Abstract
This research focused on the characterization of sediment-derived dissolved organic matter (SDOM) extracted from sediment of Yellow River and the binding behaviors of ceftazidime (CAZ) with the presence of SDOM. The morphology, surface composition and structure of SDOM and the complexation between SDOM and CAZ in terms of component features, binding capacity and sequence were studied by multiple approaches. Results showed that SDOM was in situ autochthonous-dominated with a low weight-average molecular weight and aromaticity (the value of SR was 2.523). The multiple morphological characteristics, high surface oxygen contents (53.49%) and more aliphatic (H/C = 1.91) of SDOM were further confirmed. Studies on SDOM-CAZ interaction suggested that the functional groups and chemical compositions of SDOM were susceptible to CAZ. In more detail, the aromatic protons and aliphatic protons of CAZ impacted significantly, and the binding between CAZ and SDOM might relate to noncovalent. The protein-like fractions were considered to be the primary participant with 49% fractions lost and the aromatics and amides as mainly active site interaction with CAZ. These findings have significant implications on the environmental fate of cephalosporin antibiotics and that of sediment-derived DOM.
Highlights
Cephalosporin antibiotics (CPs), one class of the most universal antibiotic drugs, has been used extensively in human and veterinary treatment (Ribeiro, 2018).Compared with penicillins, as another kind of β-lactam antibiotics which has comparatively low acid stability and resistance, cephalosporins have less susceptible and allergenic to β-lactamases and sequentially were accepted as broad spectrum antibiotics (Sader and Jones, 1992; Lin et al, 2000)
Total organic carbon (TOC) contents of sediment-derived Dissolved organic matter (DOM) (SDOM) were less than 10 mg C/L to weaken the inner filtering influences (Wu et al, 2012), and Each fluorescence measurement was subtracted with a Milli-Q water blank.Parallel factor analysis (PARAFAC) modeling is a well-established method for the characteristic of DOM components that has been introduced in detail previously (Stedmon and Bro, 2008; Bro 1997)
E2/E3 as a surrogate of the relative molecular weight of humic solutes was calculated to evaluate the relative size of DOM molecules (Helms et al, 2008; Wang et al, 2019)
Summary
Cephalosporin antibiotics (CPs), one class of the most universal antibiotic drugs, has been used extensively in human and veterinary treatment (Ribeiro, 2018). Limited studies about interaction of DOM with antibiotics were reported under environmental aquatic conditions. Aiming to investigate the interaction between SDOM and CPs, ceftazidime (CAZ), the third generation cephalosporin family, which can resistant to hydrolysis by most β-lactamases has been extensively detected from environmental level about 200 ng/L to 10 mg/L in groundwater, secondary effluent and surface water (Ali et al, 2020; Mirzaei et al, 2018; Haller et al, 2018; Yu et al, 2016), was chosen as an agency of CPs in the study. The results of our study may help to better explain the properties of sediment-derived DOM and gain an insight of environmental behavior of CPs in aqueous environments
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