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Microplastics modify plant-arbuscular mycorrhizal fungi systems in a Pb-Zn-contaminated soil
Summary
Researchers examined how six types of microplastics affect sweet sorghum growth and soil fungal communities in soil contaminated with lead and zinc. They found that microplastics generally did not inhibit plant growth and in some cases promoted it, but they increased the uptake of heavy metals into plant shoots. The study suggests that microplastics may worsen the risks of heavy metal contamination in agricultural soils by enhancing metal accumulation in crops.
Both microplastics (MPs) and potentially toxic elements (PTEs) are common contaminants that widely co-occur in various soil environments. They can interact to pose higher risks to soil-plant systems, but how precisely they do remains, as yet, unclear. Here, we explored the response of sweet sorghum-arbuscular mycorrhizal fungi (AMF) systems to six types of MPs at the doses of 0.2% and 2% ( w /w) in an agricultural soil contaminated with 415.0 mg/kg Pb and 467.9 mg/kg Zn. MPs caused type-dependent alterations in soil properties. For example, soil pH was increased by the higher doses of both polylactic acid (PLA) and polyhydroxybutyrate (PHB). Dissolved organic carbon (DOC) content was decreased by polyethylene (PE) and polystyrene (PS), but increased by 2% PLA (+14%) and 2% PHB (+7%). The activities of catalase , urease , alkaline phosphatase , and sucrase in the soil were either unaffected or stimulated by MPs, particularly biodegradable MPs. Overall, MPs did not inhibit plant growth and even promoted it, with 0.2% PS increasing shoot and root biomass by 34.74% and 132.84%, respectively. In most cases, MPs increased shoot Pb and Zn concentrations and their phytoaccumulation. Irrespective of inhibited root mycorrhizal colonization, MPs caused non-significant changes in the richness and diversity of AMF, but substantially modified their community structure. Overall, MPs may exacerbate the risks of PTEs to plant-AMF systems, which should be considered in the management of PTE-contaminated soil. • MPs showed no inhibition and even increased plant growth in some cases. • MPs increased shoot Pb and Zn concentrations and their accumulation in plants. • MPs altered AMF community structure, enriching specific taxa in PTEs-polluted soil. • The effects of MPs were dominated by their type and less by their dose.