Characterization of the pollutant build-up processes and concentration/mass load in road deposited sediments over a long dry period

Abstract

Trace metals and nutrients attached on road deposited sediments (RDS) are the main source of non-point pollution to urban waterbodies causing ecological degradation and eutrophication problems. Mathematical models of the pollutant build-up process on road surfaces can be used to develop remediation measures. However, there was lack of research on the pollutant build-up process of various sized particles during a long dry period. This research investigated the build-up behaviors of specific pollutants in size-fractioned particles during 41 antecedent dry-weather days (ADDs), which was the longest build-up period ever studied. This research revealed that the pollution concentration exhibited a mono-growth behavior, while the pollutant mass followed a cyclic behavior during the study period. The time to peak and the build-up cycle of various pollutant mass were all highly associated with the particle characteristics, and the mass and concentration levels of pollutants in various sized particles were different. Furthermore, two important phenomena were found in this study: the bioavailability of phosphorus as well as the enrichment factors of metals all increased along with time during the build-up process. These findings provide new insights in non-point source pollution build-up and improve the water quality modelling.