Recent findings that 2-anilo-5-[(4-methylpentan-2yl)amino]cyclohexa-2,5-diene-1,4-dione (6PPD-quinone), the transformation product of a common tire rubber antioxidant, is acutely toxic in stormwater-impacted streams has highlighted the need for a better understanding of contaminants in urban runoff. This study represents one of the first reports of 6PPD-quinone and other tire rubber-derived compounds in stormwater and snowmelt of a coldclimate Canadian city (Saskatoon, 2019(Saskatoon, −2020. Semiquantification of the five target compounds, N,N′-diphenylguanidine (DPG), N,Ndicyclohexylmethylamine (DCA), N,N′-dicyclohexylurea (DCU), 1cyclohexyl-3-phenylurea (CPU), and 6PPD-quinone, revealed DPG was most abundant, with average concentrations of 60 μg L −1 in stormwater and 1 μg L −1 in snowmelt. Maximum observed concentrations of DPG were greater than 300 μg L −1 , equivalent to loadings of 15 kg from a single rain event. These concentrations of DPG represent some of the highest reported in urban runoff globally. 6PPD-Quinone was detected in 57% (12/ 21) of stormwater samples with a mean concentration of approximately 600 ng L −1 (2019) and greater than 80% (28/31) of snowmelt samples with mean concentrations of 80−370 ng L −1 (2019 and 2020). Concentrations of 6PPD-quinone exceeded the acute LC 50 for coho salmon (0.8−1.2 μg L −1 ) in greater than 20% of stormwater samples. Mass loadings of all target chemicals correlated well with roads and residential land-use area.

SUMMARY1. In North America, the invasive predatory cladoceran Cercopagis pengoi was first detected in Lake Ontario. We explored the impact of Cercopagis on the lower food web of Lake Ontario through assessments of historical and seasonal abundance of the crustacean zooplankton, by conducting feeding experiments on the dominant prey of the invader, and by estimating its food requirements. 2. Between 1999 and 2001, a decrease in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high fecundity in all 3 years, indicating that food limitation was not responsible. Chlorophyll a concentration generally increased, concomitant with a decline in the herbivorous cladoceran zooplankton in the lake. 3. Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris. 4. Consumption demand of mid-summer populations of Cercopagis, estimated from a bioenergetic model of the confamilial Bythotrephes, was sufficient to reduce crustacean abundance, although the degree of expected suppression varied seasonally and interannually. 5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton, while initially very pronounced, have decreased steadily as the species became established in the lake.

There are no standardized protocols for quantifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wastewater to date, especially for population normalization. Here, a pipeline was developed, applied, and assessed to quantify SARS-CoV-2 and key variants of concern (VOCs) RNA in wastewater at Saskatoon, Canada. Normalization approaches using recovery ratio and extraction efficiency, wastewater parameters, or population indicators were assessed by comparing to daily numbers of new cases. Viral load was positively correlated with daily new cases reported in the sewershed. Wastewater surveillance (WS) had a lead time of approximately 7 days, which indicated surges in the number of new cases. WS revealed the variant α and δ driving the third and fourth wave, respectively. The adjustment with the recovery ratio and extraction efficiency improved the correlation between viral load and daily new cases. Normalization of viral concentration to concentrations of the artificial sweetener acesulfame K improved the trend of viral load during the Christmas and New Year holidays when populations were dynamic and variable. Acesulfame K performed better than pepper mild mottle virus, creatinine, and ammonia for population normalization. Hence, quality controls to characterize recovery ratios and extraction efficiencies and population normalization with acesulfame are promising for precise WS programs supporting decision-making in public health.

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