Multi-matrix pollution assessment for a road traffic-impacted drinking water catchment in Norway

Protecting drinking water sources is increasingly challenged by non-point sources of pollution mobilised from road traffic. Often, monitoring programmes rely on single-matrix assessments, failing to capture catchment dynamics critical for effectively managing traffic pollution impacts. This limitation is addressed by applying a novel multi-matrix framework designed for integrated pollution assessment in a source-water catchment impacted by a European highway (E39). Our sampling approach and analysis involved three matrices (roadside snow, streambed sediment, and water) and four seasons to map the spatial and temporal distributions of 6 heavy metals and the 16 PAHs. Routine sampling showed baseline analyte levels, whereas episodic first-flush from streams showed higher levels in spring and autumn. Source apportionment via PMF identified traffic as the dominant contributor to metal loading, with zinc (Zn) showing the highest contribution in both catchment sediment (45.4%) and water (65.9%). Future interventions should prioritise road runoff in the catchment by reducing first-flush loads.