Abstract:The study is aimed at revealing the effect of expressway overland runoff particle on the filtration of runoff heavy metals. The gravel - soil filtration columns are used to treat the pavement runoff of Maqun section of Nanjing circle highway. The filtration removal characteristics of heavy metal and the retention characteristics of particulate matter in the expressway overland runoff are studied. The relationship between the retention of particulate matter with different particle sizes and the filtration removal of heavy metal is specially expounded. At the same time, the influences of season, pH value and environmental factors on the removal of heavy metal by gravel-soil filtration are discussed. The results show that Cu and Zn concentrations present the non-linear decrease along the depth direction of gravel - soil filtration column. The 35-cm thick soil above the device has the good interception performance for the removal of the most Cu and Zn. The effect of particle removal on the removal of heavy metals in runoff is improved with the increase of the infiltration padding thickness. The season, pH value, oxidation reduction potential ORP and dry period time have the different levels of influence on the removal of heavy metals.