considering their almost indefinite persistence in the environment and the danger they pose [1-2].
Mining/smelting is one of the main sources of heavy metal pollution in the environment, and the tailings
generally contain higher concentration of heavy metals. Therefore, many researches have been done on
different metal mining tails and surroundings on the behavior of the heavy metals, and how to remove or
immobilize them to relieve the risks [3-6].
Soil aggregates are the basic units of soil constructer, formed by the cohesion and adhesion of soil
mechanical composition of different organic matter, mineral and other materials. Many important
reactions occur on the interface of soil aggregates, e.g. the deposition and release of heavy metals
from/into soil solution. Soil aggregates of different sizes separated from contaminated soil are distinct in
the heavy metals contents [7-9]. Furthermore, sorption/desorption of heavy metals by them is also distinct
due to their different physicochemical properties [10]. Chelating agents can improve soluble metal
contents in soil solution and have been widely used in leaching/washing remediation techniques for
contaminated soils [11-13]. However, most of the researches were carried out for bulk soil. Only a few
concerns the release of heavy metals from soil aggregates of contaminated soil with chelating agents.
The objective of the present study is to investigate the effects of EDTA, a typical chelating agent, on
release of heavy metals (Zn, Pb, Cd and Cu) from water-stable soil aggregates collected at a lead/zinc
tailing site. Extraction kinetics and extraction with EDTA at different pH value were performed.
Fractionation of Zn and Pb in samples after extraction with EDTA was also analyzed to help the
understating of the reaction between EDTA and heavy metals in soil aggregates.