Study On Emissions And The Atmospheric Environmental Impacts Of Gases From The Working Face Of Municipal Solid Waste Landfill

Sanitary landfills are the most important facility for harmless disposal of municipal solid waste.Emission of gases from landfills can affect atmospheric environment.Non-methane organic compounds?NMOCs?of landfill gases are a type of trace organic matter,which are the main substance of ozone precursor and also the precursor of secondary organic asreol.Some organic compounds can also cause the greenhouse effect.In this work,the environmental impacts including oxygen formation potential,secondary asreol formation potential and global warming potential of NMOCs were studied,the priority controlled materials were identified and the measures to reduce the impacts of landfills on atmospheric environment were proposed.Taking Beijing Asuwei Landfill as a typical case,the static chamber method was used to sample the gas from the working face,the concentration of NMOCs in the sample was detected by the gas chromatography mass spectrometry?GC-MS?,and the concentration and release rate of different NMOCs at the sampling point was calculated as well.The concentration of NMOCs on the working face is about 9700?g?m^-3,and the release rate is about 4900?g?m^-2?h^-1.Emission of NMOCs on the working face obeies the law:summer?29?autumn?29?spring?29?winter.Ethanol is the substance of the highest concentration and release rate of NMOCs on the working face.Oxygenates are the species with the highest concentration and release ratio.There is consistency between the high concentration and high release rate material types of NMOCs.The high release contributors on the working face of the landfill include eight substances:ethanol,dimethyl disulfide,ethyl acetate,2-butanone,n-pentane,acetone,dimethyl sulfide,and tetrachloroethylene.The propylene equivalent concentration method and the maximum incremental reaction method were used to calculate the ozone foramtion potential and the aerosol conversion coefficient method was used to calculate the secondary aerosol formation potential in this paper.By intergrating the advantage of both methods for calculating the oxygen formation potential,the calculation results show that the ozone concentration generated by NMOCs on the working face has a potential of approximately 12045?g?m^-3,and the release rate of ozone release potential is 6451?g?m^-2?h^-1.The potential for secondary aerosol concentration generation is approximately 1764?g?m^-3.The release rate of secondary aerosol formation potential is approximately 590?g?m^-2?h^-1.High ozone release contributors throughout the year are ethanol,n-pentane,ethyl acetate,m-xylene,styrene,2-methylpentane,2-butanone,isopropanol,dimethyl sulfide and o-xylene.The main contributors of secondary aerosol formation on the working face throughout the year are toluene,m-xylene,ethylbenzene,o-xylene,and n-hexane.Samples of CH₄,CO₂,and N₂O gas were collected by using a method combining the static chamber and the negative pressure chamber.Four halogenated hydrocarbons of NMOCs with above gases are used as the main greenhouse gases released from the landfill site to calculate the temperature increaseing contribution.Although the concentration and release rate of trace substances of CFC-11,N₂O and CFC-12 are extremely low?less than 1%?,their contribution to temperature increaseing can account for 20%to 30%,therefore their impacts cannot be ignored.In particular,CFC-11 is an important trace greenhouse gas in the landfill site of this study,with a contribution of11%to 17%.The release of NMOCs in landfills is controlled through the combination of horizontal guide with drainage systems and the laying of temporary covers.By promoting waste classification and seasonal regulation method,it contributes to control the release of NMOCs better.