(638d) Predicting the Photodegradation of Contaminants of Emerging Concern in Aquatic Systems

Over the past few decades, there has been a growing acknowledgment of the ecological risks associated with the presence of contaminants of emerging concern (CECs) in aquatic systems, including pharmaceuticals, personal care products, and industrial chemicals. These compounds may enter the aquatic system due to not being fully removed from wastewater effluent. Understanding the fate of these substances upon their release into aquatic environments is crucial to contribute to the mitigation of their environmental impact. Photodegradation plays a significant role in CECs fate in the environment. CECs can undergo indirect photodegradation through reactions with reactive intermediates (RIs), including triplet-state organic matter (³DOM^*), singlet oxygen (¹O₂), and hydroxyl radical (^•OH), generated when waterborne organic matter is exposed to light. Organic material found in aquatic environments can originate naturally as natural organic matter (NOM) or enter the water system from wastewater treatment effluent as effluent organic matter (EfOM).

Characterization of organic matter is essential to understand RIs formation and, therefore, photodegradation mechanisms of CECs. However, characterization methods can be costly and complex. In an effort to simplify these methods, various optical parameters have been established to gain insights into the composition and photoreactivity of organic matter from UV-Vis and fluorescence spectroscopy. Indicators such as SUVA₂₅₄, HIX, FI, S_275-295, and E2:E3 are utilized to characterize EfOM in terms of molecular weight, aromaticity, and light absorption. Consequently, optical parameters of organic matter offer potential indications of its photoreactivity. This study developed a predictive method for the photodegradation of CECs by leveraging optical parameters of EfOM solutions as inputs.

Optical parameters including SUVA₂₅₄, HIX, FI, S_275-295, and E2:E3 for various EfOM solutions were measured. The EfOM solutions spiked with two CECs, p-cresol and propranolol, were exposed to simulated sunlight and contaminant degradation was determined. We then investigated relationships between optical parameters and kinetic parameters for the photodegradation of CECs using Pearson correlation. Using the correlations found, we predicted the degradation of CECs by solving the kinetic equation of degradation of each CEC. The prediction method was validated using different initial concentrations of CECs and several EfOM samples. The results demonstrated a favorable alignment between the experimental and predicted values.

By predicting the photodegradation of CECs, researchers and policymakers can assess the effectiveness of different treatment methods to minimize CECs persistence in aquatic environments. Additionally, accurate predictions of CECs photodegradation can inform risk assessments and regulatory decisions aimed at protecting human health and ecological integrity. This innovative approach not only enhances our understanding of CECs photodegradation mechanisms in complex EfOM solutions but also offers a practical tool for predicting CECs degradation kinetics, thereby facilitating the development of effective strategies for water treatment and environmental management. Moreover, it provides insights for designing effective monitoring programs, implementing targeted remediation efforts, and developing regulatory measures to prevent or mitigate CECs pollution. Furthermore, predictive models can assist in assessing the ecological risks associated with CECs exposure to aquatic organisms and ecosystems, guiding conservation efforts and ecosystem management strategies. Overall, the prediction of CECs in aquatic systems contributes to informed decision-making and proactive measures aimed at protecting water quality, biodiversity, and ecosystem health.