ABSTRACT
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 KM 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.
ABSTRACT
Sulfadiazine (SD) is a common antibiotic administered to treat bacterial infections in livestock, and its fate and migration are greatly affected by dissolved organic matter (DOM). The soil infiltration system [a typical low-impact development (LID) facility] can significantly alter DOM properties during runoff pollution, thus affecting the complexation of SD with DOM. Here, the binding characteristics of different DOM components and SD in the soil infiltration system were explored using spectroscopic techniques (excitation-emission matrices, parallel factor analysis, and synchronous fluorescence spectroscopy). Combined with the weakening of DOM fluorescence intensity and 78.63% reduction in mean SD concentration following treatment, synchronous degradation may have occurred. The binding sequence of SD and DOM fluorophores was further explored using two-dimensional correlation spectroscopy. Effluent DOM showed greater sensitivity to SD and more binding sites than influent DOM. Moreover, hydrophobic protein-like substances exhibited higher log KM values than other fluorescent components, indicating that protein-like components play significant roles in SD complexation. The soil percolation system improved the complexation stability and binding sequence of fulvic-like substances. Thus, SD-DOM can be intercepted and degraded using LID facilities to reduce the risk of SD in aquatic environments.
