Elemental composition and speciation of some landfill leachates with particular reference to cadmium

Abstract

The elemental composition and speciation of four southern Ontario municipal solid waste landfill leachates were investigated. Leachate samples were analyzed for major cations and anions, together with the trace heavy metals Cd, Cu, Fe, Mn, Ni, Ph, and Zn. The leachates were found to contain high concentrations of alkali and alkaline earth metals and also of chloride ions. Cadmium concentrations in all of the leachate samples exceeded maximum acceptable levels for potable water. The computer model SOILCHEM was used to calculate the speciation of elements in the landfill leachates. Alkali and alkaline earth metals were predicted to exist primarily as uncomplexed metals. The heavy metals were predicted to exist as either free metals or as complexes with chloride, fulvic acid, hydroxide or sulphate. The speciation of Cd as a function of pH was investigated further for each of the leachates. Humic acid and chloride complexes dominated the aqueous chemistry of leachate Cd.