An exceptional case of long range odorant transport

Odour pollution is generally regarded as a local issue. The long range transport of odorants at levels sufficient to generate odour complaints far from their source is not normally given serious consideration, let alone subject to legislation. We argue that such an event led to an odour incident affecting much of southern and eastern England and use emission and dispersion modelling to support the contention.The specific incident discussed in this paper occurred in April 2008 with an initially unknown source and cause that resulted in hundreds of notifications of odour complaints across affected regions of England. Detailed analysis of the incident illustrates how a combination of the geographical distribution of odour reports together with emission and dispersion modelling can be utilised to trace the source location and source term of the odour. Two levels of dispersion modelling were applied. One was a simple integral model, which was used for quick feasibility and sensitivity studies, and the other a detailed trajectory and meteorological model from the UK Met. Office. Both approaches were used to assess the range of emission rates required to explain the incident.The analysis suggests that the source of the odorant was indeed not local, with Germany and the Benelux Countries the likely source region. The proposed source, sufficient to lead to odour perception hundreds of kilometres away, is the widespread application of agricultural slurry or manure. This is common practice in Europe during the spring and this has implications for future reports of odour travelling extensive distances and resulting in long range pollution events. The likelihood of further long range odour incidents in the UK is discussed, as are the general implications of the case study.

► Investigated a widespread odour incident to explain the source and cause.
► Used forward and inverse dispersion modelling, emission data and modelling.
► Concluded that long range transport of odorants occurs.
► Concluded that this could lead to complaints at long range.
► The methods employed allow accelerated response for future events.