We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
Road dust-associated microplastics as a carrier of plastic additives in urban small-scale river sediment
Summary
Researchers analyzed microplastics and 56 plastic-derived chemicals in road dust, stormwater, and urban river sediments in Kumamoto, Japan. They found that road dust-associated microplastics, including tire wear particles and polyethylene terephthalate, were transferred to river sediments via stormwater, acting as carriers of plastic-derived chemical additives at concentrations up to 32,000 nanograms per gram.
Microplastics (MPs) and plastic additives have attracted global attention as emerging environmental pollutants. Herein, we analysed MPs and 56 organic plastic-derived chemicals in road dust (n=3), stormwater (n=4) and urban small-scale river sediment (n=8) samples collected from a downtown area of Kumamoto, Japan. The MP levels were 57,500–160,000 items/kg dw, 2.2–42 items/L and 1,600–15,800 items/kg dw in road dusts, stormwater and river sediments, respectively. The compositions of the polymers (tyre road wear particles [TRWPs], polymethyl methacrylate [PMMA] and polyethylene terephthalate [PET]) were consistent among the analysed samples; this result indicates that road dust–associated MPs were transferred to the river sediment via stormwater. A large amount of glass beads, an indicator of traffic-related particulate contaminants, was found in the road dust and sediments, suggesting that the urban small-scale river was strongly impacted by traffic activities. In total, 32 plastic-derived chemicals were identified in road dust and sediments with 6,900–32,000 and 620–13,000 ng/g dw concentrations, respectively. Notably, these concentrations were positively correlated with the abundance of MPs, indicating that MPs act as carriers of plastic-derived chemicals. We determined the concentrations of plastic additives in 28 traffic-related plastic products to identify the potential source of additive-derived chemicals in the road surface environment. Several road marking sheets and road paints contained large quantities (up to 1.7% w/w) of high-concerned substances, including phthalate esters, benzotriazole ultra-violet (UV) stabilisers and benzophenones. The additive profiles of the MPs and traffic-related products were similar to those of some PMMA-based MPs detected in the samples and PMMA-based road paints. This indicates that PMMA-based road paint was identified as an original source of MPs, contributing to 24%–54% of the total number of MPs in the road dust, stormwater and river sediment. In conclusion, an urban small-scale river was highly contaminated with road dust–associated MPs and plastic additives, and high-priority plastic products were identified as an important source of those contaminants in urban road areas.