Wind
movement in the atmosphere carries away odorous gases emitted from a source. Odour
annoyance occurs when a person exposed to an odour perceives the odour as unwanted.
Using an air dispersion models, it is possible to predict the downwind odour concentration
on the basis of odour emission rates, topography and meteorological data. The
results can be used against odour impact criteria to derive an odour impact area.
Odour impact assessment is an effective tool for the
following purposes:
Preparation
of environmental management plansDevelopment
of appropriate regional and local planning and development control instrumentsOdour
regulation In essence,
odour impact assessment uses inputs of source odour concentration, ventilation
rate and odour emission rate, topography information together with meteorological
data (one-year data), dispersion model to model odour dispersion about the source.
Odour impact area is defined by plotting isopleths of odour concentration corresponding
to same value for odour impact criteria. The approach to odour impact assessment
is illustrated in Figure 2.Within an odour impact area,
typical receptors (eg. residents) may be expected to experience a certain degree
of odour nuisance. Odour impact criteria are not ambient air quality standards
but rather provide a scientifically derived benchmark for making of informed decisions
in planning, design, environmental management and regulation.
