title: Assessing the Source-to-Stream Transport of Benzotriazoles during Rainfall and Snowmelt in Urban and Agricultural Watersheds.
abstract: While benzotriazoles (BTs) are ubiquitous in urban waters, their sources and transport remain poorly characterized. We aimed to elucidate the origin and hydrological pathways of BTs in Toronto, Canada, by quantifying three BTs, electrical conductivity, and δ18O in high-frequency streamwater samples taken during two rainfall and one snowmelt event in two watersheds with contrasting levels of urbanization. Average concentrations of total BTs (∑BT) were 1.3 to 110 times higher in the more urbanized Mimico Creek watershed relative to the primarily agricultural and suburban Little Rouge Creek. Strong correlations between upstream density of major roads and total BT concentrations or BT composition within all events implicate vehicle fluids as the key source of BTs in both watersheds. Sustained historical releases of BTs within the Mimico Creek watershed have likely led to elevated ∑BT in groundwater, with elevated concentrations observed during baseflow that are diluted by rainfall and surface runoff. In contrast, relatively constant concentrations, caused by mixing of equally contaminated baseflow and rainfall/surface runoff, are observed in the Little Rouge Creek throughout storm hydrographs, with an occasional first flush occurring at a subsite draining suburban land. During snowmelt, buildup of BTs in roadside snowpiles and preferential partitioning of BTs to the liquid phase of a melting snowpack leads to early peaks in ∑BT in both streams, except the sites in the Little Rouge Creek with low levels of vehicle traffic. Overall, a history of BT release and land use associated with urbanization have led to higher levels of BTs in urban areas and provide a glimpse into future BT dynamics in mixed use, (sub)urbanizing areas.
authors.affiliation: Department of Physical and Environmental Sciences, University of Toronto Scarborough , 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
authors.forename: Abha
authors.identifier: 0000-0002-2914-2569
authors.initials: A
authors.lastname: Parajulee
authors.affiliation: Department of Physical and Environmental Sciences, University of Toronto Scarborough , 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
authors.forename: Ying Duan
authors.initials: YD
authors.lastname: Lei
authors.affiliation: Water Science and Technology Directorate, Environment and Climate Change Canada , 867 Lakeshore Road, Burlington, Ontario L7S 1A1, Canada.
authors.forename: Amila O
authors.initials: AO
authors.lastname: De Silva
authors.affiliation: Department of Physical and Environmental Sciences, University of Toronto Scarborough , 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
authors.forename: Xiaoshu
authors.initials: X
authors.lastname: Cao
authors.affiliation: Department of Physical and Environmental Sciences, University of Toronto Scarborough , 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
authors.forename: Carl P J
authors.identifier: 0000-0001-8538-5138
authors.initials: CPJ
authors.lastname: Mitchell
authors.affiliation: Department of Physical and Environmental Sciences, University of Toronto Scarborough , 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
authors.forename: Frank
authors.identifier: 0000-0003-3836-0901
authors.initials: F
authors.lastname: Wania
mesh_terms: D000383:Agriculture; D002170:Canada; D004784:Environmental Monitoring; D060587:Groundwater; D045483:Rivers; D014507:Urbanization