IN-SITU TRACKING OF OIL FROM THE DEEPWATER HORIZON OIL SPILL

USING SPECTRAL FLUORESCENCE

Corey Koch,1 Paula Coble,2 Leslie Slasor,3 Joseph Needoba,3

Andrew Barnard,1 Scott Pegau4

1-WET Labs Inc. Philomath OR. 2-University of South Florida, St. Petersburg FL. 3-Oregon Health and Sciences University,

Portland, OR. 4-Oil Spill Recovery Institute, Cordova, AK.

Photo: Dave Martin/AP

• Deepwater Horizon spill generated an underwater oil plume

• Oil Fluoresces, making it amenable to in-situ measurement

• Primarily CDOM optimized fluorometers were used

In-situ tracking

JAG_Report_1_BrooksMcCall_Final_June20

Right: WL ECO (370/460 nm) and neat LA Sweet crude oil. Left: Visible Oil

fluorescence

What causes oil to Fluoresce?• Polycyclic aromatic hydrocarbons

– Highly toxic to aquatic life, known carcinogens

– Fluorescence signatures shift due to alkylation and energy transfer effects (Ryder, 2002)

– Fluorescence correlated to API gravity, viscosity, aromaticity (Ryder 2002, Fuller et al. 2005, Budgen et al. 2008)

• Oil-in-water forms: neat (slick), emulsion/colloid (mousse, dispersion), dissolved hydrocarbons

• Weathering can transform signals (Erhardtet al., 1992; Pradier et al., 1990; Hagemann et al., 1986)

Photo: Dave Martin/AP

Christensen et al, 2005 Anal Chem

In DCM

Excitation Emission Matrix Spectra: EEMS

• Incrementally change excitation wavelength and measure entire emission spectrum

• Provide “fingerprint” of steady state fluorescence EX

EM

Excitation Emission Matrix Spectra: EEMS

• Incrementally change excitation wavelength and measure entire emission spectrum

• Provide “fingerprint” of steady state fluorescence EX

EM

Some Regions

of Interest

Excitation Emission Matrix Spectra: EEMS

• Incrementally change excitation wavelength and measure entire emission spectrum

• Provide “fingerprint” of steady state fluorescence

• SAFire spectral fluorometer

• 6 Ex and 16 Em

Excitation Emission Matrix Spectra: EEMS

• Incrementally change excitation wavelength and measure entire emission spectrum

• Provide “fingerprint” of steady state fluorescence

• SAFire spectral fluorometer

• 6 Ex and 16 Em

EX

EM

A few areas of SAFire

Spectral Fluorometer

Measurement

Excitation Emission Matrix Spectra: EEMS

• Incrementally change excitation wavelength and measure entire emission spectrum

• Provide “fingerprint” of steady state fluorescence

• SAFire spectral fluorometer

• 6 Ex and 16 Em

SAFire Grab sample

Gulf EEMs

• Oil has distinct fluorescence regions compared to CDOM

• Oil Fluorescence varies with sample site and depth, presumably due to transformations

CDOM, Florida coastal water

Filtered water near fresh oil slick

Weathered oil

EX

EM

Weatherbird cruise (Aug 2010)

From Rosette samples

acidified (pH2) and

frozen unfiltered.

Lab Experiments• Understand EEMs from Gulf

• Evaluate effects of degradation (photo, bio, aging)

• Must be able to reproduce soluble fraction formation– Controls, triplicates, daily EEMs

– ONTA Inc. crude oil kits, artificial sea water– 40:1 sea water : oil

– Minimize light, control temperature, eliminate contamination sources, sample through oil slick, minimize oxidation

– Glass bottles, Stainless steel tubing, high-purity silicone stoppers/gas tubing, Nitrogen purged headspace, postive displacement sampling, temperature controlled shaker table (90 RPM).

(Ali et al. 1995, Ziolli et al. 2002, Shiu et al. 1990,

Ashton LSU JAG report 2)

Stability of Soluble Fraction

PAH Solubility mg/L

Pyrene 0.135

Fluorene 7.22E-05

0.4

0.6

0.8

1

1.2

8-Nov 18-Nov 28-Nov 8-Dec 18-Dec

Rat

io o

f Em

issi

on

In

ten

sity

(3

45

/32

0)

Qua Iboe: Ratio of pyrene-like to fluorene-like Fluorescence

0

2

4

6

8

10

12

14

19-Oct 22-Oct 25-Oct 28-Oct

No

rmal

ize

d F

L In

ten

sity

TX Hoops Average I vs T

250/320240/345270/300270/320

Crude Oil EEMs, soluble fraction

• Oil types analyzed to-date have PAH-like fluorescence signatures.

• Light oils display the same peaks, heavier oils have red-shifted signatures.

• The soluble fraction of light oils do not exhibit CDOM-like fluorescence.

Louisiana Sweet-API 31.4 Qua Iboe (Nigerian)-API 35.8

Vasconia (Colombia)-API 24.2 Mevey (Venezuela)-API 18.7

HOOPS (Texas)-API 31.4

DSH10 Aug 2010, 400 m

Preliminary Photodegradation

• Solar simulator irradiation (4 hr)

• Differential degradation rates for components

• May provide insight into differences in field spectra

Fixed excitation wavelengths indicated by arrows. Time series wavelengths: Ex/Em

Summary

• SAFire effective at identifying oil in-situ

– Against CDOM background and as oil transforms

– Potentially put discrete fluorescence data in context

• Can reproducibly form stable dissolved oil fraction in the lab

– Permit controlled studies to understand EEM dynamics (photodegradation, biodegrade, aging)

– Facilitate ID of fluorescent components

• Identified key Ex/Em pairs to use simple fluorometers to track various oils as they transform in the environment

Acknowledgements

This work has been funded by an NSF RAPID response grant. This material is

based upon work supported by the National Science Foundation under Grant

No. OCE-1048455. Any opinions, findings, and conclusions or

recommendations expressed in this material are those of the author(s) and do

not necessarily reflect the views of the National Science Foundation.

Special thanks to:•Paula Coble, Kendra Daly, and the Weatherbird crew

•Leslie Slasor (OHSU, Lab EEMs)•Lori Ayoub (USF, field EEMs)

•Dave Stahlke and Cobie deLespinasse (WET Labs, SAFire service)

• Ali, L.N; Mantoura, R.F.C.; Rowland, S.J. (1995) The Dissolution and Photodegradation of Kuwaiti Crude Oil in Seawater. Part 1: Quantitative Dissolution and Analysis of the Seawater-Soluble Fraction. Marine Environmental Research, 40, 1-17.

• Bugden, J.B.C., Yeung, C.W., Kepkay, P.E., Lee, K., 2008. Application of ultraviolet fluorometery and excitation-emission matrix spectroscopy (EEMS) to fingerprint oil and chemically dispersed oil in seawater. Marine Pollution Bulletin 56:677-685.

• Christensen, Jan H.; Hansen, A.B.; Mortensen,J.; Andersen, O. 2005. Characterization and matching of oil samples using fluorescence spectroscopy and parallel factor analysis. Anal. Chem. 77:2210-2217

• Ehrhardt, Manfred G., Burns, Kathryn A., Bicego, Marcia C., 1992. Sunlight-induced compositional alterations in the seawater-soluble fraction of a crude oil. Marine Chemistry 37:53-64.

• Fuller, Christopher B., Bonner, James S., Kelly, Frank, Cheryl A. Page, Temitope Ojo, 2005. Real time geo-referenced detection of dispersed oil plumes. International Oil Spill Conference Monitoring:1-4. http://www.iosc.org/papers/IOSC%202005%20a356.pdf

• Joint Analysis Group, 2010. Report 1: Review of R/V Brooks McCall data to examine subsurface oil. http://ecowatch.ncddc.noaa.gov/JAG/files/JAG%20Report%20Brooks%20McCall%20final.pdf

• Joint Analysis Group, 2010. Report 2: Review of preliminary data to examine subsurface oil in the vicinity of MC252#1 May 19 to June 19 2010. http://ecowatch.ncddc.noaa.gov/JAG/files/JAG%20Data%20Report%202%20FINAL.pdf

• Hagemann, H.W. and Hollerbach A., 1986. The fluorescence behavior of crude oils with respect to their thermal maturation and degradation. Advances in Organic Geochemistry 10:473-480.

• Pradier, B., Largeau, C., Derenne, S., Martinez, L., Bertrand, P., 1989. Chemical basis of fluorescence alteration of crude oilsand kerogens—I. Microfluorimetry of an oil and its isolated fractions; relationships with chemical structure. Advances in Organic Geochemistry 16(1-3):451-460.

• Ryder, Alan G., 2002. Quantitative analysis of crude oils by fluorescence lifetime and steady state measurements using 380-nm excitation. Applied Spectroscopy 56(1):107-116.

• Ryder, Alan G., 2005. Analysis of crude petroleum oils using fluorescence spectroscopy. Reviews in Fluorescence. Ed.: C.D. Geddes and J.R. Lakowicz, Springer Science. pp 169-198.

• Shiu W.Y.; Bobra,M.; Bobra, A.M.; Maijanen, A.; Suntio, L.; Mackay, D. 1990. The water solubility of crude oils and petroleum products. Oil & Chem. Poll. 7: 57-84.

• Ziolli, R.L.; Jardim, W.F. (2002) Operational problems related to the preparation of the seawater soluble fraction of crude oil. Journal of Environmental Monitoring, 4 138-141.

References

Extra slides

Sample pH effect on EEMs

pH 2

Samples taken at 215 m depth DSH8

pH 8 pH 8 - 2

•Bringing sample pH back to 8 increases oil and CDOM signatures•pH primarily affects signal strength, although signatures of the polycyclic aromatic

hydrocarbon fluorene (330/350) and CDOM (375/450) are more evident in the spectral differences of pH 8 and pH 2

Emulsion vs. Dissolved FL response

• The form of oil could significantly effect sensor response and consequently data interpretation

WET Labs B.M. Ashton, LSU

Example of precision and control in lab experiments

-2

0

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4

6

8

10

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14

Qua Iboe Average I vs T

270/320

Controls

Error bars are ± 1 standard deviation

EEM data corrections• The correction process follows the recommendations from the AGU

chapman conference on Organic matter fluorescence. The process is:• 1) Daily check of instrument to ensure excitation and emission

monochromators are calibrated• 2) Curvette blank to check for fingerprint contamination• 3) Apply the inner filter effect correction following Lakowicz

equation (important when absorbance at any wavelength is > .05 AU• 4) We have triple checked the manufacturer instrument correction

procedure and we know use that instead of manually doing it• 5) Remove dark current signal • 6) Raman normalizedBeyond scope of current RAPID:• PARAFAC –not enough samples we need >100 different samples

(different could mean different time points, degradation points, etc). SAFire does not have enough resolution, also can not Raman normalize

• PCA/PLS – we need relevant environmental variables to include. Greater group effort is needed.