OCS Study 

BOEMRE 2010-043 

Coastal Marine Institute 

Determination of Net Flux 

of Reactive Volatile Organic Compounds 

at the Air-Water Interface 

in the Gulf of Mexico 

Cooperative Agreement

Coastal Marine Institute 

Louisiana State University 

U.S. Department of the Interior

Bureau of Ocean Energy Management, 

 Regulation and Enforcement 

Gulf of Mexico OCS Region 
OCS Study 

BOEMRE 2010-043 

Coastal Marine Institute 

Determination of Net Flux 

of Reactive Volatile Organic Compounds 

at the Air-Water Interface 

in the Gulf of Mexico 

Authors 

E.B. Overton 

M.S. Miles 

B.M. Ashton 

R.L. Wong 

December 2010 

Prepared under BOEMRE Contract 

1435-01-04-CA-32806-36186 (M05AZ10667) 

by 

Louisiana State University 

School of the Coast and Environment 

Department of Environmental Science 

Baton Rouge, Louisiana 70803 

Published by 

U.S. Department of the Interior Cooperative Agreement 

Bureau of Ocean Energy Management, Coastal Marine Institute 

 Regulation and Enforcement Louisiana State University 

Gulf of Mexico OCS Region 
iii 

DISCLAIMER 

This report was prepared under contract between the Bureau of Ocean Energy Management, 

Regulation and Enforcement (BOEMRE) and Louisiana State University. This report has been 

technically reviewed by the BOEMRE and has been approved for publication. Approval does 

not signify that the contents necessarily reflect the view and policies of the BOEMRE, nor does 

mention of trade names or commercial products constitute endorsement or recommendation for 

use. It is; however, exempt from review and in compliance with BOEMRE editorial standards. 

REPORT AVAILABILITY 

This report is available only in compact disc format from the Bureau of Ocean Energy 

Management, Regulation and Enforcement, Gulf of Mexico OCS Region, at a charge of $15.00, 

by referencing OCS Study BOEMRE 2010-043. The report may be downloaded from the 

BOEMRE website through the Environmental Studies Program Information System (ESPIS). 

You will be able to obtain this report also from the National Technical Information Service in the 

near future. Here are the addresses. You may also inspect copies at selected Federal Depository 

Libraries. 

Bureau of Ocean Energy Management, U.S. Department of Commerce 

 Regulation and Enforcement National Technical Information Service 

Gulf of Mexico OCS Region 5285 Port Royal Road 

Public Information Office (MS 5034) Springfield, Virginia 22161 

1201 Elmwood Park Boulevard Phone: (703) 605-6040 

New Orleans, Louisiana 70123-2394 Fax: (703) 605-6900 

Telephone requests may be placed at Email: bookstore@ntis.gov 

(504) 736-2519, 1-800-200-GULF, or 

Rush Orders: 1-800-553-6847 

Fax: (504) 736-2620 

CITATION 

Overton, E.B, M.S. Miles, B.M. Ashton, and R.L. Wong. 2010. Determination of net flux of 

reactive volatile organic compounds at the air-water interface in the Gulf of Mexico. U.S. 

Dept. of the Interior, Bureau of Ocean Energy Management, Regulation and Enforcement, 

Gulf of Mexico OCS Region, New Orleans, LA. OCS Study BOEMRE 2010-043. 74 pp. 

ACKNOWLEDGMENTS 

The authors would like to acknowledge the following people for all of their hard work in the 

concept preparation of this project or in the field at all the sampling locations: Ken Carney; Kyle 

Schmidt; Scott McDaniel; Arun Paga; and Ian Vice. 
iv 

ABOUT THE COVER 

Cover photo found in Microsoft Word 2007 Clip Art collection and adjusted with Adobe 

Photoshop. 
v 

ABSTRACT 

The downwind transport of primary pollutants leading to excessive secondary pollutant 

production has been gaining acceptance since the early 1990’s work of the Southern Oxidant 

Study (http://www.ncsu.edu/sos/pubs.html). Initial Southern Oxidant Study research suggested 

that transport of ozone and ozone precursors could have significant negative impacts on ozone 

and haze in downwind urban areas. Hence, the possibility that air quality problems in coastal 

urban centers, namely Texas and Louisiana, derive to some extent from downwind transport of 

natural volatile organic compounds (VOCs) and, in particular, the reactive volatile organic 

compounds (RVOCs) emitted in the gulf must be considered. Thus, the transfer of reactive 

volatile organic compounds from the sea surface to the atmosphere in the Northern GOM region 

may represent an environmentally significant source with respect to air quality problems in 

urbanized areas on the Gulf Coast. 

Currently, the impact of natural RVOC emissions on the Gulf Coast environment, especially in 

comparison with production related emissions, remains an open question. Because the emission 

areas are large and the emission time frame is long, it is critical to have a reasonably accurate 

characterization of specific RVOCs from natural emissions and the material flux from the sea 

surface to the atmosphere in order to estimate the effect these sources have on nearby (or not so 

nearby) land areas. Estimates based on generalized emission factors are useful starting points, 

but the use of unvalidated factors can lead to large, unknown errors in actual environmental 

impact. The specific contribution of RVOCs to ozone formation potential depends not only on 

the amount of RVOCs in the air mass but also on the specific RVOCs present due to the fact that 

photochemical activity for individual RVOCs varies widely. Thus, a speciated characterization 

of RVOC flux, including identification of RVOCs is necessary for creating an accurate estimate 

of the expected impact of natural GOM emissions on coastal urban centers. 

This study directly examined analytical methodology that can be used to study the net flux of 

reactive volatile organic compounds (RVOC) from the sea surface to the atmosphere in the Gulf 

of Mexico in order to provide a better understanding of factors specific to the Gulf of Mexico 

region that affect the RVOC load from non-production sources. This project also provides 

quantitative information that will allow more accurate estimates of RVOC load contributed by 

natural processes. The goal of the project is to provide technology for estimating the specific net 

flux data in terms of composition and quantity for selected exemplar areas that can then be used 

to estimate flux for a more encompassing area of the GOM. Two area types were examined: (1) 

areas near-shore to the GOM with optimum wind conditions (e.g. winds out of the south, 

southeast, or southwest); and, (2) one offshore transect in the Green Canyon, GOM. 

 

Air sampling and analysis procedures were developed and validated for two different analytical 

instrument systems, the microFAST GC and a lab based gas chromatograph-time-of-flight mass 

spectrometer system using thermal desorption tube samples. Four field validation sampling trips 

were made to near-shore locations, and to one deep sea location in the Green Canyon area of the 

Northern GOM. The goal of the field validation trips was to establish sampling and analysis 

methodologies that could identify individual RVOCs in a large number of air samples and in 

water samples. The OCS RVOC data could then be used to establish whether or not RVOCs 

emitted from natural sources in the GOM represents potential air quality problems if transported 
vi 

to an environment containing high levels of NOx (e.g. a nearby urban environment), an active 

ingredient necessary in the formation of atmospheric ozone. 

The OCS RVOC information from water and air samples can also be used to infer sea-air flux of 

RVOCs from the Green Canyon area (a well known natural seep) of the Northern GOM. In the 

very limited data set from this study, atmospheric RVOC concentrations may not be explained 

only by the flux from naturally-occurring biogenic sources (e.g. marine organisms, algae, and oil 

seeps) within the seawaters of sampled area in the northern Gulf of Mexico. Therefore, the 

concentrations of RVOCs in the marine atmosphere may be affected by anthropogenic sources 

(e.g. marine transport) and subsequent long-range transport of RVOC compounds. 
vii 

TABLE OF CONTENTS 

Page 

LIST OF FIGURES ...................................................................................................................... ix 

LIST OF TABLES ........................................................................................................................ xi 

1.0 INTRODUCTION ................................................................................................................... 1 

 1.1 Research Objectives ..................................................................................................... 6 

 1.2 Relevance ..................................................................................................................... 6 

2.0 METHODOLOGY .................................................................................................................. 7 

 2.1 Air Sampling ................................................................................................................ 7 

 2.2 microFAST GC ............................................................................................................ 8 

 2.3 Sorbent Tube Trap/GC-TOFMS ................................................................................ 10 

 2.4 Water Sampling ......................................................................................................... 12 

 2.5 Field Validation ......................................................................................................... 13 

 2.6 Estimating Net Flux of RVOCs ................................................................................. 15 

3.0 DATA AND RESULTS ........................................................................................................ 17 

 3.1 Trip #1: Grand Isle, Louisiana, August 2007 ........................................................... 17 

 3.2 Trip #2: Cameron, Louisiana, September 2007 ........................................................ 20 

 3.3 Trip #3: Port Fourchon, Louisiana, September 2007 ................................................ 22 

 3.4 Trip #4: Port Fourchon, Louisiana, October 2007 .................................................... 25 

 3.5 Trip #5: Green Canyon, GOM, June 2008 ................................................................ 26 

 3.6 Net Flux of RVOCs at Air-Water Interface ............................................................... 30 

4.0 DISCUSSION ........................................................................................................................ 33 

5.0 CONCLUSIONS AND RECOMMENDATIONS ................................................................ 37 

REFERENCES ............................................................................................................................. 39 

APPENDIX A: microFAST GC Air Sample Data Tables........................................................... 43 

APPENDIX B: Sorbent Tube Trap/GC-TOFMS Air Sample Data Tables ................................. 53 

APPENDIX C: Sorbent Tube Trap/GC-TOFMS Water Sample Data Tables ............................ 59 
ix 

LIST OF FIGURES 

Page 

Figure 1. The microFAST GC setup ......................................................................................8 

Figure 2. Flow schematic of the microFAST GC and air sampling valve ........................... 10 

Figure 3. Sorbent tube trap air sampling apparatus .............................................................. 11 

Figure 4. Schematic diagram of the thermal desorption methodology and a photo 

 of the actual desorption tube ................................................................................. 11 

Figure 5. Water sampling apparatus ..................................................................................... 13 

Figure 6. Average RVOC concentrations for on-site microFAST GC air 

 samples, Grand Isle, Louisiana, August 2007 ....................................................... 18 

Figure 7. Average RVOC concentrations for sorbent tube/GC-TOFMS 

 air samples, Grand Isle, Louisiana, August 2007 ................................................. 19 

Figure 8. Average RVOC concentrations for on-site microFAST GC air 

 samples, Cameron, Louisiana, September 2007 ................................................... 21 

Figure 9. Average RVOC concentrations for sorbent tube/GC-TOFMS 

 air samples, Cameron, Louisiana, September 2007 .............................................. 22 

Figure 10. Average RVOC concentrations for on-site microFAST GC air 

 samples, Port Fourchon, Louisiana, September 2007 ........................................... 23 

Figure 11. Average RVOC concentrations for sorbent tube/GC-TOFMS 

 air samples, Port Fourchon, Louisiana, September 2007 ...................................... 24 

Figure 12. Average RVOC concentrations for on-site microFAST GC air 

 samples, Port Fourchon, Louisiana, October 2007 ............................................... 26 

Figure 13. Average RVOC concentrations for on-site microFAST GC air 

 samples, Green Canyon, GOM, June 2008 ........................................................... 27 

Figure 14. Average RVOC concentrations for sorbent tube/GC-TOFMS 

 air samples, Green Canyon, GOM, June 2008 ...................................................... 28 

Figure 15. Average RVOC concentrations for sorbent tube/GC-TOFMS 

 water samples, Green Canyon, GOM, June 2008 ................................................. 29 
xi 

LIST OF TABLES 

Page 

Table 1. RVOC Analytes of Interest List ..............................................................................5 

Table 2. Summary of Field Validation Trips ...................................................................... 14 

Table 3. Air Sampling Methodology Adjustments ............................................................. 15 

Table 4. Sampling Information for Trip #1: Grand Isle, Louisiana ................................... 17 

Table 5. Sampling Information for Trip #2: Near Cameron, Louisiana ............................ 20 

Table 6. Sampling Information for Trip #3: Port Fourchon, Louisiana ............................. 23 

Table 7. Sampling Information for Trip #4: Port Fourchon, Louisiana ............................. 25 

Table 8. Sampling Information for Trip #5: Green Canyon, GOM ................................... 27 

Table 9. SVOC Qualitative Results for Select Air and Water Sorbent Tube Trap 

 Samples from Green Canyon ................................................................................ 30 

Table 10. RVOC Concentrations in Marine Air and Seawater from Green Canyon, 

 Northern GOM ...................................................................................................... 31 

Table 11. Estimation of RVOC Flux from Green Canyon, Northern GOM ......................... 31 
1 

1.0 INTRODUCTION 

The downwind transport of primary pollutants leading to excessive secondary pollutant 

production has been gaining acceptance since the early 1990’s work of the Southern Oxidant 

Study (SOS) (http://www.ncsu.edu/sos/pubs.html; Chameides and Cowling 1995). Initial SOS 

research suggested that transport of ozone and ozone precursors could have significant negative 

impacts on ozone and haze in downwind urban areas. Hence, the possibility that air quality 

problems in coastal urban centers, namely Texas and Louisiana, derive to some extent from 

downwind transport of natural volatile organic compounds (VOCs) and, in particular, the 

reactive volatile organic compounds (RVOCs) emitted in the gulf must be considered. The 

quantitation and characterization of RVOC emissions in the Gulf of Mexico (GOM) is an item of 

interest to Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) 

because BOEMRE is responsible for air quality management of potential ozone formation issues 

in the GOM that may affect adjacent urban areas. Therefore, information regarding the ozone 

formation potential contributed by the GOM is important for understanding and managing haze 

and ozone formation in the areas under BOEMRE responsibility and for use by planning 

agencies in downwind areas as well. 

The most visible potential sources of ozone formation precursor compounds in the Gulf of 

Mexico are production and transportation related. These emissions are being assessed with 

programs such as the Gulf Wide Emissions Inventory. In contrast, natural sources like natural 

oil seeps are easily overlooked. Some of the largest and best known natural seeps of petroleum 

and natural gas are found in the GOM, as well as, off the coast of Southern California. 

Currently, the impact on the Gulf Coast environment of these natural related emissions, 

especially in comparison with production related emissions, remains an open question. A 

number of natural factors (e.g. insolation, algae/plankton density, biological productivity, sea 

state, oil and gas seeps) may contribute to sea-air RVOC emissions. However, the precise 

correlation of these features with respect to RVOC emissions is less clear. It is important to 

eventually obtain rates and composition of RVOC emissions from these identifiable features in 

order to fully estimate future impacts of natural sources on ambient air quality. 

Offshore RVOCs can be produced from petroleum as well as biogenic activity. The most 

important RVOC compounds from petroleum are the alkyl benzene homologs with 1 to 3 alkyl 

groups on the benzene ring. These compounds generally have atmospheric lifetimes measured in 

hours, where as the saturated hydrocarbons from petroleum have lifetimes measured in days. 

Biogenic hydrocarbons, include the C2 to C6 olefins and isoprene (2-methyl-1, 3-butadiene), 

have atmospheric lifetimes measured in hours. Accordingly, RVOC compounds with significant 

tropospheric ozone formation potential in off-shore areas of the Gulf of Mexico include the alkyl 

benzenes from petroleum and the biogenic olefins and isoprene. 

Natural sources of ozone precursors never come into port, nor do they have visible man-made 

structures associated with them. RVOCs associated with natural sources may be emitted over 

very large areas so even a relatively small flux of material can represent a considerable 

atmospheric load. Natural sources such as seeps also continue to emit material more or less 

continually 7 days a week, 365 days a year. As a result, the transfer of RVOCs from the sea 

surface to the atmosphere in the Northern GOM region may represent an environmentally 

significant source with respect to air quality problems in urbanized areas on the Gulf Coast. In 
2 

order to estimate the effect of these sources on nearby (or not so nearby) land areas, it is 

important to have a reasonably accurate characterization (qualitative and quantitative) of the 

material flux from the sea surface to the atmosphere. 

The total surface area of the Gulf of Mexico is 1.5 million km2

. Even a restricted area of interest 

encompassing only the Northern Gulf easily concerns over 100,000 km2 of water surface. Using 

emission factors based on coastal California oil seeps, a 15,000 km2

 area of the Northern GOM 

was estimated to be the source of, on the order of 6,300 tons per year of VOC (Marse and 

Tsoflias 2001). Globally, natural non-methane hydrocarbon (NMHC) emissions from the sea 

surface have been estimated at 2 - 50 x 1015g/year (Shaw et al. 2003). This global total, 

however, obscures variations between locations and some areas will have higher emission levels 

than others. The GOM, having a high concentration of natural hydrocarbon seeps and high 

biological productivity, would likely be on the upper end of the emissions curve. Estimates 

based on generalized emission factors are useful starting points, but the use of unvalidated 

factors can lead to large, unknown errors in actual environmental impact. Additionally, 

estimates to date have been generally for total RVOCs. Any estimates of RVOC emissions from 

GOM waters based on currently available RVOC flux data would be suspect because of 

uncertainties in the ultimate sources of a large fraction of the total RVOC load and the absence 

of GOM specific flux information. RVOC emission rates specific to the GOM would greatly 

improve the accuracy and reliability of air impact estimates for natural reactive volatile organics. 

The specific contribution of VOCs to ozone formation depends not only on the amount of VOCs 

in the air mass but also on the specific compounds present because the photochemical activity for 

individual VOCs varies widely. Emissions from the sea surface of biogenic RVOCs, such as 

isoprene and ethene, have been demonstrated by Fall et al. (2001). Reasonable extrapolation of 

the literature results suggests that isoprene emissions alone could be as high as 100 kg/hour 

during daylight hours over the GOM region. Further, isoprene emissions may be only a fraction 

of the total reactive hydrocarbons introduced to the atmosphere by natural processes. Ethene and 

propene have been identified as principle RVOC species in seawater both at the surface and at 

depth (Bonsang 2000). As much as 40% of total NMHC (C2-C5) may be comprised of ethene 

(Plass-Duelmer et al. 1995). Studies of alkane and alkene emissions from the sea surface have 

not been convincingly correlated with insolation or chlorophyll content, suggesting 

photosynthetic or photochemical processes are not primary factors determining the concentration 

of alkanes and alkenes in seawater. Previous work on light hydrocarbons in near surface soil gas 

(Carney et al. 1996; Jones and Burtell 1996; Jones et al. 2000; Molecke et al. 1996) also showed 

the predominance of ethane and ethene in microseeps above oil and gas reservoirs. Given these 

results and the uncertainty with respect to the source of ethane and ethene at the sea-air interface, 

it is plausible that a significant fraction of ethane/ethene transported from the sea to the 

atmosphere may ultimately be derived from deep-sea hydrocarbon seeps as well as biogenic 

metabolism of dissolved organic matter (DOM). 

Hydrocarbon seeps (macroseeps) on the sea floor in the Gulf of Mexico represent a significant 

potential source of atmospheric RVOCs as the seep material rises to the sea surface and 

volatilizes. Of these geogenic RVOCs, a significant number (the alkyl benzenes) are highly 

reactive in the context of atmospheric photochemistry and may contribute significantly to ozone 

formation. These compounds may reach the surface in three ways. First, they may rise to the 
3 

surface in gas bubbles. Methane is released in many seeps and as the methane gas rises to the 

surface, the bubbles may include not only ethane and other “gaseous” constituents, but also 

volatilized heavier RVOCs. Second, the volatile compounds may be dissolved in the liquid 

phase oil from the seeps as it rises to the surface. The concentrations of these dissolved volatile 

compounds, primarily ethylene, are usually supersaturated compared to air concentrations 

(Bonsang et al. 1988). Finally, the compounds may be dissolved in the water column. Many of 

the most photochemically reactive compounds are also among the most water-soluble 

constituents of the oil. Some anthropogenic RVOCs can be transported from coastal areas after 

dissolution in water columns via ocean currents (Nutmagul and Cronn 1985). Volatilization of 

dissolved anthropogenic RVOCs over open waters has been suggested by Greenberg and 

Zimmerman (1984) to be a significant source of these compounds in the atmosphere. All of 

these mechanisms are likely to be occurring simultaneously as the oil/gas mixture works its way 

to the water surface. 

The partitioning of RVOCs among three phases (i.e. water, oil, and gas) will change as pressure 

and temperature changes with depth. Each mechanism will have its own characteristics with 

respect to transferring RVOCs to the atmosphere. Compounds entrained in gas bubbles will be 

very effectively transferred to the atmosphere. The rate of transport from depth will be relatively 

rapid and vertical, and, as the bubble erupts at the water surface, the RVOCs will be almost 

completely released to the atmosphere. Compounds dissolved in the liquid oil will not rise so 

quickly and at the surface they will more slowly volatilize from the resulting oil slick. Finally, 

the constituents that dissolve in water may take very long times to reach the surface as the 

principle transport mode to the surface for dissolved organics will be upwelling and diffusion. A 

substantial fraction of the dissolved components may never reach the surface, being biodegraded 

or otherwise removed from the water column before reaching the surface. The result of these 

various transport mechanisms is that a natural seep at the sea floor can be expected to produce 

multiple VOC emission microenvironments. The gas and liquid oil transport will produce the 

expected oil slick with possible gas bubbles erupting somewhere in the vicinity. VOCs dissolved 

in the water as the oil approaches the surface will produce a “halo” region around the oil slick 

exhibiting high volatilization rates of VOCs relative to background areas. Dissolved VOCs may 

only appear at areas of upwelling, far removed from both the actual seep location and its visible 

surface manifestation. 

The ozone formation potential associated with natural RVOC emissions in the GOM is NOx

limited. RVOCs emitted from the sea surface typically are not directly photolyzed by solar 

radiation in the lower troposphere and usually NOx levels in remote marine environments are 

lower than their urban counterparts and more than likely will not lead to significant tropospheric 

ozone creation (Greenberg and Zimmerman 1984). However, all combustion activities offshore 

produce NOx. Therefore, production, exploration and transportation activities along the Northern 

Gulf region can be considered as sources of NOx that will eventually affect RVOC 

concentrations downwind. The RVOCs emitted represent a potential to form low-level ozone 

that is fully realized when they are transported to an environment containing higher levels of 

NOx, such as an urban environment with industrial and automotive combustion sources. 

NOx and RVOCs are two primary precursors in the formation of low level ozone (Dawson et al. 

2007; Manahan 1994; Sillman 1999). Nitrogen oxides in the atmosphere participate in the 
4 

formation of ozone through a series of complex reactions that often involve RVOCs. This 

reaction sequence, simplified in the following reactions, is initiated by the presence of reactive 

hydrocarbons and hydroxyl radical formed from the reaction of atmospheric water and sunlight. 

RH + .

OH + hν → .RO2 + H2O 

This reaction is then followed by the reaction of RO2 with NO. NO is a product of the reaction 

of NO2 and sunlight energy. 

.

RO2 + NO + hν → RCHO + .HO2 + NO2

NO2 + hν → NO + .O 

The formation of tropospheric ozone occurs through the reaction of atomic oxygen created 

during the photolysis of NO2 and molecular oxygen present in the atmosphere. M in the 

following equation is an energy-absorbing third body and can be particles, trace gases, or even 

surfaces. M is the heat sink for the heat generated in production of ozone. 

.

O + O2 + M → O3 + M 

Furthermore, when RVOCs like propane, propylene butenes, and pentenes are oxidized in the 

presence of NOx peroxyacetyl nitrate (PAN) is formed. PAN is a secondary air pollutant and a 

major cause of photochemical smog (Whalley et al. 2004). A simplified equation for this 

reaction would be: 

RVOC + NOx + .

OH + hν → C2H3NO5 (aka PAN) 

PAN can then decompose to form peroxyacetyl radical and NO2 which can subsequently form 

ozone (Dawson et al. 2007; Manahan 1994) and the reaction cycle can repeat. 

The principal factor of interest with respect to air quality is the ozone formation potential that 

marine RVOC emissions represent. The photochemical reactivity of the various RVOCs that one 

may find in the marine air varies considerably. With respect to geogenic sources, some 

components (e.g. saturated hydrocarbons) may produce only a minimal effect, unless present in 

large amounts. Others, (e.g. alkyl benzenes and low molecular weight olefins) may result in 

significant additional ozone formation potential at very low concentrations. Consequently, the 

ultimate impact on nearby urban areas is a function of not only the quantity of RVOCs emitted 

into the atmosphere, but also by their composition. It is anticipated that highly reactive analytes 

of interest will include the various alkyl benzenes especially toluene, xylenes and 

trimethylbenzenes. The saturated volatile components of crude oil will be of some interest 

because they may be present in high concentrations. Further, one would expect to find olefins 

such as ethylene, propylene, isoprene and possibly the butene and pentene isomers. A list of 

RVOCs of interest is given in Table 1 along with RVOC formulae, structure, and possible 

sources (anthropogenic, biogenic, or petrogenic). 
5 

Table 1 

RVOC Analytes of Interest List 

Alkanes: Formula: Structure: Possible Sources: 

 Ethane C2H6 Petrogenic; Anthropogenic 

 Propane C3H8 Petrogenic; Anthropogenic 

 iso-Butane iC4H10 Petrogenic 

 n-Butane C4H10 Petrogenic; Anthropogenic 

 n-Pentane C5H12 Petrogenic; Anthropogenic 

 n-Hexane C6H14 Petrogenic 

Alkenes: Formula: Structure: Source: 

 Ethylene C2H4 Biogenic 

 Propylene C3H6 Biogenic 

 1-Butene C4H8 Biogenic 

 1-Pentene C5H10 Biogenic 

 1-Hexene C6H12 Biogenic 

Other: Formula: Structure: Source: 

 Acetylene C2H2 Anthropogenic 

 Isoprene C5H8 Biogenic 

 Benzene C6H6 Petrogenic; Anthropogenic 

 Toluene C6H5CH3 Petrogenic; Anthropogenic 

 Ethylbenzene C8H10 Petrogenic; Anthropogenic 

 Xylenes (m, o, p) C6H4C2H6 Petrogenic; Anthropogenic 
6 

1.1 RESEARCH OBJECTIVES

This project is designed to be a pilot study of a methodology that may yield better estimates of 

geogenic and biogenic sources of RVOCs to the atmosphere. The project involves lab studies for 

the development of RVOC sampling and analysis methods, and field evaluation of the lab 

generated methodologies. Additional objectives of this project are to preliminarily examine the 

concentration of RVOCs at the sea surface-atmosphere interface in the Northern Gulf of Mexico, 

and, to provide a quantitative methodology for more accurate estimates of RVOC loads 

contributed by natural sources and/or processes. The objectives are based on providing a better 

understanding of factors specific to the GOM region that affect the RVOC load from nonproduction sources. 

1.2 RELEVANCE

This project complements ongoing BOEMRE programs to inventory emissions related to 

production activities. In conjunction with these other BOEMRE programs, this project will start 

to enable a comprehensive judgment regarding the relative impacts of natural and production 

related processes on coastal air quality issues. A further benefit of this project will be the 

development of a methodology that can be used to establish the relationship, if any, between 

"background" emissions of compounds such as ethane and ethene with natural oil and gas seeps. 

The source of these compounds is currently not well established and it is possible that their 

widespread presence at low levels may be a manifestation of organic input by natural seeps. 
7 

2.0 METHODOLOGY 

Prior to any field validation, the analytical methodology was developed and optimized. After 

installation of the instruments, the sampling and analysis methods were evaluated and modified 

to obtain reliable and reproducible results for the targeted analytes in low parts per billion by 

volume (ppbv) concentrations. The validation of methodology encompassed the entire analytical 

process, including sampling, storage, and instrumental techniques of analysis for the laboratory 

as well as field analyses techniques. 

Samples were collected and analyzed by two different techniques and instrument systems. The 

microFAST GC (a dual column/dual flame ionization detector gas chromatograph) collected and 

analyzed ambient air samples on-site. Alternatively, sorbent trap samples were collected 

concurrently on-site but these samples had to be transported back to the laboratory for analysis. 

The sorbent trap samples were cleaned and capped with their own screw caps in the lab prior to 

sample collection. They were then stored in sealed jars in an ice chest with cold packs during 

transport into the field and during transportation back to the lab. One sorbent tube was always 

used as a trip blank. Once at the lab, the samples were transferred into a freezer and analyzed the 

next day by a gas chromatograph-time-of-flight-mass spectrometer instrument system (GCTOFMS) with a thermal desorption injection system. The instrumentation methodology was 

evaluated and modified as necessary after initial field-testing to accomplish the goals of 

speciating and quantifying RVOC concentrations. Modifications were made to the chemical 

analysis procedure, the sampling procedure, sample distribution or sampling location based the 

previous field trips. Any changes made maintained the comparability between data from the 

various sampling trips and between the different sampling area types. 

Over the course of this project, a total of 353 on-site microFAST GC air samples were analyzed 

and 108 sorbent tube/GC-TOFMS samples were collected and analyzed from five different 

locations at different times of the year. Water samples were collected during the off-shore 

sampling trip to Green Canyon, GOM due to the fact that this was the only off-shore sampling 

trip that accommodated itself to water sampling for determining net flux. Ten total water 

samples (duplicate samples at 5 locations) were collected along a sampling transect onto sorbent 

tubes for GC-TOFMS analysis at LSU. Water sampling was limited by the number of sorbent 

tube traps available during the trip since the majority of the tube traps were used for air sampling 

and two of the ten water sample sorbent tubes were analyzed for semivolatile organic 

compounds. Method development work required an additional 200-300 microFAST GC and 

GC-TOFMS runs in preparation for the field work. 

2.1 AIR SAMPLING 

A two-fold analytical procedure was used for detecting reactive volatile organic compounds 

(RVOC) in air samples at the low ppbv level. First, some samples were collected on dual bed 

sorbent tube traps and the traps returned to the laboratory for conventional thermal desorption 

GC-TOFMS analysis of the samples. Second, other air samples were collected concurrently and 

analyzed in the field with a portable GC instrument, the microFAST GC. The lab based GCTOFMS system provided higher resolution and lower detection limits than the microFAST GC 
8 

system, which was utilized as an on-site screening tool. Minimum detection limits for each 

analytical system were 0.10 ppbv and 1.0ppbv, respectively. 

 

It is important to point out that conventional environmental analyses use what is termed targeted 

compound analyses. These analytical methods determine the concentrations of a list of 

compounds, the target list, in environmental samples, and they in general only detect compounds 

that are on the list. This project has used environmental analytical methods that are designed to 

detect a wide range of organic compounds of air quality interest in the sample (i.e. highly volatile 

and reactive compounds like the C2, C3, C4 and C5 alkanes and olefins that are known to be 

ozone precursors) and is not limited to those analytes on EPA TO-17 target list. 

2.2 MICROFAST GC 

The portable microFAST GC instrument, shown in Figure 1, was used to collect and analyze air 

samples on-site at each sample location. The deployment of the microFAST GC allowed 

operators to make on-site decisions regarding sample locations and other important operational 

parameters based on near real-time analysis of ambient air samples. More importantly, due to 

this instrumentation’s fast cycle times, new samples could be analyzed every ten minutes and 

this allowed a relatively large number of analyses to be performed at each sampling location. 

The microFAST GC is shown in Figure 1 with a Portapack that supplied the power (24VDC) and 

the gases (hydrogen and air) needed to run the instrument in the field. Data acquisition and 

instrument control were achieved through use of software that runs on a laptop computer. 

Figure 1. The microFAST GC setup. 
9 

The microFAST GC was equipped with a combination of columns and trap packing material to 

detect the very light hydrocarbon compounds from ethane to the BTEX (benzene, toluene, 

ethylbenzene and the xylenes) aromatic compounds associated with petroleum. These 

compounds, particularly the olefins and alkyl benzenes, are important ozone precursors. They 

were analyzed by the microFAST GC in the field with a detection limit of 1.0 ppbv. The 

separation columns used in the field were unable to distinguish between hexane and isoprene and 

these two compounds co-eluted for this instrument system. Isoprene is a much more reactive 

ozone precursor than hexane as far as ozone reactivity is concerned, and this is an unfortunate 

limitation to these field analyses. Isoprene is believed to be naturally produced by algal 

growths/blooms in marine areas during the daylight hours and is usually not a derivative of 

petroleum. Thus, isoprene is not associated with natural petroleum seeps or petroleum 

exploration and production activities. 

The microFAST GC uses an internal microtrap to collect and concentrate air samples, and the 

analytes are then thermally desorbed onto dual high resolution GC columns for on-site 

chromatographic separations. Samples were introduced into the microFAST GC through a 

Teflon sampling valve. This valve replaced an electronic solenoid valve, which was susceptible 

to contamination with semivolatile compounds during sampling. Typically, this Teflon sampling 

valve was opened for four minutes, enabling approximately 100 mL of an air sample to be pulled 

into the microFAST GC and through the internal microtrap. The microtrap was a dual bed micro 

trap filled with 80/100 mesh Tenax GR followed by Carboxen. After sampling, the trap was 

flushed and inerted with carrier gas and then blastically heated from 40°C to 280°C. Organic 

compounds that were trapped from the sample were then backed flushed from the heated trap 

into the two capillary columns for GC separations and FID detections. In this project, the 

columns were a Gas Pro gas solid phase GC column (2 meters long, 320 microns ID), used for 

detection of the very light hydrocarbons (C2 to C7), and a DB-5 gas liquid phase GC column (2 

meters long, 320 microns ID) used for detection of the C7 to C17 range hydrocarbon compounds. 

After injection, the trap was automatically cleaned by back flushing to vent for 60 seconds while 

held at 280°C. Chromatographic separations were obtained using an isothermal initial hold time 

of 22 seconds at 40°C; a temperature program from 40°C to 280°C at 5°C/s; and a final hold at 

the upper temperature for 30 seconds. This gave a total chromatographic separation time of 100 

seconds. After chromatographic separations were completed, the GC system was returned to all 

initial temperatures in preparation for the next analysis. The total cycle time from one run to the 

next was typically 10 minutes. A diagram of the flow paths for the microFAST GC is shown in 

Figure 2, which also includes a picture of the Teflon sampling valve that was used to let air 

samples into the portable GC instrumentation. 

Two microFAST GC instruments were deployed on the aft deck of a 65-foot vessel in the Green 

Canyon sampling area of the Northern GOM for sampling and analysis of RVOCs at the low 

ppbv (>1.0 ppbv) concentrations. The vessel was positioned such that the 10-15 mph wind was 

blowing over its port side and the instruments were situated near the port side free of 

obstructions upwind. The boat’s diesel generator exhaust was vented on the starboard side, well 

downwind from the analytical instruments. At least one blank analysis was performed at each 

sampling location to ensure that there was no diesel contamination. 
10 

Figure 2. Flow schematic of the microFAST GC (left) and air sampling valve (right). 

2.3 SORBENT TUBE TRAP/GC-TOFMS

The sorbent tube collection process utilized a multitube flowmeter system with three 150-mm 

direct-reading flowtubes calibrated for air and Teflon tubing. The system was setup with a 

common exhaust with parallel inlets configuration. The flow rates were verified and adjusted 

using a battery powered digital flow meter. The flow was set at approximately 200-mL per 

minute and sampled for 10 minutes for all near-shore sampling trips and 20 minutes for the deep 

sea sampling trip to Green Canyon. These flow rates allowed for the collection of 2 - 4 L of air 

over a ten to twenty minute time frame. The vacuum for collecting the air samples was obtained 

using a 12-VDC Air Cadet vacuum/pressure pump rated at 22.6 L/minute. The air sampling 

pump apparatus that was used for collection of samples on the sorbent tube traps is shown in 

Figure 3. 

The samples were pulled through ambient temperature traps at the site of sample collection with 

the vacuum pump. The traps were immediately sealed after the targeted sample volume was 

achieved and were then refrigerated and transported to the laboratory for thermal desorption and 

GC-TOFMS analysis within a 24 hour time period. Prior to each field sampling trip, randomly 

selected sorbent tube traps were spiked with known concentrations of a RVOC analyte standard 

(AirGas, Inc., Baton Rouge, Louisiana) for standardization and calibration purposes. 
11 

Figure 3. Sorbent tube trap air sampling apparatus.

The sorbent tubes were purchased from Scientific Instrument Services, Inc. (SIS) of Ringoes, NJ 

and thermally desorbed using an SIS TD-5 short path Thermal Desorption System instrument 

interfaced to an Agilent 6890N gas chromatograph/ LECO Pegasus III time of flight mass 

spectrometer (GC-TOFMS). A schematic diagram of the thermal desorption GC/MS analyzer 

and a picture of the sorbent tube trap is given in Figure 4. The TD-5 was purged with inert 

carrier gas and rapidly heated to 300°C. During this heating, the trap was swept with carrier gas 

onto the head of the GC separation column. Immediately after desorption, the GC column was 

temperature programmed from 35°C to 280°C at 5°C/minute while eluting compounds were 

detected with the TOFMS detector. The GC-TOFMS used a 60 m, 320 micron ID Gas Pro gassolid separation column that allowed separation of the very volatile ozone precursors such as 

ethane and ethylene up to compounds as large as benzene, toluene and the xylenes. These 

compounds are known as “highly reactive” VOCs or RVOCs as far as their ability to react with 

other pollutants, especially NOx, are concerned, and this secondary reaction can result in the 

formation of tropospheric ozone through the series of reactions described earlier in the 

introduction. 

Figure 4. Schematic diagram of the thermal desorption methodology and a photo of the actual 

 desorption tube (far right).
12 

Thermal desorption GC/MS analysis of air samples provides a method for detection of unknown 

and/or unexpected compounds in air samples as well as target RVOC analytes, given in Table 1. 

It also serves as a significant quality assurance source for the on-site GC analyses, since 

detection is based on both retention time separations and mass spectral compound identification. 

No on-site sampling decisions could be made from the sorbent tube sampling. Any 

modifications in the sorbent tube sampling methodology were made after the tubes were returned 

to the lab and analyzed. 

A few randomly selected air samples from the off-shore sampling trip to Green Canyon, GOM 

were qualitatively analyzed on an Agilent 7890A GC/5975C quadrapole MS (GC/MS). The 

quadrapole GC/MS used a 30 m, 320 micron gas/liquid GC separation column coated with 0.4 

microns DB-5 liquid phase. This column allowed separation of compounds that have molecular 

sizes larger than the RVOC compounds meaning the semivolatile organic compounds (SVOCs). 

The SVOCs were not included in the analytes of interest listed in Table 1 solely because they are 

not considered to be very reactive. Therefore, the analysis for the SVOCs was done to determine 

if there were any other possible analytes of interest that may need to be included in future air 

monitoring projects. Analyzing a few of the air samples collected on the sorbent tube traps for 

both the RVOCs and SVOCs allowed for a very broad range of possible compounds at a 

detection limit of 0.1 ppbv. 

2.4 WATER SAMPLING

Water samples were taken at a depth of five meters and were then placed in a pre-cleaned 

headspace free 1-gallon amber borosilicate jar with a Teflon-lined metal lid and purged (Figure 

5). The sample jars were pre-cleaned in the lab prior to the sampling trip. They were washed in 

hot soapy water, rinsed with deionized water, rinsed with methanol, and dried in a 105°C oven 

overnight. Air was purged through the water sample and collected on the same type of sorbent 

tube traps that were used for the air sampling. 

Collection of RVOCs from the water samples utilized the exhaust from a vacuum pump that was 

routed thru Teflon tubing into a hydrocarbon gas purification cartridge. The air exited the 

cartridge through another Teflon tube into an air sparging apparatus enclosed in another 1-gallon 

amber borosilicate jar with a Teflon-lined metal lid. The purged air entered the jar through a 

1/8” stainless steel compression bulkhead fitting (top of jar, on the right in Figure 5) and then 

through a 1/8” Teflon tube into a 1/2” stainless steel spherical microbubbler. The purged air 

exited the jar via a secondary 1/8” stainless steel threaded bulkhead fitting (top of jar, on the left 

in Figure 5) screwed to a threaded desorption tube traps. Flow rates were verified and adjusted 

with a battery powered digital flow meter. Flow was adjusted using a Teflon-lined three-way 

valve positioned ahead of the hydrocarbon gas purification cartridge to a flow of 200 mL/minute 

for ten minutes. The sorbent tube traps from the purged water samples were then sealed and 

stored in a cool ice chest during the remainder of the 1-day sampling trip and during 

transportation back to the lab. Once at the lab, the sorbent tubes, in the sealed container, were 

transferred to a freezer until GC-TOFMS analysis. Keeping the sorbent tube traps cool 

prevented any speciation from occurring during transit and holding time prior to analysis. The 

GC-TOFMS methodology was the same methodology employed to analyze the ambient air 
13 

sorbent tube samples. All sorbent trap tubes were analyzed within two days (48 hours) after 

collection. 

Figure 5. Water sampling apparatus. 

2.5 FIELD VALIDATION

After the initial setup and validation period, sampling trips near and into the Gulf of Mexico 

were made. The sampling trips and dates are summarized in Table 2. At each sample location, 

air samples were collected with active sampling onto the sorbent tube traps and the microFAST 

GC was also used for rapid on-site analysis of air samples. Meteorological conditions (e.g. 

relative humidity, temperature, wind directions, etc.) were recorded for all field validation trips 

and throughout the course of the sampling period. 

Our initial field validation plan called for deployment of the sorbent tube traps and the 

microFAST GC instrumentation in near shore areas of the Gulf using a 21-foot center console 

boat (out to approximately 10 miles offshore) in calm weather conditions, and the use of a 

chartered 65-foot vessel for deep sea air and water sampling. After the hurricane season of 2005, 

turbulent near-shore sea states dominated the 2006 and 2007 summer sampling seasons which 

prohibited the use of the 21-foot boat for near-shore sampling. Furthermore, chartering the 65-

foot vessel was difficult and the cost had increased three fold which limited the deep sea 

sampling to one trip to the Green Canyon area. As a result, it was decided to do near-shore 

sampling from unobstructed areas along the beaches at Grand Isle, Port Fourchon, and near 

Cameron, Louisiana, during times when the wind was of blowing out of the south, southeast or 

southwest directions (e.g. from offshore GOM areas). These on-shore instrument deployment 

locations provided some degree of protection of the analytical instrumentation while still 

allowing detection of RVOC compounds that originated from near-shore areas of the Northern 

GOM. 
14 

Table 2 

Summary of Field Validation Trips 

Trip 

#: Date: Location: Coordinates: Average Sampling Time: 

1 August 20-23, 2007 Grand Isle, LA 29°15’37.66”N, 89°57’03.54”W 

29°15’37.68”N, 89°57’03.112”W 2 hrs 10 min 

2 September 5-6, 

2007 Cameron, LA 29°46’30.70”N, 93°18’05.34”W 2 hrs 23 min 

3 September 17, 2007 Port Fourchon, LA 29°06’49.80”N, 90°11’04.20”W 6 hrs 15 min 

4 October 1-4, 2007 Port Fourchon, LA 29°06’49.48”N, 90°11’03.54”W 8 hrs 19 min 

5 June 9-10, 2008 Green Canyon, GOM 27°48’28.56”N, 90°39’42.68”W – 

27°57’02.45”N, 90°51’35.35”W 6 hrs 30 min 

The first trip was to Grand Isle, Louisiana, and occurred after the initial instrumentation 

qualification and method validation was completed in the laboratory setting. The trip focused on 

near-shore monitoring for three days and at least 4 hours of sampling each day. The secondary 

focus of this trip was to test sampling flow rates outside of the laboratory setting for the sorbent 

tubes so that the best rate, one that minimized breakthrough, was used for future trap sampling 

trips. The methodology for both instrumentation techniques was verified prior to this trip by 

establishing linearity of each analyte of interest with 5-point calibration curves. 

The second trip took place in early September near Cameron, Louisiana. In the interim, the data 

from the first trip was evaluated and adjustments in the sampling plan were tested and 

implemented. The majority of the adjustments made to the air sampling methodologies, Table 3, 

were first tested in the lab using known concentrations of the RVOC standard and then field 

tested to ensure that the adjustments were suited for field use and that comparable results could 

be obtained. The focus of the second trip was near-shore monitoring for RVOCs and to assess 

the final lab-based adjustments to the air sampling methodologies. 

The third and fourth trips were to Port Fourchon, Louisiana. The goal for these two trips was to 

implement the finalized methodologies while performing near-shore monitoring for RVOCs. By 

trip four, the sampling and analysis protocols were firmly established and no modifications in 

procedures were required. These trips were done in mid-September and early October. The 

September trip was a day trip and the October trip lasted for four days. 

The final trip was to Green Canyon, approximately 80 miles south of Port Fourchon, and was 

made in early June 2008. A chartered boat departed from Port Fourchon around noon in order to 

arrive at the targeted sampling location around 4 pm. The vessel was situated such that the 5-10 

mph south wind was blowing over the port side of the vessel and this orientation was maintained 

for the entire sampling session. The instrumentation was set up such that there was an 

unobstructed and uncontaminated path from the south wind for the duration of on-site operations. 

The route of the trip was planned so that the bulk of the available sampling time was spent at the 

primary target area, a transect near the natural seeps that occur in the area. The sampling route 

was carefully coordinated to avoid other ship traffic and local fishing activity, both of which are 
15 

anthropogenic sources of RVOCs. Once more, surface meteorological conditions were 

monitored during the sampling period. Air samples were collected in the same manner as the 

near-shore sampling trips with active sampling onto sorbent tube traps above the water surface 

and the microFAST GC provided on-site analysis. Water samples were also collected, as 

previously described, using a subsurface water sampler, at a depth of 5 meters (approximately 16 

feet) below the water surface and the water sparging device. 

Table 3 

Air Sampling Methodology Adjustments 

microFAST GC Adjustments: Initial: Final: 

 Column Temperature Ramp 30°C - 280°C @ 5°C/sec 40°C - 280°C @ 5°C/sec 

 Isothermal Hold Time 30 sec 22 sec 

 Sample Time 45 sec 4 min 

 Trap Desorption Temperature Ramp 40°C - 250°C 40°C - 280°C 

 

Sorbent Tube Trap Adjustments: Initial: Final: 

 Sample Time and Vacuum Pump Flow Rate 10 min @ 100mL/min 

20 min @ 100mL/min 

10 min @ 200mL/min 

20 min @ 200mL/min 

2.6 ESTIMATING NET FLUX OF RVOCS

Mass flux of RVOCs to and from marine surface waters can be appropriately estimated using the 

boundary layer model outlined by Sauer (1980). This model simply predicts the flux of RVOCs 

across the air-water interface as a function of concentration gradient and molecular diffusion. 

Fluxes are determined on the assumption that there is no previous contribution of RVOC from 

the atmosphere. If components are present, flux from the seawater will be reduced due to the 

decrease in concentration difference or gradient. The RVOC flux (F in mol m-2

s

-1) can be 

calculated by using the following equation: 

F = kL (Cw – KHPcmpd), 

where kL (ms-1) represents the liquid phase transfer velocity, Cw is the seawater concentration, 

KH (mol kg -1 atm-1) is the components Henry’s Law constant, and Pcmpd is the partial pressure 

of that specific compound. The liquid phase transfer velocity, kL , is determined by using the 

following equation: 

kL = 2.778 x 10-6(0.31U2

(Sc/660)-1/2), 

where U (ms-1) represents wind velocity and Sc (dimensionless) is the Schmidt number. The 

Schmidt number (v/D) is expressed as the ratio of the transfer coefficient for momentum 

(kinematic viscosity) and mass (molecular diffusivity). 
16 

The diffusion coefficient, D, can be calculated by using a revised Othmer-Thakar equation. The 

diffusion coefficient of sparingly soluble gases, such as NMHCs, from the subsurface seawater 

can be estimated using the expression: 

Dcmvd = (13.26 x 10-5) μ

-1.4 Vm -0.589, 

where μ (cP) represents seawater viscosity and Vm (cm3

mol-1) is the molar volume of the 

individual compound. The diffusion coefficient for the individual compounds were calculated 

using an estimated molar volume in conjunction with expressions (Hayduk and Laudie, 1974) 

relating solution viscosity and molar volume. 

The seawater viscosity (μ , cP) and kinematic viscosity (Vm, cm

2

s

-1) were set at 0.894 and 8.5 x 

10-3, respectively, for all net flux calculations. The average wind speed (U) was recorded at 2.24 

ms

-1 during the Green Canyon field study. 

It is important to point out that accurate flux estimates are extremely difficult to calculate due to 

the large number of variables associated with sources and other contributions to the lifetime of 

reactive compounds in the air shed over marine areas. In fact, one of the primary goals of this 

project was the development of analytical methods that would allow collection of a large number 

of data points for accurate flux measurements. Variability caused by numerous geogenic and 

biogenic sources of RVOCs, as well as sources of NOx, in the Northern GOM can be overcome 

with enough RVOC concentration data points. 
17 

3.0 DATA AND RESULTS 

3.1 TRIP #1: GRAND ISLE, LOUISIANA, AUGUST 2007 

A total of 36 microFAST GC samples and 25 sorbent tube trap samples were analyzed for the 

initial field validation trip to the beach at Grand Isle, Louisiana. Table 4 gives the sampling 

information for Trip #1 and Figure 6 displays the average RVOC concentrations for the 

microFAST GC over the course of the sampling trip. Detailed microFAST GC analytical results 

from this sampling trip are given in Appendix A. 

Table 4 

Sampling Information for Trip #1: Grand Isle, Louisiana 

Average Temperature: 91°F 

Average Humidity: 73% 

Average Wind Speed: 5 mph, S-SE 

Date & Time Start Hours Sampled # of Samples 

08/20/2007, 15:56 3.50 7 microFAST 

5 sorbent tube trap 

08/21/2007, 10:53 1.25 17 microFAST 

5 sorbent tube trap 

08/22/2007, 10:20 1.75 12 microFAST 

9 sorbent tube trap 

08/23/2007, 10:26 1.00 6 sorbent tube trap 
18 

microFAST GC Air Sampling Data

Grand Isle, LA

 August 20-22, 2007

Ethane

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane/Isoprene

Benzene

1-Hexene

Toluene

Xylenes

Avg. Conc. (ppbv)

0

2

4

6

8

10

12

14

16

18

Figure 6. Average RVOC concentrations for on-site microFAST GC air samples, 

 Grand Isle, Louisiana, August 2007. (n=36) 

As shown in the graph, the predominant RVOCs (analytes with a 3-day average at or over the 1.0 

ppbv detection limit) detected by the microFAST GC during the sampling trip to Grand Isle were 

ethane (1.0 ppbv); ethylene (6.4 ppbv); propane (1.5 ppbv); butane (1.1 ppbv); 1-pentene (1.6 

ppbv); and, hexane/isoprene (1.3 ppbv). Hexene was not detected on any of the three days and 

the following were below the detection limit (BDL) of 1.0 ppbv: propylene; 1-butene; pentane; 

benzene; toluene; and the xylenes. 

Figures 7 display the average sorbent tube trap/GC-TOFMS concentrations for each of the four 

days of this first near-shore monitoring trip to Grand Isle. Sampling sessions were the same as 

the microFAST GC sessions previously mentioned except that sorbent tubes were collected one 

additional day, August 23rd, than the microFAST GC due to testing of sample flow rates for the 

sorbent tubes. Detailed sorbent tube trap/GC-TOFMS analytical results for this sampling trip are 

given in Appendix B. 
19 

Sorbent Tube/GC-TOFMS Air Sampling Data

Grand Isle, LA

August 20-23, 2007

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane

Benzene

1-Hexene

Toluene

Ethylbenzene

mp-Xylene

o-Xylene

Avg. Conc. (ppbv)

0

20

40

60

80

100

120

140

Figure 7. Average RVOC concentrations for sorbent tube/GC-TOFMS air samples, 

Grand Isle, Louisiana, August 2007. (n=25) 

The predominant RVOCs, analytes with a 4-day average over the 0.1 ppbv detection limit, 

collected on the sorbent tube traps and detected by GC-TOFMS during the sampling trip to 

Grand Isle were propane (0.83 ppbv); propylene (0.84 ppbv); butane (0.85 ppbv); 1-butene (1.1 

ppbv); pentane (0.78 ppbv); hexane (3.5 ppbv); benzene (0.52 ppbv); 1-hexene (0.14 ppbv); 

toluene (38 ppbv); and ethylbenzene (0.82 ppbv). Ethylene and 1-pentene were not detected 

over the course of 4 days and the xylenes were below detection limits. 

Large variations in RVOC concentrations are very apparent after this first near-shore monitoring 

trip. The reason for this variation is not known but may be due to the fact that there are periodic 

releases of RVOCs from natural oil seeps into the water column and then into the air. 

Furthermore, concentrations of RVOCs are not homogeneous in the water column and therefore, 

will not be homogeneous in the air resulting in “spikes” of RVOCs over the course of a day. 

Spikes of RVOCs were detected throughout the sampling period and since the concentrations 

presented in this report are averaged based on the number of samples, the length of the sampling 

period will affect the number of samples. If the number of samples with no RVOCs increases, 

the RVOC spikes in some of the samples are offset and appear less significant. This variation 

was evident in all the field validation trips. 
20 

3.2 TRIP #2: CAMERON, LOUISIANA, SEPTEMBER 2007 

A total of 29 microFAST GC samples and 20 sorbent tube samples were analyzed for field 

validation trip #2 to Cameron, Louisiana. Table 5 gives the sampling information for Trip #2 

and Figure 8 presents the 2-day averaged microFAST GC concentrations of RVOCs for the 

sampling trip to Cameron, Louisiana. Detailed analytical results for the microFAST GC from 

this trip are given in Appendix A. 

Table 5 

Sampling Information for Trip #2: Near Cameron, Louisiana 

Average Temperature: 91°F 

Average Humidity: 75% 

Average Wind Speed: 3 mph, S-SE 

Date & Time Start Hours Sampled # of Samples 

09/05/2007, 13:46 3.75 12 microFAST 

20 sorbent tube trap 

09/06/2007, 15:04 1.00 17 microFAST 
21 

microFAST GC Air Sampling Data

Cameron, LA

September 5-6, 2007

Ethane

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane/Isoprene

Benzene

1-Hexene

Toluene

Xylenes

Avg. Conc. (ppbv)

0

2

4

6

8

10

Figure 8. Average RVOC concentrations for on-site microFAST GC air samples, 

 Cameron, Louisiana, September 2007. (n=29)

The microFAST GC detected only one RVOC with a 2-day average over 1.0 ppbv at the 

Cameron, Louisiana, sampling site and that was ethylene (2.1 ppbv). Compounds not detected 

were 1-butene, pentane, and 1-hexene. All the other compounds were under the 1.0 ppbv 

detection limit. 

Figure 9 illustrates the average sorbent tube trap/GC-TOFMS RVOC concentrations for the air 

samples collected in Cameron, Louisiana. Sampling sessions were the same as the microFAST 

GC sessions previously mentioned except that sorbent tubes were collected on only one of the 

two days for this field validation trip. Detailed analytical results for the sorbent tube trap/GCTOFMS for Cameron, Louisiana, are given in Appendix B. 
22 

Sorbent Tube/GC-TOFMS Air Sampling Data

Cameron, LA

September 5, 2007

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane

Benzene

1-Hexene

Toluene

Ethylbenzene

mp-Xylene

o-Xylene

Avg. Conc. (ppbv)

0

2

4

6

8

10

12

14

16

18

 Figure 9. Average RVOC concentrations for sorbent tube/GC-TOFMS air samples, 

 Cameron, Louisiana, September 2007. (n=20)

The average concentrations of RVOCs detected at Cameron by sorbent tube trap/GC-TOFMS air 

sampling methodology were propane (0.71 ppbv); propylene (0.73 ppbv); butane (0.53 ppbv); 1-

butene (2.1 ppbv); pentane (0.20 ppbv); hexane (1.3 ppbv); benzene (0.38 ppbv); 1-hexene (0.21 

ppbv); toluene (7.1 ppbv); ethylbenzene (0.11 ppbv); and m+p-xylene (0.15 ppbv). O-xylene 

was below the 0.1 ppbv detection limit; and, ethylene and 1-pentene were not detected in the 

samples collected on September 5th. 

3.3 TRIP #3: PORT FOURCHON, LOUISIANA, SEPTEMBER 2007 

A total of 7 microFAST GC samples and 24 sorbent tube samples were analyzed for field 

validation of trip #3 to Port Fourchon, Louisiana. Trip #3 to Port Fourchon was a day trip 

designed to test the finalized methodologies for the sorbent tubes and the microFAST GC. A 

multiday trip back to Port Fourchon would follow this initial day trip. Table 6 gives the 

sampling information for Trip #3 and Figure 10 displays the average RVOC concentrations in 

the ambient air detected with the on-site microFAST GC. Unfortunately, on this sampling trip, 

the microFAST GC had a malfunction that could not be resolved in the field and had to be 

returned to lab for troubleshooting and correction. As a result, only seven microFAST GC 
23 

samples were collected. Again, detailed microFAST GC analytical results for this trip are given 

in Appendix A. 

Table 6 

Sampling Information for Trip #3: Port Fourchon, Louisiana 

Average Temperature: 83°F 

Average Humidity: 72% 

Average Wind Speed: 6 mph, SE 

Date & Time Start Hours Sampled # of Samples 

09/17/2009, 10:58 6.25 7 microFAST 

24 sorbent tube 

microFAST GC Air Sampling Data

Port Fourchon, LA

September 17, 2007

Ethane

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane/Isoprene

Benzene

1-Hexene

Toluene

Xylenes

Avg. Conc. (ppbv)

0

2

4

6

8

10

12

14

 Figure 10. Average RVOC concentrations for on-site microFAST GC air samples, 

 Port Fourchon, Louisiana, September 2007. (n=7)
24 

The following RVOCs detected at Port Fourchon by the microFAST GC had averages over the 

1.0 ppbv detection limit: ethylene (2.4 ppbv); butane (11 ppbv); 1-butene (6.5 ppbv); and, 

hexane/isoprene (7.7 ppbv). Ethane, propane, propylene, benzene, toluene, and the xylenes were 

below the detection limit; and, pentane, 1-pentene, and 1-hexene were not detected during the 

course of the sampling period. 

 

Figure 11 illustrates the average sorbent tube trap/GC-TOFMS RVOC concentrations for the air 

samples collected during the day trip to Port Fourchon. Detailed sorbent tube trap/GC-TOFMS 

analytical results are given in Appendix B. 

Sorbent Tube/GC-TOFMS Air Sampling Data

Port Fourchon, LA

September 17, 2007

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane

Benzene

1-Hexene

Toluene

Ethylbenzene

mp-Xylene

o-Xylene

Avg. Conc. (ppbv)

0

1

2

3

4

 Figure 11. Average RVOC concentrations for sorbent tube/GC-TOFMS air samples, 

Port Fourchon, Louisiana, September 2007. (n=24)

Average RVOC concentrations detected at or above the 0.1 ppbv detection limit of the GCTOFMS were: propane (0.20 ppbv); propylene (0.22 ppbv); butane (0.29 ppbv); 1-butene (1.4 

ppbv); pentane (0.32 ppbv); 1-pentene (0.55 ppbv); hexane (0.57 ppbv); benzene (0.10 ppbv); 

and, 1-hexene (0.44 ppbv). Toluene was below the detection limits; and ethylene, ethylbenzene, 

and the xylenes were not detected during this sampling trip. 
25 

3.4 TRIP #4: PORT FOURCHON, LOUISIANA, OCTOBER 2007 

A total of 112 microFAST GC samples were analyzed for field validation trip #4 to Port 

Fourchon, Louisiana. Sorbent tube trap samples were not performed on this sampling trip 

because the tubes were being reconditioned from the previous sampling trip to Port Fourchon on 

September 17th. This repeat trip to Port Fourchon was in addition to the day trip to Port 

Fourchon. By this point in the project, the sampling and analysis protocols were firmly 

established and no modifications in procedures were required. Table 7 gives the sampling 

information for Trip #4 and Figure 12 shows the 4-day averaged RVOC concentrations detected 

by the on-site microFAST GC. Detailed microFAST GC analytical results for this 4-day 

sampling trip are given in Appendix A. 

Table 7 

Sampling Information for Trip #4: Port Fourchon, Louisiana 

Average Temperature: 81°F 

Average Humidity: 73% 

Average Wind Speed: 9 mph, S-SE 

Date & Time Start Hours Sampled # of Samples 

10/01/2007, 10:18 10.25 38 microFAST 

10/02/2007, 09:00 8.00 25 microFAST 

10/03/2007, 11:00 12.75 41 microFAST 

10/04/2007, 07:45 2.25 8 microFAST 
26 

microFAST GC Air Sampling Data

Port Fourchon, LA

October 1-4, 2007

Ethane

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane/Isoprene

Benzene

1-Hexene

Toluene

Xylenes

Avg. Conc. (ppbv)

0

1

2

3

Figure 12. Average RVOC concentrations for on-site microFAST GC air samples, 

 Port Fourchon, Louisiana, October 2007. (n=112) 

The xylenes were the only RVOCs with 4-day average concentrations over 1.0 ppbv. Analytes 

below the detection limit include ethane, ethylene, propane, propylene, butane, 1-butene, 

pentane, 1-pentene, hexane/isoprene, benzene, and toluene. Over the course of four days at Port 

Fourchon, 1-hexene was not detected. 

3.5 TRIP #5: GREEN CANYON, GOM, JUNE 2008 

A total of 23 microFAST GC samples and 28 sorbent tube trap samples (22 air and 6 water) were 

analyzed for field validation trip #5 to Green Canyon, about 80 miles south of Port Fourchon in 

the Northern GOM. Table 8 gives the sampling information for trip #5 and Figure 13 illustrates 

the average microFAST GC RVOC concentrations for the one day sampling trip to Green 

Canyon. Detailed microFAST GC analytical results are given in Appendix A. 
27 

Table 8 

Sampling Information for Trip #5: Green Canyon, GOM 

Average Temperature: 88°F 

Average Humidity: 75% 

Average Wind Speed: 5 mph, S 

Date & Time Start Hours Sampled # of Samples 

 06/09/2008, 18:23 6.5 

23 microFAST 

32 sorbent tube trap: 

 22 air 

 6 water 

 4 SVOC

microFAST GC Air Sampling Data

Green Canyon, GOM

June 9, 2008

Ethane

Ethylene

Propane

Propylene

Butane

1-Butene

Pentane

1-Pentene

Hexane/Isoprene

Benzene

1-Hexene

Toluene

Xylenes

Avg. Conc. (ppbv)

0

5

10

15

20

25

30

 Figure 13. Average RVOC concentrations for on-site microFAST GC air samples, 

Green Canyon, GOM, June 2008. (n=23) 
28 

The RVOCs detected by the microFAST GC were hexane/isoprene (10 ppbv average), benzene 

(7.2 ppbv average), toluene (16 ppbv average), and the xylenes (8.4 ppbv average). All the other 

RVOCs were not detected by the microFAST GC during the course of the sampling period. 

Figure 14 displays the average RVOC concentrations in air collected on the sorbent tube traps 

and analyzed by GC-TOFMS from Green Canyon. Air samples were collected from 18:23 to 

00:55 for the Green Canyon sampling trip. 

Sorbent Tube/GC-TOFMS Air Sampling Data

Green Canyon, GOM

June 9, 2008

Ethylene

Acetylene

Propane

Propylene

isoButane

Butane

1-Butene

Pentane

1-Pentene

Isoprene

Hexane

Benzene

Toluene

Ethylbenzene

mp-Xylene

o-Xylene

Avg. Conc. (ppbv)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Figure 14. Average RVOC concentrations for sorbent tube/GC-TOFMS air samples, 

 Green Canyon, GOM, June 2008. (n=22) 

RVOCs detected in the sorbent tube trap/GC-TOFMS air samples were: 1-pentene (0.10 ppbv 

average); toluene (0.32 ppbv average); ethylbenzene (0.28 ppbv average); m+p-xylenes (0.28 

ppbv average); and, o-xylene (0.37 ppbv average). RVOCs under the 0.1 ppbv detection limit 

were ethylene, acetylene, propane, propylene, iso-butane, butane, 1-butene, and benzene. 

Pentane, isoprene, and hexane were not detected in any of the air samples collected during this 

sampling trip. 

Figure 15 shows the average RVOC concentrations, pmol/L, in the purged water samples 

collected on the sorbent tube traps and analyzed by GC-TOFMS from Green Canyon. Water 
29 

samples were collected at 18:23, 20:55, 21:45, and 23:01. The concentrations of RVOCs over 

the course of this sampling trip in the water samples are given in Appendix C. 

Sorbent Tube/GC-TOFMS Water Sampling Data

Green Canyon, GOM

June 9, 2008

Ethylene

Acetylene

Propane

Propylene

isoButane

Butane

1-Butene

Pentane

1-Pentene

Isoprene

Hexane

Benzene

Toluene

Ethylbenzene

mp-Xylene

o-Xylene

Avg. Conc. (pmol/L)

0

2000

4000

6000

8000

 Figure 15. Average RVOC concentrations for sorbent tube/GC-TOFMS water 

 samples, Green Canyon, GOM, June 2008. (n=8)

The majority of the target RVOCs were detected in the purged water samples using the sorbent 

tube trap/GC-TOFMS methodology. Hexane was detected in one of the sorbent tubes, but the 

average hexane concentration was below the detection limit of 100 pmol/L. Pentane and 1-

pentene were not detected in the water samples throughout the course of this sampling trip. 

Differences between the number of analytes detected in the air versus (5 out of 16 RVOCs) the 

water (12 out of 16 RVOCs) can be attributed to slight changes in wind velocities or directions. 

The air concentration of 1-pentene is right at the detection limits of the sorbent tube/GC-TOFMS 

detection limit and has a high standard deviation which may explain why 1-pentene was not 

detected in the water. Many of the RVOCs detected in the water samples were detected in the air 

samples but the air concentrations when averaged were below the detection limit. 

It should be noted that the analyte list for the GC-TOFMS methodology is slightly different than 

all the previous field validation trips. This is a result of a new standard mixture that was ordered 

prior to this sampling trip to Green Canyon. The new standard was a premixed “ozone 
30 

precursors” gas mixture prepared by the vendor. None of the target analytes were excluded from 

the standard; but, the standard did include a few additional air quality analytes like acetylene, 

iso-butane, and isoprene. A new standard was necessary due to the lapse in time between the last 

field validation trip in October of 2007 and the trip to Green Canyon in June of 2008. 

 

As previously stated in the methodology section, four sorbent tubes were qualitatively analyzed 

for semivolatile organic compounds (SVOCs). Two water samples and two air samples were 

randomly selected and analyzed using thermal desorption and GC/MS scanning methodology 

with library confirmation to get an idea of what other compounds were in each matrix sampled. 

These analyses were purely lagniappe. Some of the SVOCs present in the samples are listed in 

Table 9, in no particular order, for the air and water samples. 

Table 9 

SVOC Qualitative Results for Select Air and Water 

Sorbent Tube Trap Samples from Green Canyon 

SVOCs RESULTS 

Air Samples: 

(Tube S/N#: A4595 & A4570)

Water Samples: 

(Tube S/N#: A4614 & A5574)

Hexanal Nonanal 

Octanal Decanal 

Nonanal Hexadecane 

Decanal Heptadecane 

 Butylated Hydroxytoluene 

 1-Chloroundecane 

 1-Chlorododecane 

3.6 NET FLUX OF RVOCS AT AIR-WATER INTERFACE

Net flux estimations of the target RVOCs were determined for air and water samples collected 

during the Green Canyon, GOM field validation trip on June 9, 2008. Net flux estimations 

generated from data having large standard error typically produces results which are generalized 

and not site specific. Table 10 presents an estimation of concentrations of the project target 

analytes in marine air and seawater in the Green Canyon area of the Northern GOM. As 

previously stated in the field validation section of this report (2.5), water samples were only 

collected during the one off-shore field validation trip to Green Canyon. Concentrations of 

atmospheric RVOCs ranged from an average of 0.10 to 0.34 ppbv ± 0.13. Several of the RVOC 

compounds were not detected. The average seawater concentrations ranged from non-detect to 

3500 pmol/L. 

The calculated average fluxes for samples taken in the Northern Gulf of Mexico are displayed in 

Table 11. The flux ranged from 20 nmol m-2 day-1 for isobutene to 1000 nmol m-2 day-1 for oxylene, assuming the concentration of the individual components in the marine atmosphere were 

zero. 
31 

Table 10

RVOC Concentrations in Marine Air and Seawater from Green Canyon, Northern GOM 

Compound MW 

(g mol-1) 

Henry’s Law Constant, KH

(mol kg-1 atm-1) 

Air 

(ppbv) 

Seawater 

(pmol l-1) 

Ethylene 28 2.28E-01 bdl 1900 

Acetylene 26 4.00E-02 bdl 2000 

Propane 44 1.40E-03 bdl 1100 

Propylene 42 4.80E-03 bdl 2000 

isoButane 58 8.40E-04 bdl 580 

Butane 58 1.10E-03 bdl 300 

1-Butene 56 4.00E-04 bdl 590 

Pentane 72 7.80E-04 nd nd 

1-Pentene 70 2.50E-03 0.10 nd 

Isoprene 68 2.70E-02 nd 210 

Hexane 86 7.60E-04 nd bdl 

Benzene 78 1.80E-01 bdl 1300 

Toluene 92 1.60E-01 0.32 3500 

Ethylbenzene 106 1.20E-01 0.28 1500 

m+p-Xylene 106 1.50E-01 0.28 2100 

o-Xylene 106 1.90E-01 0.37 2600 

bdl = below detection limit nd = non-detect 

Table 11 

Estimation of RVOC Flux from Green Canyon, Northern GOM 

Compound 

Molar 

Volume, 

Vm 

(cm3 mol-1) 

Diffusion 

Coefficient, D 

(cm2

 s-1) 

Schmidt 

Number, Sc 

(dimensionless) 

Liquid Phase 

Transfer 

Velocity, kL

(m s-1) 

Flux 

(nmol m-2

day-1) 

Ethylene 41 1.7E-05 4.9E+02 5.0E-06 - 

Acetylene 41 1.7E-05 4.9E+02 5.0E-06 - 

Propane 66 1.3E-05 6.4E+02 4.4E-06 - 

Propylene 62 1.4E-05 6.2E+02 4.5E-06 - 

isoButane 86 1.1E-05 7.6E+02 4.0E-06 - 

Butane 86 1.1E-05 7.6E+02 4.0E-06 - 

1-Butene 82 1.2E-05 7.3E+02 4.1E-06 - 

Pentane 107 9.9E-06 8.6E+02 3.8E-06 - 

1-Pentene 103 1.0E-05 8.4E+02 3.8E-06 - 

Isoprene 99 1.0E-05 8.2E+02 3.9E-06 90 

Hexane 127 8.9E-06 9.5E+02 3.6E-06 - 

Benzene 91 1.1E-05 7.8E+02 4.0E-06 - 

Toluene 111 9.7E-06 8.8E+02 3.7E-06 1100 

Ethylbenzene 132 8.8E-06 9.7E+02 3.6E-06 450 

m+p-Xylene 132 8.8E-06 9.7E+02 3.6E-06 640 

o-Xylene 132 8.8E-06 9.7E+02 3.6E-06 770 
32 

Values that were looked up for the flux calculations include the molecular weight of the analytes 

and the Henry’s Law constants (KH). The air and seawater concentrations were taken from the 

Green Canyon sampling trip data. The Schmidt number, liquid phase transfer velocity and flux 

were calculated using the molar volume and diffusion coefficient values given in Hayduk and 

Laudi (1974). 
33 

4.0 DISCUSSION 

The main goal of this project was to develop and evaluate analytical methodology that could be 

used to estimate geogenic and biogenic sources of RVOCs coming from OCS areas of the 

Northern Gulf of Mexico. The process of accurately estimating OCS flux is extremely difficult 

since the water area is so large, and the possible natural sources are so variable (seeps, algal 

blooms, geogenic emissions, etc). Our secondary object focused on developing quantitative 

analytical capability to collect and analyze a large number of air and water samples across 

typical GOM areas during a variety of meteorological conditions. In order for this to be feasible, 

we also wanted to use readily accessible sampling platforms such as small fishing vessels rather 

than the large and expensive offshore research vessels. Therefore, much of the project focused 

on a twofold approach of using on-site analytical instrumentation for analysis of the primary 

RVOCs backed up with collection of concurrent samples in absorbent traps followed by GCTOFMS analysis done in a conventional laboratory setting. 

The microFAST GC data from five field validation trips shows that ethylene and 

hexane/isoprene dominated the RVOC profile due to the fact that these RVOCs were detected at 

three out of five field validation trips. Furthermore, the majority of the targeted RVOCs were 

detected above the detection limits at least one time out of five field validation sampling trips. 

The exceptions were propylene, pentane, and 1-hexene; these RVOCs were not detected above 

the detection limit at any of the five sampling locations. Butane was detected at two of the five 

validation trips; and, ethane, propane, 1-butene, 1-pentene, benzene, toluene, and the xylenes 

were detected at one of the five sampling locations. Ambient air samples taken by the on-site 

microFAST GC during the off-shore sampling trip to Green Canyon was dominated by 

hexane/isoprene and the alkyl benzenes. 

The sorbent tube trap/GC-TOFMS data from four field validation trips also shows that almost all 

the targeted RVOCs were detected, above detection limits, at each sampling event. Propane, 

propylene, butane, 1-butene, pentane, hexane, benzene, 1-hexene, toluene, and ethylbenzene 

were detected at three out of four sampling events. 1-pentene and m+p-xylenes were detected at 

two of four sampling events, and o-xylene was detected during one sampling event. Ambient air 

samples collected on the sorbent tube traps during the off-shore sampling trip to Green Canyon 

were also dominated by the alkyl benzenes. The purged water samples contained all the targeted 

RVOCs except pentane and 1-pentene. The average hexane concentrations in the purged water 

sample were below the detection limits of 100 pmol/L. Of the targeted RVOCs for the off-shore 

sampling trip to Green Canyon, the ambient air and water samples were mutually dominated by 

alkyl benzenes. 

The alkyl benzenes (benzene, toluene, ethylbenzene, m+p-xylenes, and o-xylenes, or BTEX) 

were detected at two of the five sampling trips by the on-site microFAST GC and four of the four 

sorbent tube sampling trips. BTEX can be indicative of fossil fuel combustion exhaust and other 

anthropogenic sources. On the other hand, BTEX compounds can be indicative of petrogenic 

sources and since they were detected in the air and in the water 80 miles offshore in the Green 

Canyon area of the Gulf, a well known seep area (Beukelaer et al. 2003; Kennicutt et al. 1988; 

MacDonald et al. 2002; Mitchell et al. 1999) they may have originated from natural petroleum or 

gas seeps. 
34 

Ethylene (ethene) and isoprene are two of the RVOCs detected by either the microFAST GC or 

the sorbent tube traps that have biogenic sources. Ethylene and isoprene are two of the more 

reactive RVOCs studied in this project. Ethylene is a metabolic product of microorganisms; 

plays a role in plant growth and development; and can be produced by plants under stress 

(Riemer et al 2000; Broadgate et al. 2004). Ethylene could also be formed from anaerobic 

reductions of petrogenic ethane by microorganisms. Ethylene is not a compound found in oil; 

however, detection of ethylene gas can indicate the presence of petroleum near fault lines 

(Carney et al. 1996; Jones and Burtell 1996; Jones et al. 2000). Isoprene stems from 

photosynthetic organisms in the ocean such as phytoplankton and several species of seaweed 

(Broadgate et al. 2004; Buzcu and Fraser 2006; Derwent 1999). Isoprene is species, temperature, 

and light dependent (Broadgate et al. 2004; Hagerman et al. 1997). The Green Canyon field 

validation cruise was performed in the evening (sampling started at 6:30 pm) so that the 

contribution of biogenic RVOCs (e.g. isoprene) would be lower than RVOCs that were 

emanating from the natural seeps in the area. Isoprene was detected with the sorbent tubes and 

the microFAST GC; however, the concentration decreased as the evening progressed. 

It is important to point out that the microFAST GC was configured to be more sensitive for the 

detection of the very light RVOC compounds, like ethane and ethylene, and was less sensitive to 

the larger RVOC compounds like BTEX. Hexane and isoprene co-eluted in the microFAST GC 

system as did the xylenes. Conversely, the sorbent tube/GC-TOFMS system could resolve 

hexane and isoprene and the xylenes into the m+p-xylene and o-xylene. The sorbent tube/GCTOFMS system could not detect ethane most likely due to ethane breakthrough when collecting 

the air samples on the sorbent tubes. 

The primary focus for the on-site and sorbent tube trap analyses was the detection of RVOCs. 

However, two sorbent tube traps from air sampling and two sorbent tube traps from the purging 

of water samples in the Green Canyon sampling area were analyzed for SVOCs (semi-volatile) 

in addition to the RVOC (volatile) targets. These analyses were done in scan mode (qualitative) 

on a GC/MS system to check for unexpected compounds that could have an impact on air quality 

or that could be used to determine the source of possible volatile organic compounds (such as 

petroleum contamination). Both water samples contained very low levels of a number of 

compounds that appeared to be of biogenic origin or from very low level contamination with 

food additive/skin care products (in spite of extreme efforts to prevent contamination from the 

handling of water samples during collection and sparging). There was no evidence in the two 

water samples of any of the semivolatile components commonly found in petroleum. Likewise, 

the two air samples analyzed for semivolatile compounds contained a number of straight chain 

aldehydes from C7 to C10 at very low concentrations. There was no evidence of any petroleum 

compounds in these two air samples. 

The variability in the analytical results of this study is related to two things: a non-homogeneous 

mixture of RVOCs moving through the water column and into the air; and, the reactivity of the 

target RVOC compounds with hydroxyl radicals, NOx, and ozone. The fact that some RVOCs 

were detected in spikes at some point during each sampling trip indicates that the instrumentation 

was working correctly and that the variation was a naturally occurring event. This may be 

attributed to the fact that RVOCs are not homogenously dispersed in the water column which 
35 

results in a non-homogenous mixture in the air, or “patchiness”. Patches of RVOCs were 

detected at different times throughout the sampling periods but these patches were often 

averaged out especially if a large number of samples were collected for that day, resulting in 

averages that were below the detection limit. RVOCs such as ethylene, propylene, and isoprene 

are short-lived because they are more reactive compounds. Their concentrations may be low; 

however, due to their reactivities these compounds are very important in terms of the production 

of low-level ozone (Bonsang and Lambert 1985; Bonsang et al. 1988; Bonsang and Boissard 

1999; Derwent 1999; Sillman 1999). This is not to say that the other target analytes of this study 

are not important; they just have lower reaction potentials. Saturated alkanes (e.g. ethane, 

propane) are generally detected at higher concentrations compared to alkenes due to lower 

reaction potentials (Carter 1994). The light alkanes are associated with geogenic sources of 

petroleum. Higher saturated alkane concentrations can translate into air quality problems when 

they reach NOx rich urban environments. The longer-lived RVOCs emitted from the sea surface 

typically are not directly photolyzed by solar radiation in the lower troposphere often due to the 

fact that NOx concentrations are limited in remote areas compared to urban NOx concentrations. 

Ozone increases with increasing RVOC concentrations in a NOx saturated environment; 

therefore, RVOCs with lower reaction potentials represent a tropospheric ozone forming 

potential that can be realized when they are transported to an environment containing higher 

levels of NOx (Sillman 1999). 

The data from this project is comparable to the numerous other research projects cited in this 

report and is evidence of the importance of RVOCs from marine environments. This project, 

along with similarly related projects, shows that the ultimate impact on nearby urban areas is 

likely a function of not only the quantity of RVOCs emitted into the atmosphere, but also by 

their composition. The detection of the various alkyl benzenes, especially toluene and the 

xylenes, and the highly reactive olefins, ethylene, propylene, and isoprene, was anticipated prior 

to project method development. As a result, the analytical methodologies and instrumentation 

was optimized for a full range of RVOCs. All of these RVOCs were detected at one point or 

another during the field validation trips. Since the majority of the field validation trips were 

near-shore monitoring, it is tricky to deduce marine source RVOCs from anthropogenic and 

continental sources of RVOCs. Every effort was made to make sure wind directions were 

optimum for detecting RVOCs coming from the GOM; however, wind directions and speeds can 

briefly change which could result in plumes from sources other than the GOM. 

If RVOCs are assumed to be in equilibrium between the seawater and the air boundary layer 

above it, their concentration in the seawater should be equivalent to the product of Henry’s Law 

constant (Table 10) and the partial pressure of the specific compound in the atmosphere. The 

average products (Pcmpd x KH) for the individual RVOCs within the seawater exceeded the 

equilibrium product concentrations, indicating a net flux of RVOCs from the seawater into the 

atmosphere. Results from the Green Canyon sampling trip in the Northern GOM indicate the 

flux between the seawater and air boundary layers are comparable to those of previous studies 

(Marse and Tsoflias 2001, Milne et al. 1995, and Sauer 1980). The aromatic RVOCs (e.g. BTEX 

range) were 2-3 times higher than anticipated, but may have been influenced by elevated levels 

of observed vessel traffic near the sampling transect. Atmospheric RVOC concentrations cannot 

be fully explained by the flux from naturally-occurring biogenic sources (e.g. marine organisms 

and oil seeps) within the seawaters of the Northern Gulf of Mexico. Therefore, the 
36 

concentrations of RVOCs in the marine atmosphere are more than likely affected by 

anthropogenic sources (e.g. marine transport) and subsequent long-range transport of RVOC 

compounds. 

Analytical results of the air and water samples from the Green Canyon sampling trip indicated a 

large standard deviation among the individual gas components. The large standard deviation 

implies a wide, naturally occurring RVOC distribution throughout the sampling area, but actual 

analyses indicate localization of some individual components within the Northern GOM. Given 

both biogenic and anthropogenic source contributions for the individual compounds and the 

patchiness of detectable quantities, extrapolation of these few flux rates to give estimates of 

Northern GOM marine RVOC inputs to the atmosphere requires further investigation. 
37 

5.0 CONCLUSIONS AND RECOMMENDATIONS 

Information regarding the impact of marine RVOCs has benefited over the last several years 

from an increase in field and laboratory research and air quality databases. However, even with 

an increase in research regarding marine RVOCs, it is still difficult to concisely estimate their 

impact. In general, this project proved to be much more difficult than originally anticipated, and 

was much more expensive to implement. On the other hand, this project demonstrates the ability 

to detect low part per billion levels of RVOCs, from compounds as volatile as ethane and 

ethylene to the less volatile BTEX compounds, with a relatively large number of both on-site 

analyses as well as conventional laboratory-based analyses. Furthermore, it demonstrates the 

capacity of analyzing a relatively large number of air and water samples that are needed to 

accurately estimate flux from the OCS area. The results of this study show that the day-to-day 

variations in RVOC concentrations are quite large, which emphasizes the importance of nonhomogeneous mixtures of RVOCs being released from the surface waters resulting in localized 

plumes of RVOCs from the GOM in addition to the individual reactivity of each RVOC species. 

In conclusion, this project has established three overall concepts: 

1.) The analytical methodology used for this project produced comparable data to 

other similar research cited in this report. The analytical methodologies and 

instrumentation used for this project are relatively cost-effective in 

comparison to using more complex sampling strategies (e.g. collection of air 

samples by airplane). This project demonstrates the ability to readily go into 

the field with sophisticated quantitative analytical equipment and perform onsite analyses of RVOCs at low part per billion levels. The on-site analyses 

were confirmed by conventional laboratory-based analytical methods and in 

general, there was good agreement between field analytical results and those 

produced in the laboratory. An important lesson learned in the process of 

doing field analyses was the need to have a suitable sampling platform that 

adequately protects the field equipment from salt water and the other offshore 

elements. For the offshore sampling expeditions (e.g. Green Canyon), the 

sampling platform must be stable and protective enough for both the staff and 

equipment, as well as being free of contamination from engine exhaust. 

Perhaps the use of suitable offshore production platforms as stable sampling 

locations should be considered in future analytical efforts. 

2.) There is a need for standardized, cost-effective air and water monitoring for 

RVOCs from the GOM. This would require a multi-agency and industry 

effort to accomplish a true estimation of RVOC inputs from the GOM. As 

always, the cost of such a large effort is problematic. The literature has 

numerous examples of research cruises that use on-board laboratories for 

detecting organic compounds in vast ocean areas around the world. However, 

these cruises are very expensive and, in general, result in collection of a 

relatively small number of samples and resulting data points. This sparse data 

is then extrapolated over entire ocean areas. While this process may work to 

give a global overview of inputs of naturally produced RVOCs, it is difficult 
38 

to directly correlate this information for estimating regional impact of OCS 

activities on urban ozone formation in Texas and Louisiana. Furthermore, 

many different detection techniques are utilized in the literature making it 

hard to determine which methodology is the best for the cost. The monitoring 

approach of this project is very cost effective relative to the use of a large 

research vessel collecting a relatively few samples at a very expensive total 

expedition cost. In an effort to truly characterize RVOC flux from the GOM, 

consideration should be given to the use of strategically placed monitoring 

instrumentation on fixed offshore structures such as oil platforms and the use 

of field analytical instrumentation in small movable sampling vessels for 

monitoring known oil and natural gas seeps in the GOM. The same field 

analytical instrumentation could be used for near-shore monitoring to 

determine what RVOCs are reaching land from the GOM to correlate the 

platform monitoring and small vessel monitoring to air quality problems in 

urban coastal areas. A multi-agency effort and industry cooperation would 

greatly enhance confidence in the analytical results, decrease assumptions and 

large uncertainties inherent in RVOC modeling efforts, and would allow for 

an extensive monitoring network. 

3.) Estimating RVOC flux from the GOM requires a very large number of air and 

water samples and instrumentation with very low detection limits. RVOC 

flux was calculated for only six water samples which clearly is not enough 

samples for the size of the GOM. However, the dual instrument sampling 

strategy of this project could easily result in a sufficient sample number for 

estimating flux. This project uses a field gas chromatograph, the microFAST 

GC, equipped with dual columns and dual flame ionization detector as the 

primary analytical device for on-site RVOC analyses in conjunction with 

concurrent, conformational samples that are trapped on sorbent tubes and 

returned to the laboratory for GC-TOFMS analyses. The microFAST GC has 

detection limits in the low part per billion levels but was subject to 

instrumental drift near the limits of detection. This drift was further 

complicated by operation in a field environment that is not controlled in terms 

of temperature, humidity, power, and operational utilities. Optimum control 

conditions are only available in laboratory settings. The GC-TOFMS has 

RVOC detection limits in the low part per trillion levels; however, loss of 

some of the RVOCs during the time after collection up to GC-TOFMS 

analysis occurs regardless of proper sample handling and storage 

requirements. In general, estimating RVOC flux is very complex, not only in 

terms of low RVOC detection limits and a large sample size, but in terms of 

determining the effect of water column mixing and upwells on RVOCs from 

the GOM. 
39 

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atmosphere. Marine Chemistry 88:61-73. 

Buzcu, B. and M.P. Fraser. 2006. Source identification and apportionment of volatile organic 

compounds in Houston, TX. Atmospheric Environment 40:2385-2400. 

Carney, K.R., G. Hunt, N.J. Roques, and E.B. Overton. 1996. Simultaneous one minute field 

analysis of hydrogen, helium, methane, ethane and carbon dioxide in soil gas samples. 

Chicago, IL: PittCon. 

Carter, W.P.L. 1994. Development of ozone reactivity scales for volatile organic compounds. 

Journal of Air & Waste Management Association 44:881-899. 

Chameides, W.L. and E.B. Cowling, eds. 1995. The state of the southern oxidants study: 

Policy-relevant findings in ozone pollution research 1988 to 1994. Raleigh, NC: North 

Carolina State University. 

Dawson, J.P, P.J. Adams, and S.N. Pandis. 2007. Sensitivity of ozone to summertime climate in 

the eastern USA: A modeling case study. Atmospheric Environment 41:1494-1511. 

Derwent, R.G. 1999. Reactive hydrocarbons and photochemical air pollution. In: C.N. Hewitt, 

ed., Reactive hydrocarbons in the atmosphere. Chapter 7. San Diego, CA/London, UK: 

Academic Press. 
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Fall, R., T.G. Custer, S. Kato, and V.M. Bierbaum. 2001. New directions: The biogenic 

acetone-HCN connection. Atmospheric Environment 35:1713-1714. 

Greenberg, J.P. and P.R. Zimmerman. 1984. Non-methane hydrocarbons in remote tropical, 

continental, and marine atmospheres. Journal of Geophysical Research 89:4767-4778. 

Hagerman, L.M., V.P. Aneja, and W.A. Lonneman. 1997. Characterization of non-methane 

hydrocarbons in the rural southeast United States. Atmospheric Environment 31:4017-4038. 

Hayduk, W. and H. Laudie. 1974. Prediction of diffusion coefficients for non-electrolytes in 

dilute aqueous solutions. American Institute of Chemical Engineers Journal 20:611-615. 

Jones, V.T and S.G. Burtell. 1996. Hydrocarbon flux variations in natural and anthropogenic 

seeps. In: D. Schumacher and M.A. Abrams, eds., Hydrocarbon migration and its nearsurface expression. AAPG Memoir 66:203-221. 

Jones, V.T., M.D. Matthews, and D.M. Richers. 2000. Light hydrocarbons for petroleum and 

gas prospecting. In: G.J.S. Govett, ed., Handbook of exploration geochemistry, 7:133-212. 

Kennicutt, M.C., J.M. Brooks, and G.J. Denoux. 1988. Leakage of deep, reservoired petroleum 

to the near surface on the gulf of Mexico Continental slope. Marine Chemistry 24:39-59. 

MacDonald, I.R., I. Leifer, R. Sassen, P. Stine, R. Mitchell, and N. Guinasso, Jr. 2002. Transfer 

of hydrocarbons from natural seeps to the water column and atmosphere. Geofluids 2:95-

107. 

Manahan, S.E. 1994. Environmental chemistry, 6th ed. Boca Raton, FL: CRC Press, Inc. 

Marse, T.J. and S.L. Tsoflias. 2001. Geogenic inputs to the northern Gulf of Mexico airshed. 

Denver, CO: EPA Emissions Inventory Conference 

Milne, P.J., D.D. Riemer, R.G. Zika, and L.E. Brand. 1995. Measurement of vertical 

distribution of isoprene in surface seawater, its chemical fate, and its emission from several 

phytoplankton monocultures. Marine Chemistry 48:237-244. 

Mitchell, R, I.R. MacDonald, and K.K. Kvenvolden. 1999. Estimates of total hydrocarbon 

seepage into the Gulf of Mexico based on satellite remote sensing images. San Antonio, TX: 

Ocean Sciences Meeting. 

Molecke, M.A, K.R. Carney, and W.J. Autin. 1996. Near surface gas mapping studies of salt 

geologic features at Weeks Island and other sites. Sandia Technical Report, SAND96-2502, 

Sandia National Laboratories, Albuquerque, NM. 

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hydrocarbons at remote continental and oceanic locations using photoionization/flameionization detection. Journal of Atmospheric Chemistry 2:415-433. 
41 

Plass-Duelmer, C., R. Koppmann, M. Ratte, and J. Rudolph. 1995. Light nonmethane 

hydrocarbons in seawater. Global Biogeochemical Cycles 9:79-100. 

Riemer, D.D., P.J. Milne, R.G. Zika, and W.H. Pos. 2000. Photoproduction of nonmethane 

hydrocarbons (NMHCs) in seawater. Marine Chemistry 71:177-198. 

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Sea. Limnology and Oceanography 25:338-351. 

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marine bacterium, and other phytoplankton. Marine Chemistry 80:227-245. 

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rural environments. Atmospheric Environment 33:1821-1845. 

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Determination of volatile organic compounds in ambient air using active sampling onto 

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determination of toxic organic compounds in ambient air, 2nd ed. U.S. Environmental 

Protection Agency. 

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and P. Ridgeon. 2004. Two high-speed, portable GC systems designed for the measurement 

of non-methane hydrocarbons and PAN: Results from the Jungfraujoch High Altitude 

Observatory. Journal of Environmental Monitoring 6:234-241. 
43 

APPENDIX A: 

MICROFAST GC 

AIR SAMPLE DATA TABLES
45 

Grand Isle, Louisiana 

August 20-22, 2007 

8/20/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

070820‐004 nd 33 12 4.6 4.0 nd nd nd nd bdl nd bdl bdl

070820‐005 nd nd 7.9 bdl 2.2 3.3 4.4 nd nd bdl nd bdl bdl

070820‐006 9.6 34 5.4 3.1 4.7 4.8 nd nd 11 bdl nd bdl bdl

070820‐007 nd nd 4.5 1.4 3.1 nd nd nd 9.5 bdl nd bdl bdl

070820‐008 nd 22 3.4 bdl 3.5 nd nd nd 6.1 bdl nd bdl bdl

070820‐009 nd 36 6.6 2.4 4.3 nd 4.6 nd 7.5 bdl nd bdl bdl

070820‐010 nd nd 2.8 bdl 2.9 nd nd nd 12 bdl nd bdl bdl

8/21/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

070821‐004 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070821‐005 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070821‐006 nd nd 1.7 nd 3.4 nd nd 3.6 nd bdl nd bdl bdl

070821‐007 nd 9.9 1.1 nd 1.9 nd nd nd nd bdl nd bdl bdl

070821‐008 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070821‐009 nd nd nd nd nd nd nd 3.8 nd bdl nd bdl bdl

070821‐010 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070821‐011 nd nd 1.3 nd nd nd nd 4.7 nd bdl nd bdl bdl

070821‐012 nd nd nd nd nd nd nd 5.0 nd bdl nd bdl bdl

070821‐013 nd 13 nd nd nd nd nd nd nd bdl nd bdl bdl

070821‐014 nd 12 nd bdl nd nd nd nd nd bdl nd bdl bdl

070821‐015 2.1 9.6 nd nd nd nd nd 3.7 nd bdl nd bdl bdl

070821‐016 5.6 nd 2.4 nd 2.7 nd nd nd nd bdl nd bdl bdl

070821‐017 nd nd nd nd nd nd nd 4.1 nd bdl nd bdl bdl

070821‐022 nd nd nd nd nd nd nd 3.8 nd bdl nd bdl bdl

070821‐023 nd nd nd nd nd nd nd nd nd bdl nd bdl nd

070821‐024 nd nd nd nd nd nd nd nd nd bdl nd bdl nd

8/22/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

070822‐006 nd nd nd nd nd nd nd 4.0 nd bdl nd bdl bdl

070822‐007 nd 8.9 nd nd nd nd nd 4.1 nd bdl nd bdl bdl

070822‐008 1.6 8.9 nd nd 3.1 nd nd 4.1 nd bdl nd bdl bdl

070822‐009 17 16 4.0 nd 3.1 nd nd nd nd bdl nd bdl bdl

070822‐010 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070822‐011 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070822‐012 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070822‐013 nd nd nd nd nd nd nd 3.5 nd bdl nd bdl nd

070822‐014 nd 13 nd nd nd nd nd 3.9 nd bdl nd bdl nd

070822‐015 nd nd nd nd nd nd nd 3.9 nd bdl nd bdl bdl

070822‐019 nd nd nd nd nd nd nd nd nd bdl nd bdl nd

070822‐020 nd 14 nd nd nd nd nd 3.9 nd bdl nd bdl nd

TOTAL = 36 230 53 13 39 8.1 9.0 56 46 6.6 nd 4.5 3.9

AVERAGE = 1.0 6.4 1.5 bdl 1.1 bdl bdl 1.6 1.3 bdl nd bdl bdl

STDEV = 3.3 10 2.8 bdl 1.6 bdl bdl 2.0 3.3 bdl nd bdl bdl

bdl = below detection limits

nd = non‐detect

ANALYTES:
46 

Cameron, Louisiana 

September 5-6, 2007 

9/5/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

070905‐005 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070905‐006 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070905‐007 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070905‐008 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070905‐009 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070905‐010 nd nd nd nd nd nd nd 3.8 nd bdl nd bdl bdl

070905‐011 nd nd nd nd 2.8 nd nd nd nd bdl nd bdl bdl

070905‐012 nd nd 4.9 nd nd nd nd nd nd bdl nd bdl bdl

070905‐018 13 nd 4.8 nd nd nd nd nd nd bdl nd bdl bdl

070905‐019 14 34 nd nd nd nd nd nd nd bdl nd bdl bdl

070905‐020 nd nd nd nd 2.7 nd nd 4.1 nd bdl nd bdl bdl

070905‐021 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

9/6/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

070906‐003 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070906‐004 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070906‐005 nd nd nd nd nd nd nd nd nd bdl nd nd bdl

070906‐006 nd nd nd nd nd nd nd nd nd bdl nd nd bdl

070906‐007 nd nd nd nd nd nd nd 3.9 nd bdl nd bdl bdl

070906‐008 nd nd nd nd nd nd nd 4.1 nd bdl nd bdl bdl

070906‐009 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070906‐010 nd nd nd nd nd nd nd nd bdl bdl nd bdl bdl

070906‐011 nd nd nd nd 1.9 nd nd 3.9 nd bdl nd bdl bdl

070906‐012 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

070906‐013 nd 8.6 nd nd nd nd nd nd 2.8 bdl nd bdl nd

070906‐014 nd nd nd nd nd nd nd nd nd bdl nd bdl nd

070906‐015 nd 8.9 nd nd nd nd nd nd nd bdl nd bdl bdl

070906‐016 nd 8.9 nd 1.6 nd nd nd nd nd bdl nd bdl bdl

070906‐017 nd nd nd nd nd nd nd nd nd bdl nd bdl nd

070906‐018 nd nd nd nd nd nd nd nd nd bdl nd bdl nd

070906‐020 nd nd nd nd nd nd nd nd nd nd nd nd nd

TOTAL = 27 60 10 1.6 7.3 nd nd 20 3.3 4.3 nd 1.9 2.6

AVERAGE = bdl 2.1 bdl bdl bdl nd nd bdl bdl bdl nd bdl bdl

STDEV = bdl 6.6 bdl bdl bdl nd nd bdl bdl bdl nd bdl bdl

bdl = below detection limits

nd = non‐detect

ANALYTES:
47 

Port Fourchon, Louisiana 

September 17, 2007 

9/17/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

070917‐012 nd nd nd 1.6 14 8.9 nd nd 9.5 bdl nd nd bdl

070917‐013 nd nd nd nd 11 5.4 nd nd 8.0 bdl nd bdl bdl

070917‐014 nd nd nd nd 8.0 4.9 nd nd 9.3 nd nd bdl nd

070917‐015 nd nd nd bdl 10 6.5 nd nd 6.8 bdl nd nd bdl

070917‐016 5.0 16 1.5 nd 11 7.1 nd nd 10 bdl nd bdl bdl

070917‐017 nd nd nd nd 9.7 7.1 nd nd 10 bdl nd bdl nd

070917‐018 nd nd nd bdl 9.6 5.6 nd nd nd bdl nd nd nd

TOTAL = 5.0 16 1.5 2.7 74 45 nd nd 54 bdl nd bdl bdl

SITE AVG = bdl 2.4 bdl bdl 11 6.5 nd nd 7.7 bdl nd bdl bdl

STDEV = bdl 6.2 bdl bdl 1.9 1.3 nd nd 3.6 bdl nd bdl bdl

bdl = bel ow detection limi ts

nd = non‐detect

ANALYTES:
48 

Port Fourchon, Louisiana 

October 1, 2007 

10/1/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

071001‐011 nd nd nd nd nd nd nd nd nd bdl nd bdl 3.3

071001‐012 nd nd nd nd nd nd nd nd bdl bdl nd bdl 3.1

071001‐013 nd nd nd nd nd nd nd nd nd 3.6 nd 1.8 3.0

071001‐014 nd nd nd nd nd nd nd nd nd nd nd nd 2.6

071001‐015 nd nd nd nd nd nd nd bdl nd 1.4 nd bdl 2.4

071001‐016 nd nd nd nd nd nd nd nd nd 1.5 nd bdl 2.5

071001‐017 nd nd nd nd nd nd nd bdl nd 1.1 nd bdl 2.3

071001‐018 nd nd nd nd nd nd nd nd nd 1.6 nd 1.1 2.2

071001‐019 nd nd bdl bdl bdl bdl bdl bdl bdl 1.8 nd 1.1 2.3

071001‐021 nd nd nd nd nd nd nd nd nd 1.0 nd 1.0 2.0

071001‐022 nd nd nd nd nd nd nd bdl nd 1.2 nd 1.2 2.0

071001‐023 nd nd nd nd nd nd nd bdl nd 1.3 nd 1.0 1.9

071001‐024 nd nd nd nd nd nd nd nd nd 1.0 nd 1.1 1.8

071001‐025 nd nd nd nd nd nd nd nd nd 1.0 nd 1.1 1.7

071001‐026 nd nd nd nd nd nd nd nd nd 1.2 nd 1.1 1.8

071001‐027 nd nd nd nd nd nd nd bdl nd 2.9 nd 1.6 1.8

071001‐028 nd nd nd nd nd nd nd bdl nd 1.6 nd 1.3 1.7

071001‐029 nd nd nd nd nd nd nd nd nd 1.2 nd 1.1 1.5

071001‐034 nd nd nd nd nd nd nd nd nd nd nd 3.6 9.0

071001‐035 nd nd nd nd nd nd nd nd nd 1.6 nd 1.7 1.6

071001‐036 nd nd nd nd nd nd nd bdl nd 2.3 nd 1.6 1.5

071001‐037 nd nd nd nd nd nd nd nd nd 2.1 nd 1.8 1.6

071001‐038 nd nd nd nd nd nd nd bdl nd 1.9 nd 1.8 1.6

071001‐039 nd nd nd nd nd nd nd bdl nd 1.6 nd 1.6 1.5

071001‐040 nd nd nd nd nd nd nd nd nd 1.9 nd 1.8 1.5

071001‐041 nd nd nd nd nd nd nd bdl nd 1.6 nd 1.6 1.4

071001‐042 nd nd nd nd nd nd nd bdl nd 2.0 nd 1.7 1.4

071001‐043 nd nd nd nd nd nd nd bdl nd 1.6 nd 1.7 1.2

071001‐044 nd nd nd nd nd nd nd bdl nd 1.6 nd 1.6 1.3

071001‐047 nd nd nd nd nd nd nd nd nd 2.2 nd 2.0 1.1

071001‐048 nd nd nd nd nd nd nd bdl nd 1.6 nd 1.8 1.0

071001‐049 nd nd nd nd nd nd nd nd nd 1.9 nd 1.9 1.2

071001‐050 nd nd nd nd nd nd nd nd nd 1.6 nd 1.6 1.0

071001‐051 nd nd nd nd nd nd nd nd nd 1.6 nd 1.7 1.0

071001‐052 nd nd nd nd nd nd nd bdl nd 1.8 nd 1.8 bdl

071001‐053 nd nd nd nd nd nd nd bdl nd 2.0 nd 2.0 bdl

071001‐054 nd nd nd nd nd nd nd bdl nd 1.8 nd 1.9 bdl

071001‐055 nd nd nd nd nd nd nd nd nd 1.9 nd 2.0 bdl

ANALYTES:
49 

Port Fourchon, LA (continued) 

October 2, 2007 

10/2/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

071002‐018 nd nd nd nd nd nd nd nd nd nd nd 6.1 4.1

071002‐019 nd nd nd nd nd nd nd nd nd nd nd 3.6 2.4

071002‐020 nd nd nd nd nd nd nd nd nd nd nd 1.4 bdl

071002‐021 nd nd nd nd nd nd nd nd nd nd nd 1.0 bdl

071002‐022 nd nd nd nd nd nd nd nd nd nd nd 1.2 bdl

071002‐023 nd nd nd nd nd nd nd nd nd nd nd 1.1 bdl

071002‐024 nd nd nd nd nd nd nd nd nd nd nd 1.2 bdl

071002‐025 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐026 nd nd nd nd nd nd nd nd nd nd nd 1.1 bdl

071002‐027 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐028 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐029 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐030 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐031 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐032 nd nd nd nd nd nd nd nd nd nd nd 1.0 bdl

071002‐033 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐034 nd nd nd nd nd nd nd nd nd nd nd 1.3 bdl

071002‐035 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071002‐037 nd nd nd nd nd nd nd nd nd nd nd 1.7 bdl

071002‐038 nd nd nd nd nd nd nd nd nd nd nd 1.6 bdl

071002‐040 nd nd nd nd nd nd nd nd nd nd nd 1.3 bdl

071002‐041 nd nd nd nd nd nd nd nd nd nd nd 1.2 bdl

071002‐042 nd nd nd nd nd nd nd nd nd nd nd 1.1 bdl

071002‐043 nd nd nd nd nd nd nd nd nd nd nd 1.0 bdl

071002‐044 nd nd nd nd nd nd nd nd nd nd nd 1.1 bdl
50 

Port Fourchon, LA (continued) 

October 3 & 4, 2007 

10/3/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

071003‐007 nd nd nd nd nd nd nd nd nd nd nd nd 1.2

071003‐008 nd nd nd nd nd nd nd nd nd nd nd bdl 1.6

071003‐009 nd nd nd nd nd nd nd nd nd nd nd nd 1.0

071003‐010 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071003‐011 nd nd nd nd nd nd nd nd nd bdl nd bdl 1.3

071003‐012 nd nd nd nd nd nd nd nd bdl nd nd nd 1.0

071003‐013 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐014 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐015 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐016 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐017 nd nd nd nd nd nd bdl nd nd nd nd bdl 1.2

071003‐020 nd nd nd nd nd nd nd nd nd bdl nd bdl 1.0

071003‐021 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐022 nd nd nd nd nd nd nd bdl nd bdl nd bdl bdl

071003‐023 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐024 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐025 nd nd nd nd nd nd nd nd nd 1.9 nd bdl bdl

071003‐026 nd nd nd nd nd nd nd bdl nd nd nd nd bdl

071003‐027 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐028 nd nd nd nd nd nd nd bdl nd 1.4 nd bdl bdl

071003‐029 nd nd nd nd nd nd nd nd nd 1.1 nd bdl bdl

071003‐030 nd nd nd nd nd nd nd nd nd 2.1 nd 1.1 1.5

071003‐031 nd nd nd nd nd nd nd bdl nd nd nd bdl bdl

071003‐032 nd nd nd nd nd nd nd bdl nd nd nd nd bdl

071003‐033 nd nd nd nd nd nd nd bdl nd nd nd nd bdl

071003‐034 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071003‐035 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐036 nd nd nd nd nd nd nd bdl nd nd nd nd bdl

071003‐037 nd nd nd nd nd nd nd bdl nd 1.3 nd bdl bdl

071003‐038 nd nd nd nd nd nd nd nd nd nd nd nd bdl

071003‐039 nd nd nd nd nd nd nd bdl nd bdl nd nd bdl

071003‐042 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071003‐043 nd nd nd nd nd nd nd nd nd 1.1 nd bdl bdl

071003‐044 nd nd nd nd nd nd nd bdl nd nd nd nd bdl

071003‐045 nd nd nd nd nd nd nd nd nd bdl nd bdl bdl

071003‐046 nd nd nd nd bdl nd nd bdl nd nd nd bdl bdl

071003‐047 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071003‐048 nd nd nd nd nd nd nd nd nd nd nd bdl bdl

071003‐049 nd nd nd nd nd nd nd bdl nd bdl nd nd bdl

071003‐050 nd nd nd nd nd nd nd nd nd nd nd bdl nd

071003‐051 nd nd nd nd bdl nd nd nd nd bdl nd bdl bdl

10/4/2007 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

071004‐006 nd nd nd nd nd nd nd nd nd 1.4 nd bdl bdl

071004‐007 nd nd nd nd nd nd nd nd bdl 2.8 nd 1.4 bdl

071004‐008 bdl nd nd nd nd nd nd nd bdl 2.8 nd 1.2 bdl

071004‐010 bdl nd nd nd nd nd nd nd nd 1.8 nd 1.1 nd

071004‐011 1.2 bdl nd nd nd nd nd nd nd 2.1 nd 1.8 bdl

071004‐012 bdl bdl nd nd nd nd nd nd nd 1.7 nd 1.1 nd

071004‐013 bdl nd nd nd nd nd nd nd nd 2.4 nd 1.1 nd

071004‐014 bdl nd nd nd nd nd nd nd nd 1.5 nd bdl nd

TOTAL = 4.7 1.0 0.1 0.1 nd 0.1 0.4 3.2 1.7 88 nd 106 116

AVERAGE = bdl bdl bdl bdl nd bdl bdl bdl bdl bdl nd bdl 1.0

STDEV = bdl bdl bdl bdl nd bdl bdl bdl bdl bdl nd bdl 1.1

bdl = below detection limits

nd = non‐detect
51 

Green Canyon, GOM 

June 9, 2008 

6/9/2008 Ethane Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene

Hexane/

Isoprene Benzene 1‐Hexene Toluene Xylenes

Sample ID: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

080609‐007 nd nd nd nd nd nd nd nd 52 20 nd 18 58

080609‐008 nd nd nd nd nd nd nd nd 17 9.0 nd 38 12

080609‐009 nd nd nd nd nd nd nd nd 13 12 nd 32 7.0

080609‐011 nd nd nd nd nd nd nd nd 20 8.0 nd 19 7.0

080609‐017 nd nd nd nd nd nd nd nd 13 8.0 nd 16 6.0

080609‐018 nd nd nd nd nd nd nd nd 12 6.0 nd 21 6.0

080609‐019 nd nd nd nd nd nd nd nd 11 8.0 nd 22 5.0

080609‐020 nd nd nd nd nd nd nd nd 7.0 5.0 nd 20 4.0

080609‐021 nd nd nd nd nd nd nd nd 10 5.0 nd 12 3.0

080609‐022 nd nd nd nd nd nd nd nd 5.0 4.0 nd 11 3.0

080609‐023 nd nd nd nd nd nd nd nd 5.0 4.0 nd 13 5.0

080609‐024 nd nd nd nd nd nd nd nd 10 6.0 nd 21 7.0

080609‐032 nd nd nd nd nd nd nd nd 7.0 10 nd 8.0 14

080609‐034 nd nd nd nd nd nd nd nd 6.0 5.0 nd 10 6.0

080609‐035 nd nd nd nd nd nd nd nd 5.0 4.0 nd 8.0 3.0

080609‐036 nd nd nd nd nd nd nd nd 6.0 7.0 nd 8.0 3.0

080609‐037 nd nd nd nd nd nd nd nd 6.0 7.0 nd 13 5.0

080609‐038 nd nd nd nd nd nd nd nd 5.0 6.0 nd 16 6.0

080609‐039 nd nd nd nd nd nd nd nd 6.0 6.0 nd 18 11

080609‐041 nd nd nd nd nd nd nd nd 6.0 6.0 nd 8.0 5.0

080609‐042 nd nd nd nd nd nd nd nd 5.0 7.0 nd 11 6.0

080609‐043 nd nd nd nd nd nd nd nd 5.0 7.0 nd 9.0 6.0

080609‐044 nd nd nd nd nd nd nd nd 6.0 6.0 nd 6.0 6.0

TOTAL = nd nd nd nd nd nd nd nd 238 166 nd 358 194

AVERAGE = nd nd nd nd nd nd nd nd 10 7.2 nd 16 8.4

STDEV = nd nd nd nd nd nd nd nd 10 3.4 nd 7.9 11

bdl = below detection limi ts

nd = non‐detect

ANALYTES:
53 

APPENDIX B: 

SORBENT TUBE TRAP/GC-TOFMS

AIR SAMPLE DATA TABLES
55 

Grand Isle, Louisiana 

August 20-23, 2007 

08/20/2007: Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene Hexane Benzene 1‐Hexene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

A5372 nd 0.47 0.51 0.79 0.35 nd nd nd 0.20 nd 0.60 nd nd nd

A5380 nd 1.2 1.8 1.2 0.91 nd nd 1.9 0.48 nd 6.3 nd nd nd

A4836 nd nd nd nd nd nd nd nd nd nd nd nd nd nd

A4751 nd 0.99 0.54 0.72 0.63 nd nd 1.7 0.38 nd 4.1 nd nd nd

A5567 nd 0.58 0.49 1.1 4.0 nd nd nd 0.19 0.40 0.71 nd nd nd

08/21/2007: Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene Hexane Benzene 1‐Hexene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

A5438 nd 0.15 0.42 1.9 0.55 nd nd nd 0.31 nd 1.7 nd nd nd

A4572 nd 0.65 0.75 0.76 1.5 nd nd 1.5 0.27 nd 16 nd nd nd

A4531 nd 0.73 1.3 0.94 2.9 nd nd 0.70 0.21 0.40 34 nd 0.33 nd

A4618 nd 1.4 1.4 0.82 0.48 1.4 nd 4.6 0.82 0.20 2.8 nd nd nd

A5272 nd 0.46 0.91 0.93 2.0 nd nd nd 0.42 0.42 81 nd nd nd

08/22/2007: Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene Hexane Benzene 1‐Hexene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

A5121 nd 0.69 0.54 0.42 0.40 nd nd 1.4 0.32 nd 1.3 nd nd nd

A4581 nd 1.8 1.9 0.73 0.60 1.3 nd 2.1 0.26 nd 2.1 nd nd nd

A5444 nd nd 1.4 0.64 0.51 1.6 nd 13 0.73 nd 2.1 nd nd nd

A5574 nd 0.71 0.68 0.37 0.39 nd nd nd 0.20 nd 0.87 nd nd nd

A5458 nd 0.45 0.39 1.2 0.70 nd nd 0.75 0.28 nd 20 nd nd nd

A4622 nd 0.79 1.6 0.64 3.5 0.81 nd 4.6 0.38 0.37 14 nd nd nd

A5363 nd nd 0.51 0.56 0.28 2.8 nd 18 3.6 0.35 nd 21 nd 0.29

A5347 nd 0.50 0.54 0.84 0.46 nd nd 1.8 0.32 nd 3.3 nd nd nd

A5246 nd nd 0.67 0.60 0.51 1.1 nd 2.9 0.69 nd 2.1 nd nd nd

08/23/2007: Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene Hexane Benzene 1‐Hexene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

A5399 nd nd 0.49 0.34 0.23 nd nd 1.5 0.20 nd 15 nd nd nd

A5356 nd 0.68 0.40 0.48 0.40 nd nd nd nd nd 2.1 nd nd nd

A5691 nd 4.6 1.3 2.6 3.5 5.7 nd 15 1.2 1.1 337 nd 0.25 nd

A5357 nd 0.56 0.57 0.65 0.41 1.5 nd 2.0 0.25 nd 38 nd nd nd

A5431 nd nd 0.63 nd 0.43 nd nd nd 0.17 nd 44 nd nd nd

A5537 nd 3.5 1.4 2.0 2.5 3.4 nd 16 1.1 0.29 329 nd nd nd

TOTAL = nd 21 21 21 28 20 nd 88 13 3.5 958 21 0.6 0.3

AVERAGE = nd 0.83 0.84 0.85 1.1 0.78 nd 3.5 0.52 0.14 38 0.82 bdl bdl

STDEV = nd 1.1 0.50 0.59 1.2 1.4 nd 5.5 0.71 0.25 91 4.1 bdl bdl

bdl = below detection limits

nd = non‐detect

ANALYTES:
56 

Cameron, Louisiana 

September 5, 2007 

09/05/2007: Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene Hexane Benzene 1‐Hexene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

A5458 nd 0.32 0.44 nd 0.22 nd nd nd 0.29 0.23 2.6 nd nd nd

A5246 nd 0.26 nd nd 0.46 nd nd nd 0.39 nd 1.5 nd nd nd

A5444 nd 0.28 0.42 0.39 nd nd nd nd 0.34 nd 4.2 nd nd nd

A4618 nd 0.41 0.23 0.22 0.19 nd nd nd 0.10 nd 0.93 nd nd nd

A5091 nd 0.74 0.59 0.45 0.41 nd nd 1.3 0.57 nd 5.8 nd nd nd

A5272 nd 1.0 1.6 0.81 4.8 1.2 nd 4.0 0.60 0.38 35 0.36 0.56 nd

A4531 nd 0.64 1.9 1.1 8.6 nd nd 3.2 0.44 0.47 8.5 0.49 0.97 0.73

A4581 nd 1.2 0.73 0.55 0.50 0.65 nd nd 0.46 0.29 4.7 nd nd nd

A5431 nd 0.69 2.1 0.86 12 0.46 nd 2.7 0.52 0.57 24 0.40 0.64 0.41

A5510 nd 0.82 0.43 0.28 0.65 nd nd 1.6 0.64 nd 6.2 nd nd nd

A5121 nd 1.2 2.4 0.92 9.1 nd nd 2.3 0.47 0.67 16 nd 0.70 nd

A4572 nd 1.1 0.58 0.53 0.69 nd nd nd 0.44 0.35 1.7 nd nd nd

A3742 nd 0.31 0.60 0.31 0.87 nd nd nd 0.39 nd 2.9 nd nd nd

A5347 nd 0.96 0.43 0.37 0.32 nd nd nd 0.29 0.15 4.3 nd nd nd

A4836 nd 0.60 0.43 0.79 0.72 nd nd nd 0.30 nd 3.8 nd nd nd

A5363 nd nd 0.20 0.32 0.26 nd nd nd 0.22 nd 1.2 nd nd nd

A4966 nd nd nd 0.45 0.36 0.57 nd 8.6 nd 0.20 0.18 0.93 nd nd

A5438 nd nd 0.38 0.31 nd nd nd nd 0.15 nd 2.5 nd nd nd

A5372 nd 1.7 0.37 0.80 0.59 nd nd nd 0.39 0.81 1.3 nd nd nd

A5574 nd 1.9 0.81 1.0 0.99 1.1 nd 1.8 0.67 0.14 14 nd 0.20 nd

TOTAL = nd 14 15 11 42 3.9 nd 26 7.7 4.3 142 2.2 3.1 1.1

AVERAGE = nd 0.71 0.73 0.53 2.1 0.20 nd 1.3 0.38 0.21 7.1 0.11 0.15 bdl

STDEV = nd 0.55 0.69 0.33 3.5 0.38 nd 2.2 0.18 0.25 8.9 0.25 0.30 bdl

bdl = bel ow detection limi ts

nd = non‐detect

ANALYTES:
57 

Port Fourchon, Louisiana 

September 17, 2007 

09/17/2007: Ethylene Propane Propylene Butane 1‐Butene Pentane 1‐Pentene Hexane Benzene 1‐Hexene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

A4966 nd 1.1 0.86 1.7 0.17 nd nd 1.6 0.43 8.6 bdl nd nd nd

A5246 nd nd nd nd nd nd nd nd nd nd nd nd nd nd

A4611 nd nd 0.12 nd 1.7 nd nd nd nd nd nd nd nd nd

A4652 nd nd 0.17 0.43 3.2 nd 0.43 nd nd nd nd nd nd nd

A5363 nd nd nd 0.14 3.5 nd nd nd nd nd nd nd nd nd

A4531 nd nd nd nd nd 5.3 nd 4.5 nd nd 0.40 nd nd nd

A5438 nd nd 0.18 0.25 6.3 nd 0.68 nd nd nd nd nd nd nd

A5510 nd nd 0.26 nd nd nd nd nd nd nd nd nd nd nd

A5361 nd 1.0 nd 0.16 nd nd 1.1 1.6 nd nd nd nd nd nd

A4575 nd nd 0.21 0.43 nd nd 1.2 nd nd nd bdl nd nd nd

A4756 nd nd 0.25 0.81 nd nd nd nd 0.07 nd nd nd nd nd

A5417 nd nd 0.17 nd nd nd 0.71 nd nd 0.23 nd nd nd nd

A5177 nd nd 0.08 0.26 nd nd 0.87 nd nd nd nd nd nd nd

A4561 nd nd 0.36 0.83 nd nd 4.1 4.4 nd 1.2 nd nd nd nd

A4738 nd 0.27 0.99 nd nd 2.5 nd nd 1.8 nd nd nd nd nd

A4910 nd nd 0.24 0.35 3.9 nd 0.52 nd nd nd 0.15 nd nd nd

A5243 nd nd 0.20 0.29 3.7 nd nd nd nd nd nd nd nd nd

A5347 nd 0.73 0.33 0.41 3.8 nd 1.6 1.7 nd nd 0.19 nd nd nd

A4893 nd nd 0.36 0.20 2.1 nd 0.95 nd nd nd nd nd nd nd

A4696 nd nd 0.14 0.31 3.2 nd 0.97 nd nd 0.56 nd nd nd nd

A5537 nd 1.6 0.22 0.26 0.43 nd nd nd nd nd nd nd nd nd

A4838 nd nd nd nd 0.71 nd nd nd nd nd nd nd nd nd

A5458 nd nd nd nd 0.75 nd nd nd nd nd nd nd nd nd

A5356 nd nd 0.19 0.24 1.1 nd nd nd nd nd nd nd nd nd

TOTAL = nd 4.8 5.3 7.0 35 7.8 13 14 2.3 11 0.85 nd nd nd

AVERAGE = nd 0.20 0.22 0.29 1.4 0.32 0.55 0.57 0.10 0.44 bdl nd nd nd

STDEV = nd 0.45 0.25 0.37 1.8 1.2 0.91 1.3 0.37 1.8 bdl nd nd nd

bdl = below detection limi ts

nd = non‐detect

ANALYTES:
58 

Green Canyon, GOM 

June 9, 2008 

06/09/2008: Ethylene Acetylene Propane Propylene isoButane Butane 1‐Butene Pentane 1‐Pentene Isoprene Hexane Benzene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv ppbv

A5399 nd nd nd bdl bdl nd nd nd nd nd nd bdl 0.87 0.37 0.68 0.57

A4521 nd nd nd bdl nd nd nd nd nd nd nd bdl 0.54 0.45 0.88 0.86

A5272 nd nd nd nd nd nd nd nd nd nd nd bdl 0.92 0.47 0.87 0.81

A4922 nd bdl nd bdl nd bdl nd nd nd nd nd bdl 0.29 0.40 0.25 0.55

A5177 nd nd nd nd nd nd nd nd 0.10 nd nd bdl 0.13 0.30 0.19 0.40

A5567 0.12 0.12 nd 0.16 nd nd bdl nd nd nd nd bdl 0.18 0.38 0.24 0.54

A4966 nd nd nd bdl bdl bdl nd nd nd nd nd bdl 0.59 0.30 0.53 0.51

A5121 0.17 nd nd nd nd nd nd nd nd nd nd nd 0.10 0.16 0.10 0.23

A5361 nd nd nd bdl nd nd nd nd nd nd nd nd 0.18 0.29 0.18 0.38

A4622 bdl bdl 0.11 bdl bdl bdl nd nd nd nd nd bdl 0.48 0.51 0.34 0.33

A4751 0.12 nd nd nd nd nd 0.11 nd nd nd nd bdl 0.41 0.20 0.34 0.34

A4561 bdl bdl nd nd nd nd bdl nd nd nd nd nd 0.17 0.19 0.12 0.26

A5417 bdl nd nd nd nd nd bdl nd 0.40 nd nd bdl 0.12 nd nd nd

A5363 bdl nd 0.12 bdl bdl bdl nd nd 0.15 nd nd nd 0.12 0.31 0.20 0.44

A5458 bdl nd bdl nd nd nd 0.21 nd bdl nd nd nd bdl nd nd nd

A4575 bdl nd nd nd nd nd nd nd 0.62 nd nd bdl 0.15 0.46 0.32 0.32

A4738 bdl nd nd bdl bdl bdl bdl nd nd nd nd 0.11 0.16 0.25 0.16 0.35

A5246 nd nd nd nd nd nd nd nd nd nd nd nd 0.13 0.22 0.15 0.32

A4618 nd nd nd nd nd nd bdl nd nd nd nd bdl 1.0 0.38 0.24 0.52

A5091 nd bdl nd nd nd nd bdl nd 0.19 nd nd nd bdl bdl bdl nd

A5431 nd nd nd bdl nd nd nd nd 0.37 nd nd nd 0.18 0.20 0.13 0.28

A5243 bdl nd nd bdl nd nd bdl nd 0.28 nd nd bdl 0.19 0.13 bdl 0.17

TOTAL = 0.66 0.28 0.34 0.60 0.19 0.14 0.52 nd 2.2 nd nd 0.46 6.4 6.0 6.0 7.9

AVERAGE = bdl bdl bdl bdl bdl bdl bdl nd 0.10 nd nd bdl 0.32 0.28 0.28 0.34

STDEV = bdl bdl bdl bdl bdl bdl bdl nd 0.17 nd nd bdl 0.30 0.15 0.25 0.23

bdl = bel ow detection limi ts

nd = non‐detect

GREEN CANYON AIR SAMPLES

ANALYTES:
59 

APPENDIX C: 

SORBENT TUBE TRAP/GC-TOFMS

WATER SAMPLE DATA TABLES
61 

Green Canyon, GOM 

June 9, 2008 

06/09/2008: Ethylene Acetylene Propane Propylene isoButane Butane 1‐Butene Pentane 1‐Pentene Isoprene Hexane Benzene Toluene Ethylbenzene mp‐Xylene o‐Xylene

Tube #: pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L pmol/L

A4755 nd nd nd 1395 nd nd 274 nd nd nd nd 535 7696 2500 6332 4701

A4572 nd 2464 nd 2306 nd 664 692 nd nd nd nd 581 8290 2309 4972 3801

A5390 nd nd nd nd nd nd nd nd nd nd nd 1718 2461 767 1569 3294

A4581 2857 nd nd 2262 nd nd nd nd nd 1638 nd 4007 5504 3791 2429 5269

A5347 382 nd nd 2063 351 nd 1965 nd nd nd nd 766 806 nd nd nd

A4838 nd 3466 nd 1614 nd nd nd nd nd nd nd 1120 2225 2557 1564 3541

A5372 2328 4613 1816 nd 860 nd nd nd nd nd 580 1152 nd nd nd nd

A5468 9312 5381 6809 5945 3441 1721 1782 nd nd nd nd 512 760 nd nd nd

TOTAL = 14879 15924 8625 15586 4652 2385 4713 nd nd 1638 580 10392 27742 11924 16866 20607

AVERAGE = 1860 1990 1078 1948 582 298 589 nd nd 205 bdl 1299 3468 1490 2108 2576

STDEV = 3224 2287 2401 1860 1195 620 829 nd nd 579 bdl 1169 3257 1479 2393 2224

bdl = bel ow detection limi ts

nd = non‐detect

GREEN CANYON WATER SAMPLES

ANALYTES: