The Effect of Applying Model Nanoplastic Particles to Soil on the Composition of Its Microbial Community

Soil microorganisms play pivotal roles in biogeochemical cycling and plant growth promotion, directly impacting crop productivity and ecosystem stability. While assessing their responses to emerging contaminants like micro/NPs is critically important, research remains challenging due to highly variable effects contingent upon (1) soil physicochemical properties and (2) plastic characteristics (type, size, morphology, concentration, and other parameters). A one-month laboratory incubation experiment using 0.55 µm polystyrene latex nanoplastics (NPs) allowed us to investigate the microbial communities in soils in the southern taiga zone (near Saint Petersburg, Russia) react to the addition of polystyrene NPs. It was found that sandy Podzols were more resistant to the addition of NPs than loamy Retisols and Fluvisols. The most responsive components of the soil microbiome were those that were initially more abundant. These include representatives of the following phyla: Pseudomonadota, Bacillota, Actinomycetota and Planctomycetota. The alpha diversity parameters of the microbial community, expressed in the number of operational taxonomic units and bio-diversity indices (Shannon and Simpson), decreased under the influence of NPs. The dynamics of alpha diversity of the microbial community were the least pronounced in Podzol soil. Beta-diversity parameters changed the most in Hortic Retisol, slightly less in Fluvisol, and not at all in Podzol. Thus, it was found that agricultural soils were most affected by NPs (in terms of microbial community dynamics) compared to the region’s two zonal soils. Studies carried out indicate that, in the future, a threshold for the harmfulness of NPs in relation to soils should be developed, taking into account the differentiation of soils as standardized objects in terms of particle size distribution.