Browsing by Author "Shafi, Sophie"

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    Evaluating fugacity models for trace components in landfill gas.
    (Elsevier Science B.V., Amsterdam., 2006-12-01T00:00:00Z) Shafi, Sophie; Sweetman, Andrew; Hough, Rupert L.; Smith, Richard; Rosevear, Alan; Pollard, Simon J. T.
    A fugacity approach was evaluated to reconcile loadings of vinyl chloride (chloroethene), benzene, 1,3-butadiene and trichloroethylene in waste with concentrations observed in landfill gas monitoring studies. An evaluative environment derived from fictitious but realistic properties such as volume, composition, and temperature, constructed with data from the Brogborough landfill (UK) test cells was used to test a fugacity approach to generating the source term for use in landfill gas risk assessment models (e.g. GasSim). SOILVE, a dynamic Level II model adapted here for landfills, showed greatest utility for benzene and 1,3-butadiene, modelled under anaerobic conditions over a 10 year simulation. Modelled concentrations of these components (95 300 μg m−3; 43 μg m−3) fell within measured ranges observed in gas from landfills (24 300–180 000 μg m−3; 20–70 μg m−3). This study highlights the need (i) for representative and time-referenced biotransformation data; (ii) to evaluate the partitioning characteristics of organic matter within waste systems and (iii) for a better understanding of the role that gas extraction rate (flux) plays in producing trace component concentrations
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    A fugacity approach for generating a landfill gas trace component source term.
    (2005-10-03T00:00:00Z) Shafi, Sophie; Pollard, Simon J. T.; Smith, Richard; Sweetman, Andrew; Rosevear, Alan
    The quality of risk assessment output is determined by the input data used in environmental distribution, dispersion and exposure models. Whilst recent focus has been on the development of regulatory exposure assessment models for landfills, risk analysts are keenly aware of the need for improved source term models in order to improve confidence in risk assessments and allow better targeting of risk management actions. This research sought to reconcile measured concentrations of selected priority trace components in landfill gas with potential source term loadings that could be generated within landfilled waste. A fugacity approach estimated the loadings of four priority trace components required to generate the source-term for landfill gas risk assessment models; vinyl chloride (chloroethene), benzene, 1,3- butadiene and trichloroethylene. Three fugacity models, coded originally for soils, were adapted for an evaluative landfill environment, developed using data from the Brogborough (UK) test cells. Modelled concentrations were within the range of those observed in the field.