Rafaella-Eleni P. Sotiropoulou

A Methodology to Estimate Odors around Landfill Sites: The Use of Methane as an Odor Index and Its Utility in Landfill Siting

Abstract The estimation of odor production and dispersion from landfill sites is a very complicated task because of the different chemical species that exist in biogas. To site a new landfill, it is necessary to know the distance that odors can travel around the landfill under atmospheric conditions that increase the concentration of pollutants. Although CH4 is an odorless gas, it can be used as an index to determine the dispersion of low-reactivity odorous species around a landfill site. Methane production rates, estimated by biogas production models, were used by an air dispersion model to determine the spatial distribution of CH4 around landfill sites. By utilizing dispersion models under extreme atmospheric conditions, a maximum CH4 concentration around the landfills was determined. Based on the ratio between CH4 and odorous chemical species, the spatial distribution of the concentration of an odorous species was determined for those species with low reactivity in the atmosphere. For odorous species with high reactivity in the atmosphere, a dispersion-reaction model must be used. In this way, the acceptable distance between new landfills and residential areas can be determined. The proposed methodology could be used as a design tool for those who are interested in landfill siting.

Modeling New Particle Formation During Air Pollution Episodes: Impacts on Aerosol and Cloud Condensation Nuclei

The impact of new particle formation on regional air quality and CCN formation is for the first time explored using the UAM-AERO air quality model. New particles are formed by ternary nucleation of sulfuric acid, ammonia and water; subsequent growth of clusters to large sizes is driven by condensation of sulfuric acid and organic vapors, as described by the recently developed nano-Köhler theory. Application of the model in Athens (GAA) and Marseilles (GMA) reveals higher sulfuric acid condensational sink and gaseous sulfuric acid (hence nucleation rate) for the latter. However, limited quantities of organic vapors in the GMA inhibit the growth of the formed clusters; therefore new particle formation is more efficient in the GAA. A sensitivity analysis demonstrates that (1) uncertainty in vaporization enthalpy does not affect organic carbon formed by nucleation, and (2) an accommodation coefficient of unity gives excellent agreement of condensation sink with in-situ observations. Nucleation affects the aerosol size distribution, and can be an important contributor to CCN; locally it can be more important than chemical ageing of pre-existing aerosols.

An estimation of the spatial distribution of agricultural ammonia emissions in the Greater Athens Area

An assessment of the magnitude and the spatial distribution of ammonia emissions originating from agricultural practices in the Greater Athens Area (GAA) is performed due to the primary role of ammonia in aerosol formation. As no emission factors are available for the area of interest, the emissions were estimated using typical emission factors for the emissions from animals, fertilized and unfertilized cultures, as well as the 1996 primary statistical data of the agricultural census for the GAA. Our analysis estimated the annual ammonia emissions from agricultural sources to be approximately 13,250+/-40% t of ammonia per year. This detailed ammonia emission record can and will be used for the study, via modeling, of the serious aerosol problem in the GAA.

Atmospheric methane transport near landfill sites

Methane production rates that have been estimated by a biogas production model (MICROGEN) are combined with an air dispersion model in order to determine the spatial distribution of methane around landfill sites. By utilising dispersion models under extreme atmospheric conditions, a maximum methane concentration around the landfills can be determined. The factors that enhance the maximum methane concentrations, using the meteorological model CALMET in conjunction with the dispersion model CALPUFF, are found to be the wind speed and the percentage of cloud cover. The rates of temperature and pressure variation, as well as the land use category seem to have no effect on the maximum methane concentrations. A rapid reduction of methane concentration is observed a few metres away from the landfill centre while a slower reduction is observed at distances greater than 300 m from it. The performance of this methodology is evaluated by comparing measured concentrations with model predictions.