title: Pongamia pinnata inoculated with Bradyrhizobium liaoningense PZHK1 shows potential for phytoremediation of mine tailings.
abstract: Mine tailings contain high concentrations of metal contaminants and only little nutrients, making the tailings barren for decades after the mining has been terminated. Effective phytoremediation of mine tailings calls for deep-rooted, metal accumulating, and soil fertility increasing plants with tolerance against harsh environmental conditions. We assessed the potential of the biofuel leguminous tree Pongamia pinnata inoculated with plant growth promoting rhizobia to remediate iron-vanadium-titanium oxide (V-Ti magnetite) mine tailing soil by pot experiment and in situ remediation test. A metal tolerant rhizobia strain PZHK1 was isolated from the tailing soil and identified as Bradyrhizobium liaoningense by phylogenetic analysis. Inoculation with PZHK1 increased the growth of P. pinnata both in V-Ti magnetite mine tailings and in Ni-contaminated soil. Furthermore, inoculation increased the metal accumulation capacity and superoxide dismutase activity of P. pinnata. The concentrations of Ni accumulated by inoculated plants were higher than the hyperaccumulator threshold. Inoculated P. pinnata accumulated high concentration of Fe, far exceeding the upper limit (1000 mg kg-1) of Fe in plant tissue. In summary, P. pinnata-B. liaoningense PZHK1 symbiosis showed potential to be applied as an effective phytoremediation technology for mine tailings and to produce biofuel feedstock on the marginal land.
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China. yuxiumeicool@163.com.
authors.forename: Xiumei
authors.identifier: http://orcid.org/0000-0002-5776-4795
authors.initials: X
authors.lastname: Yu
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China.
authors.forename: Yangxin
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China.
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China.
authors.forename: Chaohua
authors.initials: C
authors.lastname: Xu
authors.affiliation: Sichuan Academy of Natural Resource and Sciences, Chengdu, People's Republic of China.
authors.forename: Yongliang
authors.initials: Y
authors.lastname: Cui
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China.
authors.forename: Quanju
authors.initials: Q
authors.lastname: Xiang
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China.
authors.forename: Yunfu
authors.initials: Y
authors.lastname: Gu
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China.
authors.forename: Ke
authors.initials: K
authors.lastname: Zhao
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Environmental Sciences, University of Helsinki, Helsinki, Finland.
authors.forename: Petri
authors.initials: P
authors.lastname: Penttinen
authors.affiliation: College of Resources, Sichuan Agricultural University, Chengdu, People's Republic of China. cqiang@sicau.edu.cn.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Chen
mesh_terms: D001673:Biodegradation, Environmental; D020369:Bradyrhizobium / Q000378:metabolism*; D008906:Mining
keywords: Bradyrhizobium; Iron–vanadium–titanium oxide mine tailings; Nickel soil; Phytoremediation; Pongamia pinnata