Identifying and Monitoring the Landfill Leachate Contamination in Groundwater with SEC-DAD-FLD-OCD and a Portable Fluorescence Spectrometer

Landfill leachate contains high concentrations of dissolved organic matter (DOM), which might leak into the groundwater as a contaminant plume. In this study, 6 landfill leachates, 11 landfill solid waste and soil samples, and 102 groundwater samples around 24 landfills were collected, in order to identify the suitable tracers and develop a convenient technique for monitoring groundwater contamination from landlill leachate. Characterized by the size exclusion chromatography-diode array detector-fluorescence detector-organic carbon detector (SECDAD-FLD-OCD) chromatograms, DOM in landlill leachate consisted of a characteristic humic-like fluorophore with triple- excitation peaks at Ex similar to 250, 310, and 365 nm/Em similar to 460 nm (HS-Em460-Ex3). With an apparent MW of 1.4-2.5 kDa, this unique HS-Em460-Ex3 fluorophore was refractory to biodegradation and possibly originated from the biotransformation of dyes in municipal solid wastes. Via principal factor analysis, groundwater samples were clustered into two groups mainly by the PC1 dimension, which mainly represented the variances in DOM concentration. The samples in Group II all showed the characteristic HS-Em460-Ex3 fluorophore, which could serve as an intrinsic fluorescence tracer of landfill leachate contamination. Checked by SEC-FLD analysis, the humic-like fluorescence threshold value was proposed as 50 QSU to indicate the pollution risks of groundwater around landfills, and the portable UV-LED fluorescence spectrometer provides an on-site tool for fast screening groundwater contamination from landfill leachate. The SEC-FLD fingerprint and the portable fluorescence spectrometer were developed for identifying and fast screening groundwater contamination from landfill leachate.