Toxicity Identification Evaluation Techniques Isolate Zinc and 6PPD-Q as Causes of Acute Lethality to Rainbow Trout in Municipal Stormwaters

As prolonged dry periods and extreme rain events are expected to increase due to climate change, the monitoring and treatment of urban stormwaters during rain events becomes of heightened concern. Of particular interest is road runoff in urban areas, which has been found to be acutely lethal to salmonids and frequently contains elevated concentrations of metals and organic contaminants. In this study, samples of road runoff stormwaters were collected in the Metro Vancouver area of British Columbia, Canada and assessed for acute lethality to rainbow trout (Oncorhynchus mykiss). Three of the four stormwaters tested exhibited complete mortality after the 96-h test. The causes of toxicity in samples that exhibited toxicity were characterized by using Toxicity Identification Evaluation (TIE) techniques, and included zinc, as well as an organic constituent. Subsequent investigation of the organic component implicated 6PPD-Q, and the potential contribution of 6PPD-Q to acute toxicity of rainbow trout was assessed by performing TIE techniques on a standard solution of 6PPD-Q in parallel with collected stormwater. Chemical analysis of the solution phase 6PPD-Q concentration using Condensed-Phase Membrane Introduction Mass Spectrometry (CP-MIMS) was used to support toxicity assessments. This is the first study to use the TIE approach to provide a fingerprint for 6PPD-Q toxicity.