Influence On Plant Growth And Soil Fixation Mechanism And Mechanical Properties By Lead Polluted Soil

Soil is polluted by heavy metals. Phytoremediation has attracted much attention due to its economy and environmental protection in the numerous soil remediation methods. The present research mainly focuses on the use of heavy metal enrichment plant to remede contaminated soil. Screening of patience plants with the properties of resistance to lodging has not been reported. Evaluation remediation plant from the perspective of vegetation fixed contaminated soil has not been reported.A pot experiment was conducted to study the growth characteristics of 14 native herbaceous plants and the influence on bulk density, total porosity, content of soil aggregate and organic matter and shearing strength of Pb polluted soil.In the article the lodging resistance was clarified, soil resistance to erosion was studied, the relationship between plant growth and the morphological transformation of Pb was discussed in the terms of mechanics characteristics of the plant and the influence of the morphological transformation of Pb, in order to provide theoretical and practical reference in vegetation construction in Pb polluted soil and ecological restoration. The main results are as follows:(1) A greenhouse pot experiment was conducted to study the effects of Pb (0,500,1000,1500 mg·g-1) on the growth of 14 roadside dominant herbaceous plants in Shanxi Province and their absorption and accumulation of Pb. The results showed that Amaranthus retroflexus and Sorghum bicolor×S. sudanese appeared obvious toxic symptoms with increasing Pb content, while the plant height and biomass of the other 12 plants had no significantly decrease compared with control which suggested the high Pb tolerance of these plants.(2) The results showed that Chenopodium album, Psathyrostachys juncea, Amaranthus tricolor of ’red leaf’ and Medicago sativa are highly tolerant to Pb. Root length, root’s biomass and activity are all higher than control. Aster tataricus, Amaranthus retroflexus and Sorghum bicolor×S are sensitive to Pb. Root length, root’s biomass and activity are significantly lower than control in 1500 mg·kg-1 Pb treatment. Tolerance to Pb of other 7 plants are between the two kinds of plants. The result will provide theoretical basis of ecological restoration in Pb-polluted soil.(3) The results showed that maxinum tensile loads, maxinum shear loads, elastic modulus of tensile strength and shear modulus of Amaranthus retroflexus, Sorghum bicolor×S.sudanense and Aster tataricus decreased gradually with increasing Pb content, while the four value had significantly decrease compared with control in 1500 mg/kg Pb treatment. Maxinum tensile loads, maxinum shear loads, elastic modulus of tensile strength and shear modulus of Chenopodium album, Amaranthus tricolor of ’green leaf’, Amaranthus tricolor of ’red leaf’ and Rumex patientia×R.tianschanicus cv.Rumex K-1 had increase compared with control in all Pb treatment,which were higher than other 10 plants, indicating they could be chosen as remediation plants in Pb-polluted area and bad environment area.(4) The results showed that effects of soil reinforcement and soil erosion resistance in different plants had great difference. Biomass of roots and shear strength of Amaranthus retroflexus, Sorghum bicolor×S. sudanense and Aster tataricus decrease gradually with increasing Pb content which suggested the poor Pb tolerance and effects of soil reinforcement and soil erosion resistance of these plants. Other 11 plants suggested high Pb tolerance and effects of soil reinforcement and soil erosion resistance. Shear strength of Rumex patientia×R. tianschanicus cv. Rumex K-1, Chenopodium album and Medicago sativa are more than Dactylis glomerata and Psathyrostachys juncea, Dactylis glomerata and Psathyrostachys juncea are more than other 6 plants in 0-10cm soil layer. So Rumex patientia×R. tianschanicus cv. Rumex K-1, Chenopodium album and Medicago sativa could be used in phytostabilization and revegetation in shallow layer of Pb-polluted soil. Shear strength of Chenopodium album and Medicago sativa are more than Dactylis glomerata and Psathyrostachys juncea, Dactylis glomerata and Psathyrostachys juncea are more than other 7 plants in 10-15cm soil layer. So Chenopodium album and Medicago sativa could be used in phytostabilization and revegetation in deep layer of Pb-polluted soil.(5) The results showed that effects of different plants on Pb speciations in soil had great difference. Exchangeable Pb in all Pb treatment in the soil of Chenopodium album and Psathyrostachys juncea were less than the control, and the control was less than other 12 plants; and residual Pb was the highest in all plants with the value of 717.74 and 700.45 mg/kg in 1500 mg/kg Pb treatment respectively, indicating both had strong ability in inactivating Pb and could be used in phytostabilization and revegetation in Pb-polluted soil. In the soil of Amaranthus tricolor of ’red leaf and ’green leaf’, exchangeable Pb was the highest in all plants in all Pb treatment, with the value of 71.39,69.40 mg/kg in 1500 mg/kg Pb treatment which were respectively 3.7,3.6 times of the control; residual Pb and total Pb were significantly lower than control and they were the lowest in all plants. The value of total Pb were 1 372,1 388 mg/kg in 1 500 mg/kg Pb treatment, dropped 7.9% and 6.8% respectively compared with the control, suggesting they could dissolve Pb and could be used in activation and extraction Pb of polluted soil.