Toward more intercomparable road dust studies

Road dust (RDS) often contains elevated concentrations of pollutants, especially metals. Numerous studies were performed in the last two decades investigating the concentrations of metals like Cu, Pb, and Zn in RDS. In a literature search 177 studies were found where RDS bulk samples were analyzed. In another 49 studies the RDS samples were split into a number of size fractions to consider also the size dependence of the metal concentrations. In RDS bulk sample studies, the upper size limit (USL) of the RDS samples ranged from 2 µm to more than 2000 µm. This is partly a result of the different aims of the studies. However, the concentrations of metals in RDS particles are quite size-dependent. Consequently, comparing of results from different studies makes little sense. Based on the available literature, a standardized sample preparation sequence is proposed in this work. To serve the various aims of RDS studies the separation of the samples into four size fractions is suggested: <10 µm, 10–63 µm, 63–250 µm, and 250–2000 µm. The determination of the mass fractions of the size fractions parallel to the chemical analysis then allows calculation of the concentrations for RDS bulk samples with the four different USLs.