Toxicological effects of WS nanomaterials on rice plants and associated soil microbes.

As an important member of transition-metal dichalcogenides family, tungsten disulfides nanomaterials (WS NMs) have a wide range of applications. To date, their environmental risks remain largely unknown. In this study, rice plants were grown in soil amended with different concentrations (0, 10, and 100 mg/kg) of WS NMs for 4 weeks. WS NMs at 100 mg/kg significantly increased MDA (malondialdehyde) content and decreased total antioxidant capacities of leaves, indicating the oxidative response induced by WS NMs. Meanwhile, WS NMs at 100 mg/kg significantly decreased root biomass compared to control, indicating the negative impacts of WS NMs on plant growth. While exposure to 100 mg/kg WS NMs significantly increased soil bioavailable Cu, Fe, Zn, and Olsen-P, and increased the content of Cu, Fe, Zn, and P in rice leaves. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis showed that W was taken up by rice roots and translocated into leaves. The impact of WS on soil microbial communities was evaluated by 16S rRNA gene sequencing. WS NMs at 100 mg/kg significantly decreased soil microbial diversity, as indicated by decreased Shannon index. In addition, 100 mg/kg WS shifted the soil microbial profile, the relative abundance of the phylum Acidobacteriota decreased, and Actinobacteriota increased. Taken together, the soil microbial community's diversity and composition have been altered upon exposure to 100 mg/kg WS NMs. The results of this study provide some basic information regarding the environmental behavior and phytotoxicity of WS NMs, which is valuable for safe use of WS NMs.