Leachate migration investigation at an unlined landfill located in granite region using borehole groundwater TDS profiles

• Published in: Engineering geology 2021-10, Vol.292, p.106259, Article 106259
• Main Authors: Wu, Linbo, Zhan, Liangtong, Lan, Jiwu, Chen, Yunmin, Zhang, Shuai, Li, Junchao, Liao, Gengqiang
• Format: Article
• Language: English
• Subjects: Borehole investigation; Granite; Groundwater contamination; Leachate migration; Total dissolved solid; Unlined landfill
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2021.106259

Special hydrogeological properties of granite regions control leachate migration in municipal solid waste (MSW) unlined landfills there. This study aimed to investigate leachate migration at an unlined landfill located in a granite region and explore an in-situ borehole groundwater TDS-profile method (BGTM) for identifying vertical distribution of leachate plume at landfill sites in granite regions. On basis of detailed site investigation using multiple methods (e.g., borehole investigation, water quality monitoring, and rock packer tests), hydrogeological model of the surveyed MSW landfill was established, and horizontal distribution of four contaminants including chemical oxygen demand, ammoniacal nitrogen showed that leachate plume could reach over 200 m away from downstream boundary of the source landfill. BGTM was demonstrated to be able to identify boundary of leachate plume under a field average influx >1.0 × 10−7 cm/s and a hydraulic conductivity of the evaluated layers >5.0 × 10−5 cm/s. Based on the site investigation, granite joints were found to be the major leachate migration channels in the lateral slope of the granite valley, and highly permeable layers such as alluvium were identified as the major leachate migration channels in the valley outlet. Meanwhile, a two-piece function was fitted between groundwater total dissolved solid (TDS) and electrical conductivity (EC) in the landfill site, and EC = 500 μS/cm was the limit between the two intervals. •Hydrogeological model for an unlined landfill site in granite region was built.•Joint network was the main leachate leakage channel across granite valley slope.;•Sediment layers was the main leachate leakage channel at granite valley's outlet.•A novel borehole groundwater TDS-profile method was proposed.•Vertical distribution of leachate plume was identified by BGTM.