1

Aerostat Sampling of PCDD/PCDF Emissions from the 

Gulf Oil Spill In Situ Burns 

Johanna Aurell1 and Brian K. Gullett2,*

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

1

National Research Council Post Doctoral Fellow to the U.S. Environmental Protection Agency

2

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 
2

emission factor of 0.088 kg/kg carbon burned. The average plume concentration approximately 200-300 

m from the fire and about 75-200 m above sea level was < 0.0002 ng TEQ/m3

. 

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 
3

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 
4

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.
5

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. 

Aerostat and Flyer

Tether line

Collection boom

Oil burn
6

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 nondispersive 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 
7

CO2 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 μm) 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 μg 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 TO9A

(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 

HOBO

PM PM Pump

Battery

Semi-volatile 

sampler 

Venturi CEM CO2

HOBO Data 

logging CEM particle 

filter

GPS

Telemetry: data 

transmitter

HOBO

PM PM Pump

Battery

Semi-volatile 

sampler 

Venturi CEM CO2

HOBO Data 

logging CEM particle 

filter

GPS

Telemetry: data 

transmitter
8

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 
9

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). Presampling, 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 μm 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 precleaned 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
10

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 μm 

film thickness × 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 μL) 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 μA 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 presampling HRGC/HRMS calibration curve was developed with standards appropriate for a final extract 

volume of 20 μL. 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 
11

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, σ, 6.88 min), recording an average CO2

rise over ambient of 70 ppm (σ = 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 

prevented further sustainable in situ burns. The total carbon collected as CO2 from the 26.6 m3 sample 

volume was 1.318 g. PM filters were collected daily during the 27 plumes, amassing 0.01094 g from 

2.731 m3 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.
12

Table 1. Plume and Sampling Parameters and Results.

Plume 

ID #

Date Burn 

start

Burn 

stop

Cumulative 

Sample time 

(min)

Average 

Temperature 

(°C)

PCDD/PCDF 

plume

sample volume 

(m3)

Average 

∆CO2

(ppm)

Carbon 

from 

CO2 (g)

PM 

density 

(g/m3

)

PM 

Emission 

Factor

(g/g 

carbon)

Carbon 

from 

PM

(g)

Total 

Carbon 

(g)

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
13

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 2010-07-16 09:51 10:10 14.1 31 2.061 142 0.174

[Composite PM sample 4]

24 2010-07-16 10:45 10:53 0.2 30 0.026 59 0.001

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
14

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 

170.9 m3

. 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 

was 373 ppm. The background PM concentration was 0.0127 μg/m3 during collection of 18.46 m3

. 

The emission sample from the in situ burn plume (26.6 m3

) 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 
15

(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. 
16

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

PCDD/PCDF 

plume 

concentration

(fg TEQ/m3)

*

Emission Factor

(ng TEQ/kg Carbon 

burned)*

Emission Factor

(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

1,2,3,4,7,8-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. 
17

#

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) (fg TEQ/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 110

* 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.
18

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). 
19

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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