Phytoremediation of OTC-Cu/Zn contaminated sediment: Synergetic removal mechanism and microbial community response

Abstract

Antibiotics and heavy metals (HMs) from aquiculture enter waters and eventually sink into sediments. However, sediments carrying excessive contaminants can become a source of contamination. Macrophytes are frequently employed to treat water contaminated with HMs due to their adaptability, rapid growth rate, and ability to extract contaminants. In this study, oxytetracycline (OTC), and copper (Cu)/zinc (Zn) were chosen to be the target contaminants of antibiotics and HMs in the sediment. A pot experiment was conducted to investigate the phytoremediation effect of two types of macrophytes, Canna indica and Iris pseudacorus. The removal percentages of OTC, Cu, and Zn range from 93.6 % to 97.6 %, 67.4–86.0 %, and 69.8–82.9 % from the sediment, respectively. Adding Cu/Zn facilitated the decomposition of OTC in the sediments, while the presence of OTC transformed Cu/Zn into a more stable form. Both macrophytes extracted HMs mainly through roots accumulation. Higher concentrations of bioavailable forms of Cu/Zn in sediments inhibited plant growth and development, while lower concentrations promoted that. The inhibitory of leaf chlorophyll a+b synthesis by various contaminant treatments showed that OTC>OTC-HMs>HMs and the stimulation of carotenoid synthesis indicated HMs≥OTC-HMs≥OTC. The dehydrogenase (DHA) activities, microbial diversity and abundance in sediment were severely inhibited by HMs, and the inhibition was alleviated by OTC-HMs with C. indica. Proteobacteria, Actinobacteria, and Firmicutes were the dominant bacterial phyla. This study expands the understanding of phytoremediation potential and outlines their physiological and microbial responses to combined antibiotics-HMs.