Fluorescence of leachates from three contrasting landfills

摘要

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.