Time-dependent molecular progression and acute toxicity of oil-soluble, interfacially-active, and water-soluble species reveals their rapid formation in the photodegradation of Macondo Well Oil

Huan Chen; Amy M McKenna; Sydney F Niles; Joseph W Frye; Taylor J Glattke; Ryan P Rodgers

doi:10.1016/j.scitotenv.2021.151884

Time-dependent molecular progression and acute toxicity of oil-soluble, interfacially-active, and water-soluble species reveals their rapid formation in the photodegradation of Macondo Well Oil

Sci Total Environ. 2022 Mar 20:813:151884. doi: 10.1016/j.scitotenv.2021.151884. Epub 2021 Nov 26.

Authors

Huan Chen¹, Amy M McKenna², Sydney F Niles³, Joseph W Frye³, Taylor J Glattke³, Ryan P Rodgers⁴

Affiliations

¹ National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Dr., Tallahassee, FL 32310, USA. Electronic address: huan.chen@magnet.fsu.edu.
² National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Dr., Tallahassee, FL 32310, USA; Department of Soil and Crop Sciences, Colorado State University, 1170 Campus Delivery, Fort Collins, CO 80523, USA.
³ National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Dr., Tallahassee, FL 32310, USA; Department of Chemistry and Biochemistry, 95 Chieftan Way, Florida State University, Tallahassee, FL 32306, USA.
⁴ National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Dr., Tallahassee, FL 32310, USA; Department of Chemistry and Biochemistry, 95 Chieftan Way, Florida State University, Tallahassee, FL 32306, USA. Electronic address: rodgers@magnet.fsu.edu.

PMID: 34838916
DOI: 10.1016/j.scitotenv.2021.151884

Abstract

Photodegradation is a significant weathering process that transforms spilled oil, yet, the fate, degradation rate, and molecular transformations that occur through photoinduced pathways remain relatively unknown. The molecular complexity combined with the increased polarity of photoproducts challenges conventional analytical techniques. Here, we catalogue the molecular progression of photochemical transformation products of Macondo Well Oil by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We track the molecular compositions of oil-soluble, interfacially-active, and water-soluble oil species formed at varying time intervals in photomicrocosm experiments. Short photoirradiation periods (<24 h), not previously reported, are included to reveal rapid photooxidation of native oil components. Surface oil films exposed to solar irradiation were shown to increasingly contribute to the dissolved organic carbon pool as a function of increased irradiation time. FT-ICR MS analysis of acidic species of each fraction identifies tens of thousands of oil-soluble, interfacially-active, and water-soluble phototransformation products, including O_x, NO_x, and SO_x species. Oil-soluble species incorporate oxygen as a function of irradiation periods. After 96 h of irradiation, ~14 wt% of the photooxidized oil film was interfacially active and contained phototransformed species with up to 12 oxygen atoms per molecule. Water-soluble species correspond to highly oxygenated compounds. Importantly, photochemical oxidation is shown to occur within the first hour. Beyond 24 h, photoproducts remain compositionally similar, highlighting the rapid effect of photodegradation to transform oil species into water-soluble compounds. Molecular fingerprints provided by FT-ICR MS highlight the oxygen dependence on oil/water solubility. Microtox® analysis indicates that the toxicity of water-soluble photoproducts rapidly increases at early irradiation time points (first 24 h) compared to the dark control and reaches a maximum at 6 h of irradiation. Results highlight the temporal, molecular progression of photoproducts as they partition from oil-soluble to oil-soluble interfacially-active, and finally to water-soluble species.

Keywords: Acute toxicity; Deepwater Horizon oil spill; FT-ICR MS; Microtox®; Photooxidation; Solar simulation.

MeSH terms

Acids*
Mass Spectrometry
Oxidation-Reduction
Petroleum* / toxicity
Photolysis

Substances

Acids
Petroleum