[Occurrence Characteristics and Ecological Risk Assessment of Antibiotics in Suspended Particulate Matter in the Yellow River Delta].

To investigate the distribution and ecological risks of antibiotics in the aquatic environment of the Yellow River Delta （YRD）， the pollution characteristics of 45 typical antibiotics， including fluoroquinolones， sulfonamides， tetracyclines， and macrolides were determined in water and suspended particulate matter （SPM） samples collected from the lower reaches of the YRD， YRD Nature Reserves， and the YRD Estuary. This study use a high performance liquid chromatography tandem triple quadrupole mass spectrometry to measure the concentrations. The results showed that 12 and 18 antibiotics were detected at concentration levels in the range of N.D.-4 249.79 ng·L^-1 and N.D.-8 535.39 ng·g^-1 in the water and SPM samples， respectively. Among them， norfloxacin， enoxacin， doxycycline， pefloxacin， and sarafloxacin， belonging to fluoroquinolones and tetracyclines， were mostly detected； for the sulfonamides， the detection rate and concentration levels were relatively low， and macrolides were not detected in any samples. Moreover， due to the significant influences of human activities， the levels of antibiotic pollution were generally higher downstream than those upstream in the YRD water bodies. The levels of antibiotic pollution were positively correlated with the salinity of the waters in the nearby estuary. Conversely， the total concentrations of target antibiotics in the suspended particulate matter （SPM） were higher upstream than those downstream， which were consistent with the content of SPM along the sampling sites. Furthermore， the partition coefficient （K_d） of the detected antibiotics between water and SPM were calculated， showing that the K_d（L·kg^-1）values were in the range of 1.2×10³ （doxycycline）-8.7×10³ （sarafloxacin）. These results suggested that the detected antibiotics tended to be associated with SPM once entering the investigated area. Of particular note， it was observed that the K_d values followed the rank order： fluoroquinolones>tetracycline>sulfonamides， and there was a significant spatial variability. The correlation analysis of K_d and water environment factors showed that the partition of target antibiotics in the water-SPM interface was largely dependent on the properties of organic matter. In addition， the microstructure and composition of SPM also played an important role in the interaction between the antibiotics and SPM. The ecological risk assessment results showed that norfloxacin in water presented a high risk to aquatic organisms， doxycycline presented a moderate risk to algae and invertebrates， chlortetracycline and sulfadimethoxine had a low risk to invertebrates with a low trophic level， and other antibiotics had a small risk. However， when considering the multiple risk of simultaneous pollutants， all sites appeared as high risk and require further attention.