An artificial sweetener and pharmaceutical compounds as co-tracers of urban wastewater in groundwater

Groundwater in urban areas can be affected by numerous wastewater sources. Distinguishing these sources can facilitate better management of urban water resources and wastewater, and protection of urban aquatic environments. A single wastewater tracer, even if ideal (i.e. low background levels, non-reactive, low detection limits, etc.), would be unable to accomplish this task. Here, we investigated the potential advantages of using a suite of anthropogenic chemicals as co-tracers to distinguish wastewater sources that contribute to groundwater contamination at two urban sites. We considered both relatively ubiquitous and non-ubiquitous tracers in wastewater. At the Jasper (Alberta, Canada) site, concentrations of an artificial sweetener, two pharmaceutical compounds, and a degradate of nicotine in groundwater were strongly correlated as co-tracers. This evidence, along with the similar spatial distributions of these co-tracers could be used to delineate and distinguish a single municipal wastewater plume. At the Barrie (Ontario, Canada) site, there was moderate to strong correlation of the wastewater co-tracers, but local differences in their distributions and in the ratios of their concentrations could be used to infer that mixtures of two or more domestic septic plumes were present in the groundwater at this site. This study demonstrates the benefit of applying a suite of tracers to urban groundwater affected by wastewater contamination. This approach should be applicable at other urban sites.