259
15.4 FTICR-MS Characterization of Dissolved Organic
Matter and Its Relevance for Oil Spill Assessments
Aquatic dissolved organic matter (DOM) comprises a cocktail of hundreds of
thousands of different compounds, which can be classified into four broad groups
of compounds based on their origin: (i) biomolecules released, exuded, excreted,
or leached from the living and decaying biota; (ii) biomolecules released from the
detritus of marine organisms; (iii) biomolecules percolating from surrounding
waters, atmospheric deposition, sediments, and terrigenous sources; and (iv)
molecules from anthropogenic input (such as oil spills, agricultural and industrial
runoffs) (Gonsior et al. 2011; Mopper et al. 2007). These molecules are commonly polyfunctional, heterogeneous species, have disperse molecular weights,
and are dissolved in natural marine waters at low concentrations in a ∼0.6 M ionic
strength inorganic salt solution, which further adds to the chemical complexity
and analytical challenges. The characterization of aquatic DOM with FTICR-MS
allows the complexity of the range of species in DOM to be identified by their
molecular formulas, which demonstrates not only the large complexity and variability of this carbon reservoir but also its response to environmental processes
that affect its molecular-level composition (Stubbins et al. 2010), which, in turn,
can be leveraged for oil spill assessment.
The physicochemical properties of crude oils change upon their release in the
aquatic environment, due to microbial degradation and weathering processes such as
evaporation, aqueous dissolution, volatilization, biodegradation, etc. (Atlas and
Hazen 2011; Radović et al. 2012), which selectively remove the low molecular
weight petroleum compounds, leaving the relatively heavier compounds, like those
found in the asphaltene and resin fractions of crude oil, in the marine environment for
years (Howard et al. 2005). Prior to the advent of ultrahigh-resolution mass spectrometry, the understanding of the oil spill signature in the marine environment was
limited to the GC-amenable parent oil compounds (Aeppli et al. 2012; Blumer et al.
1973; Harayama et al. 1999; Radović et al. 2014). The capability of FTICR-MS to
analyze high molecular weight, polyfunctional, and polar compounds makes it ideal
to determine the fate of oil and its transformation products in the aquatic DOM.
The studies using FTICR-MS to characterize aquatic DOM reveal FTICR-MS
spectra enriched in multi-oxygenated species (C x H y O z ) (Koch et al. 2007; Sleighter
and Hatcher 2008). The aquatic DOM spectra display a similarity in terms of the
broad compound class distribution, attributed to the constant diagenetic transformations in marine ecosystems due to microbial degradation and photooxidation (Jaggi
2018; Mentges et al. 2017). With the use of ultrahigh-resolution mass spectrometry,
Liu and Kujawinski (2015) identified molecular fingerprints for oil input in the
marine environment in the form of preferential partitioning of compounds with
higher heteroatom to carbon ratios from the oil to the water phase. These watersoluble oil-derived organics exhibit smaller molecular size than the natural marine
solid phase extracted DOM, as determined by Seidel et al. (2016).
Further, FTICR-MS has also been utilized as a valuable tool in tracking the fate of
dispersants applied following oil spills in the water column. Kujawinski et al. (2011)
15 Applications of FTICR-MS in Oil Spill Studies
15.4 FTICR-MS Characterization of Dissolved Organic
Matter and Its Relevance for Oil Spill Assessments
Aquatic dissolved organic matter (DOM) comprises a cocktail of hundreds of
thousands of different compounds, which can be classified into four broad groups
of compounds based on their origin: (i) biomolecules released, exuded, excreted,
or leached from the living and decaying biota; (ii) biomolecules released from the
detritus of marine organisms; (iii) biomolecules percolating from surrounding
waters, atmospheric deposition, sediments, and terrigenous sources; and (iv)
molecules from anthropogenic input (such as oil spills, agricultural and industrial
runoffs) (Gonsior et al. 2011; Mopper et al. 2007). These molecules are commonly polyfunctional, heterogeneous species, have disperse molecular weights,
and are dissolved in natural marine waters at low concentrations in a ∼0.6 M ionic
strength inorganic salt solution, which further adds to the chemical complexity
and analytical challenges. The characterization of aquatic DOM with FTICR-MS
allows the complexity of the range of species in DOM to be identified by their
molecular formulas, which demonstrates not only the large complexity and variability of this carbon reservoir but also its response to environmental processes
that affect its molecular-level composition (Stubbins et al. 2010), which, in turn,
can be leveraged for oil spill assessment.
The physicochemical properties of crude oils change upon their release in the
aquatic environment, due to microbial degradation and weathering processes such as
evaporation, aqueous dissolution, volatilization, biodegradation, etc. (Atlas and
Hazen 2011; Radović et al. 2012), which selectively remove the low molecular
weight petroleum compounds, leaving the relatively heavier compounds, like those
found in the asphaltene and resin fractions of crude oil, in the marine environment for
years (Howard et al. 2005). Prior to the advent of ultrahigh-resolution mass spectrometry, the understanding of the oil spill signature in the marine environment was
limited to the GC-amenable parent oil compounds (Aeppli et al. 2012; Blumer et al.
1973; Harayama et al. 1999; Radović et al. 2014). The capability of FTICR-MS to
analyze high molecular weight, polyfunctional, and polar compounds makes it ideal
to determine the fate of oil and its transformation products in the aquatic DOM.
The studies using FTICR-MS to characterize aquatic DOM reveal FTICR-MS
spectra enriched in multi-oxygenated species (C x H y O z ) (Koch et al. 2007; Sleighter
and Hatcher 2008). The aquatic DOM spectra display a similarity in terms of the
broad compound class distribution, attributed to the constant diagenetic transformations in marine ecosystems due to microbial degradation and photooxidation (Jaggi
2018; Mentges et al. 2017). With the use of ultrahigh-resolution mass spectrometry,
Liu and Kujawinski (2015) identified molecular fingerprints for oil input in the
marine environment in the form of preferential partitioning of compounds with
higher heteroatom to carbon ratios from the oil to the water phase. These watersoluble oil-derived organics exhibit smaller molecular size than the natural marine
solid phase extracted DOM, as determined by Seidel et al. (2016).
Further, FTICR-MS has also been utilized as a valuable tool in tracking the fate of
dispersants applied following oil spills in the water column. Kujawinski et al. (2011)
15 Applications of FTICR-MS in Oil Spill Studies