Characteristics of road sediment fractionated particles captured from paved surfaces, surface run-off and detention basins

This study presents the results of evaluating changes in properties of road sediment fractionated particles at the source (dry pavement), during transport (highway runoff) and after deposition (dry detention basin). A total of 38 solid particle samples were collected from paved surface, highway runoff, and from three locations within detention basins. Each sample was size-fractionated ranging from 38 μm to 1000 μm. Key results were that: (i) less than 2% of total particle mass in four vacuumed solid samples was associated with the < 38 μm fraction compared to 47 to 82% in centrifuged highway runoff samples and 25% for detention basin sediments, (ii) based on number concentrations more than 90% of particles from all sources were smaller than 38 μm, (iii) the densities of fractionated particles were generally within the range from 1.5 to 2.2 g/cm3; (iv) all collected particles were predicted to resist aggregation in solution with a typical measure of surface potential, the zeta potential, typically ranging from − 15 to − 30 mV, (v) metal concentrations increased with decreasing particle size for vacuumed samples from the highway shoulder and parking lot, however, size dependent trends in metal concentrations were less apparent in centrifuged highway runoff samples and detention basin sediment samples; (vi) the distributions of metal mass across sieved size fractions generally followed patterns of particle mass distribution in which less than 10% of the total Cu, Pb, and Zn mass was associated with particles < 38 μm; (vii) metal mass distributions tended toward increasing metal fractions in finer particle fractions along a gradient from the inlet to the outlet of the detention basins; and (viii) individual particle morphology (1 < dp < 10 μm) showed that particles were not smooth or spherical, clearly deviating from the assumptions typically used in estimating particle settling velocities using Stokes' Law.

► Variable density (1.5–2.2 g/cm3) was measured for different particle size ranges.
► All captured particles had negative surface potential ranging from − 15 to − 30 mV.
► Metal concentrations generally increased with decreasing particle size.
► Generally, no obvious trend was observed in metal mass distributions.
► Particle morphology showed that particles were not smooth or spherical.