Determining toxicity of leachates from Florida municipal solid waste landfills using a battery-of-tests approach

The toxicity and physicochemical parameters of municipal solid-waste (MSW) landfill leachates from six sites in north and north-central Florida, United States, were determined. Landfill leachates are complex mixtures of organic and inorganic constituents. Leachate toxicity was assayed using the acute C. dubia (48-h) and Microtoxtrade mark (15-min) assays and the chronic S. capricornutum (96-h) assay. The landfill leachates were shown to be highly toxic to both C. dubia and S. capricornutum with an EC(50) < 10% and < 15%, respectively. However, Microtoxtrade mark was not as sensitive to the leachates. Based on these results, the assays were ranked for their sensitivities to the landfill leachates; C. dubia > S. capricornutum > Microtoxtrade mark. Chemical analyses showed high concentrations of un-ionized ammonia and salts in the landfill leachates but low concentrations of heavy metals. The toxicity of the landfill leachates varied between the sites sampled and within each of the landfill sites. A significant relationship was found between the total ammonia content of the leachates and toxicity as determined by the C. dubia and S. capricornutum assays. Although the chemical constituents in Florida MSW landfill leachates may be more dilute, the toxicity of the leachates is equivalent to that from industrial waste landfills.