Phytoremediation And Toxicity Reduction Of Potentially Toxic Trace Elements In Mines And Industrial Polluted Soils Through Streptomyces Pactum And Biochar

The excessive release of potential toxic trace elements(PTEs)in the biosphere is a global concern.The rapid industrialization and expanding agricultural activities,smelting,mines explorations,coal combustion,and dumping of municipal solid wastes have seriously contaminated the natural environment.PTEs pose toxicity to plants and public health,contaminate groundwater,degrade soil and alter the natural ecosystem.PTEs can reduce the biosynthesis of chlorophyll,reduce respiration and hamper enzymatic activities in plants and soil.Many physical,chemical and biological techniques are used for the remediation of PTEs.Recently biological techniques and organic amendments have got recognition in the scientific societies due to their low cost and sustainable remediation.This research was planned to elucidate the interactive effect of Streptomyces pactum(Act12)and biochar in three different level contaminated soils.Act12 and biochar both were applied as single doses or in combinations to the polluted soils(Tonguan,Feng county and Chenzhou).The main objective of this research was to increase the phytoremediation and reduce phytotoxicity of PTEs by growing Sorghum bicolor and Brassica juncea.The results are as follow.1)Application of Streptomyces pactum(Act12)along with medical stone compost(MSC)in Feng County(FC)and Tongguan(TG)showed that Zn,Pb,Cd and Cu uptake in shoot and root of Brassica juncea increased by(7,28%),(54,21%),(16,17%)and(8,10%), respectively in FC.The Zn and Pb uptake in the shoot and root were increased by(40,14%) and(82,15%)in TG soil,respectively.Shoot Cd uptake remained below detection,while Cu decreased by 52% in TG.Cd and Cu root uptake was increased by 17 and 33%,respectively. Results showed that PTEs uptake in shoot increased with increasing Act12 dose.Brassica shoot/root dry biomass,chlorophyll and carotenoid content were significantly influenced by Act12 rates in FC and TG samples.The antioxidant enzymatic activities(POD,PAL,PPO and CAT)in Brassica juncea implicated enhancement in the plant defense mechanism against the PTEs induced stress.The extraction potential of Brasssica juncea was further evaluated by BCF,TF and MEA.2)The immobilization and phytotoxicity reduction of bamboo biochar(BB)in mines polluted soil of Feng county(FC)and Tongguan(TG)was investigated.Results showed that BB application to mines contaminated soil immobilized PTEs(Zn,Pb,Cd and Cu).Soil pH and EC increased and reduced the bioavailability of PTEs in FC and TG,while Pb and Cu increased in TG soil.BB addition reduced PTEs uptake in shoot/root of Brassica juncea. Physiological responses showed that BB application improved the shoot/root growth,dry biomass,and enhanced chlorophyll(a and b)and carotenoid concentration in Brassica. Incorporation of BB improved the soil health and accelerated enzymatic activities(β- glucosidase,alkaline phosphatase and urease)in PTEs stress.Antioxidant activities(POD, PPO,CAT and SOD)were also used as natural biomarkers to determine the PTEs stress in Brassica grown on polluted soil.Overall,the immobilization potential and phytotoxicity reduction of the PTEs was also confirmed by BCF,TF and MEA for both soils.3)Act12 was applied at different levels along with 1% biochar,enhanced the growth and PTEs extraction in Sorghum from mines,smelter and industrial polluted soils of TG,FC and CZ. Soil pH and EC varied after biochar and Act12 application.Extractable Zn and Pb was higher in TG,FC and CZ soil as a result of compost addition.Cd decreased in TG and CZ,with no change in FC soil.Act12 and biochar increased the uptake of PTEs(Zn,Pb)in shoots an roots in TG soil,while the extraction was increased in shoot and lowered in CZ roots. Similarly,Zn,Pb and Cu uptake in Sorghum shoot significantly increased and Cd declined in FC soil.However,Zn and Cd uptake in root decreased,while Pb and Cu uptake was improved after Act12 + biochar application.Cd content in shoot was below detection level and mostly stored in the TG roots.The shoot/root uptake of Cd decreased in CZ soil.Plant growth promoting features(shoot,root dry biomass and chlorophyll)significantly improved after Act12 and biochar application.Soil enzymes(β-glucosidase,alkaline phosphatase and urease)were improved,plant antioxidant enzymatic activities(POD,PAL,PPO)and lipid peroxidation(MDA)were significantly decreased in Sorghum leaves.BCF,TF and MEA also confirmed the role of Act12 in the translocation of PTEs in contaminated soil.Further experiments on different hyperaccumulators will verify the potential of Act12 and biochar to provide new insights into the restoration of contaminated soils and assess PTEs transfer into food chain.Therefore,Streptomyces pactum and biochar increased the phytoremediation and lowered the phytotoxicity of PTEs and improved the soil and plant enzymatic activities in the polluted soil.