Unveiling the characteristics of fluoroquinolones in China marginal seas: Spatiotemporal distribution, environmental fate, and mass inventory

Fluoroquinolones (FQs) are widely used antibiotics, frequently detected in marine environments with serious ecological risks. This study reviewed FQs usage in China, their spatiotemporal distribution in offshore waters, and their marine fates. FQs consumption initially declined but increased after 2013. Studies on antibiotics in China's offshore areas were concentrated in the Bohai Sea, particularly in Bohai Bay and Laizhou Bay, while fewer studies were conducted in the East and South China Seas. NOR, OFL, CIP, and ENR exhibited the highest detection frequencies and concentrations, with enoxacin (ENO) also commonly found in the South China Sea. The total concentration of FQs (∑FQs) in seawater ranged from 0.2 to 960 ng/L, following the order Bohai Sea > Yellow Sea ≈ East China Sea > South China Sea, with a decreasing trend in the Bohai and South China Seas since 2013. ∑FQs concentrations in sediments were lower, ranging from 0.02 to 170.18 ng/g, with no regional differences. Estimated ∑FQs mass inventories ranged from 7.42 to 671.13 tons in the Bohai Sea and from 7.90 to 478.23 tons in the Yellow Sea. Seawater exchange influenced FQs accumulation, with long-term discharge retention in the Bohai Sea and recent inputs in the Yellow Sea. A strong correlation was observed between FQs usage and their marine inventories, with NOR and CIP exhibiting higher environmental stability than OFL and ENR. This study provides important scientific evidence for a systematic understanding of the relationship between the use, occurrence, and environmental fate of FQs in China.