Effects of Plant Growth–Promoting Rhizobacteria (PGPR) on the Phytoremediation of Pyrene-Nickel-Contaminated Soil by Juncus effusus

In the contaminated soil, the plants are often threatened by pollutants, reducing the efficiency of phytoremediation. Plant growth–promoting rhizobacteria (PGPR) screened from plant rhizosphere can alleviate this phenomenon. Juncus effusus (J. effusus) has good effects on the remediation of heavy metal pollution but rarely used in soil research. This study aims to determine how PGPR affects the process of the remediation on pyrene-Ni-contaminated soil by J. effusus. PGPR was combined with J. effusus to strengthen the phytoremediation efficiency. The pot experiments were used to investigate the influences of inoculation PGPR on physiological conditions, soil enzyme activity, pyrene, and Ni enrichment ability. PGPR could promote J. effusus growth and nutrient absorption. PGPR was beneficial to promoted soil dehydrogenase activities and pyrene degradation rate in soil. Pyrene degradation rate were 97.3% and 97.1% in pyrene-contaminated soil and pyrene-Ni-contaminated soil, respectively. After inoculation with PGPR, the Ni content in roots of Ni contaminated soil increased from 69.5 to 111.5 mg kg−1, and that of pyrene-Ni-contaminated soil increased from 92.9 to 123.4 mg kg−1. Furthermore, PGPR could promote the chemical morphology transformation of Ni and improved the content of exchangeable Ni in soil significantly. The results showed that PGPR could alleviate the stress of pyrene and Ni on J. effusus, and have a good effect on the remediation of pyrene-Ni in contaminated soil. Further study should focus on the mechanism of PGPR to reduce toxicity of pyrene and Ni to J. effusus.