Tire wear particles (TWPs) emitted due to the friction of tires on road surfaces during vehicle driving and braking are increasingly being recognized as a dominant fraction of microplastic in traffic-affected areas. TWPs vary in density, size, and composition. Tire material has long been a subject of ecotoxicity assessment due to the potential for toxic leachates Recent studies have linked TWP leachates from storm events to acute mortality episodes in Coho Salmon. TWPs are abundant in roadside soils and may accumulate in stormwater ponds, but more research is needed to examine the fate of TWPs in grey-stormwater infrastructure. This study asks: how effective are newer stormsewer inlet devices (also called manufactured treatment devices, MTDs) in capturing TWPs? To evaluate these sediments were sampled from seven MTDs in Mount Pleasant, SC. The MTDs came in two varieties: a multi-chambered, flow-through baffle design and a single-chambered hydrodynamic vortex separator. Road dust samples and sediment around the surface water discharge points were also taken. Density separations were performed on a sieved fraction (63-500 micron) using a supersaturated NaCl solution and sodium polytungstate to distinguish between the low- and high-density fractions and digested to remove organic matter interferences. TWPs were enumerated using microscopy and hot probe response. The concentrations of TWPs in different size and density classes were compared between the different sample sites (road, MTD, discharge). Early analysis of one multi-baffle style MTD shows, low-density range (&lt;1.2g/cm3) TWPs were between 450-2100 particles/g dry wt. For high-density (1.2-1.9 g/cm3), the amount of TWPs ranged from 750-4200 particles/g dry wt. Site evaluation is still underway, but early results show MTD TWP concentrations to be ~2x higher than road dust and ~1.3x higher than the outfall sediments. We will continue to compare the capture of TWP by different MTD designs and assess particle size distribution and heavy metals to test whether capture efficiencies are related.

Evaluation of stormsewer inlets to capture low- and high-density tire wear particles from roadway runoff

ACS Spring 2022

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