GRSP-induced diversity change of dissolved organic matter enhances the availability of PAHs in soil

The positive effects of glomalin related soil protein (GRSP) on soil ecological environment functions have been widely reported. However, the molecular mechanisms underlying GRSP-enhanced availability of polycyclic aromatic hydrocarbons (PAHs) in soils remain poorly understood. The desorption of both phenanthrene and pyrene from soils increased significantly with rising GRSP concentrations across the tested range (0-1000 mg/L), demonstrating a dose-responsive relationship. The results from Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and UV-vis spectrophotometry revealed that GRSP addition altered the molecular diversity of dissolved organic matter (DOM), enriched phenyl structures and high-molecular-weight compounds in the retained DOM. This modification promoted DOM-PAH associations in solution and further enhanced PAH desorption from soil, thereby elucidating a potential molecular mechanism for GRSP-mediated PAH availability. These results further clarify the role of GRSP in reduction and control PAH-contaminated risks in soil, enrich people's understanding of the environmental functions of GRSP, and also provide a theoretical basis for regulating the pollution risk of PAHs by increasing the GRSP content in the soil.