Event Title

Quantifying Hydroxyl Radical in Natural Waters: Role of Dissolved Organic Matter in Determining Production Rates

Location

CSU Ballroom

Start Date

21-4-2014 10:00 AM

End Date

21-4-2014 11:30 AM

Student's Major

Chemistry and Geology

Student's College

Science, Engineering and Technology

Mentor's Name

John Thoemke

Mentor's Email Address

john.thoemke@mnsu.edu

Mentor's Department

Chemistry and Geology

Mentor's College

Science, Engineering and Technology

Description

Reactive oxygen species, such as the hydroxyl radical, have gained more attention over the last several years due to their presence in natural water sources. These oxygen species are highly reactive and generated from the photochemical reaction between sunlight and dissolved organic matter. The concern for these species is their potential role in transforming other chemical pollutants. The presence of hydroxyl radical in natural waters has been determined but its high reactivity makes it difficult to quantify. We used a molecular probe, terephthalic acid, to quantify hydroxyl radical. Terephthalic acid binds selectively to hydroxyl radical forming 2-hydroxyterephthalic acid, which is measurable using high performance liquid chromatography with fluorescence detection. In this study, the hydroxyl radical was created by exposing nitrate solutions to ultraviolet light (UVB 320-290nm). Although nitrate has been found to contribute to the production of hydroxyl radical, we determined that under the conditions prevailing in surface waters, it plays a minimal role compared to the amount produced by dissolved organic matter. We also discovered that nitrate exposed to natural light (UVA 400-320nm) produces significantly less hydroxyl radical than nitrate exposed to UVB. This detection method has also been used to determine how the origin of dissolved organic matter (terrestrial vs. microbial) affects the concentration of hydroxyl radical produced.

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Apr 21st, 10:00 AM Apr 21st, 11:30 AM

Quantifying Hydroxyl Radical in Natural Waters: Role of Dissolved Organic Matter in Determining Production Rates

CSU Ballroom

Reactive oxygen species, such as the hydroxyl radical, have gained more attention over the last several years due to their presence in natural water sources. These oxygen species are highly reactive and generated from the photochemical reaction between sunlight and dissolved organic matter. The concern for these species is their potential role in transforming other chemical pollutants. The presence of hydroxyl radical in natural waters has been determined but its high reactivity makes it difficult to quantify. We used a molecular probe, terephthalic acid, to quantify hydroxyl radical. Terephthalic acid binds selectively to hydroxyl radical forming 2-hydroxyterephthalic acid, which is measurable using high performance liquid chromatography with fluorescence detection. In this study, the hydroxyl radical was created by exposing nitrate solutions to ultraviolet light (UVB 320-290nm). Although nitrate has been found to contribute to the production of hydroxyl radical, we determined that under the conditions prevailing in surface waters, it plays a minimal role compared to the amount produced by dissolved organic matter. We also discovered that nitrate exposed to natural light (UVA 400-320nm) produces significantly less hydroxyl radical than nitrate exposed to UVB. This detection method has also been used to determine how the origin of dissolved organic matter (terrestrial vs. microbial) affects the concentration of hydroxyl radical produced.

Recommended Citation

Sellner, Andria. "Quantifying Hydroxyl Radical in Natural Waters: Role of Dissolved Organic Matter in Determining Production Rates." Undergraduate Research Symposium, Mankato, MN, April 21, 2014.
http://cornerstone.lib.mnsu.edu/urs/2014/poster_session_A/43