Highway runoff and wastewater effluents as drivers of platinum dynamics in an urban river: Insights from a comprehensive monitoring study

Abstract

The contribution of a single rain event to daily and annual platinum (Pt) transport in an urban river (Jalle River, South-West of France), assessed from high resolution and annual monitoring, is discussed in terms of dissolved (Pt_d) and particulate (Pt_p) partitioning, sources and fluxes. In normal discharge conditions, the Jalle River Pt_d and Pt_p concentrations are respectively 1.90 ± 1.62 ng L⁻¹ and 19.8 ± 6.9 μg kg⁻¹ and Pt is mostly transported in the dissolved form (∼96 %, 110 ± 123 mgPt_d d⁻¹), due to low sediment yield and urban discharges from a wastewater treatment plant (WWTP). The Pt_d flux in sewage (36–340 mgPt_d d⁻¹) was mainly attributed to excretions from patient undergoing chemotherapy with Pt-drugs (up to 480,000 mgPt_d yr⁻¹ at the watershed scale). After a 2-months dry period, an intense rainstorm discharged ≥112 mg of Pt_p in 4 h from the urban highway, resulting in additional 295 mgPt_p d⁻¹ exceptionally transported by the Jalle River. In contrast to normal conditions, during the rainstorm up to ∼95 % of Pt was transported in particulate form during the first flush, and 80 % of the highway Pt_p flux during the first 40 min contributing to ∼one third of the annual Pt_p flux. Short, intense discharge events must be monitored at a high resolution to accurately estimate annual Pt fluxes in urban rivers.