Spatiotemporal variation of water pollution near landfill site: Application of clustering methods to assess the admissibility of LWPI

Abstract

In this study, spatiotemporal variation of water pollution near a municipal solid waste dumpsite was investigated. For this purpose, the analyses of heavy metals and 23 physicochemical parameters were performed. Three surface water and six groundwater resources both in dry and wet seasons were monitored between September 2016 and August 2017. Landfill water pollution index (LWPI) was calculated and the results were compared with those obtained from Principal Component Analysis (PCA) and Self Organizing Map (SOM). The important objective of spatiotemporal pollution assessment of surface water and groundwater was to evaluate the performance of LWPI measure in determining polluted regions in comparison to linear (i.e., PCA) and nonlinear (i.e., SOM) clustering methods. The results indicated low water quality in both surface water and groundwater due to leachate penetration. Surface water and groundwater samples close to the dumpsite showed the most pollution impact according to LWPI, where for samples with LWPI >1 are considered as polluted water due to landfill leachate. In this study the polluted samples ranged from 1 to 42.5 with the mean value of 7.46. The seasonal assessment of pollution indicated that more severe leachate impact was observed during the wet season. The clustering results indicated that both PCA and SOM categorized surface water and groundwater samples into five clusters, while LWPI classified them into three groups including unpolluted, semi polluted, and polluted regions. In spite of different numbers of clusters, the PCA and SOM and LWPI results, showed identical outcome about range of pollution in spatial analysis of water quality, therefore, application of LWPI with only ten parameters instead of PCA and SOM clustering methods, which were implemented based on several physicochemical parameters, is suggested as the main practical implication of this study.