance with regulations for moored aerostats (8). Due to increased air traffic in support of oil spill
operations several additional operational requirements were coordinated with the Federal Aviation
Administration (FAA) and Incident Command Post (ICP). These requirements included daily altitude
restrictions, a dedicated air traffic observer, two-way radio contact on Common Traffic Advisory
Frequency, and availability of a signal flare if necessary to visually alert aircraft to our presence. The
FAA published a daily Notice to Airmen (NOTAM) advising pilots that tethered aerostat operations
were being conducted in the area. The FAA also required notification prior to each flight operations
period including precise location in relation to the Deepwater Horizon source, any position changes of
more than 1.85 km, and termination of the daily flight operations. As a further precaution, the Aerostat
Flyer was equipped with a radio-controlled deflation valve in the unlikely event it became loose from its
tether. Filling the aerostat with helium and lofting the Flyer to the sampling altitude took approximately
30 min. The MV Allison maneuvered directly underneath the burn plumes, maintaining a distance of at
least three to five burn diameters from the fire required by the U.S. Coast Guard (USCG) for safety.
Sampling was opportunistic and was conducted on a non-interference basis to the burns. As such, the
MV Allison avoided crossing the path of the boom vessels and creating a wake, each which would
disrupt the oil collection and potentially extinguish the flame (see Figure 1). An industrial hygienist on
board the MV Allison monitored the air conditions for the aerostat team. The aerostat height,
maintained below the FAA-mandated ceiling of 228 m, was adjusted to the center of the plume by the
length of the tether; this was aided by spotters aboard a second, nearby vessel, the MV Jamie G. Minor
lateral corrections for the plume center were done by walking the tether line fore and aft of the winch.
When the oil fire diminished, the MV Allison withdrew and proceeded to the next likely oil fire, with
the aerostat staying aloft and the sampler off.
4

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Collection boom
Figure 1. Schematic illustration of the in situ burn operations and plume sampling.
Sampling. The intention of the sampling effort was to take at least three samples to target statistical
robustness of the determined plume concentration and emission factor. The minimum amount of
emission mass targeted for sampling was based on the authors' prior experience with burning multiple
fuel types (9-11). Relatively clean-burning fuels, in terms of PCDD/PCDF production per mass of fuel
combusted, require collection of a minimum of 4 g of carbon from the combusted fuel emissions in
order to avoid non-detects amongst the 17 PCDD and PCDF congeners which comprise the toxic
equivalency (TEQ). This carbon is measured, in part, during the course of the run by on-line
measurement of CO2. Other sources of carbon in the emissions include particulate matter (PM), CO,
and total hydrocarbons. Of these, only PM was considered a relatively significant contributor to the
total carbon emitted (up to 10% by mass (3)) and targeted for sampling. Over 80% of the PM mass was
considered to be elemental carbon based on previously published measurements of oil fires (3). As
such, plume sampling consisted of on-line measurement of CO2 and simultaneous filter sampling of PM.
5

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It was anticipated that each of the three targeted samples would take at least four hours of in-plume
sampling to get the minimum of 4 g of carbon to comprise a single, complete sample. This anticipated
sampling duration was based on the sampling rate as well as the CO2 concentration data of others (6)
during at-sea oil burns, although dissimilarities in experimental approaches made this comparison
approximate. Since fires typically were less than one hour, multiple plumes would be sampled with the
same sorbent, resulting in a single, composite sample.
A background sample was taken to compare the plume concentration with ambient levels. The same
design of sampler was used for the background and the lofted plume sampling to ensure consistency of
methods. Background sampling was conducted overnight when burns were suspended and during the
departure and return to port in order to compare PCDD/PCDF levels against those found while sampling
the burning oil plume. The Flyer was positioned on the bridge of the MV Allison to avoid capture of
any fumes from the diesel engines. A trip blank and a field blank were also included for quality
assurance.
Instruments. The Flyer (Figure 2) was comprised of multiple instruments powered by 12 V Li-ion
and AA batteries. CO2 was continuously measured in accordance with EPA Method 3A (12) using non-
dispersive infrared (NDIR) instrument (LI-820 model, LI-COR Biosciences, USA). This unit is
configured with an optional 14 cm optical bench, giving it an analytical range of 0-20,000 ppm with an
accuracy specification of less than 2.5% of reading. The LI-820 calibration range was set to 0-4,500
ppm. A particulate filter precedes the optical lens. The LI-820 was equipped with a programmable
trigger circuit which activated collection of all samples at a user-set CO2 concentration above
background levels, indicating that the Flyer was within the emission plume. This trigger conserved
batteries and avoided dilution of the sample with ambient air. The initial trigger setting was 500 ppm
CO2 but was changed to 400 ppm CO2 after the first two plumes showed minimal CO2 elevation above
the background CO2 concentration. Daily measurements of background CO2 were used to calculate the
6

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C02 elevation in the plumes. These measurements were taken from the lofted Flyer and ranged from
371 to 374 ppm over the four days of sampling. The CO2 level also triggered a total PM sampler
comprised of a 47 mm tared Teflon filter (pore size of 2.0 |im) and a Leland Legacy sample pump
(SKC Inc., USA) with a constant airflow of 13 L/min. An internal flow sensor on the Leland pump
measures flow directly and acts as a secondary standard to constantly maintain the set flow. Total PM
was measured gravimetrically using pre-tared filters transported in sealed petri dishes. The weigh scale
was accurate to ±1 |ig and all filters were conditioned to 20-23 °C and 30-40 % relative humidity for a
minimum of 24 h before weighing. Measurements are reported at actual sample temperature and
humidity without normalization.
Figure 2. Schematic illustration of the "Flyer" used for plume sampling.
Emissions were sampled for PCDD/PCDF by drawing the plume sample through a polyurethane
foam/XAD-2/polyurethane foam (PUF) sorbent cartridge. In a modification of EPA Method T09A
(13), the cartridge was followed, rather than preceded, by a glass fiber filter (70 mm dia.) to ensure that
the filter catch did not fall off during flight. This filter was changed out daily. The 12 V sampling pump
(MINIjammer, AMETEK, USA) had a nominal sampling rate of 160 L/min. Flowrate through the pump
was measured by pressure drop through a pre-calibrated venturi and the voltage equivalent recorded on a
7

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data logger. An on-board data recorder (HOBO U12-013, Onset Computer Corporation, USA) saved
the CO2 concentrations and flowrate as voltage equivalents data every 2-3 sec. The HOBO also
measured temperature and relative humidity. The HOBO maintains an internal time with an accuracy of
± 1 min per month.
The Flyer also had a Geko 301 (Garmin, USA) global position system (GPS) for location and height
above sea level, saving data every 10 seconds. A wireless telemetry and data recorder system (Seagull
Sea Pro 900. Eagle Tree Systems, LLC) on the Flyer was used to transmit signals to the vessel. This 9 V
system transmitted CO2 concentrations (as a voltage), flowrate (as a voltage), ambient temperature, and
battery output to the aerostat crew on the MV Allison. This information was used as an aid in
positioning the aerostat within the plume, monitoring volumetric sampling rate to determine whether a
filter change was necessary, and conveying residual battery capacity. These data together with the
telemetry's GPS data were saved every millisecond and used as a secondary data logger.
Quality Assurance. Prior to field sampling and analysis, a quality assurance (QA) project plan was
written and approved by the EPA QA Manager to insure that the operation of the instruments, sampling
procedures, analytical data, and calculations were consistent with QA Category 1, EPA's highest
category of quality assurance (14). A technical systems audit of the sampling was conducted by the EPA
QA Manager, who was present for the entire duration of the sampling. A technical systems audit of the
dioxin laboratory analysis was also performed with auditors witnessing the extraction, cleanup, and
HRGC/MS injection of the sample and blanks. Auditors also witnessed the weighing of the PM
samples. The results from the audits suggested that appropriate controls and methods were applied to
ensure the quality and usefulness of the data.
The LI-820 was calibrated for CO2 on a daily basis in the field using a zero (nitrogen) and one span
gas (4,500 ppm CO2 in nitrogen) and checks with two intermediate CO2 gas concentrations (1,500 and
8

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400 ppm CO2) in accordance with U.S. EPA Method 3A (12). The Leland Legacy sample pump was
calibrated daily in the field with a Gilibrator Air Flow Calibration System (Sensidyne LP, USA), which
is a primary standard airflow calibrator; the accuracy goal for the Leland Legacy pump system is ±5%.
The flow rate through the venturi was measured with a pressure transducer, and verified by a Roots
meter both prior to and after the field campaign.
A field and trip blank were taken during the sampling for determination of PCDD/PCDF
concentration. The trip blank was sealed at the laboratory, taken to the test site, and returned to the
laboratory unopened. During a period when no oil burns were present, the field blank was assembled
into the Flyer's sampler, left on the deck for 1 h, and removed for return to the laboratory. Both field
and trip blanks underwent analysis as per the plume and background sample.
Analysis Methods. Analysis of PCDD/PCDF followed procedures in EPA Method 8290A (15). Pre-
sampling, pre-extraction, and recovery standards were used, allowing sample collection, extraction, and
instrument efficiency to be determined as well as sample quantification via the Method's isotope
dilution procedure. The combined PUF/XAD-2/PUF and glass filters were extracted in a soxhlet
apparatus overnight with toluene. The raw extracts were concentrated using three-ball Snyder columns
to about 100 mL, filtered with a 0.2 |im Teflon syringe filter, and concentrated further with flowing N2
using an automated evaporator (Biotage, Sweden) to 0.5 mL. The extracts were diluted in hexane then
cleaned and fractionated using an automated, multi-column liquid chromatography system (Power Prep
Dioxin System, FMS Fluid Management Systems, Inc., USA). The columns consisted of
acidic/basic/neutral (ABN) silica gel, basic alumina, and carbon/celite. The plume sample was pre-
cleaned through an additional ABN silica gel column due to the amount of residual color in the extract.
Concentrations of PCDDs/PCDFs in the sample were determined by high resolution gas
chromatography/high resolution mass spectrometry (HRGC/HRMS) consisting of a Hewlett-Packard gas
9

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chromatograph 6890 Series equipped with a CTC Analytics Combi PAL autosampler (CTC Analytics,
Switzerland) and coupled to a Micromass Premiere (Waters Inc., UK) double-focusing high resolution
mass spectrometer. A 60 m DB-Dioxin (Agilent/J&W Scientific, U.S.A.) column was used (0.15 [j,m
film thickness x 0.25 mm i.d). The temperature program for PCDDs/PCDFs was from an initial
temperature of 150 to 260 °C at 10 °C/min with a final hold time of 55 min. Two microliters (2 |iL) of
the extract were injected under splitless mode (the injection port temperature was 270 °C). The HRMS
was operated in an electron impact (35 eV and 650 [iA current) selective ion recording (SIR) mode at
resolution R > 10 000 (5% valley). The temperature of the ion source was kept at 250 °C. The pre-
sampling HRGC/HRMS calibration curve was developed with standards appropriate for a final extract
volume of 20 [xL. The criterion for identification of a congener peak was a 2.5/1 signal to noise ratio.
TEQ values were calculated from the World Health Organization 2005 factors (16) using non-detect
congeners as zeros and as their detection limit values.
Calculations. CO2 concentrations determined by the NDIR and PM mass from gravimetric filter
analyses were linked with their corresponding flowrate measurements to determine the total carbon mass
sampled, volume sampled, and time of sampling. This permitted normalization of the PCDD/PCDF
mass by the amount of gas volume sampled and the amount of carbon collected, the latter using the
carbon mass balance method (17). Gravimetric determinations of particulate mass were related to
carbon mass captured based on the carbon percentage (-84%) determined by particle sampling (3)
during in situ oil burn trials (2). The amount of carbon collected can be related to the amount of fuel
combusted by the oil stoichiometry, resulting in an emission factor in terms of the amount of oil burned.
The fuel's carbon mass percentage was 85% based on an average of cited literature (86% (3), 84% (18)).
RESULT AND DISCUSSION
Four days of sampling, from July 13 to 16, resulted in capture of emissions from 27 plumes (Table 1)
from which only a single, composite PCDD/PCDF sample was obtained. This single sample contained
10

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less carbon than was projected to be necessary for PCDD/PCDF analysis. Five composite PM samples
were obtained (Table 1) over four sampling days. The plumes from the oil fire were typically lofted and
did not impinge on the water surface. Characteristic vortices of black smoke were the norm.
Substantial variation of in-plume CO2 concentration indicated significant dilution and mixing even at a
nominal 250 m distance from the fire source. Minimal elevation of plume temperature (about 1 to 2 C°)
above ambient levels was observed (Table 1). Pressure drop and filter plugging were minor; the largest
decline in flowrate for the PCDD/PCDF sampler during a sampling day was 11% of its maximum.
The average, cumulative residence time of the Flyer in each plume when the CO2 concentration
exceed the 400 ppm trigger was 7.98 min (standard deviation, o, 6.88 min), recording an average CO2
rise over ambient of 70 ppm (o = 43 ppm). Only a single, composite PCDD/PCDF sample was
collected; by July 15 the well leak had been capped, the surface oil had diminished, and the sea state
"3
prevented further sustainable in situ burns. The total carbon collected as CO2 from the 26.6 m sample
volume was 1.318 g. PM filters were collected daily during the 27 plumes, amassing 0.01094 g from
"3
2.731 m sample volume on the five filters. Of this PM mass, 84% was assumed to be carbon based on
data cited earlier (3). The PM emission factor was 0.088 g/gcarbon with a relative standard deviation
(rsd) of 26% over the five measurements (Table 1). This low rsd value affirms the assumption that
plume mixing was sufficient to meet the carbon balance requirement that PCDD/PCDF, CO2, and PM
are in constant proportion. The total carbon collected was 1.41 g, 95% of it from CO2. This was less
than that desired for a single sample (4 g) and the sole sample from the field was short of the targeted
number of three samples for the campaign.
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Table 1. Plume and Sampling Parameters and Results.
Plume
Date
Burn
Burn
Cumulative
Average

PCDD/PCDF
Average
Carbon
PM PM Carbon
Total
ID#

start
stop
Sample
time
Temperature
plume

aco2
from
density Emission from
Carbon




(min)

(°C)

sample volume
(ppm)
C02(g)
(g/m3) Factor PM
(g)








(m)

















(g/g (g)













carbon)

1
2010-07-13
13:24
13:36

5.9

31

0.472
109
0.036


2
2010-07-13
14:21
14:41

2.1

29

0.112
84
0.007


3
2010-07-13
15:05
15:20

2.9

30

0.270
27
0.005
[Composite PM sample 1]

4
2010-07-13
16:24
16:56

12.4

31

1.427
58
0.053


5
2010-07-13
17:04
17:21

13.2

31

1.629
99
0.099


6
2010-07-13
18:23
19:58

22.0

31

2.314
57
0.084


SUM




58.4

31

6.224
72
0.284
0.0041 0.10 0.021
0.305
7
2010-07-14
11:03
11:10

1.1

30

0.110
38
0.003


8
2010-07-14
12:36
12:53

1.9

30

0.156
22
0.002


9
2010-07-14
14:31
14:45

10.6

31

1.414
73
0.064


10
2010-07-14
15:08
15:12

1.8

31

0.192
57
0.008


11
2010-07-14
15:49
15:55

1.4

31

0.137
26
0.002


12
2010-07-14
17:15
17:35

4.1

34

0.458
37
0.012
[Composite PM sample 2]

13
2010-07-14
17:56
18:09

7.0

32

0.805
31
0.016


14
2010-07-14
18:16
18:30

6.7

31

0.728
37
0.019


15
2010-07-14
18:49
19:04

9.5

31

1.219
62
0.097


16
2010-07-14
19:41
19:50

4.7

30

0.625
66
0.023


17
2010-07-14
19:52
20:25

17.7

30

2.500
76
0.106


12

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SUM



66.6
31
8.344
47
0.352
0.0044 0.11 0.031
0.383
18
2010-07-15
15:08
15:19
7.6
31
0.994
55
0.035


19
2010-07-15
16:42
17:25
6.9
31
0.811
33
0.002


20
2010-07-15
17:39
17:45
3.8
35
0.452
29
0.008
[Composite PM sample 3]

21
2010-07-15
18:20
18:22
1.0
36
0.100
28
0.002


22
2010-07-15
19:26
20:03
28.3
30
3.700
52
0.121


SUM



47.6
33
6.057
39
0.184
0.0028 0.10 0.014
0.198
23
24
2010-07-16
2010-07-16
09:51
10:45
10:10
10:53
14.1
0.2
31
30
2.061
0.026
142
59
0.174
0.001
[Composite PM sample 4]

SUM



14.3
31
2.087
101
0.175
0.0073 0.087 0.013
0.188
25
2010-07-16
14:48
15:09
14.6
31
2.103
153
0.194


26
2010-07-16
16:53
17:23
6.0
31
0.905
195
0.101
[Composite PM sample 5]

27
2010-07-16
17:43
17:57
7.9
30
0.940
46
0.028


SUM



28.6
31
3.948
131
0.323
0.0032 0.044 0.011
0.334
TOTAL



215

26.660

1.318
0.090
1.408
AVG




31

70

0.0044 0.088

13

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The trip blank and field blank resulted in non-detects (Supporting Information, Table S-2) for all but
one congener, implying confidence in the overall cleanliness of the sampling media and handling
procedures. The one detected congener (1,2,3,4,7,8-HxCDF) is a contaminant in the surrogate standards
(pre-sampling spike) and is a consequence of the relatively high level of the surrogate to target
concentrations. This contamination was confirmed by analysis of the commercial standard solutions.
The single, composite background PCDD/PCDF sample was collected intermittently over six days,
primarily during nighttime, for a total of 24 h 8 min (1,448 min) resulting in a total sample volume of
"3
170.9 m . As with the trip and field blanks, the only detected congener in the background sample was
that of the standard contaminant (1,2,3,4,7,8-HxCDF).
Concurrent background measurements were taken of CO2 and PM. The average CO2 concentration
3	3
was 373 ppm. The background PM concentration was 0.0127 (J,g/m during collection of 18.46 m .
"3
The emission sample from the in situ burn plume (26.6 m ) had 13 detectable 2,3,7,8-Cl-substituted
congeners of the 17 that comprise the TEQ value. This is in distinct contrast with the background
sample which had all non-detects (excluding the standard contaminant) despite almost seven times the
sample volume. This confirms the net formation of PCDD/PCDF from the in situ oil fires.
Measurement of PCDD/PCDF above background levels is in contrast with conclusions from limited,
previous data from in situ ocean (6, 7) and mesoscale laboratory oil spill burns (4). Their conclusions
may have been reached based on insufficient sampling due to positioning their sampler outside of the
plume at sea/ground level, low sample volume, high trip blank concentrations, and high detection limits
(6).
Concentration and emission factor data by congeners and TEQ values are listed in Table 2 while Table
3 lists the homologue data. Values are listed with the non-detect (ND) congeners treated as both zeros
14

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(0) and at their detection limit (DL). The use of ND=DL provides for an upper bound of the
concentration and emission factor based upon these sampling data. The 27-sample PCDD/PCDF
concentration is 110 fg TEQ/m3 (190 fg TEQ/m3 at ND = DL). The calculated emission factor is 2.0 ng
TEQ/kg carbon burned (3.5 ng TEQ/kg carbon burned at ND = DL) or 1.7 ng TEQ/kg fuel burned (3.0
ng TEQ/kg fuel burned at ND = DL). These values are roughly 25 to 65 times higher than observed for
controlled combustion of waste engine oil (19), within the range of PCDD/PCDF emission factors
determined for open biomass burning (20-22), and over two orders of magnitude lower than open
burning of residential waste (10). While only a single, composite sample from 27 plumes could be
obtained, the precision of its emission factor would likely be better than those from burning of more
heterogeneous biomass samples, where the relative standard deviations were significantly less than
100% (20, 23). This fact, combined with the low rsd value for the PM emission factor (26% over five
measurements) suggests that the PCDD/PCDF emission factor is accurate within a factor of two. When
the emission factor range, 1.7 ng TEQ/kg fuel burned (ND = 0) to 3.0 ng TEQ/kg fuel burned (ND =
DL), is applied to the estimated amount of oil burned in the Gulf clean up operation, 220,000 and
310,000 barrels of oil (1), the total amount of PCDD/PCDF released is about 0.05 to 0.13 g TEQ. This
can be compared with the U.S. EPA inventory of sources (24) which amounts to over 1,300 g TEQ/year
from all quantifiable sources.
15

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Table 2. PCDD/PCDF Concentration and Emission Factor Values for the Plume Sample.

PCDD/PCDF
1
Emission Factor
Emission Factor

plume
concentration
(fgTEQ/m3)*
(ng TEQ/kg Carbon
burned)
(ng TEQ/kg fuel
burned)
2,3,7,8-TCDD
ND [19.]
ND [0.36]
ND [0.30]
1,2,3,7,8-PeCDD
ND [58.]
ND [1.1]
ND [0.94]
1,2,3,4,7,8-HxCDD
6.8
0.13
0.11
1,2,3,6,7,8-HxCDD
4.5
0.085
0.072
1,2,3,7,8,9-HxCDD
9.0
0.17
0.14
1,2,3,4,6,7,8-HpCDD
1.5
0.028
0.024
1,2,3,4,6,7,8,9-OCDD
0.14
0.0027
0.0023
Sum PCDD
22.
0.41
0.35
2,3,7,8-TCDF
18.
0.34
0.29
1,2,3,7,8-PeCDF
3.4
0.064
0.054
2,3,4,7,8-PeCDF
40.
0.77
0.65
l,2,3,4,7,8-HxCDF#
13.
0.24
0.21
1,2,3,6,7,8-HxCDF
4.5
0.085
0.072
1,2,3,7,8,9-HxCDF
ND [1.6]
ND [0.031]
ND [0.027]
2,3,4,6,7,8-HxCDF
3.8
0.071
0.060
1,2,3,4,6,7,8-HpCDF
1.3
0.024
0.020
1,2,3,4,7,8,9-HpCDF
0.75
0.014
0.012
1,2,3,4,6,7,8,9-OCDF
ND [0.026]
ND [0.0050]
ND [0.00043]
Sum PCDF
85.
1.6
1.4
Sum PCDD/PCDF (ND = 0)
110.
2.0
1.7
Sum PCDD/PCDF (ND = DL)
190.
3.5
3.0
Limit of detection values within brackets.

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"Uncorrected for contaminant observed in the trip and field blanks. Correction would decrease the
Sum values < 6%.
Sums may not add directly after accounting for significant digits.
Table 3. PCDD/PCDF Homologue Concentrations for the Plume Sample.
PCDD/PCDF concentration
Homologues
(fg/m3)
(fgTEQ/m3)*
TCDD
ND
ND [18]
PeCDD
ND
ND [58]
HxCDD
270
20
HpCDD
240
1.5
OCDD
470
0.14
Sum PCDD
980
22
TCDF
2500
18
PeCDF
580
44
HxCDF#
350
21
HpCDF
200
2.0
OCDF
ND
ND [0.026]
Sum PCDF
3600
85
Total PCDD/PCDF (ND = 0) 4600
	S	!									T—					1
110
V	1
Limit of detection values within brackets.
"Uncorrected for contaminant observed in the trip and field blanks.
Sums may not add directly after accounting for significant digits.
17

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Sea, weather, and oil conditions during this sampling resulted in plumes of varying appearance,
duration, and intensity. A composite sample from 27 of these plumes resulted in emission factors and
concentrations that were representative of the Gulf in situ oil fires. The extent to which these values
may be applied to emissions from other in situ oil fires remains to be determined. Incorporation of the
emission factor into transport and deposition models can provide information on potential receptor
exposure on land and water, allowing the impact of PCDD/PCDF emissions from in situ oil burns on
environmental and other routes of human health exposures to be assessed. These studies would be
useful in balancing the overall ecosystem and health impact of in situ burning versus alternative cleanup
strategies and their environmental impacts.
ACKNOWLEDGMENT
This work was funded and managed by the U.S. EPA, Office of Research and Development. This
research was performed while Johanna Aurell held a National Research Council Research Associateship
Award at the National Risk Management Research Laboratory, U.S. EPA. Technical support for the
sampling mission was provided by Arcadis-US, Inc., under contract EP-C-09-27 with the U.S. EPA.
The aerostat piloting expertise provided by Rob Gribble (ISSI, Inc.) and field crew support from Cheryl
A. Hawkins (U.S. EPA/OSRTI/ERT), Chris Pressley (U.S. EPA/ORD/NRMRL), James Staves (U.S.
EPA Region 6), and Steve Terll (Arcadis-US, Inc.) was critical and much appreciated. The crews of the
MV Allison and MV Jamie G. are thanked for their hospitality and accommodation. The authors
recognize the critical analytical support and specialized expertise provided by Dennis Tabor (U.S.
EPA/ORD/NRMRL), Barbara Wyrzykowska and Mike Tufts (Arcadis-US, Inc.), and Joseph Ferrario
(U.S. EPA/OCSPP/OPP). The authors acknowledge the quality assurance, on-site audits during both the
sampling and analysis phases, and procurement support of Robert Wright and Paul Groff (U.S.
EPA/ORD/NRMRL).
18

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Many people were critically involved in the development, preparation, and implementation of the
sampling plan, including Sam Coleman (U.S. EPA Region 6), Wyman Briggs and MSTCS Andrew
Jaeger (USCG), Peter Collinson (BP), Jeffrey Frithsen and John Schaum (U.S. EPA/ORD/NCEA),
Marshall Gray (U.S. EPA/ORD/NERL), Marc Greenberg and Brian Kovak (U.S. EPA/OSRTI/ERT),
Dave Guinnup and Richard Wayland (U.S. EPA/OAR/OAQPS), Nancy Jones and Jon Raucher (U.S.
EPA Region 6), Stacey Katz and Gail Robarge (U.S. EPA/ORD/NCER), Shawn Ryan, Paul Lemieux,
and Cynthia Sonich-Mullin (U.S. EPA/ORD/NHSRC), Deborah McKean (U.S. EPA Region 8), Dana
Tulis (U.S. EPA/OSWER/OEM), and Lee Ann Veal (U.S. EPA/OAR/ORIA).
The views expressed in this article are those of the authors and do not necessarily reflect the views or
policies of the U.S. EPA. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
SUPPORTING INFORMATION AVAILABLE
Supporting information includes analytical notes and detailed sample results.
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