Long-Term Environmental Consequences and Fate of the Oil Residues Found
along Alabama's Beaches after the Deepwater Horizon Oil Spill on the
Gulf of Mexico
Abstract
The explosion of the Deepwater Horizon (DWH) oil platform in April 2010
on the Gulf of Mexico (GOM) released more than 700 million liters of
crude oil. This catastrophe is the largest oil spill in US history and
one of the largest in the world that resulted in over 1000 km of oiled
shoreline across four different states (FL, AL, MS, and LA). When the
floating emulsified oil approached sandy beaches, a portion of the
emulsified oil interacted with suspended sediments and sank, forming
submerged oil mats (tarmats). Since their formation, hydrodynamic
processes fragmented the tarmats to form tarballs. The tarballs are
highly mobile in the nearshore environment and can be found on GOM
beaches to date. The objective of this proposal is to complete a
comprehensive long-term chemical characterization study to investigate
the fate of petroleum biomarker compounds used for
chemical-fingerprinting of the tarballs collected at different times
over the past 10 years along the Alabama shoreline. Petroleum biomarkers
are geochemical organic compounds present in crude oils that can be
related to their unique biological precursors. Currently, the most
common method used for identifying and fingerprinting the oil spill
source is characterizing these biomarkers. Hence, the long-term fate of
three groups of biomarker compounds (terpanes, steranes, and triaromatic
steranes) present in the tarballs collected from the Alabama shoreline
is investigated for using them for fingerprinting purposes. There have
been contradicting literature data on the degradation levels of these
biomarkers, and this field-scale characterization study demonstrates
that most of the investigated biomarkers remain recalcitrant after 10
years of natural weathering. We also quantified the changes in the
concentration levels of toxic polycyclic aromatic hydrocarbons (PAHs)
present in these tarballs, and the results show that many of these PAHs
are recalcitrant. These results are consistent with previous studies
that indicated that certain heavy toxic and carcinogenic PAHs, such as
chrysene, can be recalcitrant and remain in the tarballs for a long
time. Therefore, it is important to track the levels of these
recalcitrant PAHs in the tarballs to determine their potential toxicity
effects.