Molecular structure and evolution characteristics of dissolved organic matter in groundwater near landfill: Implications of the identification of leachate leakage

Landfills can cause groundwater contamination, the pollution characteristics in groundwater near landfill sites have been extensively investigated, while the rapid identification of leachate leakage remained unclear. Comprehensively characterizing dissolved organic matter (DOM) is crucial for tracing the source, species, and migration of contaminants within groundwater and protecting groundwater sources. Here, we showed that DOM composition from newer landfills was mainly composed of newly-produced tryptophan and tyrosine, and protein-like and humic-like substances were more abundant in landfills that were relatively older. DOM in landfill groundwater was initially dominated by outputs from microbial activities, followed by terrigenous input. Leaked leachate contained an additional dye-derived fluorescent matter at the excitation/emission wavelength of 240-260/440- 460 nm that was absent in uncontaminated groundwater. Leachate leakage increased the concentrations of humic-like substance, DOM molecular weight, and microbial activity in the downstream groundwater, resulting in the microorganisms rapidly multiply and secrete large amounts of microbial metabolism by-products, making them suitable indicators of groundwater pollution. Three criteria were proposed to establish an interpretable fluorescence method to identify leachate pollution. The obtained results provide a novel insight into not only the monitoring, early warning, and identification but also the transport, fate and removal or transformation of groundwater leachate in landfills. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The composition of dissolved organic matter (DOM) in groundwater near landfills varies depending on the age of the landfill, with newer landfills showing higher levels of tryptophan and tyrosine, while older landfills have more protein-like and humic-like substances. Leachate leakage introduces unique dye-derived fluorescent matter into contaminated groundwater, leading to increased concentrations of humic-like substances, DOM molecular weight, and microbial activities, making them reliable indicators of groundwater pollution. Identifying leachate pollution can be achieved through a fluorescence method, with the results providing insights into monitoring, early warning, and addressing groundwater pollution in landfills.