Polycyclic aromatic hydrocarbon, trace element, and nutrient

distributions as affected by the Deepwater Horizon Oil Spill

Shiller, A.M.(1), D. Joung(1), T.L. Wade(2), J.L. Sericano(2), S.T. Sweet(2), K.M. Yeager(3), C.A.

Brunner(1), and P. Louchouarn(4)

(1)---USM; (2)---TAMU; (3)---UKy; (4)---TAMU-G With assistance from S.B. Joye, V.L. Asper, L. Guo

Thanks to NSF & BP for support

Sampling

• Deepwater Horizon explosion: April 20• R/V Pelican…..early May• R/V Walton Smith…..late May• Leak stopped: July 15• R/V Cape Hatteras…..mid Oct 2010• R/V Cape Hatteras…..right now!

• Plus sediment sampling in MS Sound & Bight and coastal marshes through 2010

Why Trace Elements in Oil?• 10’s to >100’s of ppm of some metals• Some (especially V and Ni) bound by

porphyrins• Also, Ba from drilling muds• But Macondo oil low in metals• Solubilization by components of

dispersant?

“DOSS” surfactantsodium dioctyl sulfosuccinate

Late May/Early June (R/V Walton Smith)

Fe (nM)

0.0 0.5 1.0

Dep

th (m

)

600

800

1000

1200

1400

Co (nM)

0.00 0.05 0.10 0.15

Ba (nM)

50 75 100

Cu (nM)

1.2 1.6 2.0

600

800

1000

1200

1400

What are PAH’s?(and who cares?)

• Polycyclic aromatic hydrocarbons• Naturally present in fossil fuels; also

produced during combustion• Some are carcinogenic• Widely dispersed through environment• Can fingerprint source• Macondo well source ~1% PAH

28.6

28.7

28.8

28.9

-89 -88.8 -88.6 -88.4 -88.2

Latit

ude

Longitude

Walton Smith sample locations--late May Surface

Subsurface

Wellhead

0

400

800

1200

1600

0 50 100 150

Dep

th (m

)

PAH (µg/L)

0

40

80

120

0 10 20 30

Tota

l PA

H (µ

g/L)

Distance from wellhead (km)

Sub-surface samples

Late May PAH Data(R/V Walton Smith)

Physiological effects on embryonic & larval marine fish reported for PAH < 5 µg/L

Late May PAH Data(R/V Walton Smith)

Similar observations on R/V Pelican cruise (Diercks et al.,

2010)

0

400

800

1200

1600

0% 25% 50% 75% 100%

Dep

th (m

)Percent Methyl Naphthalenes

0%

20%

40%

60%

1 10 100% M

ethy

l Nap

htha

lene

s

Distance from Wellhead (km)

Macondo well source: ~50% of PAH’s were methyl naphthalenes

Surface water

Dibenzothiophene/Phenanthrene Ratios: C3 vsC2 derivatives---ratios should weather similarly

D3/P3

0.0 0.2 0.4 0.6 0.8

D2/

P2

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Deep PlumeSfc WaterHemi-pelagic sedsShallow sedsCoastal marsh sedsWellhead

MP/P = methylphenanthrenes/phenanthreneFl/(Fl + Py) = Fluoranthene/(Fluoranthene + Pyrene)

More “pyrogenic” towards lower right

Fl/(Fl+Py)

0.2 0.4 0.6 0.8

MP

/P

0

5

10

15

20 Deep PlumeSfc WaterHemi-pelagic sedsShallow sedsCoastal marsh sedsWellhead

More “pyrogenic” towards upper right

(Phe+An)/(Phe+An+C1Phe)

0.0 0.2 0.4 0.6 0.8

Fl/(F

l+P

y)

0.2

0.4

0.6

0.8Deep PlumeSfc WaterHemi-pelagic sedsShallow sedsCoastal marsh sedsWellhead

Low to high MW PAH ratio vsChrysene/Benzo(a)anthracene ratio

Low values of each ratio imply “pyrogenic”

Chr/BaA

0 2 4 6 8 10 12

LMW

/HM

W

0.01

0.1

1

10

100

1000

Deep PlumeSfc WaterHemi-pelagic sedsShallow sedsCoastal marsh sedsWellhead

Pyrogenic Index (Wang)

0.001 0.01 0.1 1 10

Frac

tion

Met

hyl-n

apht

hale

nes

0.0

0.2

0.4

0.6

0.8Deep PlumeSfc WaterHemi-pelagic sedsShallow sedsCoastal marsh sedsWellhead

Methane Update

• Latest news from R/V Cape Hatteras…methane low nM and no significant blips on the Chelsea Aquatracka. But they’re still ~20 km from wellhead.

• (Thanks to Hannah Roberts and DongJoo Joung for updates from the ship)

Conclusions

• Small trace element anomalies probably due to oil (Co) and drilling muds (Ba, Cu?)

• Fe limiting (?) but benthic source (?)• Fractionation of PAH’s observed from

wellhead through the environment• Use pyrogenic indicators cautiously

Life at sea was good

(as long as there was no crude smell)