Review of environmental fate of chiral antibiotics in the vadose zone

Abstract

To date, the systematic summarization and comprehensive review of analysis, distribution, migration, and degradation of chiral antibiotics in the vadose zone are limited. This review indicates that the physicochemical characteristics of chiral antibiotics are quite different, for instance, the solubility and octanol-water partition coefficient (lg Kow) of S-gemifloxacin are 301 times and 9.8 times larger than the values of R-gemifloxacin, which will affect their migration and degradation in the environment. High performance liquid chromatography with chiral column and chiral ligand-exchange chromatography are the common methods on the chiral antibiotics analysis. The concentrations of chiral antibiotics in soils, waters, and agricultural products in China and abroad are reported; flumequine, lomefloxacin and ofloxacin are the most common antibiotics. The adsorption rate and partition coefficient (Kd) of chiral antibiotics during their adsorption on minerals and microplastics are different, especially in the presence of natural organic matter (NOM); however, there is no relationship among the various types of chiral antibiotics. Chiral antibiotics can be complexed with the common cations, and their stability constants are quite different in the groundwater, for instance, the stability constant of Mg2+-levofloxacin is 22.9 times larger than that of Mg2+-ofloxacin. During the biodegradation process, the degradability and rate of chiral antibiotics are also different. Additionally, the chiral antibiotics can be transformed reciprocally. In this review, the distribution, migration, and degradation of chiral antibiotics in the vadose zone are investigated, which is beneficial to the study on the chiral antibiotics in the groundwater. As to the environmental fate of chiral antibiotics in the vadose zone, the following researches are recommended: (1) the resolution, analysis, toxicology, and standard establishment of chiral antibiotics; (2) the investigation, migration, and degradation of multiple chiral antibiotics; (3) the environmental processes of chiral antibiotics in the multi-interface