Chronic toxicity effects of sediment-associated polystyrene nanoplastics alone and in combination with cadmium on a keystone benthic species Bellamya aeruginosa.

Nanoplastics (NPs) are emerging pollutants that may adversely affect aquatic fauna. However, the adverse effects of NPs and heavy metals, both alone and combined on freshwater benthic fauna remain largely unclear. Here, we performed a 28-day sediment toxicity test with Bellamya aeruginosa to examine the effects of exposure to polystyrene nanoplastics (PSNPs) and co-exposure to PSNPs and Cd. Cd bioavailability, the bioaccumulation of PSNPs and Cd, and changes in multiple biomarkers were determined. The results revealed that PSNPs significantly increased Cd bioavailability and thereby facilitated Cd bioaccumulation; however, PSNPs displayed a negligible vector role in Cd uptake by B. aeruginosa. The results demonstrated that PSNPs can accumulate in B. aeruginosa and induce oxidative damage and DNA damage. Co-exposure to PSNPs and Cd significantly enhanced oxidative damage and DNA damage and reduced metallothionein levels. The integrated biomarker response index analysis showed that co-exposure to PSNPs and Cd considerably increased toxic stress in B. aeruginosa compared to single PSNPs or Cd exposure, suggesting that PSNPs may have a synergistic effect with Cd. Collectively, our findings highlight that PSNPs not only cause toxicity to B. aeruginosa but also significantly enhance the toxicity of Cd by increasing Cd bioavailability in the sediment.

Insights into the nurse effect of a native plant Ficus tikoua on Pb‒Zn tailing wastelands in western Hunan, China.

Lead‒zinc (Pb‒Zn) processing and extraction activity generates large volumes of highly toxic and bare tailing (BT) wastelands which poses a potentially extreme risk to the surrounding environment. Revegetation in the Pb‒Zn tailing wastelands is usually considered a beneficial approach. Ficus tikoua is a native vine which can successfully colonize on Maoping Pb‒Zn mine tailing wastelands in western Hunan, China. This study involved examination of the nurse effect of F. tikoua on Pb‒Zn tailing wastelands, to provide insights into the potential mechanism of F. tikoua influencing soil quality and vegetation succession. The vegetation characteristics, nutrient properties, and heavy metal contents of three different types of vegetation patches associated with F. tikoua in Pb‒Zn tailing wastelands, representing different stage of succession, were investigated. The height, coverage, and aboveground and underground biomass of these vegetation patches showed an increasing trend from vegetation patch I (VP-I) to patch III (VP-III). The nutrient pool and chemical properties of these tailing wastelands gradually re-established from BT wasteland to VP-III. From VP-I to VP-III, the total heavy metal contents (i.e., Pb, Zn, Cu, and Cd) and DTPA-extractable Pb, Cu, and Cd contents significantly decreased, while the DTPA-extractable Zn content remained unchanged. Our findings suggested that F. tikoua exerts a distinct nurse plant effect by increasing the essential nutrient content of soil, reducing the available heavy metal content, and subsequently increasing the number of plant species and the biomass. Therefore, F. tikoua may be used as a promising nurse plant for triggering revegetation and phytostabilization of Pb‒Zn tailing wastelands at the initial stage of remediation.

Evaluating the potential of KOH-modified composite biochar amendment to alleviate the ecotoxicity of perfluorooctanoic acid-contaminated sediment on Bellamya aeruginosa.

Modified composite biochar offers a cost-effective solution for the remediation of contaminated sediments; however, few studies have evaluated the effects of modified composite biochar amendment on the ecotoxicity of contaminated sediment based on benthic macroinvertebrates. A 21-day sediment toxicity test was conducted using the freshwater snail Bellamya aeruginosa to examine the intrinsic ecotoxicity of a novel KOH-modified composite biochar (KOH-CBC) and its efficacy for reducing the bioavailability, uptake, and ecotoxicity of perfluorooctanoic acid (PFOA). It was found that KOH-CBC is toxic to B. aeruginosa, which may be attributed to its high polycyclic aromatic hydrocarbons (PAHs) content and alkalinity. The addition of KOH-CBC to PFOA-contaminated sediments can markedly reduce the bioavailability and uptake of PFOA by more than 90% and 50%, respectively, and subsequently alleviate the toxicity of PFOA to B. aeruginosa by at least 30%. Increasing the KOH-CBC dosage is not beneficial for further mitigating the toxicity of PFOA-contaminated sediments. Our findings imply that KOH-CBC is a promising sorbent for the in-situ remediation of PFOA-contaminated sediments. Application of acidified KOH-CBC at a dosage of approximately 1-3% will be sufficient to control the ecotoxicity of PFOA; however, its long-term environmental effects should be further validated.