Date of Award

Spring 1-1-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Karl Linden

Second Advisor

Fernando Rosario-Ortiz

Third Advisor

Kaelin Cawley

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 (kHO•) of the individual compounds. This research found that significant direct photolysis of either PG or 2-BE from sunlight is unlikely. The kHO• 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.

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