332
integrated into a multidisciplinary analytical approach that helped explain a large
sedimentation pulse that occurred in 2010 as a product of the DWH spill (Brooks
et al. 2015). Moreover, oil residues were found after 3 years in the same deep-sea
areas with little post-deposition biodegradation (Romero et al. 2017). Other studies
have also used GC-MS/MS-MRM for monitoring of toxic compounds (e.g., polycyclic aromatic hydrocarbons (PAHs)) in complex matrices such as sediments from
submerged coastal and deep-sea areas (Adhikari et al. 2017; Yin et al. 2015), seafood (fishes, shrimp, oysters, and crabs) from areas affected by the DWH spill (Xia
et al. 2012), and mesopelagic fishes over a long term in the nGoM (Romero et al.
2018). Altogether these studies have demonstrated a widespread occurrence of the
DWH oil residues in the nGoM and a persistence of oil residues in the environment
years after the spill with little human risk, but with potential adverse ecological
effects across multiple levels of biological organization.
Similarly, GC-MS/MS-MRM analysis of biomarkers in the sGoM has been
used to assess the source and weathering status of tar samples collected from mangrove prop roots (mangrove trees aerial network of roots; see Fig. 20.2).
Recalcitrant ratios (e.g., 18α(H)-22,29,30-trisnorneohopane (Ts)/17α(H)22,29,30-trisnorhopane (Tm); Ts/17α(H),21β(H)-hopane (HC30); 30,31-bishomohopane-22S/HC30) suggest Ixtoc 1 oil as the source of the tar samples. The
effect of weathering over 37 years after the Ixtoc 1 spill on these samples was
calculated as the percentage remaining of each hydrocarbon compound group
(n-alkanes, PAHs, hopanes, steranes, and triaromatic steroids (TAS)) normalized
to HC30 (recalcitrant internal marker; see Prince et al. (1994) and Garrett et al.
(1998)) and compared to the normalized value in the reference Ixtoc 1 oil (%
remaining = [compound a /HC30] sample /[compound a /HC30] Ixtoc 1 oil ). Results indicate
remarkable persistence of homohopanes C27–C32 (~100% remaining), followed
by TAS (~90% remaining) and high molecular weight PAHs (~60% remaining).
Other compound groups showed lower relative amounts remaining in the tar samples, like homohopanes C33–C35 (~45%), steranes C27 (~30%), n-alkanes
(~10%), and low molecular weight PAHs (~5%). In these coastal samples, high
enrichment, relative to Ixtoc 1 crude oil, was found for steranes C28–C29 compounds (140–200%). Trends observed in homohopanes C27–C32 are similar to
those found in previous studies 2–3 years after the DWH spill (Aeppli et al. 2014).
However, differences in weathering patterns were found in the tar samples from
the mangrove forests relative to previous studies after the DWH spill, showing low
% remaining of steranes C27 and high % remaining of TAS and high molecular
weight PAHs (Fig. 20.3).
20.3.2 FTICR-MS
Contrary to the GC-MS/MS, Fourier transform ion cyclotron mass spectrometry
(FTICR-MS) is a non-targeted instrumental technique with a broad range of species
detection and ultrahigh mass resolution, making it a tool for exploratory qualitative
J. R. Radović et al.
integrated into a multidisciplinary analytical approach that helped explain a large
sedimentation pulse that occurred in 2010 as a product of the DWH spill (Brooks
et al. 2015). Moreover, oil residues were found after 3 years in the same deep-sea
areas with little post-deposition biodegradation (Romero et al. 2017). Other studies
have also used GC-MS/MS-MRM for monitoring of toxic compounds (e.g., polycyclic aromatic hydrocarbons (PAHs)) in complex matrices such as sediments from
submerged coastal and deep-sea areas (Adhikari et al. 2017; Yin et al. 2015), seafood (fishes, shrimp, oysters, and crabs) from areas affected by the DWH spill (Xia
et al. 2012), and mesopelagic fishes over a long term in the nGoM (Romero et al.
2018). Altogether these studies have demonstrated a widespread occurrence of the
DWH oil residues in the nGoM and a persistence of oil residues in the environment
years after the spill with little human risk, but with potential adverse ecological
effects across multiple levels of biological organization.
Similarly, GC-MS/MS-MRM analysis of biomarkers in the sGoM has been
used to assess the source and weathering status of tar samples collected from mangrove prop roots (mangrove trees aerial network of roots; see Fig. 20.2).
Recalcitrant ratios (e.g., 18α(H)-22,29,30-trisnorneohopane (Ts)/17α(H)22,29,30-trisnorhopane (Tm); Ts/17α(H),21β(H)-hopane (HC30); 30,31-bishomohopane-22S/HC30) suggest Ixtoc 1 oil as the source of the tar samples. The
effect of weathering over 37 years after the Ixtoc 1 spill on these samples was
calculated as the percentage remaining of each hydrocarbon compound group
(n-alkanes, PAHs, hopanes, steranes, and triaromatic steroids (TAS)) normalized
to HC30 (recalcitrant internal marker; see Prince et al. (1994) and Garrett et al.
(1998)) and compared to the normalized value in the reference Ixtoc 1 oil (%
remaining = [compound a /HC30] sample /[compound a /HC30] Ixtoc 1 oil ). Results indicate
remarkable persistence of homohopanes C27–C32 (~100% remaining), followed
by TAS (~90% remaining) and high molecular weight PAHs (~60% remaining).
Other compound groups showed lower relative amounts remaining in the tar samples, like homohopanes C33–C35 (~45%), steranes C27 (~30%), n-alkanes
(~10%), and low molecular weight PAHs (~5%). In these coastal samples, high
enrichment, relative to Ixtoc 1 crude oil, was found for steranes C28–C29 compounds (140–200%). Trends observed in homohopanes C27–C32 are similar to
those found in previous studies 2–3 years after the DWH spill (Aeppli et al. 2014).
However, differences in weathering patterns were found in the tar samples from
the mangrove forests relative to previous studies after the DWH spill, showing low
% remaining of steranes C27 and high % remaining of TAS and high molecular
weight PAHs (Fig. 20.3).
20.3.2 FTICR-MS
Contrary to the GC-MS/MS, Fourier transform ion cyclotron mass spectrometry
(FTICR-MS) is a non-targeted instrumental technique with a broad range of species
detection and ultrahigh mass resolution, making it a tool for exploratory qualitative
J. R. Radović et al.