Abundance and fate of glass microspheres in river sediments and roadside soils: Lessons from the Świętokrzyskie region case study (south-central Poland)

Abstract

Traffic-related glass microspheres in fluvial and roadside soil settings were used as an indicator for the occurrence and extent of road dust as a source of emissions. Microspheres were found in sediments of two rivers, at a distance of approximately 25 km of the city of Kielce (south-central Poland). Their highest contents in sediments were recorded near street stormwater drains into the Silnica River flowing through the city. The study also showed no influence of local bridges on the spatial distribution of glass microspheres in the river deposits. In contrast, soils adjacent to a two-lane highway revealed the presence of microspheres as far as 60 m of the roadway. As opposed to other road dust components, which have commonly been applied in traffic contamination studies, glass microspheres were a good indicator for road dust contamination. Most microspheres showed diverse concentrations of all minor and trace metal(loid)s. The mean contents of As, Pb and Sb (n = 601) were: 0.003 wt%, 0.014 wt% and 0.010 wt%, respectively, and only in some microspherules these elements exceeded EU current/expected regulatory standard levels (0.02%/0.015% for each). Although generally considered to be non-toxic, silica rich microbeads might be the best proxy for non-exhaust particle matter discharged from the road traffic into the environment.