Influences of plant growth‐promoting bacteria from an e‐waste dismantling site on ryegrass growth, heavy metal enrichment, and translocation

Abstract The continuous accumulation of electronic waste (e‐waste) poses a significant risk to environmental health. However, e‐waste contains trace metals such as copper, zinc, and cadmium, as well as precious metals like gold and silver. This study investigated the effects of inoculating two plant growth‐promoting bacteria (PGPB), Microbacterium sp. MO4 and Rhizobium sp. RH3 , on soil properties and ryegrass performance in heavy‐metal‐contaminated soil. PGPB inoculation increased ryegrass biomass by 26.1% and chlorophyll content by 18.4% ( p < 0.05), while reducing soil pH by 0.41 units and increasing available phosphorus by 62.3% ( p < 0.01). The concentrations of Cu, Zn, and Cd in shoots increased by 32.6%, 54.2%, and 198.7% ( p < 0.05), respectively. The weak‐acid‐extractable fractions of these metals also rose by 2%–5%, whereas Cr and Pb were stabilized in less bioavailable forms. These results demonstrate that PGPB enhance soil nutrient cycling and promote the synergistic remediation of heavy metals through both activation and immobilization mechanisms.