Biodegradable EDDS ( S,S - ethylenediaminedisuccinic acid) is an emerging chelant for enhancing heavy metal extraction from contaminated soils.EDDS excess is often encountered at soil washing.In this study,an empirical model,which utilized the initial metal distribution in soils and a set of parameter values independently determined from sequential extraction,was developed for estimating the time - dependent heavy metal extraction by EDDS from multi - metal contaminated soils.The model simulation provided a satisfactory description of the experimental results of the 7 - d extraction kinetics of Cu,Zn and Pb in both artificially contaminated and field -contaminated soils under excess EDDS concentration in batch kinetic experiments.Thus,independent and prior assessment of extraction efficiency would be available to facilitate the engineering applications of EDDS.Furthermore,a simple empirical equation using the initial metal distribution was also proposed to estimate the extraction efficiency at equilibrium.