Seasonal analysis of pollutants in Leachate and downstream river water of Banchare Danda and Sisdol landfill sites

The direct discharge of leachate into the water bodies severely affects the aquatic ecosystems, nearby agricultural areas, and thus poses a serious threat to human and environmental health. Major landfills in Nepal are also suffering from such threats due to the lack of proper leachate management practices. Thus, this study aims to analyze the status of physicochemical contaminants in the leachate of Banchare and Sisdol landfills, along with the water of the downstream river. The variation of pollutants was also evaluated in two distinct seasons, viz., pre-monsoon and monsoon. As a result, pre-monsoon samples recorded a more acidic pH with higher conductivity compared to the monsoon samples. From the Principal Component Analysis (PCA) within the variation of 94.6 %, the heavy metal contaminations were more severe in the Banchare Field (BF) and Sisdol Field (SF) sampling sites. Detectable amounts of heavy metals with higher values compared to control were also reported in the Banchare Downstream River (BW) and Sisdol Downstream River (SW) sites, such as Zinc (2.48 mg/L in BW and 1.94 mg/L in SW), Cadmium (only detected with 0.01 mg/L in BW), Iron (1.29 mg/L in SW and 1.04 mg/L in BW), and Copper (0.06 mg/L in SW and 0.04 mg/L in BW). The PCA also supported this result by providing the cluster of heavy metals in the BW and SW sites. The concentrations of most of the heavy metals in leachate were above the FAO guidelines for irrigation water during pre-monsoon, raising serious concerns regarding the proper leachate management in both landfills. To prevent the deterioration of nearby water, the installation of leachate treatment systems in Banchare and proper post-closure management in Sisdol is urgent. • Pre-monsoon leachate showed a more acidic pH and higher conductivity. • Severe heavy metal contamination is reported in landfills and river sites. • Heavy metals exceeded irrigation limits, urging urgent leachate control.