334
FTICR-MS played an important role in the post-DWH research – it expanded
the analytical window for the chemical assessment of the source Macondo well
(MW) oil, released during the DWH blowout, to include thousands of neutral,
basic, and acidic species, typically not analyzed with traditional methods
(McKenna et al. 2013); but more importantly, it helped to characterize weathered
coastal residues of the DWH spill. In combination with other tools such as thinlayer chromatography, infrared spectroscopy, and comprehensive two-dimensional gas chromatography, FTICR-MS confirmed that weathering processes,
such as photooxidation and biodegradation, were indeed responsible for the conversion of parent oil compounds, aromatic species, and saturated hydrocarbon
species, to oxygen-containing weathering products (Aeppli et al. 2012; Radović
et al. 2014; Ruddy et al. 2014; Hall et al. 2013). The identified products included
ketone, carboxylic acid, and higher numbered (>3) oxygen-containing species
(Ruddy et al. 2014).
Similarly, APPI-P (atmospheric pressure photoionization in positive mode)
FTICR-MS analyses of weathered coastal residues collected in the sGoM show the
presence of numerous oxidized classes of compounds, likely weathering transformation products. This is particularly evident in the samples collected in the lowenergy, protected mangrove areas, for example, at the Isla Arenas site (Fig. 20.2),
which are abundant in oxygen-bearing compound classes, such as O 1 -O 4 , akin to
“oxyhydrocarbons” observed in the nGoM coastal residues (Aeppli et al. 2012;
Ruddy et al. 2014), and various types of O x S x classes (Fig. 20.4), most likely weathering products of parent sulfur species presented in the spilled oil. Here we have to
note that the parent Ixtoc 1 oil has appreciably higher sulfur content in comparison
to the MW oil spilled during the DWH blowout, which is a characteristic feature of
most of the petroleum systems of the Campeche Sound basin, where the Ixtoc 1 well
was drilled (Atwood 1980; Guzman-Vega and Mello 1999; Santamarıa-Orozco
et al. 1998). To illustrate, sulfur-to-carbon ratio (S/C), as calculated from the APPI-P
FTICR-MS data, is approximately four times higher in the Ixtoc 1 source oil than in
the MW oil (S/C of 0.0142 and 0.0035, respectively). In comparison, in the weathered oil residue collected in the Isla Arenas mangroves and putatively related to
Ixtoc 1 oil, S/C ratio is 0.0097; under a very simplified assumption of direct conversion of parent sulfur compounds to weathering products, this would signify that
during 37 years, approximately 30% of sulfur species initially present in the Ixtoc 1
oil have been transformed to O x S x, and other products. On the other hand, in the oil
residues found at supratidal rocky shores in the sGoM, such as at the Punta Delgado
or Montepio sites (Fig. 20.2), the most prominent chemical feature, as detected
by the APPI-P FTICR-MS, is the pronounced abundance of sulfur-containing
species, including classes of compounds with multiple sulfur heteroatoms (up to
four S atoms), and also the presence of O x S x compound classes (Fig. 20.4). For
example, S/C ratio of heavily weathered tar residues collected at the Punta
Delgado and Montepio shores is, respectively, ~1.2 and 2.3 times higher than in
the reference Ixtoc 1 oil. Potential implications of these observations are discussed
in the section below.
J. R. Radović et al.
FTICR-MS played an important role in the post-DWH research – it expanded
the analytical window for the chemical assessment of the source Macondo well
(MW) oil, released during the DWH blowout, to include thousands of neutral,
basic, and acidic species, typically not analyzed with traditional methods
(McKenna et al. 2013); but more importantly, it helped to characterize weathered
coastal residues of the DWH spill. In combination with other tools such as thinlayer chromatography, infrared spectroscopy, and comprehensive two-dimensional gas chromatography, FTICR-MS confirmed that weathering processes,
such as photooxidation and biodegradation, were indeed responsible for the conversion of parent oil compounds, aromatic species, and saturated hydrocarbon
species, to oxygen-containing weathering products (Aeppli et al. 2012; Radović
et al. 2014; Ruddy et al. 2014; Hall et al. 2013). The identified products included
ketone, carboxylic acid, and higher numbered (>3) oxygen-containing species
(Ruddy et al. 2014).
Similarly, APPI-P (atmospheric pressure photoionization in positive mode)
FTICR-MS analyses of weathered coastal residues collected in the sGoM show the
presence of numerous oxidized classes of compounds, likely weathering transformation products. This is particularly evident in the samples collected in the lowenergy, protected mangrove areas, for example, at the Isla Arenas site (Fig. 20.2),
which are abundant in oxygen-bearing compound classes, such as O 1 -O 4 , akin to
“oxyhydrocarbons” observed in the nGoM coastal residues (Aeppli et al. 2012;
Ruddy et al. 2014), and various types of O x S x classes (Fig. 20.4), most likely weathering products of parent sulfur species presented in the spilled oil. Here we have to
note that the parent Ixtoc 1 oil has appreciably higher sulfur content in comparison
to the MW oil spilled during the DWH blowout, which is a characteristic feature of
most of the petroleum systems of the Campeche Sound basin, where the Ixtoc 1 well
was drilled (Atwood 1980; Guzman-Vega and Mello 1999; Santamarıa-Orozco
et al. 1998). To illustrate, sulfur-to-carbon ratio (S/C), as calculated from the APPI-P
FTICR-MS data, is approximately four times higher in the Ixtoc 1 source oil than in
the MW oil (S/C of 0.0142 and 0.0035, respectively). In comparison, in the weathered oil residue collected in the Isla Arenas mangroves and putatively related to
Ixtoc 1 oil, S/C ratio is 0.0097; under a very simplified assumption of direct conversion of parent sulfur compounds to weathering products, this would signify that
during 37 years, approximately 30% of sulfur species initially present in the Ixtoc 1
oil have been transformed to O x S x, and other products. On the other hand, in the oil
residues found at supratidal rocky shores in the sGoM, such as at the Punta Delgado
or Montepio sites (Fig. 20.2), the most prominent chemical feature, as detected
by the APPI-P FTICR-MS, is the pronounced abundance of sulfur-containing
species, including classes of compounds with multiple sulfur heteroatoms (up to
four S atoms), and also the presence of O x S x compound classes (Fig. 20.4). For
example, S/C ratio of heavily weathered tar residues collected at the Punta
Delgado and Montepio shores is, respectively, ~1.2 and 2.3 times higher than in
the reference Ixtoc 1 oil. Potential implications of these observations are discussed
in the section below.
J. R. Radović et al.