Leachates from land disposal of solid waste varies in chemical composition widely from one location to another. Certain chemical characteristics of municipal solid waste (MSW) leachate, for example, influence the rate of movement of heavy metals through soils more than others. The most prominent fall into broad categories such as pH (as it reflects organic acids), concentration of the soluble common salts (EC or IONS), total soluble organic carbon compounds (TOC) and certain naturally occurring metals notably iron (Fe). The solubility of the components of MSW leachate changes markedly as a result of pH fluctuations, aeration, dilution by water, drying and wetting, freezing and thawing, and stage of biodegradation.