Collaborative Research: Experimental and Computational Studies of the Role of Effluent Organic Matter in the Sensitized Transformation of Organic Contaminants
The role of effluent organic matter (organic matter contained in treated wastewater that is discharged to the environment) in the photochemical processing of microcontaminants is relatively unexplored. The overall objective of this project is to evaluate the photochemistry of aquatic pollutants, specifically focusing on the measurement of photochemically produced reactive intermediate production and quenching from effluent organic matter and the prediction of micropollutant rate constants using computational chemistry techniques. The innovative aspects of the proposed research are: 1) the focus on aquatic contaminants with specific functional groups susceptible to indirect photolysis; 2) the side-by-side comparison of photochemically produced reactive intermediate production/quenching from effluent organic matter and from natural organic matter; 3) the relation of photochemically produced reactive intermediate production/quenching by organic matter properties; and 4) the use of computational chemistry to predict reactivity with photochemically produced reactive intermediates, evaluate specific structural details in contaminants that influence reactivity, and distinguish which compound classes merit attention with regards to processing via indirect photolysis. The goals will be met through a combination of field sampling, laboratory experiments, and computational studies via collaboration between a major research institution (University of Minnesota; UMN) and an undergraduate institution (Seattle University; SU). The project emphasizes research as an important component of the undergraduate learning experience and has been designed to have a major, substantive contribution from undergraduate researchers. The PIs will continue to recruit female, minority, and first-generation college students into their research groups, thus broadening their impact on the scientific community. The relationship between SU and the UMN will establish connections between these two institutions and between science and engineering.
A major impetus for this work is that effluent organic matter and micropollutants are co-located in the waters downstream from wastewater treatment plants, and it is hypothesized that the role of effluent organic matter exerts substantial control over the fate of these contaminants. Photochemical half-lives for a series of contaminants in role of effluent organic matter solutions will be measured and related to the steady-state concentrations of photochemically produced reactive intermediates determined from molecular probe and quenching experiments. In this way, an understanding of the photochemical processes controlling the fate of contaminants emanating from wastewater treatment plants and the role of role of effluent organic matter in contaminant transformations will be developed. Additionally, the role of effluent organic matter plays in quenching photochemically produced reactive intermediates and its role as an antioxidant will be elucidated. The computational chemistry studies will lead to new predictive tools and insights into potential reaction mechanisms. Thus, the experimental and computational findings of this work will be critical in modeling pollutant fate and predicting contaminant reactivity in effluent-dominated surface waters. Information regarding photochemically produced reactive intermediates in role of effluent organic matter -impacted waters is also relevant to pathogen inactivation and carbon/nutrient cycling, making the results of interest to the broader scientific community.