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<p>Riparian zones serve as critical ecotones between terrestrial and aquatic ecosystems, yet they are increasingly threatened by co-contamination from polycyclic aromatic hydrocarbons (PAHs) and heavy metals—two pervasive pollutant classes originating from shared anthropogenic sources. The combined effects of these co-occurring pollutants on soil bacterial communities in dynamic riparian environments remain poorly understood, particularly in ecologically sensitive regions such as China’s Loess Plateau. To address this knowledge gap, we investigated the dispersion patterns of PAHs and heavy metals and their joint impacts on bacterial community structure in soils along the Beiluo River riparian zone. Soil samples were collected from 16 sites at varying distances from the riverbank, and bacterial assemblages were characterized using environmental DNA metabarcoding of the 16&#xa0;S rRNA gene (V3–V4 region). The total concentrations of 16 US EPA-listed PAHs ranged from 3.00 to 131.76 ng/g, with low molecular weight PAHs (2–3 rings) predominating. Heavy metal concentrations were relatively consistent across sites, with chromium (123.75–153.46&#xa0;mg/kg) and zinc exhibiting the highest levels, while cadmium and mercury were detected at significantly lower concentrations (0.03–0.15&#xa0;mg/kg). Proteobacteria (22.6–52.18%), Actinobacteriota (3.18–35.37%), and Bacteroidota emerged as the dominant phyla, reflecting their known capabilities for PAH degradation and environmental adaptation. Notably, Pielou’s evenness and Simpson’s diversity indices varied significantly with distance from the riparian zone, strongly correlated with soil moisture content. Partial Least Squares Path Modeling revealed that soil water content exerted the strongest direct positive effect on bacterial abundance (path coefficient = 0.768), while PAHs and heavy metals exhibited significant negative effects (path coefficients = -0.497 and − 0.343, respectively). These findings elucidate the complex interplay between bacterial communities and co-occurring pollutants in riparian soils, highlighting soil moisture as a pivotal modulator of microbial responses to multi-pollutant contamination. This study provides valuable insights for ecological risk assessment and bioremediation strategies in river ecosystems facing combined pollution pressures.</p>

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Co-occurring polycyclic aromatic hydrocarbons and heavy metals drive bacterial community shifts regulated by soil water content in China’s Beiluo River riparian soils

  • 期刊论文

  • 发表日期：

    2026年7月2日

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  • Xibo Pu,
  • Yingchuan Yang,
  • Jiahua Guo,
  • Baoxuan Zhuo,
  • Tamao Kasahara,
  • Yulu Tian,
  • Chenghao Li,
  • Jipu Guo,
  • Haotian Sun

摘要

Riparian zones serve as critical ecotones between terrestrial and aquatic ecosystems, yet they are increasingly threatened by co-contamination from polycyclic aromatic hydrocarbons (PAHs) and heavy metals—two pervasive pollutant classes originating from shared anthropogenic sources. The combined effects of these co-occurring pollutants on soil bacterial communities in dynamic riparian environments remain poorly understood, particularly in ecologically sensitive regions such as China’s Loess Plateau. To address this knowledge gap, we investigated the dispersion patterns of PAHs and heavy metals and their joint impacts on bacterial community structure in soils along the Beiluo River riparian zone. Soil samples were collected from 16 sites at varying distances from the riverbank, and bacterial assemblages were characterized using environmental DNA metabarcoding of the 16 S rRNA gene (V3–V4 region). The total concentrations of 16 US EPA-listed PAHs ranged from 3.00 to 131.76 ng/g, with low molecular weight PAHs (2–3 rings) predominating. Heavy metal concentrations were relatively consistent across sites, with chromium (123.75–153.46 mg/kg) and zinc exhibiting the highest levels, while cadmium and mercury were detected at significantly lower concentrations (0.03–0.15 mg/kg). Proteobacteria (22.6–52.18%), Actinobacteriota (3.18–35.37%), and Bacteroidota emerged as the dominant phyla, reflecting their known capabilities for PAH degradation and environmental adaptation. Notably, Pielou’s evenness and Simpson’s diversity indices varied significantly with distance from the riparian zone, strongly correlated with soil moisture content. Partial Least Squares Path Modeling revealed that soil water content exerted the strongest direct positive effect on bacterial abundance (path coefficient = 0.768), while PAHs and heavy metals exhibited significant negative effects (path coefficients = -0.497 and − 0.343, respectively). These findings elucidate the complex interplay between bacterial communities and co-occurring pollutants in riparian soils, highlighting soil moisture as a pivotal modulator of microbial responses to multi-pollutant contamination. This study provides valuable insights for ecological risk assessment and bioremediation strategies in river ecosystems facing combined pollution pressures.