Exploring the combination characteristics of dissolved organic matter with erythromycin in a soil infiltration system

Erythromycin (ERY), as a common macrolides antibiotic, is widely used for sterilisation and disinfection of humans or livestock whose migration and transformation in the surface water environment are significantly related to dissolved organic matter (DOM). The characteristics of DOM can be greatly influenced by the complexation between ERY with itself in soil infiltration system. Using spectroscopic techniques (excitation-emission matrices, parallel factor analysis, Fourier infrared spectroscopy, and synchronous fluorescence spectroscopies) to explore the complexation properties of each DOM component with ERY in the system. The binding order of ERY with DOM functional groups was determined by two-dimensional correlation spectroscopy combined with FTIR. The amide I band v(C = O) exhibited stronger binding affinity. After the treatment, the DOM fluorescence intensity sharply decreased and the ERY concentration declined by 88.36%. Thus, synchronous degradation may occur between them. The result of synchronous fluorescence spectroscopy integrated with two-dimensional correlation spectroscopy indicated that the complexation sequencing and ability of DOM with ERY can be changed by a soil infiltration system. There are more binding sites exhibited in DOM with ERY in effluent than influent. A protein-like component of DOM showed priority binding order and more stable binding with ERY and had the highest Log K_M value of 3.61. These results demonstrated that the binding of DOM with ERY in a soil infiltration system could take out most fluorescent DOM, and reduce the concentration and risk of ERY in the surface water body.