| Soil contamination with potentially toxic elements(PTEs)has become a worldwide concern because of its adverse effects on ecosystem health and food security.This study was designed to investigated the efficiency of Ca-hydroxide(CH),Ca-bentonite(CB),tobacco biochar(TB)and natural zeolite(NZ)amended alone,combined and in mixture at 1% on immobilization mechanism and uptake of Pb,Cd,Cu and Zn by maize(Zea mays L.)after harvesting of(Brassica campestris L).Two pot trials were performed by using contaminated top soils viz.Tongguan contaminated(TG-C);Fengxian heavily contaminated(FX-HC)and Fengxian low contaminated(FX-LC).The obtained results revealed that the feasible amendments significantly(p <0.05)immobilize the DTPA-extractable Pb 53.11% with CH + CB + TB + NZ,Cd 36.26% with CH + TB + NZ,Cu 90.22% with CH + TB and Zn 56.07% with CH + CB + NZ,but the greatest mobilization of Pb was observed 22.13% with CH + NZ and Zn 34.92% with CB in TGC soil after(Brassica chinensis L.).Similarly,the residual impact of amendments potentially immobilized the Pb 62.59% with CB + TB,Cd 61.68% with CH + TB,Cu 83.31% with CH + TB and Zn 52.06% with CH + CB + NZ combined treatments,where as maximum mobilization of Pb was observed 22.13% with CH + NZ and Zn 34.92% with CB in TG-C soil after(Brassica chinensisL.).Similarly,the residual impact of amendments potentially immobilized the Pb 62.59% with CB + TB,Cd 61.68% with CH + TB,Cu 83.31% with CH + TB and Zn 52.06% with CH + CB + NZ.But,the maximum mobilized was detected by Pb 28.61% with CH + TB + NZ,Cu 53.56% with CH + CB and Zn 31.91% with TB alone after(Zea mays L.),respectively.Indeed,the maximum immobilization of PTEs in FX-HC soil after harvesting of(Brassica chinensisL.)which was obtained by Pb33.90% with CH + CB,Cd 47.69% with CH + CB + TB + NZ,Cu 91.53% with TB + NZ and Zn 64.75% with alone CH,on the other hand the greatest solubility of Zn was noticed by 35.40% with CB + TB + NZ followed by other treatments.Subsequently,the residual impact of amendments was highly effective for immobilization of Pb 87.80% with CH + CB + TB + NZ,Cd 51.13% with CH + NZ,Cu 36.57% in CH + CB + NZ and Zn 72.34% with CH + TB + NZ,whereas the greatest Zn mobilization was observed by 48.65% with CH + CB + TB after(Zea mays L.),followed by other treatments.In addition,the maximum fixation of PTEs in FX-LC soil was received by Pb 20.04% with CB + NZ,Cd 22.03% with CB + TB,Cu 16.30% with CH and Zn 82.34% with CH + NZ,but the maximum mobilization was detected by Cd 4.45% with CH + CB + TB,Cu 27.56% with TB and Zn 4.80% with CB + TB after(Brassica chinensisL.)followed by other treatments.Meanwhile,the residual impact of amendments potentially immobilized the Pb 63.87% with CB + NZ,Cd 83.53% with CH + CB + TB + NZ,Cu 98.85% with CB + TB + NZ and Zn 39.15% with CH + CB + TB,while the greatest mobilization especially for Zn was received by 65.94% with alone TB after(Zea mays L.)respectively.The changes in plant dry biomass yield(shoot and root)were observed after addition of amendments.However,the maximum dry biomass of(Brassica chinensisL.)in TG-C soil which was observed by 3.58 folds with CH + CB treatment,while the lowest which was received by 11.36 folds with CB + TB for crop followed by other treatments.Furthermore,the residual impact of amendments maximally promoted the total dry biomass about 1.13 folds with TB alone treatment,but CH + NZ had reduced up to 3.78 folds(Zea mays L.),respectively.Subsequently,the greatest plant dry biomass in FX-HC soil was obtained by 1.46 folds with TB + NZ,whereas the lowest dry biomass was received up to 4.96 folds with CH + TB + NZ for(Brassica chinensisL.)in comparison with other treated samples.Conversely,the residul impact of amendment evidently reduced the total dry biomass of(Zea mays L.),which was accounted up to 3.42 folds with CH + CB + TB,respectively.Similarly,the greatest total dry biomass of(Brassica chinensis L.)in FX-LC soil was noticed by 1.56 folds with CB + TB,however CH +TB had minimize the total dry biomass nearly 2.66 folds with CH + TB followed by other treated samples.Meanwhile,the residual impact of amendments drastically reduced the(Zea mays L.)dry biomass yield,while the maximum reduction which was documented by 7.79 folds in CH alone treatment,respectively.Indeed,the response of amendments to TG-C soil considerably reduced the PTEs in(Brassica chinensis L.)shoot by Pb71.80% with TB + NZ treatment,Cd 67.59% with CH + CB + TB + NZ,Cu 71.63% with TB + NZ and Zn 57.37% with CH + CB + TB + NZ,where as the maximum uptake in plant shoot biomass was detected by Pb 18.11% with CH + NZ followed by other treatments.Indeed,the residual impact of dramatically declined the Pb uptake in shoot by(Zea mays L.),which was nearly 45.03% with CB + NZ,Cd 51.18% with CH + CB + TB + NZ,Cu 43.21% with CB + NZ and Zn 44.35% with CH + NZ,but the greatest accumulation in plant shoot was obtained by Pb 33.04% with CH + TB + NZ,Cu 23.96% with CH + TB + NZ and Zn 11.65% with CB + TB,respectively.Consequently,the response of amendments to FX-HC soil in greater extent reduced the Pb uptake in(Brassica chinensis L.)shoot by 58.36% with CH + CB,Cd 64.64% with CH,Cu 47.84% with TB + NZ and Zn 9.26% with CH + CB,while the maximum uptake was noticed by Cd 9.85% with CH + CB + TB,and Zn 61.14% with TB alone treatment as compared to other treatments.The residual impact of amendments significantly reduced the Pb uptake in(Zea mays L.)shoot by 55.98% with CH + TB + NZ,Cd 54.54% with CH + CB + TB + NZ,Cu 59.83% with CH + CB + TB + NZ and Zn 19.16% with CH,but NZ alone had enhanced the uptake of Zn up to 19.00%,respectively.In addition,the incorporation of amendments to FX-LC soil significantly reduced the Pb uptake in(Brassica chinensis L.)shoot by 73.55% with CH + CB + TB,Cd 61.30% with CH + CB,Cu 43.76% with CH + TB + NZ and Zn 58.14% with CH + CB + TB + NZ,whereas the maximum enhancing the accumulation of Pb which was detected by 1.76% with CH + NZ,and Zn 28.52% with TB + NZ as compared with other treatments.Furthermore,the residual response of amendments potentially decreased the uptake of Pb in(Zea mays L.)shoot by 58.76% with TB alone,Cd 68.53% with CH + TB + NZ,Cu 68.17% with CH + CB + TB + NZ and Zn 69.47% with CH + CB,while CH + TB + NZ had increased Zn uptake in shoot by 60.21%,respectively.In addition,the mixing of amendments to TG-C soil significantly reduced the Pb content in(Brassica chinensis L.)root by 68.21% with CH + CB + NZ treatment,Cd 83.03% with CH + CB + TB + NZ,Cu 94.00% with TB + NZ and Zn 61.13% with CB + TB + NZ,but the maximum accumulation of Pb in plant root was received by 84.74% with TB + NZ and Zn 27.91% with CH + TB followed by other treatments.Furthermore,the residual impact of amendments considerably reduced the Pb absorption in(Zea mays L.)root by 78.76% with CH + CB + NZ,Cd 65.07% CH + CB + TB + NZ,Cu 34.64% with CH + TB and Zn 62.60% with CH + NZ,whereas the greatest accumulation of Pb in plant root was detected by 66.99% with CH + TB and Cu 29.62% with CH + CB,respectively.Furthermore,in case of FX-HC soil the maximum decline of Pb in(Brassica chinensis L.)root was noticed by 86.70% with CB + TB,Cd 41.76% with CH + CB + TB + NZ,Cu 97.02% with CB + TB and Zn 33.03% with CH + NZ,while the greatest accumulation of Zn in root was noticed by 52.76% with CH + CB + TB as compared to rest of treatments.In addition,the residual impact of amendments potentially reduced the accumulation of Pb in(Zea mays L.)root by 52.08% with CH + CB,Cd 71.02% with CH + CB + TB + NZ,Cu 85.84% with TB + NZ and Zn 45.54% with CH + CB + TB + NZ,but the maximum uptake of Pb in root was obtained by 2.27% with CH + CB + TB + NZ,respectively.Moreover,the studied amendments significantly reduced the PTEs concentration in root by(Brassica chinensis L.),which was grown in FX-LC soil;however the maximum reduction of Pb in root was documented by 50.06% CH + CB + TB + NZ,Cd 66.84% with CH + TB,Cu 87.36% with CB + TB + NZ and Zn 50.00% with CH + CB + TB + NZ treatment.Conversely,the greatest accumulation of Zn in plant root was received by 35.50% with CH + TB followed by other treatments.Meanwhile,the residual impact of amendments evidently decreased the Pb in(Zea mays L.)root by 46.68% with CH + CB + TB + NZ,Cd 38.53% with CH + NZ,Cu 54.99% with CB and Zn 48.79% with CH + NZ,while the maximum Zn uptake in plant root was detected by 5.19% with TB alone treatment,respectively.Based on our study findings,it is concluded that the incorporation of amendments to studied soils was highly effective for immobilization especially for Cd than Cu Pb and Zn.While,residual impact of amendments was highly effective for reducing Cd and Cu in shoot and root by plants than Pb and Zn.Because,of the modification in soil chemical properties such as,EC,p H,OM,HA,FA,CEC and DOC,which might be alkaline nature of additives,PTEs forms and soil types.Overall,it is suggested that this study should be verified the impact of these emerging and feasible amendments on PTEs fractionation,microbial diversity,enzymes activity,soil physical properties and other plant genotypes under long-term field condition. |
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