Fluorescence of leachates from three contrasting landfills

Abstract

Landfill leachates are composed of a complex mixture of degradation products including dissolved organic matter, which includes a wide range of potentially fluorescent organic molecules and compounds. Here we investigate the excitation–emission matrix fluorescence of landfill leachates from three contrasting landfill sites. Landfill fluorescence properties are all characterized by intense fluorescence at λ ex=220–230 nm, and λ em=340–370 nm which we suggest derives from fluorescent components of the Xenobiotic Organic Matter fraction such as naphthalene, as well as at λ ex=320–360 nm, and λ em=400–470 nm from a higher molecular weight fulvic-like fraction. Landfill leachates are characterized by intense fluorescence, with ∼10 2 intensity units of fluorescence at λ ex=220–230 nm, and λ em=340–370 nm mg −1 of total organic carbon, demonstrating leachate detection limits of <0.1 mg l −1 total organic carbon. We demonstrate that for all landfill sites, leachate fluorescence intensity has a strong correlation with ground water quality determinants ammonia, total organic carbon and biochemical oxygen demand. We investigate both within-site and between-site leachate fluorescence properties, and demonstrate that although there is significant within-site variability, leachates from all 3 sites can be statistically discriminated using just fluorescence properties (65% success rate) or with a combination of fluorescence and basic geochemical parameters (85%). Our findings suggest that fluorescence can be used as a rapid and sensitive tracer of leachate contamination of ground water, as well as help discriminate, together with geochemical determinants, leachates from different landfill sources.