Degradation of Pensacola Beach Tar Balls from the Deep
Water Horizons Explosion
Stacia Dudley*, John Kaba, Markus Huettel
Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, Fl
Our objectives were to analysis the amount of matter
released from the tar balls over time by testing the
DOC, CDOM, TPH release from tarballs into the water
column and quantitfy the rate of decomposition per
gram of weathered petroleum.
Determine bacterial activity in oil contaminated samples
Oxygen consumption and DIC production. Assess
some of the potential risks to organism living in
saturated sediments while weathered petroleum
decomposition is occur.
Incubation
Studies
Tar balls were taken from
Pensacola beach and
homogenized in the lab.
They were then formed
into pellets ranging in
weight from 0.4g, .8g,
1.2g, 1.6g, 2.0g.
These pellets were
transferred to 40 mL and
with filter seawater and
rolled in a 25C room for 1
day, 1 week, and 1 month.
Each vial was initially tested for oxygen. After the
designated incubation period vials were tested for
oxygen consumption, dissolved inorganic carbon (DIC),
dissolved organic carbon (DOC) and Colored Dissolved
Organic Mater (CDOM). Another Experiment was then
conducted incubating vials of the same tar
concentrations for 1 day,2 days, 3 days and 7 days. In
order to get a range of activity occuring under oxic
conditions.
O2 consumed
200
0
1
150
2
100
3
4
50
5
0
0
2
4
6
250
200
0
150
1
2
100
3
4
50
5
0
8
0
Day
5
10
15
Fig 1: Oxygen consumed per gram of tar over a
one week time period
DIC (umol C)
1
2
3
4
5
1
2
3
4
5
6
7
8
Sample Day
0
1
2
3
4
5
0
5
10
25
30
DOC (umol C)
6000
5000
0
4000
1
3000
2
3
2000
4
1000
5
0
30
8000
7000
6000
5000
4000
3000
2000
1000
0
0
1
2
3
4
5
0
40
2
4
6
8
Day
Fig 6: Total dissolved organic
carbon released into the water
column at increase concentrations
of tar through a one month
incubation.
days
Fig 5: Total dissolved organic carbon
released into the water column at
increasing concentration of tar during a
week incubation.
Graphical Analysis
CDOM Emission Results
Nitrogen
120
100
80
0
60
1
40
2
3
20
4
0
0
10
20
30
40
5
Sample Day
Fig 7: Total nitrogen in the water column for
increasing concentration of tar though out a
seven day incubation.
Fig 8: CDOM present in sea
water (blank) after a one day
incubation
Key:
C humics excited by UVC
A humics excited by UVA
M marine organic matter
T Tryptophan
Fig 9: CDOM released into
the water column from 1.2
grams of tar after a one day
incubation.
Fig 10: CDOM released
into the water column
from 2.0 grams of tar after
a one day incubation.
35
Total Carbon
7000
Graphical Analysis of Data
20
Fig 4: DIC released into the water
column over a one month period
8000
20
15
Sample Days
Total Carbon
10
35
2700
2600
2500
2400
2300
2200
2100
2000
1900
1800
1700
Fig 3: DIC released into the water column
over a one week period
0
30
DIC
0
0
25
Fig 2: Oxygen consumer per gram of tar
over a one month time period.
DIC
2600
2550
2500
2450
2400
2350
2300
2250
2200
20
Day
Nitrogen (umol)
In general: As bacterial activity increases oxygen
availability in saturated sediments decreases.
A number of laboratory and field studies have
shown the ability for certain microbes to degrade
oil and tar substances. However the length of
time this process takes per amount of petroleum
hydrocarbons present as been difficult to quantify.
As the amount of petroleum hydrocarbons
increase the amount of bacterial activity should
Increase.
It is possible that a saturation level exists were
bacterial activity reaches a maximum even if
concentrations of petroleum hydrocarbons are
increased.
Cross section of Pensacola
beach sediment, July 30th
2010
250
Nitrogen
Nitrogen (μmol)
Introduction
Pensacola Beach State Park, July
2010
The results of the incubation studies for each of
the trials are shown in the following figures.
Generally, as the concentration of tar increased
the faster oxygen was consumed in the water
column (Fig.1). In most samples oxygen was only
present for one week (Fig. 2). The greatest
release in DIC occurred within the first week,
after one week DIC continued to be emitted into
the water column but at a slower rate (Fig. 4).
DOC was released in slowly increasing amounts
through both incubations, except in the 3rd
concentration where a shop decrease was noted
(Fig. 5 and 6). However, this is likely due to some
difficulties with the filtration process. Overall
samples containing higher concentrations of tar
released a greater amount of nitrogen into the
water column. The release of nitrogen could be
due to the decomposition of deceased microbes.
A greater amount of CDOM was released into the
water column for samples containing high
concentrations and over a longer period of time
(Fig. 8-10).
300
DOC umol
On April 20th 2010 the Deep Water Horizon oilrig exploded
discharging 4.9 million barrels of oil into the Gulf of Mexico
over the course of 97 days. Oil washed up onto the shores of
the Gulf of Mexico. In Pensacola Florida beach sands
weathered oil petroleum hydrocarbon were found in
concentrations ranging from 3.1 to 4,500 mg kg-1 (Kostka et
al, 2011). This study analyzed the amount of time it would
take the weathered petroleum in beach sands to degrade and
to assess the ecological impact of the degradation process on
the beach sands. Homogenized Pensacola Beach tar balls
were molded into standardized pellets of 1g, 2g, 3g, 4g, 5g
concentrations. The pellets were incubated for 1 day, 1 week
and 1 month and tested for oxygen consumption, dissolved
inorganic carbons, dissolved organic carbons and colored
dissolved organic matter which were released into the water
columns. The 4g to 5g concentration of weathered petroleum
oil led to greater microbial degrading processes. The
degradation process caused a greater release of dissolved
hydrocarbons and an increased rate of oxygen consumption
leading to the creation of anaerobic condition in saturated
sediments. The conditions caused by the oil degrading
microbes were determined to be detrimental to the organism
living in saturated sediments.
DIC (μmol C)
Pensacola Beach State Park
Oxygen consumption, DOC
and DIC in the water column
O2 consumption
300
O2 consumed
umol/L
Abstract
Pensacola Sample Collection Sites
O2 Consumption
20
15
0
10
1
2
5
3
0
0
2
4
Sample Day
6
8
4
5
Fig 8: Total nitrogen in the water column for
increasing concentrations of tar though out a
month incubation.
Conclusions
Most of the decomposition appears to be occurring between day 1 and day 3
while oxygen is still present.
Higher oil concentrations appear to consume oxygen faster and produce greater
amounts of DIC and CDOM
Rapid Nitrogen consumption in the initial days is like due to increase bacterial
activity.
Nitrogen increase in changes in microbial activity as oxygen is consumed