SEES:7000 Colloquium - Thursday, 9/24/26, 3:30pm, 255 MacBride Hall

Bill Arnold (Dept. of Civil, Environmental, and Geo-Engineering, University of Minnesota)

Title: Spatial and Temporal Dynamics of Tire-derived Chemicals and Pesticides in a (sub)Urban River and Stormwater Ponds

Abstract: Stormwater carries a mixture of micropollutants including pesticides, industrial chemicals, and tire-derived chemicals to stormwater infrastructure and ultimately surface waters. The inputs will be driven by temporal events, and the specific contaminants present will be dependent upon spatial factors, including land use. To assess annual trends, weekly water samples were taken for one year in the Upper Mississippi River to assess the occurrence, temporal dynamics, sources, and mass loadings of pesticides, a pharmaceutical, a corrosion inhibitor, and tire-derived chemicals. Tire-derived chemicals exhibited pronounced concentration maxima during spring snowmelt, whereas pesticide concentrations peaked in June and July following seasonal agricultural application. Cross-compound correlation patterns further suggest distinct source regimes. (Sub)urban stormwater ponds were investigated by a regional survey of thirteen (sub)urban stormwater retention ponds and year-long, approximately biweekly sampling of a subset of four ponds. Like the occurrence in Mississippi River, tire-derived chemicals displayed concentration peaks in early spring, whereas peak concentrations of pesticides were detected in early summer. Principal component analysis and Spearman correlations revealed that tire-derived chemicals and urban pesticides co-occurred spatially and temporally. A geostatistical analysis was performed to evaluate relationships between micropollutant occurrence and land use types. Finally, three different filter media—sand, compost-sand, biochar-sand were tested in column studies to evaluate mitigation of the micropollutants, demonstrating that both sorption and biodegradation are processes that could lead to contaminant removal.