Environmental implications of MoS nanosheets on rice and associated soil microbial communities.

Molybdenum disulfide (MoS) is a transition metal dichalcogenides (TMDCs) material that is seeing rapidly increasing use. The wide range of applications will result in significant environmental release. Here, the impact of MoS nanosheets on rice and associated soil microbial communities was evaluated. Rice plants were grown for 4 weeks in a natural paddy soil amended with either 1T or 2H phase MoS nanosheets at 10 and 100 mg kg. The 1T MoS nanosheets have a significantly greater dissolution rate (58.9%) compared to 2H MoS (4.4%), indicating the instability of 1T MoS in environment. High dissolution rate resulted in a high Mo bioaccumulation in rice leaves (272 and 189 mg kg under 1T and 2H exposure at 100 mg kg). However, this did not induce overt phytotoxicity, as indicated by a range of phenotypic or biochemical based determine endpoints, e.g., biomass, photosynthetic pigments, and malondialdehyde (MDA) content. Additionally, rice P uptake was significantly increased upon exposure to 1T and 2H MoS (10 mg kg). Gas chromatography-mass spectrometry (GC-MS) reveals that both phases of MoS in soil systematically enhanced the carbon and nitrogen related metabolic pathways in exposed plants. Soil 16S rRNA gene sequencing data show that soil microbial community structure was unchanged upon MoS exposure. However, both phases of MoS remarkably increased the relative abundance of N-fixation cyanobacteria, and 2H MoS exposure increased a plant growth-promoting rhizobacteria-Bacillus. Overall, our results suggest that MoS nanosheets at tested doses did not exert negative impacts on rice plant and the associated soil microbial community.