Ecological effects and multi-factor synergistic driving mechanisms of antibiotic mixtures in aquatic–terrestrial transition zones

Abstract

Aquatic–terrestrial transition zones are essential to sustain aquatic ecosystem balance. Antibiotics, as widespread emerging organic contaminants, have received limited research attention within these interfacial environments. This study focuses on the transition zones of the Chaohu Lake, adopting the risk quotient (RQ) method, the absolute principal component score-multiple linear regression model, and partial least squares structural equation modeling (PLS-SEM) to investigate the ecological effects of antibiotics and their multi-factor driving mechanisms. The results revealed 13 antibiotics, with total concentrations ranging from 69.35 to 136.66 ng L⁻¹, dominated by tetracyclines. Antibiotic distribution showed significant spatial heterogeneity, with the most severe contamination observed at the inlets of the Jiyu, Nanfei, and Shiwuli Rivers. Ecological risk assessment indicated moderate to high risks to algae posed by roxithromycin (RQ = 0.82), erythromycin (RQ = 1.21), and chlortetracycline (RQ = 1), whereas risks to invertebrates and fish were low (all RQ < 0.01). Source apportionment identified domestic sewage (40.8%), livestock and poultry farming (34.2%), and aquaculture (24.9%) as the primary sources. PLS-SEM analysis demonstrated significant positive effects of total nitrogen, total phosphorus, and ammonia nitrogen on antibiotic occurrence, with factor loadings of 0.807, 0.753, and 0.825, respectively. Sulfonamides (SAs), fluoroquinolones (FQs), and macrolides (MLs) were mainly driven by nitrogen and phosphorus, with path coefficients of 0.791, 0.703, and 0.861, respectively, whereas tetracyclines (TCs) were more influenced by other unmodeled factors (R² = 0.28). This study reveals the multi-factor synergistic mechanisms of antibiotic mixtures in aquatic–terrestrial transition zones, supporting ecological risk prevention of emerging organic pollutants.