Title:

From rain to drain: Understanding urban pond pollution

Abstract:

Assessing the environmental risk pollution poses to aquatic biota depends on adequately evaluating the exposure to contaminants. Traditional approaches to exposure characterization often rely on the instantaneous sampling of water or sediment, which can miss toxicologically important temporal variations in contaminant occurrences and concentrations. In urban aquatic ecosystems, where temporal variation in hydrology and contaminant loads can be extreme, misinterpreting contamination dynamics can lead to underestimating risk, and consequently insufficient mitigation action. A lack of comprehensive screening can also mischaracterize exposure; particularly in urban areas where a high density and diversity of activities, and thus contaminant sources, can occur resulting in a large number of potential contaminants that could end up in the aquatic environment. As a common end-of-pipe control in stormwater management regimes in Ontario, stormwater management ponds can receive large contaminant loads, yet are often neglected from water quality monitoring schemes despite the known ecological consequences of their effluent on receiving water bodies. We surveyed the presence of urban-use contaminants at 21 stormwater management ponds in Brampton, Ontario using 3 sampling methods: weekly grab water samples, biofilms cultured on artificial substrates, and passive diffusive samplers (o-DGTs). We analyzed the water and biofilm samples for 542 current-use and legacy pesticides, and the o-DGT samplers for 492 urban contaminants. We also analyzed 15 biofilm samples for 21 metals and metalloids. Additional water grab samples were taken during the survey period to measure nutrient loads, chloride concentration, and coliform bacteria. We will present the detections of contaminants found by these sampling methods and discuss the relative sensitivity, biological relevance, practicality, and reproducibility of each monitoring approach.