Emissions Of Non-methane Organic Compounds From Municipal Solid Waste Landfills And Their Air Dispersion Modeling

Landfilling is the major municipal solid waste disposal approach in China.However,odor nuisances caused by landfills are capturing public concerns,which are also the main reasons for the Not In My Back Yard（NIMBY）phenomenon.Huge amount of fresh wastes are dumped,spread and compacted on the working face of landfill sites,and the wastes are usually piled up and exposed to the environment before being well covered.Non-methane organic compounds（NMOCs）were emitted from the working face into the atmosphere through direct volatilization and/or degradation of the wastes.In the current study,a self-designed wind tunnel system was developed for the measurement of fugitive NMOCs emissions from the working face.The emission patterns and temporal variations of NMOCs were studied on the basis of long-term field sampling campaigns.Then the potential adverse effects on air quality and global warming of landfill NMOCs emissions were studied.In addition,an unstable numerical atmospheric dispersion model,Model of odor dispersion（ModOdor）,was developed.Coupling the model with uncertainty theory,odor pollutions in the vicinity of landfill sites were investigated.All above offering a support for the determination of buffer zone of landfill sites.In the current study,a modified wind tunnel system was developed for the measurement of fugitive NMOCs emission rates on the working face,which has been proved to be a reasonable and efficient method.The optimal sweeping velocity was 0.26m×s^-1.In the studied landfill,a total of 35 NMOCs were quantified as common compounds,in which aromatics were identified with diversity species（a total of 18species）,and hydrocarbons were detected with highest average emission rates(227.56±115.30mg×m^-2×s^-1).Morning was the period with greast NMOCs emissions during a day and summer was the season with highest emissions.The probable density functions（pdf）of NMOCs emission rates followed Normal,Log-normal,Gamma and Weibull distributions.Working face is a significant source of propylbenzene,a-pinene and decane compared with other anthropogenic sources.Landfill emissions of propyl benzene,a-pinene and decane comprise 74%,43%and 18%of anthropogenic sources,respectively.Decane,limonene,toluene and 1,3,5-trimethylbenzene were compounds with greatest ozone formation potential.Limonene was the greatest contributor for the formation of secondary organic aerosol formation and CFC-113 was the most significant global warming substance.A 3D unstable numerical air dispersion model named ModOdor was developed.ModOdor is capable of generating potential flow solutions associated with complex terrain features,simulating temporal and spatial variation of metrological conditions（wind conditions and dispersion conditions）,and implement physical/chemical reactions（i.e.chemical reactions,dry or wet depositions）.The reliability of ModOdor was tested with analytical solutions and field sampling results,and the errors of calculation results were acceptable.Monte Carlo analysis was coupled with ModOdor for the investigation of uncertainty caused by the variations of NMOCs emissions and meteorological conditions.Monte Carlo-ModOdor method was applied to analysis odor pollution near landfill.Methyl mercaptan was the greatest contributor of odor pollution in the studied landfill.Odor pollution was released with the increase of distance.South was the most polluted downwind direction.The probability of odor pollution caused by methyl mercaptan exceeded 3%within 2 km around the landfill.