Abstract
The method of Three-Dimensional Excitation Emission Matrix Fluorescence Spectrophotometer was used to identify the interaction mechanism between humic acid (HA) and antibiotics. The effects of antibiotic concentration, temperature, and pH on the bonding strength between HA and antibiotics were investigated. The results showed that with the increase of antibiotics concentration, the quenching effect on HA was enhanced. The quenching of HA by both oxytetracycline (OTC) and sulfadiazine (SD) is a single static quenching of the complexes, and the interaction forces are mainly a hydrogen bond and the van der Waals force. The quenching constant KsvOTC > KsvSD and the binding constant KbOTC > KbSD, indicates that HA has a more obvious quenching effect on OTC. The Kb of HA by OTC ranged from 3.223 × 103 to 12.784 × 103 L·mol−1 in the range of 298 K to 313 K, while the Kb of HA by SD ranged from 2.051 × 103 to 5.533 × 103 L·mol−1. With the increase of temperature, the quenching constant Ksv and binding constant Kb of both OTC and SD by HA gradually decrease, and the low temperature is beneficial to the interaction. The composite of OTC and HA is more stable than SD. Under neutral alkaline conditions, both OTC and SD had the strongest quenching effect on HA, and the resulting complex was the most stable. However, the Ksv and Kb of HA by OTC were greater than SD in the pH range of the experiment and the pH effect on quenching of HA by OTC (Ksv) was greater than that of SD.
Highlights
Soil organic matter (SOM) widely existing [1,2] is the sum of all natural and thermally altered biologically derived organic material found in the soil or on the soil surface irrespective of its source [1,2,3,4,5]
Soil scientists argue that these substances do not exist in the environment as that they are extractable by a strong alkaline method [9,10,11]
Current research is still focused on simple substances such as humic acid (HA), which reveal the mechanism of the SOM interaction with contaminant and migration, and the transformation and ecological effects of the pollutants under the interaction between HA and the contaminants remain hotspots in the field of environmental biogeochemistry [6,8,12,13]
Summary
Soil organic matter (SOM) widely existing [1,2] is the sum of all natural and thermally altered biologically derived organic material found in the soil or on the soil surface irrespective of its source [1,2,3,4,5]. Of three-dimensional fluorescence three-dimensional fluorescence to studytypes the of role of humus and different types for of spectroscopy to study the role ofspectroscopy humus and different antibiotics is of great significance antibiotics is ofthe great significance for understanding of humusand anditsantibiotics understanding mechanism of humus and antibioticsthe in mechanism a water environment migration in anda water environment and its migration and transformation patterns In this thisstudy, study,humic humic acid selected asrepresentative the representative substance of humus, two acid waswas selected as the substance of humus, and two and different different types of antibiotics, oxytetracycline (OTC) and sulfadiazine (SD), as target types of antibiotics, oxytetracycline (SD), were used as were targetused contaminants.
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