Impacts of biochar aging on its interactions with As(III) and the combined cytotoxicity.

Despite the extensive use of biochar (BC) in soil and aqueous media for pollutant immobilization, the environmental behaviors and health risks of aged BC with multiple pollutants, especially with metal ions possessing various valence states, remain unexplored. Here, we prepared fresh banana peel BC (BP-BC) and aged BP-BCs by acidification (ABP-BC) and oxidation (OBP-BC). ABP-BC was then chosen to explore its environmental behaviors (i.e., adsorption, desorption, and arsenic valence transfer) towards As(III)-Cu(II) and the combined cytotoxicity of BCs with As(III)-Cu(II) was investigated in Human Gastric epithelium cells (GES-1). Our results demonstrate that the aging process notably alters the physicochemical properties of BP-BC, including surface morphology, elemental composition, and surface functional groups, which are key factors affecting the long-term environmental behaviors of BC with As(III)/Cu(II). Specifically, the aging process significantly enhanced the adsorption of As(III) on BC but reduced the adsorption of Cu(II). Although the oxidation of As(III) to As(V) did not change much, the aging process improved the stability of ABP-BC-metal ion complexes, alleviating the release of As(III) in acidic solution. Consequently, the combined cytotoxicity induced by ABP-BC-As(III)-Cu(II) was reduced compared to BP-BC-As(III)-Cu(II). The study highlights the critical roles of the aging process in regulating the As(III) adsorption/desorption dynamics on BCs and their combined cytotoxicity in the presence of multiple metal ions.

Thallium's Threat to Aquatic Life: Stage-Specific Toxicity in Zebrafish Embryos and Larvae.

The escalating frequency of thallium (Tl) contamination incidents amplifies its environmental risk. However, the potential risk of Tl to aquatic organisms, especially across varying developmental stages, remains poorly understood. In this study, we employed zebrafish as a representative model organism and exposed zebrafish embryos and larvae at distinct developmental periods (specifically, 6 h postfertilization (hpf) and 72 hpf) to low concentrations of Tl(I) (0.25 and 0.50 mg/L). The exposure was performed for a short duration of 24 h, followed by a 96 h depuration period. Our results revealed that Tl(I) exerted disparate biological effects on zebrafish at different developmental stages. Embryos exhibited negligible uptake of Tl(I), whereas larvae showed a significant accumulation of Tl(I) and struggled with its rapid elimination. Notably, Tl(I) was able to permeate the blood-brain barrier, thereby posing a risk to the nervous system. Transcriptomic analysis indicated that Tl(I) triggered distinct toxicological pathways in embryos and larvae. It mainly interfered with metabolic processes in embryos, while in larvae, it mainly disrupted intracellular ion homeostasis, both consequently provoking neurotoxicity. This emphasizes that the multifaceted nature of Tl(I) toxicity depends on the developmental stages of the organism. This study clearly shows that the bioeffects of Tl are intricately related to the developmental stage of zebrafish, offering a valuable perspective for the pollutant toxicity assessment.