Odour annoyance assessment around landfill sites: methods and results

Assessing odour annoyance generated by landfill areas involves a number of difficulties due to the fugitive, diffuse and multiple characters of odour sources. Analyses of ambient air by GC-MS, spot FID measurements or the determination of the odour concentration by dynamic olfactometry on the basis of samples collected through flux chambers, while providing valuable results, do not allow to encompass the different odour emissions as a whole and unique source. An alternative and interesting approach is applied to 9 landfill sites in Belgium. It is an adaptation of the method of sniffing team campaigns to the particular case of landfill site odours. The paper presents the main results of those campaigns, highlighting many advantages, but also different problems. One of the main advantages of the method is that the feeling of the observers is close to the resident one. However, as field inspection often occurs during the activity period it does not account for evening or night situations, when sometimes the atmosphere is quieter or when landfill gas could be preferentially emitted. Another problem arises from the fact that a model is used, with its hypothesis and its uncertainties due to the large sensitivity of some estimated parameters. If absolute value of the odour emission rate is necessary, then further validation of the method is needed, e.g. by using surveys and neighbour panellists. Anyhow, the method is particularly adapted to obtain relative results, for comparing different sites or for monitoring long term evolution of odour emissions.