• The required minimum 30-year post-closure care period for municipal solid waste (MSW) landfills can be shortened by reducing or eliminating of MSW components with long-terms effect in gas and leachate. The objectives of this study were to evaluate the relative persistence of landfill gas, leachate quantity, and selected leachate parameters using post-closure monitoring data from a case study landfill in south Florida. The relative persistence of selected decomposition byproducts in leachate were evaluated by both zero order and first order models based on monitoring data from the case study landfill. The analyses show that although gas and leachate production rates diminish very quickly, some contaminants remain in leachate as the decomposition process continues at a slower rate. For the case study landfill, the parameters which have been detected consistently at high concentrations (above MCL) included chloride, TDS, iron, bicarbonate, benzene, and vinyl chloride. Among these, vinyl chloride has the fastest and TDS has the slowest rate of disappearance in the landfill environment. The effect of waste diversion on persistence times of the selected persistent leachate quality parameters was evaluated. For example, a 40% reduction in the amount of plastics deposited in the landfill could reduce the monitoring time for benzene from 59 to 39 years. Zero order model underestimates the persistence times of the contaminants in leachate due to its linear nature. Shortening the monitoring times can provide significant savings for municipalities who need to continue monitoring leachate quality until the MCL levels are reached. © 2011 Springer Science+Business Media B.V.