RUI: Determination of the Kinetic Expressions and Mechanisms of the Photochemical Degradation and Oxidation of Dicamba

Gustavus Adolphus College, Saint Peter MN

Investigators

Abstract

This award by the Environmental Chemical Sciences Program of the Chemistry Division supports work by Professor Amanda Nienow at Gustavus Adolphus College. She is examining chemical reactions of the herbicide dicamba. Although dicamba has been on the market for over thirty years, it is being used more often on agricultural fields now as new genetically-modified soybean plants can tolerate dicamba. The 2017 growing season saw the first use of these soybeans in the US - and by the end of the summer, there were thousands of complaints from farmers on land adjacent to fields. Herbicide drifting through the air appeared to be causing crop damage in down-wind fields. In this project, environmental systems (for example, water or air based systems) are examined to understand how dicamba changes through reactions with other compounds in the environment and through interactions with sunlight. In addition, this project provides research opportunities for undergraduate students, which prepares them to enter the workforce or graduate or professional schools. These students will also help develop and institute a "Chemistry Night" for regional high school students. The team also collaborates with international partners in France. The photochemistry and reactivity of the chlorinated herbicide dicamba and the impact of additives in formulated agricultural products is being examined from several angles. These include heterogeneous photochemistry on the surface of epicuticular waxes and leaves, gas-phase photochemistry, and heterogeneous reactivity with hydroxyl radical, the primary gas-phase oxidant. The influence of surfactants and inactive ingredients in the commercial formulation of dicamba on these reactions is examined. The results may provide insight into the photodegradation and oxidation mechanisms and (photo)products of dicamba. This research enhances the current understanding of the environmental chemistry of dicamba. This work also provides new methods to examine the photolysis of chemicals sorbed to surfaces and heterogeneous reactions with gas-phase oxidants. Undergraduates participate in all aspects of this interdisciplinary project and gain experience in a wide range of fields. Prior success with chemistry outreach with young students is expanded upon with programming for regional, mostly rural, high school students. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.