ADMS-Airport

Comprehensive software for air quality management for airports

Model options

One of the most important advanced modules in ADMS-Airport is the chemistry module. The following options are available:

• NO_x – NO₂ chemistry
• The Trajectory model
• Sulphate chemistry

Other advanced modules are:

• Street canyons
• Buildings

These modules are based on the latest understanding of the way these features affect the movement of airflow around the sources, and all have been shown to have considerable affect on observed concentrations.

Chemistry module

NO_x – NO₂ chemistry

ADMS-Airport models NO_x chemistry using the 8 reaction Generic Reaction Set (Venkatram et al., 1994) that includes reactions with ozone and hydrocarbons.

In most urban areas, the dominant pollution source is road traffic, and the pollutants usually of major interest are NO_x and PM₁₀. The NO_x chemical reactions take place over a relatively short time period and in order to get accurate predictions of NO₂ concentrations, NO_x chemistry should be taken into account. The Generic Reaction Set predicts changes in ozone concentrations that are also of interest.

The Trajectory model

A simple Lagrangian Trajectory Model is used to calculate background concentrations for the air approaching the main modelling area. This model includes the effects of emissions, chemistry, deposition and ozone entrainment.

By nesting the main model domain within a larger domain, such as a large urban conurbation, the Trajectory Model calculates a spatially varying background ambient concentration that takes into account the chemical reactions and processes occurring over the larger domain.

Sulphate chemistry

The reactions between SO₂ and other compounds in the air to produce particulates are based on those used in the EMEP model (Tsyro, 2001).

These reactions have a significant effect on the concentrations of particulates in areas where there are a large number of industrial sources emitting SO₂ or downwind from a large emitter of SO₂.

Street canyons

'Street canyons' are defined as the deep, narrow, valley-like spaces created when a road is enclosed by tall buildings on both sides. High pollution levels are often observed in street canyons. ADMS-Urban includes two modules for modelling street canyons.

The basic street canyon module is based on the Danish Operational Street Pollution Model (OSPM, Hertel and Berkowicz, 1990, Hertel et al., 1990).

The advanced street canyon module (Hood et al., 2014) can be used if a more detailed model of the street canyon is required. It differs from the basic module in the following ways:

• The model has been formulated to consider a wider range of canyon geometries, including the effects of tall canyons and of canyon asymmetry;
• The concentrations predicted by the model vary with height within the canyon;
• Emissions may be restricted to a subset of the canyon width so that they may be specified only on road lanes and not on pedestrian areas;
• There is the option to include consideration of 'network' effects, where pollutants reaching the end of one street canyon can pass into a connected canyon; and
• Concentrations both inside and outside a particular street canyon are affected when running this model option.

Buildings

Users can include the effect of up to 10 dominant buildings on point source emissions. ADMS-Airport creates an effective building for each point source from the user-defined buildings and models the re-circulating flow in the lee of the building, the cavity region, as well as the building main wake.

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