Dispersant-enhanced photodissolution of macondo crude oil: A molecular perspective

David C Podgorski; Jacob Walley; Matthew P Shields; Deja Hebert; Maxwell L Harsha; Robert G M Spencer; Matthew A Tarr; Phoebe Zito

doi:10.1016/j.jhazmat.2023.132558

Dispersant-enhanced photodissolution of macondo crude oil: A molecular perspective

J Hazard Mater. 2024 Jan 5:461:132558. doi: 10.1016/j.jhazmat.2023.132558. Epub 2023 Sep 15.

Authors

David C Podgorski¹, Jacob Walley², Matthew P Shields³, Deja Hebert³, Maxwell L Harsha³, Robert G M Spencer⁴, Matthew A Tarr³, Phoebe Zito⁵

Affiliations

¹ Department of Chemistry, University of New Orleans, 2000 Lakeshore Drive New Orleans, LA 70148, United States; Chemical Analysis & Mass Spectrometry Facility, University of New Orleans, 2000 Lakeshore Drive New Orleans, LA 70148, United States; Pontchartrain Institute for Environmental Sciences, Shea Penland Coastal Education and Research Facility, University of New Orleans, 2000 Lakeshore Drive New Orleans, LA 70148, United States. Electronic address: dcpodgor@uno.edu.
² Department of Natural Sciences, Gardner-Webb University, Boiling Springs, NC 28017, United States.
³ Department of Chemistry, University of New Orleans, 2000 Lakeshore Drive New Orleans, LA 70148, United States.
⁴ National High Magnetic Field Laboratory, Geochemistry Group, Department of Earth, Ocean and Atmospheric Sciences, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, United States.
⁵ Department of Chemistry, University of New Orleans, 2000 Lakeshore Drive New Orleans, LA 70148, United States; Chemical Analysis & Mass Spectrometry Facility, University of New Orleans, 2000 Lakeshore Drive New Orleans, LA 70148, United States.

PMID: 37729707
DOI: 10.1016/j.jhazmat.2023.132558

Abstract

Previous laboratory studies developed a conceptual model based on elevated non-volatile dissolved organic carbon (NVDOC) concentrations after photodegradation and subsequent dissolution of Macondo oil following the Deepwater Horizon blowout. However, those experiments did not account for the effects of ∼1 million gallons of dispersant applied to the surface oil. Here, laboratory results show photodissolution in the presence of dispersant results in > 2x increase in NVDOC concentrations after extensive photoprocessing relative to oil without dispersant. This result corresponds with an apparent increase in the percentage of surface oil photodissolution from approximately 4% in the absence of dispersant to 7% in the presence of dispersant. The oil and dissolved products were analyzed by excitation-emission matrix spectroscopy and ultrahigh resolution mass spectrometry. The compounds that persisted in the oil phase are relatively aromatic without dispersant, while those in the presence of dispersant are highly aliphatic, paraffinic, wax-like compounds. The composition of the dissolved compounds produced from both treatment types are nearly identical after 240 h of exposure to simulated sunlight. The NVDOC and chemical composition information indicate that the photodissolution of MC252 oil in the presence of dispersant is enhanced and accelerated, suggesting that the effects of dispersants should be included in mass transfer calculations from the oil to the aqueous phase.

Keywords: Corexit EC9500A; Dissolved organic carbon; Dissolved organic matter; Hydrocarbon oxidation products; Oil spill; Photochemistry.