315
The limited information available from reports documenting the sedimentary
footprint of the Ixtoc 1 spill immediately following the blowout (e.g., Boehm and
Fiest 1980) precludes multi-decadal time-series approaches to understanding the
fate of the oil in the deep southern GoM. Forensic investigations using conventional
gas chromatography-mass spectrometry (Lincoln et al. 2017) and ultrahighresolution mass spectrometry (Radović et al. 2017) in tandem with sediment geochronology, however, have provided a means of assessing whether Ixtoc 1 oil
residues reached deep sediments, evaluating the fidelity and longevity of diagnostic
fingerprints, and provide insight into the preservation and transformation of petroleum compounds in the oceans over multi-decadal time scales.
19.3 Sources of Petroleum Constituents in the Southern Gulf
of Mexico
The southern Gulf of Mexico is a dynamic marine system with multiple natural and
anthropogenic petroleum inputs, many of which have the potential to confound oil spill
forensic efforts. Oil seeps are numerous and broadly distributed in the region (HolguinQuiñones et al. 2005; MacDonald et al. 2015; Sun et al. 2015), and rivers transport petroleum hydrocarbons from land to coastal sediments (e.g., Ruiz- Fernández et al. 2016).
Terrestrial sources of hydrocarbons include onshore seeps, sediments, urban runoff, and
pollution from petroleum refineries and infrastructure in the increasingly industrialized
watersheds of the southern GoM. The petroleum industry has a long history on the GoM
coast, with small refineries active in Tuxpan and Papantla as early as 1876 and 1880
(Alvarez de la Borda 2006). Rapid development of the prolific offshore oil fields in the
Bay of Campeche in the 1970s increased the risk of direct crude oil release into southern
GoM waters (García-Cuéllar et al. 2004). Industry infrastructure and operations may be
both episodic and chronic sources of contamination; for instance, all produced waters
from Bay of Campeche oil fields are discharged from the port of Dos Bocas (Fig. 19.1),
and sediments near it contain biomarker ratios consistent with a mature petroleum signal
(Schifter et al. 2015). Storm activity, coastal erosion, and resuspension of petrocarbon
from sites previously impacted by spills or natural sources also have the potential to complicate efforts to identify Ixtoc 1 impact horizons in sediments.
Finally, although the Ixtoc 1 spill was the largest spill in the southern GoM, it was not
an isolated incident, and accidental industrial releases of hydrocarbons such as the one
caused by the Abkatun platform explosion (O’Malley et al. 2016) continue to occur.
19.4 Previous Assessments of Hydrocarbon Contamination
in Southern Gulf of Mexico Sediments
Early-response cruises attempted to assess oil contamination in sediments near the Ixtoc
1 wellhead in 1979 (Farrington 1983). Based on total petroleum hydrocarbon (TPH)
data, Boehm and Fiest (1980) estimated that 1–3% of the oil was deposited in sediments
19 Molecular Legacy of the 1979 Ixtoc 1 Oil Spill in Deep-Sea Sediments…
The limited information available from reports documenting the sedimentary
footprint of the Ixtoc 1 spill immediately following the blowout (e.g., Boehm and
Fiest 1980) precludes multi-decadal time-series approaches to understanding the
fate of the oil in the deep southern GoM. Forensic investigations using conventional
gas chromatography-mass spectrometry (Lincoln et al. 2017) and ultrahighresolution mass spectrometry (Radović et al. 2017) in tandem with sediment geochronology, however, have provided a means of assessing whether Ixtoc 1 oil
residues reached deep sediments, evaluating the fidelity and longevity of diagnostic
fingerprints, and provide insight into the preservation and transformation of petroleum compounds in the oceans over multi-decadal time scales.
19.3 Sources of Petroleum Constituents in the Southern Gulf
of Mexico
The southern Gulf of Mexico is a dynamic marine system with multiple natural and
anthropogenic petroleum inputs, many of which have the potential to confound oil spill
forensic efforts. Oil seeps are numerous and broadly distributed in the region (HolguinQuiñones et al. 2005; MacDonald et al. 2015; Sun et al. 2015), and rivers transport petroleum hydrocarbons from land to coastal sediments (e.g., Ruiz- Fernández et al. 2016).
Terrestrial sources of hydrocarbons include onshore seeps, sediments, urban runoff, and
pollution from petroleum refineries and infrastructure in the increasingly industrialized
watersheds of the southern GoM. The petroleum industry has a long history on the GoM
coast, with small refineries active in Tuxpan and Papantla as early as 1876 and 1880
(Alvarez de la Borda 2006). Rapid development of the prolific offshore oil fields in the
Bay of Campeche in the 1970s increased the risk of direct crude oil release into southern
GoM waters (García-Cuéllar et al. 2004). Industry infrastructure and operations may be
both episodic and chronic sources of contamination; for instance, all produced waters
from Bay of Campeche oil fields are discharged from the port of Dos Bocas (Fig. 19.1),
and sediments near it contain biomarker ratios consistent with a mature petroleum signal
(Schifter et al. 2015). Storm activity, coastal erosion, and resuspension of petrocarbon
from sites previously impacted by spills or natural sources also have the potential to complicate efforts to identify Ixtoc 1 impact horizons in sediments.
Finally, although the Ixtoc 1 spill was the largest spill in the southern GoM, it was not
an isolated incident, and accidental industrial releases of hydrocarbons such as the one
caused by the Abkatun platform explosion (O’Malley et al. 2016) continue to occur.
19.4 Previous Assessments of Hydrocarbon Contamination
in Southern Gulf of Mexico Sediments
Early-response cruises attempted to assess oil contamination in sediments near the Ixtoc
1 wellhead in 1979 (Farrington 1983). Based on total petroleum hydrocarbon (TPH)
data, Boehm and Fiest (1980) estimated that 1–3% of the oil was deposited in sediments
19 Molecular Legacy of the 1979 Ixtoc 1 Oil Spill in Deep-Sea Sediments…