Study On Plant-microorganism-soil Improvement Combined Remediation Of Heavy Metals-contaminated Soils

Exploitation of mineral resources not only brings great development to economic, but also negative effects to environment. In particular, heavy metals-contaminated soils are increasingly serious, which causes an threat to human health and affect the sustainable development of social economy.This study adopted soil of abandoned mine area in Peking City as the research object. Throughing field investigation, soil samples collected were measured and analyzed the heavy metal content and existing form of mining area soil. This study chose Lolium perenne as remediation plant to absorb the heavy metal of mine area soil. A greenhouse pot experiment was carried out using sewage sludge compost to improve the soil, microbial enhanced phytoremediation and combined remediation of soil contaminated to relect the effect research. The main conclusions are as follows:Lolium perenne grew normally in the soil of the mining area under the control treatment. The addition of sewage sludge compost had a significant effect on the growth of Lolium perenne. When the 30% proportion of sewage sludge compost was applied, the biomass of aboveground and underground of Lolium perenne was higher than that of control treatment 405.75% and 97.14% respectively. The effective content of Cu, Zn and Cd in rhizosphere soil and non-rhizosphere soil was increased by sewage sludge compost. After planting Lolium perenne, Cu, Zn, and Cd content of soil decreased in some extent, the removal rate reached maximum in sewage sludge compost dosage of 30%,10%,40% and 30% respectively, namely 39.12%,54.90%,12.94% and 22.71% respectively. All in all, a preliminary determination was found that sewage sludge compost dosage of 30% was suitable for the plant growth.The addition of Thiobacillus ferrooxidans promoted increased the biomass of Lolium perenne, when 60 mL bacterial liquid was applied, the biomass of aboveground and underground of Lolium perenne was higher than that of control treatment 92.67% and 269.11% respectively. And Thiobacillus ferrooxidans enhanced the content of acid soluble of Cu, Pb and Cd in the rhizosphere soil and promoted the transformation of Zn to reducible Zn. The enrichment ability of heavy metals in aboveground of Lolium perenne was Cu> Zn> Cd> Pb, and the enrichment ability of heavy metals in underground of Lolium perenne was in the order of Cd> Cu> Pb> Zn. After planting Lolium perenne, the removal rate of Cu, Zn and Cd in soil reached maximum in 30 mL,60 mL,30 mL and 45 mL bacterial liquid treatment respectively, namely 23.57%,36.85%,62.67% and 19.27%.The addition of Thiobacillus ferrooxidans liquid and sludge compost can evidently promote the growth of Lolium perenn in the 10% sludge compost and 15 mL bacterial liquid treatment grew better, and improved the enrichment of Cu, Zn and Cd, especially Pb enrichment in the part of the Lolium perenne. After planting Lolium perenne, the content of Cu, Zn, Cd and Pb in soil were significantly reduced, especially the best removal effect of Cd in soil, the removal rate reached to 59.55%. In addition, the heavy metal content of Lolium perenne was significantly positively correlated with the acid soluble state of heavy metals in the rhizosphere soil(P<0.05), therefore, the content of acid soluble form heavy metals as the basis for the evaluation of bioavailability of heavy metals in soil, four metals bioavailability in size for Cu> Zn> Pb> Cd. In summary, the effect of 20-30% sludge compost and 30-45 mL bacteria liquid on remediation of heavy metal polluted soil were better.