The Remediation Potential Of Several Plants On Pb And Cu Contaminated Soils

In recent years, large areas of farmland soil subjected to heavy metal pollution in our country, the agricultural heavy metal exceeds standard problem has been frequently reported, the heavy metal in soil takes a serious threat to food safety, human health and the sustainable development of agriculture. Although the "10th five-year plan" "11th five-year plan" and" 12th five-year"issued a number of policy supported the ecological security evaluation and protection and governance on soil heavy metal pollution, but the heavy metal pollution in soil is still not optimistic, the remediation of heavy metal polluted soil is extremely urgent. Due to the compound pollution in the realistic environment, a variety of concentration and the ratio are different between the heavy metal elements, Therefore, the absorption and enrichment of plants under different concentrations of copper (Cu) and lead (Pb) were studied, which is of great significance for the selection of enriched plants in the practical application of Cu and Pb pollution levels. In this study, there are two main parts:(1) Medicago sativa L., Lolium perenne L., Pennisetum alopecuroides (L.) Spreng and [Sorghum bicolor (L.) Moench × S. sudanense (Piper) Stapf.] were choosed as the experimental material, different concentration gradient of Cu, Pb single pollution was set to explore the different degree of Cu and Pb pollution on four kinds of seed germination and seedling growth;(2) Also with the four plants as test object, set different concentration combinations of Cu, Pb pollution, the biomass, the concentration of the plant and the enrichment factor and the transfer coefficient were analyzed, to predict the ability of plants to repair Cu and Pb contaminated soil at a certain concentration of pollution and determine which plants to use, in order to find out the ideal species that could be able to seeding directly rather than transplanting to Cu. Pb contaminated areas.The main results were as follows:(1) Because of the difference of heavy metals, the effect of the same concentration of heavy metals on germination is different. From the germination energy and germination rate, the effect of Cu pollution on seed germination was more obvious. When the Cu concentration above 150 mg·kg-1, the germination of seeds with postponed phenomenon in four species. The seed germination was delayed in Pb contaminated soil, but the germination rate of Lolium perenne L., Pennisetum alopecuroides (L.) Spreng and [Sorghum bicolor (L.) Moench × S. sudanense (Piper) Stapf.] were not affected.(2) When Cu, Pb≥300 mg·kg-1, the germination energy and germination rate of Pennisetum alopecuroides (L.) Spreng and [Sorghum bicolor (L.) Moench × S. sudanense (Piper) Stapf.] were significantly higher than that of Medicago sativa L.and Lolium perenne L., reflecting a better adaptability on the Cu, Pb polluted soil.(3) In the Cu concentration of 600 mg·kg-1, the seedling growth of Medicago sativa L., Lolium perenne L., Pennisetum alopecuroides (L.) Spreng and [Sorghum bicolor (L.) Moench×S. sudanense (Piper) Stapf.] was almost completely inhibited, and shows unnormal growth. Pb concentration range of 0-600 mg·kg-1 in soil, the root length of Lolium perenne L. and Pennisetum alopecuroides (L.) Spreng were not significantly effected, indicating a good tolerance under Pb polluted soil.(4) From the biomass, the Cu tolerance of Medicago sativa L. is poor, Pennisetum alopecuroides (L.) Spreng and [Sorghum bicolor (L.) Moench × S. sudanense (Piper) Stapf.] for Cu, Pb contamination tolerance is strong, their biomass were found to have not significantly reduced in all treatment groups.(5)Under the condition of Cu concentration range:0～400 mg·kg-1, Pb concentration range:0～800 mg·kg-1, with the increase of heavy metal pollution, heavy metal content in plant also increases accordingly in single pollution treatment group, while the situation of compound pollution is different. The effects of compound pollution of heavy metals on plant accumulation, not only depends on the concentration of the element, and is associated with the combination of related parts and elements, is not a simple add or antagonism effect.(6) The Cu and Pb content in roots were greater than the part on the ground, and from the perspective of the accumulation characteristics of plant of Cu, Pb, Medicago sativa L., Lolium perenne L., Pennisetum alopecuroides (L.) Spreng and [Sorghum bicolor (L.) Moench x S. sudanense (Piper) Stapf.] does not have the basic characteristics of super enriched plant. The main parts for heavy metals Cu, Pb accumulation is roots, The accumulation and transfer effect of Lolium perenne L. Pennisetum alopecuroides (L.) Spreng and [Sorghum bicolor (L.) Moench× S. sudanense (Piper) Stapf.] are relatively better in low Pb concentrated soil.