High resolution mass spectrometry screening of urban stormwater for identification of novel contaminants and their sources

Untreated urban runoff transports many chemical contaminants, toxicants, and other bioactive chemicals, thus contributing to poor water quality in receiving waters. The identity and key sources of many of these contaminants are unknown or poorly defined, thus impairing our ability to effectively protect ecosystem and human health. However, the identification of contaminants in complex mixtures such as urban runoff is a challenging analytical task. Additionally, it can be difficult to determine key sources of contaminants to receiving waters, especially when multiple sources are contributing similar contaminants to receiving waters. Here, we present the use of high-resolution quadrupole time-of-flight mass spectrometry to characterize the occurrence and fate of known and novel trace organic contaminants in stormwater runoff. Key transformation products and structurally related compounds are presented for a variety of sources, highlighting the importance of reactive processes to contaminant fate in stormwater. In addition, we linked the occurrence of several of the dominant runoff-derived contaminants to their primary sources by creating a variety of synthetic solutions, leachates or extracts from key chemical sources in urban stormwater. These sources included tire and plastic leachates, antifreeze, motor oil, and other automotive fluids. We then developed non-target “chemical fingerprints” or “signatures” for subsets of feature detections in these samples types, and used dilution series of these fingerprints to estimate the contributions of these sources to highway runoff. In particular, leachates of used motor oil and tires were especially rich in uncharacterized features, including highly abundant features that often dominated feature detections in urban waters, pointing to the importance of these specific sources to polluted waters