Evaluation of Leachate Quality and its Effects on Agriculture in the Vicinity of Zanjan Landfill

Landfills can be considered as a potential threat to groundwater resources, considering the potential of groundwater pollution by leachate with the pollutants such as hydrocarbons and heavy metals. In this study, spatial changes in groundwater quality used in agriculture, in the vicinity of landfill site of municipal solid wastes in the southwest of Zanjan city were investigated. For this purpose, analysis of 18 physicochemical, heavy metals and bacterial parameters in leachate and 14 groundwater samples were investigated around the dumpsite up to a 5 km radius from landfill during two sampling periods (i.e., December 2020 and June 2011). In this study, several indices including leachate pollution index, sodium absorption ratio, Killie index, soluble sodium percentage and permeability index were used to investigate groundwater pollution in the study area due to leachate or other sources. According to the results of LPI, none of the groundwater samples were polluted with leachate. Also, the quality of these resources for use in agriculture was evaluated favorably according to SAR, KR and PI indices, however, according to SSP, 64% and 86% of samples during December 2020 and June 2021, respectively, were reported polluted. In general, the results of qualitative study of groundwater samples in dry season (December 2020) were more pronounced than pollutants. Although based on the results of agricultural indicators and LPI in well number 5 as the closest well to the landfill, no contamination by leachate has been reported, however the high chlorine concentration which was at maximum of allowed range, the potential dangers of landfill leachate were shown. It is noted that chlorine acts as a leachate detector in groundwater. Therefore it is recommended that monitoring wells be dug at different depths and at distances of less than one kilometer from the landfill, and sampling be done in successive periods to determine even the smallest effects of leachate on groundwater.