Oil Spill Source Identification by Principal Component Analysis of Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectra

Abstract

One fundamental challenge with either acute or chronic oil spills is to identify the source, especially in highly polluted areas, near natural oil seeps, when the source contains more than one petroleum product or when extensive weathering has occurred. Here we focus on heavy fuel oil that spilled (~200,000 L) from two suspected fuel tanks that were ruptured on the motor vessel (M/V) Cosco Busan when it struck the San Francisco-Oakland Bay Bridge in November 2007. We highlight the utility of principal component analysis (PCA) of elemental composition data obtained by high resolution FT-ICR mass spectrometry to correctly identify the source of environmental contamination caused by the unintended release of heavy fuel oil (HFO). Using ultrahigh resolution electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry, we uniquely assigned thousands of elemental compositions of heteroatom-containing species in neat samples from both tanks and then applied principal component analysis. The components were based on double bond equivalents for constituents of elemental composition, CcHhN1S1. To determine if the fidelity of our source identification was affected by weathering, field samples were collected at various intervals up to two years after the spill. We are able to identify a suite of polar petroleum markers that are environmentally persistent, enabling us to confidently identify that only one tank was the source of the spilled oil: in fact, a single principal component could account for 98% of the variance. Although identification is unaffected by the presence of higher polarity, petrogenic oxidation (weathering) products, future studies may require removal of such species by anion exchange chromatography prior to mass spectral analysis due to their preferential ionization by ESI.

Chemical dispersants can suppress the activity of natural oil-degrading microorganisms

“…4 A and B), agreeing with previous studies reporting that crude oil (40), including Macondo oil (39), contains numerous biodegradable polar and water-soluble organic nitrogen compounds. The WAF treatments exhibited the highest rates of degradation of oil-derived nitrogen-containing compounds (∼8% vs. ∼1% in the CEWAF treatment, Fig.…”

“…High-resolution FT-ICR-MS analysis provides a much more robust way to assess the molecular diversity of hydrocarbons in oil than does conventional GC-MS analyses (39,40). The FT-ICR-MS results further suggest that significantly more oil-derived dissolved organic molecules were degraded in the WAF compared with CEWAF (± nutrients) treatments, again leading to the conclusion that more extensive biodegradation occurred in the absence of dispersant (Fig.…”

Biodegradation of crude oil and dispersants in deep seawater from the Gulf of Mexico: Insights from ultra-high resolution mass spectrometry

“…2B, D, and F). This is consistent with previous ESI-FT-ICR-MS analyses of crude oil which showed high relative abundances of molecular formulae in the r 300 Da mass range (Corilo et al, 2013). In the present study, the WAF of oil molecular formulae clustered in specific areas in van-Krevelen space: molecular formulae with negative loadings on CA2, which were most abundant in the oil-only incubations, exhibited lower O/C ratios than the natural marine SPE-DOM (blue circles in Supplementary Fig.…”

“…It is possible that oil-derived and seawater DOM served as N, S and P sources to the microorganisms growing in the oil-amended treatments and that these nutrients fueled the observed accumulation of biomass when CHO compounds were metabolized. In particular, N-containing oil compounds were proposed to serve as substrate for microbes when N assimilation is stimulated during oil degradation (Lu et al, 2012) and several N-compound oil classes have been shown to undergo significant degradation (Corilo et al, 2013). The data presented here argue strongly for microbial assimilation of both seawater and oil-derived nitrogen to support their growth.…”

“…Thus, the WAF of the analyzed oil exhibited a specific molecular fingerprint which can be used to track the fate of these compounds during incubation. In fact, the oil molecular fingerprint may be useful to identify future oil spill sources in the environment (Corilo et al, 2013).…”