In Search of Nontargeted Contaminants of Concern in Surface Waters

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Research on the occurrence and fate of trace organic contaminants (TrOCs) and their transformation products (TPs) is critical to prevent environmental degradation and deterioration of water resources. We propose here a novel way to keep up with the changes in manufacturing and consumer practices that have a direct impact on the inputs of TrOCs in the environment. We selected the St. Lawrence River (SLR) to apply the proposed research program since it is the main river in a watershed that supports ~ 40 % of the Canadian population. Over the short term (5 years), my research program will answer three important questions: (1)What are the most frequently occurring nontargeted TrOCs in the SLR? We plan to perform a year-long sampling campaign and identify unknown TrOCs using passive samplers and a nontargeted screening (NTS) method developed by our research group. To prioritize the compounds observed, we will apply a spatiotemporal scheme based on the detection frequency profiles of TrOCs at 4 different locations along the SLR. Such profiles will allow us to sort out the data and identify the most relevant compounds. Expected outcome : a list of unknown TrOCs that are of potential interest to monitor in the SLR. (2)Are TPs of TrOCs observed in a pilot-scale watershed environmentally relevant? Here we plan to study the transformation of contaminants of concern such as sartans (pharmaceuticals for cardiovascular diseases) and tire additives in an outdoor artificial watershed facility. Then we will look the TPs observed in the local rivers to validate their environmental relevancy. Expected outcome: identify new TPs of contaminants of concern and their molecular structures which are critical to predict their toxicity and to understand their transport. (3)What are the most concerning unknown TrOCs found in the SLR? We will answer this question by developing two types of models of prediction. The first will be used to semi-quantitatively determine the concentration of unknown TrOCs without analytical standards. The second is a QSAR model that will allow us to predict the toxicity of unknown TrOCs towards a model aquatic species (Daphnia magna). Expected outcome: rank the discovered unknown TrOCs according to their ecotoxicological risk. Overall impact of my research program: My research program will contribute to: (i) widening the applicability of nontargeted analysis techniques and integrating them in water monitoring programs; (ii) discovering unknown TrOCs of concern that should be monitored in the SLR and other Canadian surface waters; (iii) developing a new way to study environmental transformation of contaminants under realistic conditions; and (iv) developing new models to predict concentrations and toxicity of unknown contaminants without analytical standards. These contributions are critical to protect our aquatic ecosystems and our water resources by focalizing water contamination mitigation strategies into the most concerning TrOCs.