Study On Vegetation And Soil Of The Landfill In The Late Stabilization Period

Vegetation recovery is one of the important links in closure treatment of landfills, and the quality of topsoil is also a necessary reference to reuse the sites. There are often some illogical treating methods resulting in a slow rehabilitation project. At the same time, systematic and comprehensiveevaluation and consideration are always defective on the quality of topsoil of landfills. It’s positive significantly in improving vegetation recovery technologies and reusing sites of landfills reasonably to explore the succession laws and know clearly about topsoil quality.Survey research about plant communities was conducted at Heishitou Landfill and its periphery for 3 years. The laws and differences on plant commuties’ composition and its nature, growth form and life form, a diversity and β diversity between inside and outside the landfill were analyzed. The results showed that the abundance of the community in landfill were 23,24,21 and in periphery were 28,25,30. They were relatively similar but obvious variability existed. The dominant specie of arborous layer remained unchanged but the speices of shrub layer and grass layer were still replacing frequently. Herbage,which reached 40%, is the main growth form both in Heishitou Landfill and its periphery. The ratios of trees, bushes and vines were close in the landfill but in its periphery. In terms of life form, the ratio of therophyte of the landfill was higher than the periphery, phanerophyte and chamaephytes were lower and hemicryptophyte was close. There were no obvious law in a diversity and β diversity showed no improvement on the similarity of the two communities and the fluctuation came from Herbage and inside the landfill. In summary, the community in landfill was gradlly more similar to the one of periphery but some differences existed in commuties’composition and structure.Contents of heavy metal such as Cd, Hg, As, Cu, Pb, Cr, Zn,Ni and physicochemical properties such as bulk density, aeration porosity, capillary porosity, organic matter, available phosphoruso, rapidly available potassium, alkali-hydrolyzale nitrogen of topsoil from Heishitou Landfill were detected and analyzed. The results showed that heavy metal contents of topsoil from all the points accorded with the secondary standard soil environmental quality standard and Cd, Hg, As, Cu, Pb Ni accorded with theprimary standard. Nemerow Indexes, whose maximum value was 0.51, indicated grade of safety. Most heavy metal contents were higher than the background values of Beijing, except for Hg. Hakanson Indexes, whose maximum value was 109.1, indicated slight ecological hazard. The topsoil had good bulk density and aeration porosity, but capillary porosity and void ratio was lower than normal values.Organic matter and rapidly available N, P, K of topsoil can meet the growing demand of greening. Comprehensive assessment of nutrient indicated a better than average condition. In summary, the topsoil of Heishitou wasn’t polluted badly and the physicochemical properties were able to accord with the need of greening.