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Microplastics (MPs) are emerging contaminants in agricultural soil, whereas their effects on the rhizosphere microbial ecosystems and biogeochemical nitrogen cycles during plant growth remain unknown. Here, a 70-day greenhouse experiment was carried out with black and fluvo-aquic soil to evaluate the influence of polyamide (PA), polyethylene (PE), polyester (PES), and polyvinyl chloride (PVC) MPs on the bacterial communities and functions in the soybean rhizosphere. The PA treatment consistently affected the rhizobacterial alpha diversity in the fluvo-aquic soil at soybean vegetative and reproductive growth stages, whereas the PE, PES, and PVC treatments had a short-term effect on the bacterial alpha diversity. At two growth stages, 6 and 23 biomarkers were consistently abundant in the PA treatment in the black soil and fluvo-aquic soil, respectively, and order Rhizobiales was found to be a biomarker for PA MPs contamination in both soils. Additionally, PA treatment decreased bacterial network complexity and tightness, whereas the effects of the PE, PES, and PVC on bacterial co-occurrence patterns varied depending on the soil types. Furthermore, PES and PVC treatments inhibited ammonification processes in the soybean rhizosphere, and PE could temporarily inhibit ammonia oxidation and denitrification processes according to the variations of N-cycling gene abundances. These effects on soil N-cycling also varied with soil types and soybean growth stages. This study provides profound information for understanding of MPs residues on the assembly of the soybean rhizosphere communities and function during plant development., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Microplastics (MPs) are a contaminant of increasing concern in the environment. However, the impacts of MPs on soil ecosystems and biogeochemical processes like nitrogen cycle have not been well elucidated. In this study, we designed an indoor microcosm experiment to investigate the effects of exposure to low density polyethylene (LDPE) MPs on soil bacterial community and nitrogen cycling function over a 90-day incubation. Next-generation sequencing of the 16S rRNA genes revealed that both 2% and 7% LDPE MPs exposure slightly affected the soil bacterial diversity. Further analysis at the genus level showed differential tolerance to LDPE MPs, the genera Pedomicrobium, Steroidobacter, Pseudonocardia, Nitrospira and Turicibacter were enriched in the soil with 2% (w/w) LDPE MPs amendment, while the genera Pedomicrobium, Mycobacterium and Hyphomicrobium were significantly enriched in the soil with 7% (w/w) LDPE MPs amendment on days 15 and 30. Co-occurrence network analysis further suggested that LDPE MPs changed bacterial network complexity and modularity and Acidobacteria formed intimate associations with each other in responding to LDPE MPs exposure. Additionally, LDPE MPs in soil increased the abundance of nifH, AOBamoA and nirK genes involved in nitrogen cycling in different incubation phases compared to the control. The abundance of AOAamoA genes decreased on day 15 and then increased. Conversely, the abundance of nirS genes increased during the first 15 days and then decreased. These results suggested that both 2% and 7% LDPE MPs impact soil bacterial network structure and alters functional groups involved in soil nitrogen cycling processing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Microplastics (MPs) could act as a vector for various kinds of pollutants due to their small size. Compared to nonpolar and nondegradabale MPs, the sorption of organic pollutants on polar and degradable MPs has been seldom studied. In this study, the sorption behavior of two nonpolar polycyclic aromatic hydrocarbons (PAHs, phenanthrene and pyrene), two polar derivates of PAHs (1-nitronapthalene and 1-napthylamine) and a heterocyclic chemical (atrazine) by three polar MPs including polybutylene succinate (PBS), polycaprolactone (PCL) and polyurethane (PU) and a typical nonpolar MP, polystyrene (PS) were investigated. The sorption followed the pseudo-second-order kinetics and sorption equilibrium was achieved within 5 days. Sorption isotherms could be well fitted by both Linear (R 2 >0.946) and Freundich models (R 2 >0.945) and the values of nonlinear index (n) from Freundlich model in most cases were close to 1, suggesting that hydrophobic partition was a primary process controlling the sorption. The sorption coefficients (K d ) of the five organic compounds ranged from 29. 6 to 1.42 × 10 5 (L/kg). The log K OC /log K OW of PAHs and derivates of PAHs on polar MPs were greater than 1, especially for 1-naphthylamine (1.30-1.40), confirming the great contribution of hydrogen bonding. PU contains a benzene ring and showed greater sorption compared the other two polar MPs, indicating the existence of π (n) -π electron donor-acceptor interactions. Morevoer, the sorption of phenanthrene and pyrene on PU were better fitted by Langmuir model and the maximum adsorption capacities were 1.06 × 10 4 and 5.87 × 10 3  mg/kg, respectively., Competing Interests: Declaration of competing interest The authors declare no financial interests., (Copyright © 2020 Elsevier Ltd. All rights reserved.)