Anthropogenic Influence on Antibiotic Dynamics in Laizhou Bay: A Comprehensive Spatial Analysis of Sources and Removal Processes

The widespread use of antibiotics has led to their misuse, posing a global environmental challenge. In Laizhou Bay (LZB), anthropogenic activities such as terrestrial runoff and marine aquaculture have driven a continuous rise in the types and concentrations of antibiotics. To study LZB antibiotics, 22 surface seawater/SPM (suspended particulate matter) samples and 28 sediment samples were collected. HPLC-MS/MS (UltiMate 3000 UPLC coupled with a Thermo Scientific Triple Quadrupole mass spectrometer) was used for antibiotics analysis. Combined with remote sensing data to analyze antibiotics spatial distribution in LZB from the perspectives of their sources and removal. A total of 15 target antibiotics were detected in LZB, with concentrations ranging from 2.32 to 116.40 ng/L in surface seawater, 142.90 to 17694 ng/g in SPM, and 3.77 to 29.70 ng/g in sediments. The results revealed significant spatial variations in antibiotics concentration, with higher levels observed in the southwestern LZB due to river inputs and limited photodegradation. The distribution of antibiotics in SPM was significantly influenced by anthropogenic activities and adsorption-desorption processes. Furthermore, the Yellow River, as a major sediment source, contributed to elevated antibiotic levels in sediments near its estuary. Importantly, under effective management, antibiotic levels in LZB have shown a significant decline. These findings provide critical insights for the management of antibiotic pollution in semi-enclosed bays and highlight the need for targeted mitigation strategies.