The Photodegradation of Endocrine Disrupting Compounds in Aqueous Solutions

Author

Peyton C. Morss, Bowdoin CollegeFollow

Year of Graduation

2014

Level of Access

Restricted Access Thesis

Embargo Period

5-15-2014

Department or Program

Chemistry

First Advisor

Soren Eustis

Abstract

Endocrine Disrupting Compounds (EDCs) are hormonal pollutants that negatively impact the reproductive system in humans and animals. Many of these compounds are commercially available in hormone therapies and contraceptives, and are therefore entering the water supply at worrying rates¹. 17α-ethinylestradiol (EE2) is a synthetic estrogen that has been found in natural waters in potent, bioactive concentrations². Wastewater treatment mechanisms are only 85% effective³ at removing this compound, and during the treatment process EE2 can react with hypobromous acid to form brominated derivatives.⁴ The effect of EE2 on the environment is well understood to have extremely negative consequences for ecosystems and human health⁵; of the effect of its brominated derivatives, little is known at all. In this paper, I examined the photochemistry of EE2 and two of its brominated derivatives. I aimed to determine how EE2 reacted in direct sunlight, and then to extrapolate to how it would degrade in the natural environment. Natural sunlight was mimicked using a photoreactor to simulate terrestrial solar irradiation, and the degradation was monitored using HPLC with a diode-array detector. The rate of degradation was calculated, and used to calculate the quantum yield or reaction efficiency. EE2 and its mono-brominated derivative had small quantum yields, but they were still within the range where direct photolysis would be a relevant environmental reaction. LC-MS/MS was used to attempt to characterize photoproducts and then hypothesize a mechanism of degradation.The reaction rates and quantum yields were successfully calculated, but little headway was made characterizing products. It was determined that EE2 was reacting during the ionization process, and so it was difficult to discern gas-phase chemistry from photochemistry. While knowledge of products could have led to a proposed mechanism, giving us molecular targets for removal and potential removal pathways that could hopefully be optimized for better wastewater treatment alternatives, the quantum yield of EE2 shows that future studies of its direct photochemistry will be environmentally relevant.