Spectral Characteristics of Dissolved Organic Matter in Landfill Groundwater

Abstract

Landfills have been the most common methods of organized waste disposal in China posing an incredible groundwater pollution threat. Dissolved organic matter (DOM) can be used to trace the source, species and migration of contaminants in groundwater, and the investigations of its composition, structure, and distribution play a role in environmental protection. This study investigated the DOM source, composition, and molecular structure in groundwater at landfills for different years of operation, and explored the dynamics of groundwater DOM evolution over time, usingmodern spectroscopy in combination with multivariate statistical analysis. The results showed that DOM in landfill groundwater was initially dominated by outputs from microbial activities, and this was followed by autogenous terrigenous input. In the early stages of landfilling, the DOM of microbial origin was significant; however, towards the late stages of landfilling, the presence of microbial DOM has weakened. The groundwater DOM with short landfill times were mainly composed of newly produced tryptophan and tyrosine, which had low humification, aromaticity, and molecular weight. Microbial activity was strong, and while there were initial, significant differences between sampling points, evidence of its presence could be used for early warning of contamination and monitoring should be conducted for its presence. Microbial activity weakened with longer landfill operation time, landfill waste tended towards stability, and the DOM in groundwater with high humification, aromaticity and molecular weight, was able to reduce the landfill impact on groundwater.