Study On Remedial Of Cd And Cr Contamination In Soil By Several Plants

With the development of industries and industrial discharges of pollutants, the heavy metal pollution has become increasingly the world wide environmental problem. The heavy metal in soil not only destroy the function of the soil ecosystem, but also take a serious threat to human health. Usually, The heavy metal in soil is not only a kind of heavy metals, but also a coexistence of a variety of heavy metals, forming a composite soil pollution. A variety of heavy metal compound together is likely to change each other’s biological effectiveness, Therefore, it is of great significance to explore the influence on different metal in compound polluted soil. Lolium perenne L.,Sorghum bicolor (L.) Moench x S. Sudanense (Piper) Stapf, Pennisetum alopecuroides (L.) Spreng were investigated in this study, different concentration gradient of cadmium (Cd), chromium(Cr) single and compound pollution were set to explore the potential of these three kinds of forage grass to repair Cr and Cd contaminated soil.The main results were as follows:1. The heavy metals Cr and Cd mainly concentrated in the roots of Lolium perenne (L.), Pennisetum alopecuroides (L.) Spreng, Sorghum bicolor (L.) Moench × S. Sudanense (Piper) Stapf. All the plants did not reach the level of the super enriched plants,However, they also have some potential for remediation of heavy metal Cd, Cr single and combined pollution.2. Enrichment of Lolium perenne L. to high concentration of Cd is higher than that of low concentration, so Lolium perenne L. can be used to repair Cd contaminated soil of high concentration. The enrichment of Cd under single Cd stress was mainly concentrated in the late growth stage; With the increase of Cr concentration in the early stage of growth, the enrichment ability of Lolium perenne L. to Cr increased correspondingly. However, with the growth of Lolium perenne L., the ability of Lolium perenne L. to Cr enrichment decreased gradually under high Cr stresS. The enrichment of Cr was mainly concentrated in the early stage of growth under single Cr stress; Under the Cd and Cr combined pollution, the enrichment of Cr mainly concentrated in the early growth stage, while in the middle and late growth for Cd.3. The enrichment of Sorghum bicolor (L.) Moench X S. Sudanense (Piper) Stapf was considerable in the low Cd contaminated soil, and the enrichment of Cd was mainly concentrated in the late growth stage; The Sorghum bicolor (L.) Moench X S. Sudanense (Piper) Stapf shows a stronger enrichment of Cr in low Cr contaminated soil in the early and medium-term growth. While in the late growth stage it shows a stronger enrichment of Cr in high Cr contaminated soil. The enrichment of Cr was mainly concentrated in the late growth stage; the enrichment of Cd was mainly concentrated in the late growth stage and in the middle and late growth stages for Cr under the combined pollution of heavy metal Cd and Cr.4. Pennisetum alopecuroides (L.) Spreng shows stronger enrichment ability in low Cd contaminated soil. The enrichment of Cd was mainly concertfrated in the late growth stage under the single Cd stress; In the growth of Pennisetum alopecuroides (L.) Spreng, enrichment ability to Cr decreased gradually under high Cr stresS. The enrichment of Cr was mainly concentrated in the middle of the growth period under single Cr stress; the enrichment of Cd was mainly concentrated in the medium-term growth stage and in the early growth stage for Cr under the combined pollution of heavy metal Cd and Cr. The enrichment time was different from the single stress of Cr.5. Pennisetum alopecuroides (L.) Spreng shows strongest enrichment ability of Cd in Cd contaminated soil; Lolium perenne L. shows strongest enrichment ability of Cr in Cr contaminated soil in early growth stage, Sorghum bicolor (L.) Moench X S. Sudanense (Piper) Stapf shows the best enrichment ability of Cr in Cr contaminated soil in late growth stage; Lolium perenne L. shows strongest enrichment ability of Cd in high concentration of Cd and low concentration of Cr, high concentration of Cd and high concentration of Cr; Sorghum bicolor (L.) Moench X S. Sudanense (Piper) Stapf shows the best enrichment ability of Cd in low concentration of Cd and high concentration of Cr; Pennisetum alopecuroides (L.) Spreng shows strongest enrichment ability of Cd in low concentration of Cd and low concentration of Cr, at the same time shows the best enrichment ability of Cr in Cd,Cr compound pollution.Therefore Pennisetum alopecuroides (L.) Spreng can be used as enrichment plant for Cr in Cd,Cr compound pollution.6. Cr and Cd will affect each other in Cr, Cd compound contaminated soil, There was a synergistic effect between low concentration Cr and low concentration Cd, which could promote the accumulation of heavy metals in plants. High concentration of Cd can inhibit the accumulation of Cr in plants. And with the growth and development of the plant, the effect of the interaction between the two kinds of heavy metals will also change.