Insights into the characteristics of changes in dissolved organic matter fluorescence components on the natural attenuation process of toluene

Natural attenuation (NA) is of great significance for the remediation of contaminated groundwater, and how to identify NA patterns of toluene in aquifers more quickly and effectively poses an urgent challenge. In this study, the NA of toluene in two typical soils was conducted by means of soil column experiment. Based on column experiments, dissolved organic matter (DOM) was rapidly identified using fluorescence spectroscopy, and the relationship between DOM and the NA of toluene was established through structural equation modeling analysis. The adsorption rates of toluene in clay and sandy soil were 39% and 26%, respectively. The adsorption capacity and total NA capacity of silty clay were large. The occurrence of fluorescence peaks of protein-like components and specific products indicated the occurrence of biodegradation. Arenimonas, Acidovorax and Brevundimonas were the main degrading bacteria identified in Column A, while Pseudomonas, Azotobacter and Mycobacterium were the main ones identified in Column B. The pH, ORP, and Fe(II) were the most important factors affecting the composition of microbial communities, which in turn affected the NA of toluene. These results provide a new way to quickly identify NA of toluene Toluene, a common pollutant in petroleum-contaminated sites, poses a challenge because its remediation processes are time-consuming and the long-term monitoring of its natural attenuation in groundwater is time consuming. Therefore, by analysing the fluorescence spectra of DOM, we can understand the primary sources of DOM in the environment, thereby assessing the sources and migration pathways of pollutants. A conceptual model describing the response mechanism between DOM, hydrochemical factors and microbial communities in the NA of toluene was established by SEM, revealing the response of DOM in the NA process of toluene, and providing guidance for the assessment and control of pollution risks at actual sites.