Effect of heavy metal pollution on soil microorganisms: Influence of soil physicochemical properties. A systematic review

This review examines the complex interaction between heavy metals and soil microorganisms, focusing on five common heavy metals (HM) (chromium -Cr-, copper -Cu-, nickel -Ni-, lead -Pb-, and zinc -Zn-) in polluted areas worldwide. The systematic review was performed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The literature selection procedure involved searching four databases (Web of Science, Scopus, Google Scholar, and PubMed) with a variety of search queries and inclusion and exclusion criteria. As a result of the review, 106 scientific articles that addressed Cr, Cu, Ni, Pb and/or Zn effect on soil microorganisms between 2018 and 2022 were identified. Soil microorganisms, crucial for soil functions/functioning, are impacted by heavy metal pollution, affecting essential functions such as nutrient cycling, organic matter cycling, and carbon sequestration. Various microbial properties (microbial activity -including enzymatic activity-, microbial community composition/diversity, microbial biomass/abundance), reflecting heavy metal effects, show diverse microbial responses influenced by both heavy metal pollution and soil properties (soil pH, organic matter content, texture). Although extensive research has been conducted in this field, further studies are needed to better understand the intricate relationship between heavy metal (HM) pollution, soil microbial responses, and soil properties influence. This review explores the most common methodologies and their main challenges and underscores the need for methodologies to specifically assess HM toxicity. Understanding these details is essential for developing effective strategies to mitigate the adverse effects of HM pollution on soil ecosystems.