Monitoring-based discrimination of pathways of traffic-derived pollutants

Abstract

We conducted a systematic monitoring study of roadside pollution based on surface-based samplers (U-channels) and samplers at different heights (poles). The study aim was to discriminate pathways of traffic-derived pollutants by surface runoff, splash water and airborne transport, and to assess the use of magnetic parameters for efficient monitoring concepts. At two high traffic density roads in southern Germany, we installed vertical poles at 0.5-m and 1.5-m distances from the roadside with samplers at various heights (surface, 0.5 m and 2 m), along with 4-m long U-channels (at the surface and 2.5 cm above it) perpendicular to the road. Clean quartz sand was used as collector material. Mass-specific magnetic susceptibility (χ), heavy metal (HM) and polycyclic aromatic hydrocarbon (PAH) concentrations all showed a significant increase over one year in pole and U-channel collectors. Systematic differences of χ, PAH and HM concentrations in samples at various heights and distances from the road indicate a common pathway of magnetic particles and pollutants and a dominance of splash-water transport. A magnetite-like phase turned out to be responsible for the enhancement of χ. Significant positive correlations between χ and total PAHs as well as HMs suggest that χ can be used as a proxy for traffic-derived PAH and HM pollution. The results of our monitoring studies could be used to provide basic knowledge to support the development of new monitoring approaches for traffic-derived pollution along roadsides.