EFFECTS OF CHEMICAL POLLUTANTS ON SOIL MICROBIAL COMMUNITIES: MECHANISMS, ECOLOGICAL CONSEQUENCES, AND SUSTAINABLE MANAGEMENT

Abstract

Soil microorganisms regulate nutrient transformations that sustain plant productivity and ecosystem resilience. Chemical pollutants can disrupt these functions by altering microbial abundance, community composition, enzyme activity, functional gene expression, and interactions among microorganisms. This critical review examines the effects of pesticides, herbicides, heavy metals, antibiotics, petroleum hydrocarbons, and persistent organic pollutants (POPs) on soil microorganisms involved in nitrogen (N), phosphorus (P), and sulfur (S) cycling. Evidence indicates that pollutant effects are strongly contextdependent, varying with chemical structure, concentration, exposure duration, soil pH, organic matter content, nutrient status, and pre-existing microbial adaptation. Pesticides and herbicides can inhibit potential nitrification, N-acetylglucosaminidase activity, diazotrophic activity, and N-cycle functional genes, although some field studies report transient community shifts or recovery after dissipation. Heavy metals commonly constrain microbial biomass, enzyme activities, and nutrient mineralisation through toxicity, oxidative stress, membrane damage, and selection for resistant taxa. Antibiotics may alter microbial N transformations and promote communities carrying resistance determinants, whereas petroleum hydrocarbons and POPs can suppress sensitive nitrifiers and nutrient-cycling taxa while enriching pollutant-degrading organisms. Disrupted P cycling often manifests as altered phosphatase activity, phosphate-solubilising populations, and microbial P immobilisation; effects on S cycling, including arylsulfatase activity and sulfate reduction or oxidation, remain comparatively underexamined. These changes may reduce nutrient availability, destabilise soil organic matter turnover, impair plant growth, increase N losses, and compromise sustainable agriculture. Sustainable management should prioritise pollution prevention, integrated pest management, contaminant-specific risk assessment, organic amendments, biochar, phytoremediation, and microbiome-informed bioremediation. Future research should combine long-term field experiments with multi-omics, direct rate measurements, and assessments of pollutant mixtures to distinguish temporary compositional changes from persistent loss of soil function.