To evaluate environmental impacts of solid waste landfilling, groundwater quality near the MSW landfill in a semi-arid climate of Iran (Hamedan) and its leachates were analyzed. To this aim, heavy metal concentrations, COD, BOD5, TOC, EC, NO3−, Cl−, TDS, and pH of two leachate ponds (active and closed sites) as the sources of contamination as well as the shallow groundwater of the area were measured. Monthly and seasonal monitoring program of 13 sampling points in the area were designed during the period of 2014–2016. Principal components analysis has been carried out using chemical data to deduce relationship between the samples. A special statistical approach including a main factor (age of leachate) and a subfactor (distance fromthe source of pollutant) was designed in order to identify the landfill role on the groundwater contamination. The physicochemical analysis of the leachate characteristics confirmed a high variation in the contaminants (i.e., organic compounds, salts, and heavy metals) related to leachate age. The BOD5/COD ratio of the active (0.73) and closed (0.77) sites ponds indicated that the leachates were in a biodegradable and unstabilized condition. The seasonal physicochemical analysis of the leachates showed that rainfall events increase the decomposition rate of the waste and affect pollutant concentration of the leachate. The proposed statistical analysis illustrated a direct relationship between the groundwater quality parameters and the leachates physicochemical characteristics.
