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The distribution and source of polychlorinated biphenyls (PCBs) pollution in the Beiluo River, the secondary tributary of the Yellow River, still remain unclear. With the purpose of determining the distribution, origins, and pollution levels of PCBs and their consequences on ecological risks, the concentrations of 27 PCBs at 17 locations in the sediments of the Beiluo River were examined in this study. The results showed that the mass concentrations of ∑PCBs in the sediment ranged from 0.12 to 1.25 ng∙g−1 (DW), with the highest point at sampling site B13 downstream of the river. Compared to most river sediments, both domestically and internationally, the concentration of PCBs in the sediment of the Beiluo River was at a low level, with 10-PCB and 6-PCB as the main components, indicating that the PCBs that are difficult to volatilise and degrade are more likely to remain in the sediment. The origins of PCBs in the sediments of the Beiluo River were examined by using positive matrix factorisation (PMF). The results revealed that the contamination of PCBs in the sediments of the Beiluo River mainly resulted from industrial emissions, technical PCB mixtures, and coal and wood combustion. The results of the ecological risk assessment indicated that PCBs in the sediments of the study area rarely contribute to adverse biological effects and the potential low risk to the environment.

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Chlorella vulgaris (C. vulgaris) and Raphidocelis subcapitata (R. subcapitata) are two model algal species applied for the testing of chemicals, whereas a considerable variation in their sensitivity to antibiotics has been reported. The difference in species sensitivity may be attributed to the xenobiotic‐induced oxidative stress in algal cells. Thus, this study compared the responses of these two model green algae toward the exposure of erythromycin (ERY), a macrolide antibiotic, at the concentration levels of 0, 20, 40, 60 μg/L, and elucidated the toxic mechanism of action from the point of oxidative damage and antioxidant defense. To achieve this, effects on the endpoints of algal growth, malondialdehyde (MDA), antioxidants (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GP], glutathione, and glutathione S‐transferase), and photosynthetic pigment contents were evaluated. After exposing for seven days, the growth of R. subcapitata was significantly stimulated at ERY 20 μg/L but inhibited at the higher exposure level of 60 μg/L. Contrarily, hormesis in C. vulgaris exposed to all ERY treatments was detected. With the increase in ERY exposure, MDA content, and the antioxidant activity of SOD, CAT, GP in R. subcapitata were gradually enhanced. In C. vulgaris, a declining trend in the MDA content and the activity of SOD, CAT, and GP was detected. These results provide insights into the ERY‐altered production of reactive oxygen species and the antioxidant responses in two algae.