Environmental characterisation of the sulphidic tailings in Lavrion

Abstract

Intensive mining and metallurgical activities in Lavrion over a time span of over 2700 years resulted in the formation of huge spoils of mining, milling and metallurgical wastes and tailings, most of them characterised as toxic and hazardous. Toxic elements are released by a number of mechanisms and migrate to the surrounding area, contributing to the widespread soil contamination. Three main types of spoils exist: sulphidic flotation tailings, oxidic-carbonaceous-silicate beneficiation tailings and metallurgical slags. This paper deals with the sulphidic flotation tailings. For the estimation of the risk that these tailings pose to the environment and for the conceptual development of a remediation strategy, complete characterisation was done according to the following methodology: Drillholes were placed within the spoils and undisturbed core samples were taken and characterised chemically and mineralogically, their net neutralisation potential (NNP) was determined using static tests and their toxicity using the EPA TCLP test, speciation of the toxic metals was determined in some cases using the sequential extraction technique and the bioavailable fraction determined by EDTA extraction. Some geotechnical characteristics of the spoils, as density and permeability were determined in-situ. Piezometers were installed within the boreholes and the pore water quality and level was monitored. The above information is being critically assessed and employed for the selection and design of the optimum rehabilitation scheme.