Investigation Of Vegetation In Landfill And Microbiological Mechanism Of Tolerant Plants Under The Stress Of Landfill Gas

Sanitary landfill technology plays an important role in disposing municipal solid waste (MSW) in China. However, limitations of the recent landfill technology in China, such as water and air pollution, large quantities of cover soil consumption, land occupation as well as scenery destroy, has been challenging its application. Therefore, developing a novel revegetation technique on the purpose of fast landfill plant recovery with the reduction of water and odor pollution and the decrease of cover soil consumption is urgent.Researches in investigating vegetations inside and around Tianziling landfill plant, screening of plants tolerant to the high stress of landfill gas, and understanding the mechanisms of some tolerant plant have been performed. Result showed that there were 67 plant species inside the landfill plant, which belong to 33 families. Among them, 18 species belong to 11 arborous and bushy families and 49 species belong to herbaceous families. Around the landfill, totally 38 plant species were found with 11 belongs to arbor and 27 belongs to subcanopy plants. Moreover, distribution of vegetation inside the plant was obviously influenced by the landfilling time. In contrast to the rich species and poor plant coverage in younger landfill sites, less plant species and relatively high cover percentage were found in the older landfill site.On the base of the plant investigation and the mode of "arbor+bush+herb " , 20 arborous and bushy species and 9 herbaceous species were selected and planted in a 1200 m2 experimental plot which located in Tianziling landfill site to screen plants tolerant to the stress of high concentration of land fill gas. Result indicated that Pinus elliottii, Cercis julianae, Cercis chinensis, Photinia serrulata Eragrostis pilosa, Festuca ovina, Chenopdium glaucum are tolerant plants suitable to be planted in young landfill site. When the thickness of the landfill cover soil is 60 cm, the optimal concentration of sewage sludge added to the soil for the growth of selected plants is 10%.In addition, Pinus elliottii, a selected plant, was used to investigate its microbiological mechanism in tolerating the landfill gas. Result showed that the total number of bacteria and Shannon index of bacterial diversity in rhizosphere soil of Pinus elliottii planted in landfill site were decreased as compared to that in non-landfill site, indicating that the growth and metabolism of rhizosphere bacteria could be inhibited by the landfill gas. On the contrary, numbers of methane oxidation bacteria in rhizosphere soil of Pinus elliottii increased with the stress of landfill gas and with the addition of sewage sludge. Nevertheless, there was no relationship between the number of methane oxidation bacteria and the methane oxidation activities in rhizosphere soil of Pinus elliottii with or without the addition of sewage sludge. Furthermore, the addition of sewage sludge into the cover soil can either increase the number of bacteria, fungi and actinomycete or Shannon index of bacterial diversity in rhizosphere soil of Pinus elliottii planted in landfill site. However, with the increase of sewage sludge in cover soil, Shannon index of bacterial diversity in rhizosphere soil of Pinus elliottii planted in landfill site became relatively stable.Results indicated that the addition of certain quantities of sewage sludge is conducive to keep the bacterial community composition in rhizosphere of Pinus elliottii planted in landfill site.