The composition and mercury complexation characteristics of dissolved organic matter in landfill leachates with different ages

Dissolved organic matter obtained from landfill leachate was separated into hydrophobic acid, base, neutral (HOA, HOB, HON) and hydrophilic (HIM) fractions. Fluorescence excitation–emission matrix spectra and parallel factor analysis were employed to characterize the composition, and fluorescence quenching titration technique was applied to study the complexation between Hg (II) and HON, HOA, and HIM fractions. Protein-like substances, humic-like compounds and xenobiotic organic matters (XOM) were identified in all fractions. The HOA, HOB and HON fractions comprised mainly XOM, while the HIM fraction consisted primarily of humic-like compounds. The complexation ability of protein-like substances was higher than that of humic-like compounds. The complexation ability of the HIM was highest for protein-like substances, while the complexation ability of the HON fraction was the highest for humic-like substances. The results suggested that the toxicity and bioavailability of the mercury in the young leachates was the highest, and decreased with landfill time.

► Protein-like, humic-like and xenobiotic matters were identified in landfill leachate.
► The complexation ability of the protein-like was higher than that of the humic-like.
► The complexation ability of hydrophilic matter was highest for protein-like substances.
► The binding ability of hydrophobic neutral matter was the highest for the humic-like.
► The toxicity and bioavailability of mercury in leachates decreased with years.