| Plant-microbial bioremediation is an emerging remediation of heavy metals polluted soil.In this study,a variety of heavy metals enrichment plants and cadmium-tolerant plant growth promoting rhziobacteria were screened from the heavy metals polluted lead-zinc mine,which provided the materials and theoretical basis for plant-microbial bioremediation of heavy metals contaminated soil.The main results were as follows:1.The content of 8 kinds of heavy metals(As,Cd,Cr,Cu,Mn,Ni,Pb and Zn)in soils were determined.The results showed that the soil was seriously polluted by heavy metals,and all of heavy metals contents exceeded the background values of elements in Nanjing.As,Cd,Mn,Pb and Zn were significantly correlated,forming the first principal component.Cr,Cu and Ni were significantly correlated to form the second principal component.The single factor pollution index of As,Cd,Mn,Pb and Zn reached 12.59,45.71,11.68,10.40 and 4.46 respectively,which were seriously polluted.The potential ecological risk indices of As,Cd and Pb reached 474.91,7217.05 and 450.03 respectively,indicated that the ecological risk severity.The Nemerow index(35.15)and the integrated potential ecological risk index(8279.79)indicated that the heavy metals pollution in this area was serious.2.The contents of heavy metals(Cd?Cr?Cu?Mn?Pb and Zn)in 14dominant plants were analyzed.Among them,Pteris multifidi and Trachelospermum jasminoides had stronger abilities to accumulate heavy metals.Zn concentration in all dominant plants were beyond the normal range,however,only the bio-concentration factor(BCF)of Digitaria sanguinalis for Zn exceeded 1.While the heavy metals bio-transfer factors(BTF)of the 14 species were generally high.The BTF of Helianthus tuberosus and Dendranthema indicum for the 6 heavy metals were greater than 1.According to the heavy metals accumulation mechanisms,the 14plant species were classified into 3 types:accumulators(Helianthus tuberosus,Dendranthema indicum,Phytolacca Americana,Justicia procumbens,Digitaria sanguinalis,Sonchus brachyotus,Solanum nigrum and Setaria viridis),root compartment(Pteris multifidi and Trachelospermum jasminoides)and excluders(Solidago decurrens,Duchesnea indica,Carex breviculmis and Cyrtomium fortunei).3.A strain named SY-2 with the ability of cadmium tolerance was isolated from plant rhizosphere soil by successive subcultures in liquid beef extract-peptone medium with 0.5 mmol·L-1Cd.According to the homologous analysis of 16S r DNA sequence,the strain was identified as Stenotrophomonas maltophilia.The maximum tolerable Cd concentration of strain SY-2 was 1.0 mmol·L-1.In addition strain SY-2 has a strong ability of Cd adsorption,the maximum Cd adsorption rate up to 98.61%.The Cd adsorption mechanism of SY-2 was studied preliminarily.The lipids and proteins on the surface of the cell were involved in the adsorption process.And the functional groups that play a major role were O-H,C=O,C-N and C-H.4.The growth-promoting ability of strain SY-2 was studied.Results showed that the strain had high ability to resolve organic phosphorus and synthesize IAA.After soaking in the SY-2 culture,the germination rate of Capsicum annuum seeds did not obviously increase.However,the root growth significantly improved.The root length was 1.68 times that of sterilized water soaking treatment.Seed soaking in SY-2 culture could relieve the inhibition of C.annuum growth by Cd stress.Under 0.25mmol·L-1 Cd treatment,the root length of strain SY-2 treatment was 1.59times that of the control.Therefore,the strain SY-2 had potential application in plant-microbial remediation of soil heavy metal pollution. |
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