Study On The Effects Of Biochar On Growth And Cadmium Accumulation Of Solanum Nigrum L.

Heavy metal pollution has become one of the serious threats to human health and the environment.Biochar was widely developed for the soil amendment and remediation in heavy metal contaminated soil.The Cd hyperaccumulator,Solanum nigrum L.,has been paid much more attention with the wide application of phytoremediation.In order to study the effect of biochar amendment on the capacities of Solanum nigrum L.to accumulate Cd and growth of Solanum nigrum L.under different Cd contaminated level in the soil.A 60-day pot experiment of Solanum nigrum L.with four Cd concentrations?0,25,50and 100 mg/kg?and three biochar doses?0,1%and 5%?was conducted to study the effect of biochar amendment on soil physical and chemical properties,growth of Solanum nigrum L.,available heavy metals,different heavy metal components,enrichment ability of Solanum nigrum L.,soil enzyme activity and soil microbial community.The results of this study will provide important basic theoretical and practical basis for the application of biochar and phytoremediation in Cd-contaminated soil.The main results of the paper are as follows:?1?The application of biochar does not significantly change the mineral nitrogen content?NO₃^–-N and NH₄⁺-N?.Under the same heavy metal concentration treatments,5%biochar application significantly increased EC.The availability of Cd obtained by ETPA extraction significantly decreased after biochar application.The application of biochar caused the fraction of easily exchangeable cadmium and carbonate-bound cadmium to decrease,while the organically bound cadmium increased.?2?The application of biochar promotes the growth of Solanum nigrum L.The 1%biochar dose significantly increased leaf dry weight compared with the control in higher Cd concentrations?50 and100 mg/kg?.The application of biochar did not significantly affect the bioconcentration factor?BCF?of Solanum nigrum L.In the presence of biochar,the bioconcentration factor?BCF?increased under the Cd concentrations of 50 and 100 mg/kg.The translocation factors?TF?decreased with the biochar doses under the Cd concentration of 100 mg/kg.Biochar enhanced the Cd contents of shoot and root at the Cd concentration of 50 mg/kg.?3?For different enzymes,biochar application has different effects on its activity.The dose of 5%biochar significantly increased the urease activity by 41.18%compared to the 1%biochar addition in the Cd contaminated soil of 50 mg/kg concentration.The activities of acid phosphatase were inhibited by 1%biochar dose in all the Cd contaminated soils.The dry weight of the root of Solanum nigrum L.was significantly negatively correlated with acid phosphatase activity and BCF,respectively,indicating acid phosphatase in the rhizosphere soil of Solanum nigrum L.were repressed by Cd toxicity despite of biochar amendment.Biochar has no negative effect on Cd accumulation ability of Solanum nigrum L..Two-way ANOVA analysis showed that both biochar and Cd significantly affected the height of Solanum nigrum L.and the dry weight of leaf and stem.The application of biochar has caused significant changes of soil organic carbon in the treatments with 0 mg/kg and 50 mg/kg Cd.The fraction of actinomycetes,gram-positive bacteria and gram-negative bacteria increased with the application of biochar in l Cd treated groups.Acidobacteria decreased with the addition of biochar.Acidobacteria was negatively correlated with pH.This study implies that the simultaneous application of biochar and hyperccumulator Solanum nigrum L.is promising during the remediation of Cd-contaminated soil.This study provided a new insight that biochar application did not affect the capacities of Solanum nigrum L.to accumulate Cd and promoted the growth of Solanum nigrum L.