Trifolium repens L. regulated phytoremediation of heavy metal contaminated soil by promoting soil enzyme activities and beneficial rhizosphere associated microorganisms

TLDR

Rhizosphere soil physiochemical properties, enzyme activities and rhizosphere‑associated microbial communities are central to modulating phytoremediation in heavy‑metal contaminated soil. The study examined the rhizosphere micro‑ecological characteristics of phytoremediation across seven contaminated soil groups with varying heavy‑metal species and concentrations. The authors investigated these characteristics by analyzing soil physiochemical properties, enzyme activities, and microbial communities. The study found that heavy‑metal enrichment suppressed plant growth yet increased uptake of Cr(VI), Cd²⁺, and Pb²⁺ (19–169 mg kg⁻¹ in roots, 11–87 mg kg⁻¹ in shoots), that Trifolium repens L.

Abstract

Rhizosphere soil physiochemical properties, enzyme activities and rhizosphere associated microbial communities are of the central importance for modulating phytoremediation in heavy metal contaminated soil. In this study, the rhizosphere micro-ecological characteristics of phytoremediation in seven groups of contaminated soil with different heavy metal species and concentrations were examined. The results showed that heavy metal-enrichment inhibited plant growth, but enhanced both anions (Cr2O72−) and cations (Cd2+ and Pb2+) uptake with corresponding mean values ranging from 19.37 to 168.74 mg/kg in roots and 10.89–86.53 mg/kg in shoots. Trifolium repens L. planting was able to compensate the lost caused by the heavy metal on the soil organic matter, available N, available P, available K and enzyme activities as well. According to the cluster, some species like Lysobacter, Kaistobacter and Pontibacter, was significantly related to heavy metal accumulation while others such as Flavisolibacter, Adhaeribacter and Bacillus promoted plant growth. The importance of root-associated microbial community could relatively regulate plant growth and heavy metal uptake. Our study not only illustrated the correlation among rhizosphere micro-ecological parameters, and the possible mechanisms of phytoremediation regulation, but also provide clear strategy for improving the phytoremediation efficiency.