Road-deposited sediments mediating the transfer of anthropogenic organic matter to stormwater runoff

It has been regarded that road-deposited sediment (RDS) is one of the important sinks of anthropogenic pollutants as well as the major source of pollutants in stormwater runoff. However, the role of RDS, as a mediator of pollutants to the stormwater runoff, has not yet been investigated so far. Therefore, in this study, the leaching of dissolved pollutants, especially dissolved organic matter (DOM) from RDS, in synthetic precipitation was investigated. A significant amount of metals, nutrients, dissolved compounds, and DOM was leached. The leaching of DOM during 10 sequential leachings was 1811.3 and 2301.7 mg C/kg for larger (63 mu m-2 mm) and smaller (<63 mu m) RDS, respectively. The results of UV/ V is spectroscopy, fluorescence spectroscopy, and size exclusion chromatography showed that the leached DOM was of anthropogenic/abiotic origins with lower molecular weight and humification degree. It is ubiquitous in stormwater runoff and industrial discharges and differs from natural organic matter. The results strongly suggest that RDS is an important mediator transferring anthropogenic pollutants to stormwater runoff. In addition, the removal of RDS, such as sweeping, would significantly reduce the pollutants input to the runoff.