The formation of plastisphere on plastics and their potential impact on freshwater ecosystems have drawn increasing attention. However, there is still limited information about the effects of plastisphere on the heavy metal adsorption capacity and the related mechanism of plastic debris in different freshwaters. Herein, the trace metal adsorption capacity, kinetics and adsorption mechanisms of virgin and biofilm-covered plastic debris were investigated. Polypropylene (PP) and polyethylene terephthalate (PET) plastic debris were placed in three freshwaters (Xuanwu Lake, Donghu Lake and the Qinhuai River) for 45 days to incubate biofilms. Batch adsorption experiments were performed to compare the adsorption processes of trace metal on virgin and biofilm-covered plastics. Results showed that biofilms increase the adsorption of metals on plastics, and the adsorption isotherms were well fitted by the Langmuir model. Furthermore, the adsorption capacities for lead (Pb(II)) were higher than that of cadmium (Cd(II)) and zinc (Zn(II)), with 256.21 and 277.38 μg/g (Pb(II)) adsorbed in biofilm-covered PP and PET, respectively, in Xuanwu Lake. The adsorption kinetics of metals on plastic debris were significantly affected by the biofilms, by switching the intraparticle diffusion for virgin plastic debris to film diffusion for the biofilm-covered plastic debris. Moreover, the complexation of functional groups within the biofilms might mainly contribute to the increases of metal adsorption, involving the participation of oxygen and nitrogen groups. Overall, these results suggested that biofilms reinforce the potential role of plastics as a carrier of trace metals in freshwaters.

Heavy metals were typical contaminants in aquatic ecosystems, while their effects on the biotoxicity and metabolism of algal cells in the presence of organic ligands were still unclear. In this study, the contrasting effects of Cu and humic acids (HA) on the growth inhibition, oxidative stress and extracellular secretion of microalga Chlorella vulgaris were studied at environmentally relevant concentrations of Cu (0~2 mg/L) and HA (0~20 mg/L). Results showed that, with increased Cu addition, the algal growth rate decreased while concentrations of superoxide dismutase and malondialdehyde increased showing evident growth inhibition and oxidative damage in the sole presence of Cu. However, the presence of HA could significantly alleviate the Cu-induced toxicity damage, and higher concentrations of HA exhibited greater alleviation efficiencies. Fluorescence spectroscopy combined with flow field flow fractionation revealed that secretion of 50 kDa~0.45 μm of extracellular protein-like substances was the critical fractions responsible for the biotoxicity alleviation. Analysis of Cu contents within extracellular polymeric substance (EPS) matrix showed that not only the secretion amounts but also the acquisition capacities of EPS matrix decreased due to the addition of HA. This study benefited an in-depth understanding toward the toxicity of heavy metals to aquatic microorganisms in natural waters that contained abundant organic ligands.

Antibiotic resistance genes (ARGs) have emerged as globally concerning environmental contaminants, posing serious threats to ecosystem health and public safety. This systematic review summarizes global research trends on ARGs across three key aspects: (i) identification and distribution in river and lake ecosystems, (ii) sources and environmental behaviors, and (iii) ecological and human health risks. Concentration data of ARGs in various rivers and lakes across China were compiled to reveal their spatial distribution patterns. The analysis of ARGs sources and environmental behaviors provides essential insights for designing effective mitigation strategies. Furthermore, this review highlights the potential ecological and human health hazards of ARGs and discusses limitations and improvement directions of current risk assessment methodologies. The main findings indicate that ARGs are widely present in rivers and lakes across China; higher abundances occur in eastern and southern regions compared with central–western and northern areas, such as 4.93 × 10²–8.10 × 10³ copies/mL in Qinghai Lake and 6.7 × 10⁷–1.76 × 10⁸ copies/mL in Taihu Lake. The environmental behaviors of ARGs are highly complex, involving multiple mechanisms and influenced by climatic conditions, nutrient levels, and additional environmental factors. Based on these findings, future efforts should prioritize long-term site-specific monitoring, evaluate their prolonged impacts on aquatic ecosystems, and develop integrated risk assessment models to support evidence-based environmental management.