Exploring relationships among landfill leachate parameters through multivariate analysis for monitoring purposes

Elucidating the properties of landfill leachate and the relationships among leachate parameters is crucial for efforts to determine appropriate landfill leachate monitoring activity and management strategies. This study investigated the physical, chemical and optical parameters of leachate in an old Japanese landfill over a 13-month period. The parameters were explored based on their relationships with the maximum fluorescence (F_max) of three components (microbial humic-like C1, terrestrial humic-like C2 and protein-like C3) deconvoluted from excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis. Dissolved organic carbon (DOC), chemical oxygen demand (COD), Cl^- and SO₄^2- concentrations and pH ranged from 2.6 to 38.2 mg C L^-1, 9 to 324 mg L^-1, 14 to 972 mg L^-1, 26 to 1554 mg L^-1 and 6.9 to 11.6, respectively. Linear regression analysis suggested that the F_max values of C2 and C3 represented DOC, whereas the F_max value of C2 alone could serve as a COD indicator. Hierarchical cluster analysis and principal component analysis were employed to successfully categorise leachate samples based on their locations. Higher dissolved organic matter levels were observed in leachate within the old disposal area, whereas elevated levels of inorganic components such as SO₄^2- and Cl^- were found in leachate collected from the extended disposal area and at a treatment facility. Statistical analysis provides crucial tools for assessing and managing various areas of a landfill, supporting targeted and effective waste management strategies.