title: Elevated CO2benefits the soil microenvironment in the rhizosphere of Robinia pseudoacacia L. seedlings in Cd- and Pb-contaminated soils.
abstract: Soil contamination by heavy metals in combination with elevated atmospheric CO2has important effects on the rhizosphere microenvironment by influencing plant growth. Here, we investigated the response of the R. pseudoacacia rhizosphere microenvironment to elevated CO2in combination with cadmium (Cd)- and lead (Pb)-contamination. Organic compounds (total soluble sugars, soluble phenolic acids, free amino acids, and organic acids), microbial abundance and activity, and enzyme activity (urease, dehydrogenase, invertase, and β-glucosidase) in rhizosphere soils increased significantly (p < 0.05) under elevated CO2relative to ambient CO2; however, l-asparaginase activity decreased. Addionally, elevated CO2alone affected soil microbial community in the rhizosphere. Heavy metals alone resulted in an increase in total soluble sugars, free amino acids, and organic acids, a decrease in phenolic acids, microbial populations and biomass, and enzyme activity, and a change in microbial community in rhizosphere soils. Elevated CO2led to an increase in organic compounds, microbial populations, biomass, and activity, and enzyme activity (except for l-asparaginase), and changes in microbial community under Cd, Pb, or Cd + Pb treatments relative to ambient CO2. In addition, elevated CO2significantly (p < 0.05) enhanced the removal ratio of Cd and Pb in rhizosphere soils. Overall, elevated CO2benefited the rhizosphere microenvironment of R. pseudoacacia seedlings under heavy metal stress, which suggests that increased atmospheric CO2concentrations could have positive effects on soil fertility and rhizosphere microenvironment under heavy metals.
authors.affiliation: School of Environmental Science and Engineering, Chang'an University, Xi'an 710054, PR China.
authors.forename: Shuping
authors.initials: S
authors.lastname: Huang
authors.affiliation: School of Environmental Science and Engineering, Chang'an University, Xi'an 710054, PR China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, Xi'an 710054, PR China; Key Laboratory of Environmental Protection & Pollution and Remediation of Water and Soil of Shaanxi Province, Chang'an University, Xi'an 710054, PR China. Electronic address: jiaxianavy@163.com.
authors.forename: Xia
authors.initials: X
authors.lastname: Jia
authors.affiliation: The School of Earth Science and Resources, Chang'an University, Xi'an 710054, PR China.
authors.forename: Yonghua
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: School of Environmental Science and Engineering, Chang'an University, Xi'an 710054, PR China.
authors.forename: Bo
authors.initials: B
authors.lastname: Bai
authors.affiliation: School of Environmental Science and Engineering, Chang'an University, Xi'an 710054, PR China.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Chang
mesh_terms: D001673:Biodegradation, Environmental; D018533:Biomass; D002104:Cadmium / Q000032:analysis*; D002245:Carbon Dioxide / Q000737:chemistry*; D007854:Lead / Q000032:analysis*; D058441:Rhizosphere; D031301:Robinia / Q000254:growth & development*; D036226:Seedlings / Q000254:growth & development; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D002245:Carbon Dioxide; D007854:Lead
keywords: Cd- and Pb-contaminated soil; Elevated atmospheric CO(2); Rhizosphere microenvironment; Robinia pseudoacacia L. seedlings