Assessment of water quality suitability for agriculture in a potentially leachate-contaminated region

Dump sites pose a significant threat to groundwater resources due to the possibility of leachate leakage into the aquifer. This study investigated the impact of leachate on groundwater quality in the southwest region of Zanjan City, Iran, where groundwater is utilized for drinking, agricultural, and industrial purposes. We analyzed 18 parameters of dump site leachate, including physicochemical, heavy metals, and bacterial properties, alongside 13 groundwater samples. Sampling was conducted twice, in November 2020 and June 2021, within a five-kilometer radius of the Zanjan dump site. We utilized the Leachate Pollution Index (LPI) to evaluate potential groundwater contamination by leachate leakage from nearby dumpsite. Additionally, due to the predominant agricultural activities in the study area, various indices were employed to assess groundwater quality for agricultural purposes, such as Sodium Adsorption Ratio (SAR), Soluble Sodium Index (SSI), Kelly Ratio (KR), and Permeability Index (PI). Our analysis revealed no observed contamination related to leachate in the study area according to the LPI results. However, with the persistent pollution threat, implementing sanitary measures at the dump site is crucial to prevent potential impacts on groundwater quality. Moreover, the assessment of groundwater quality adequacy for irrigation yielded satisfactory results for SAR, KR, and PI indices. However, during both the dry (November 2020) and wet seasons (June 2021), the SSP index indicated that 80% of the samples were not classified as excellent, suggesting groundwater may not be suitable for agriculture. Overall, our qualitative study highlights the significant impact of the dry season on groundwater quality in the study area, attributed to elevated concentration levels of the investigated parameters within groundwater sources during the dry season.