317
Bouchot et al. 1997; Carmona Uristegui 2015; Schifter et al. 2015; Ruiz-Fernández
et al. 2016). Chronic PAH sources can be significant: Gracia et al. (2016) estimated
that PAH input from Laguna de Términos (Fig. 19.1) inlets were as much as 0.1
metric tons/day from 2004 to 2010. Information about hydrocarbon contamination
in deep-sea sediments is more limited. PAH and TPH measurements were monitored
by PEMEX studies in the deep southern GoM during 2005–2010 and reported in
internal documents (Gracia 2012). Recently investigations of sediment hydrocarbons were carried in the southern Gulf of Mexico in an area encompassing
150,000 km
2
in a 187–3800 m depth range and related to bacterial diversity (GodoyLozano et al. 2018).
Oil spill fingerprinting employs a broad suite of petroleum biomarkers, reviewed in
Stout and Wang (2016). The molecule 17α(H),21β(H) C 30 hopane (referred to hereafter
as “hopane”) is one of the most commonly used markers. Hopane, a pentacyclic triterpane biomarker that is a diagenetic product of many bacterial membrane lipids, is a
common constituent of crude oils. It has been widely used as a tracer for petroleum
input to the environment, including northern GoM sediments impacted by the DWH
spill (e.g., Valentine et al. 2014). Hopane has been considered recalcitrant (highly resistant to degradation) and likely to persist in the environment over long time scales, but
several recent studies have found it may be less conservative than previously thought
(Huesemann et al. 2010; Bagby et al. 2017). Nevertheless, it is likely to remain a useful
member of the broad array of oil spill forensic biomarkers, all of which have individual
limitations and are most powerful when employed as a suite.
Reportedly low concentrations of pentacyclic triterpanes in Ixtoc 1 oil, together
with the pervasive hopane background in southern GoM sediments, precluded the use
of hopanes in forensic studies just after the spill (Boehm and Fiest 1980). Few reports
of hopanes or other hydrocarbon biomarkers in Bay of Campeche sediments have
been published in the decades following the Ixtoc 1 spill. Available data are from
surficial sediment samples collected in 1998 or later, likely to have been too recently
deposited to contain any primary record of Ixtoc 1 oil input. They can, however, provide insight into the nature and extent of petroleum inputs to the region. Carmona
Uristegui (2015) reported moderate hopane contamination (56–96 ng/g) of coastal
sediments near the Terminal Marítima Dos Bocas, Tabasco, but did not attribute it to
a specific source or discuss terpane biomarker distributions. In a study of sediments
near the mouth of the Coatzacoalcos River (Fig. 19.1), a major tributary of the southern GoM and site of multiple refineries and chemical plants, Farrán et al. (1987)
reported a uniform hydrocarbon pollution signature, with n-alkane, hopane, and sterane distributions showing no clear spatial trends. Scholz-Böttcher et al. (2008, 2009)
analyzed biomarkers in seafloor sediments collected during a PEMEX environmental
monitoring program and compared them to asphalt seep, crude oil, and drill cuttings
from the region. They found complex hydrocarbon backgrounds, with sediments containing varying proportions of a mature petroleum component, recent organic matter,
and a low-to-moderate maturity component thought to be derived from drill cuttings
disposed of offshore. The seafloor surface sediment focus of this study meant that it
was unlikely to have detected a primary, autochthonous Ixtoc 1 spill record, which
would have been buried by several decades of sedimentation.
19 Molecular Legacy of the 1979 Ixtoc 1 Oil Spill in Deep-Sea Sediments…
Bouchot et al. 1997; Carmona Uristegui 2015; Schifter et al. 2015; Ruiz-Fernández
et al. 2016). Chronic PAH sources can be significant: Gracia et al. (2016) estimated
that PAH input from Laguna de Términos (Fig. 19.1) inlets were as much as 0.1
metric tons/day from 2004 to 2010. Information about hydrocarbon contamination
in deep-sea sediments is more limited. PAH and TPH measurements were monitored
by PEMEX studies in the deep southern GoM during 2005–2010 and reported in
internal documents (Gracia 2012). Recently investigations of sediment hydrocarbons were carried in the southern Gulf of Mexico in an area encompassing
150,000 km
2
in a 187–3800 m depth range and related to bacterial diversity (GodoyLozano et al. 2018).
Oil spill fingerprinting employs a broad suite of petroleum biomarkers, reviewed in
Stout and Wang (2016). The molecule 17α(H),21β(H) C 30 hopane (referred to hereafter
as “hopane”) is one of the most commonly used markers. Hopane, a pentacyclic triterpane biomarker that is a diagenetic product of many bacterial membrane lipids, is a
common constituent of crude oils. It has been widely used as a tracer for petroleum
input to the environment, including northern GoM sediments impacted by the DWH
spill (e.g., Valentine et al. 2014). Hopane has been considered recalcitrant (highly resistant to degradation) and likely to persist in the environment over long time scales, but
several recent studies have found it may be less conservative than previously thought
(Huesemann et al. 2010; Bagby et al. 2017). Nevertheless, it is likely to remain a useful
member of the broad array of oil spill forensic biomarkers, all of which have individual
limitations and are most powerful when employed as a suite.
Reportedly low concentrations of pentacyclic triterpanes in Ixtoc 1 oil, together
with the pervasive hopane background in southern GoM sediments, precluded the use
of hopanes in forensic studies just after the spill (Boehm and Fiest 1980). Few reports
of hopanes or other hydrocarbon biomarkers in Bay of Campeche sediments have
been published in the decades following the Ixtoc 1 spill. Available data are from
surficial sediment samples collected in 1998 or later, likely to have been too recently
deposited to contain any primary record of Ixtoc 1 oil input. They can, however, provide insight into the nature and extent of petroleum inputs to the region. Carmona
Uristegui (2015) reported moderate hopane contamination (56–96 ng/g) of coastal
sediments near the Terminal Marítima Dos Bocas, Tabasco, but did not attribute it to
a specific source or discuss terpane biomarker distributions. In a study of sediments
near the mouth of the Coatzacoalcos River (Fig. 19.1), a major tributary of the southern GoM and site of multiple refineries and chemical plants, Farrán et al. (1987)
reported a uniform hydrocarbon pollution signature, with n-alkane, hopane, and sterane distributions showing no clear spatial trends. Scholz-Böttcher et al. (2008, 2009)
analyzed biomarkers in seafloor sediments collected during a PEMEX environmental
monitoring program and compared them to asphalt seep, crude oil, and drill cuttings
from the region. They found complex hydrocarbon backgrounds, with sediments containing varying proportions of a mature petroleum component, recent organic matter,
and a low-to-moderate maturity component thought to be derived from drill cuttings
disposed of offshore. The seafloor surface sediment focus of this study meant that it
was unlikely to have detected a primary, autochthonous Ixtoc 1 spill record, which
would have been buried by several decades of sedimentation.
19 Molecular Legacy of the 1979 Ixtoc 1 Oil Spill in Deep-Sea Sediments…