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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)