Nanospecific effect rather than dissolved Cu²⁺ dominates the impact of CuO nanoparticles on soil microbiota

CuO nanoparticles (NPs) have raised significant concerns due to their extensive application in agriculture and potential ecological impacts in recent decades. Identification of the action mechanisms for soil microbiota response in a long exposure time with respect to the chemical speciation of CuO NPs remained scarce. A 63-day laboratory soil microcosms experiment was conducted to evaluate the impact of CuO NPs along with its dissolved Cu²⁺ on soil microbiota. Illumina MiSeq sequencing of microbial communities revealed that CuO NPs significantly (p < 0.05) reduced both bacterial diversity and richness, as well as a shift in overall bacterial community composition and structure. Some genera responded differently to CuO NPs and Cu²⁺, while for the most of impacted genera, no matter inhibition or facilitation induced by CuO NPs was much stronger than Cu²⁺. The dissolution rate of CuO NPs was substantially lower compared to that of Cu(NO₃)₂ in soil. It was demonstrated that nanospecific effect played a crucial role in shaping the response of microbial communities to CuO NPs, rather than dissolved Cu²⁺. This finding has significant implications for understanding the ecological consequences of agriculture application of CuO NPs as antibacterial agents and for developing appropriate management strategies to mitigate their negative impacts.