Photochemical Fate of Solvent Constituents of Corexit Oil Dispersants

Kover, Stephanie C.

Graduate Thesis Or Dissertation

Photochemical Fate of Solvent Constituents of Corexit Oil Dispersants Pubblico Deposited

Analytics

Scarica il pdf

Citations

Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/wp988k21z

Abstract

In 2010, an estimated 1.87 million gallons of chemical dispersants were applied to open ocean waters in Gulf of Mexico as part of the response to the Deepwater Horizon blowout. This unprecedented volume of dispersant application highlighted the importance of dispersant chemical formulations, raising questions of dispersant fate and transport in the open ocean and spurring research into formulation improvements. The research presented here elucidates the contribution of sunlight-driven processes to the degradation of solvent constituents of these dispersant mixtures to aid in optimizing the operational effectiveness. Specifically, the compounds propylene glycol (PG) and 2-butoxyethanol (2-BE) were examined. A series of photodegradation experiments were conducted to determine the contribution of direct photolysis and indirect photolysis via hydroxyl radical (HO^•) to compound degradation. Experiments were performed using both a low pressure (LP) and medium pressure (MP) mercury vapor ultraviolet (UV) lamp system, and a solar simulator. Sample matrices included ultrapure water, nitrate amended water, hydrogen peroxide (H₂O₂) spiked water, Gulf of Mexico seawater, and Boulder Creek surface water. Preliminary experiments included determination of the molar absorption coefficients (ε) and the HO^• reaction rate constants (k_HO•) of the individual compounds. This research found that significant direct photolysis of either PG or 2-BE from sunlight is unlikely. The k_HO• for PG and 2-BE were determined to be 6.15 × 10⁸ M^-1 s^-1 and 1.15 × 10⁹ M^-1 s^-1,respectively. Solar simulation and UV experiments indicate that in natural systems, neither PG nor 2-BE is expected to undergo significant, rapid degradation due to direct or indirect photolysis. PG and 2-BE are effectively degraded through indirect photolysis in the presence of high HO^• concentrations, as witnessed in the UV/H₂O₂ experiments conducted in this study, suggesting UV/H₂O₂ is a feasible alternative for the treatment of waters containing PG and 2-BE.

Creator