Influence of Low Impact Development practices on urban diffuse pollutant transport process at catchment scale

Understanding the entire urban diffuse pollutant transport process in a Low Impact Development (LID) pilot catchment is critical for developing efficient and reliable LID strategies to remove stormwater pollutants. Previous studies focused on the LID performance at a system scale and modeling work. However, the influence of LID practices on the entire urban diffuse pollutant transport process at a catchment scale through field studies remains unclear. The present study analyzed particle loads, particle size distribution and heavy metal concentrations during the accumulation-release-transport process of urban diffuse pollutants. It was found that 13.11% particles can be washed-off from the road surfaces, and a vast majority (12.40%) of suspended solids (SS) in the road surface runoff was retained by LID while only a small fraction (0.71%) can overflow through the LID system and finally 0.42% SS was discharged from the drain outlet. This result implies that LID practices can significantly reduce the contribution of road deposited sediments pollution to urban receiving water. Outcomes also found that most heavy metals in stormwater are particulate, and furthermore, finer particles contain more heavy metals and are easily removed by the stormwater runoff. Therefore, it is essential to consider the influence of particle size on SS removal performance of LID and apply enhanced LID techniques which can remove the fine particles, especially the particles 10-105 mu m, in the stormwater. (C) 2018 Elsevier Ltd. All rights reserved.