Impact maps of emission activities

Territorial planning tools are key aspects for the impact reduction of emission activities in their surroundings. In most cases emission activities are located in the predominant sector of wind direction to the inhabited areas, mainly due to the employment of economical and soil availability criteria when placing them in the territory. Hence, impact prediction maps are in this case key tools to avoid the above mentioned drawbacks when installing an emission activity in an area. Impact maps display the exact spots in the urban areas with maximum and minimum impacts from the current and/or future activities. Additionally, this methodology enables us to locate the sampling devices in time intervals (month of the year, hourly slot, …) to obtain representative results, as well as determine the locations in the territory where the ubication of an emission activity would have potentially a minimum impact in the inhabited areas. The information obtained through the impact maps is also useful for the schedule of the most emitting activities of a facility during the periods of lower predicted impacts in the populated areas.

Dispersion models

The different models that can be used to predict pollutants concentrations hour by hour for periods up to a year are usually semi-empirical/analytic models based in Gaussian puffs. These models use either a simple surface based meteorological file (AERMOD), or the results from a diagnostic model of the wind field from slight accessible observations (calculation of the meteorology in a concrete point of a gird of several kilometres (CAKPUFF)). The TAPM model used by our laboratory solves the transport fundamental fluid-dynamic equations to predict meteorology and pollutants concentrations for the evaluation and control of air quality. TAPM consists in coupled components of meteorological prognostic and pollutants concentrations, avoiding the necessity of having surface meteorological observations in the study area, generally influenced by the situation of the local meteorological station. The model predicts the flows important to local-scale air pollution, such as sea breezes and terrain-induced flows, against a background of larger-scale meteorology provided by synoptic analyses.

The meteorological component of TAPM is an incompressible, optionally non-hydrostatic, primitive equation model with a terrain-following vertical coordinate for three-dimensional simulations. The model solves the momentum equations for horizontal wind components, the incompressible continuity equation for vertical velocity, and scalar equations for potential virtual temperature and specific humidity of water vapour, cloud water and rain water.

The air pollution component of TAPM uses the predicted meteorology and turbulence from the meteorological component, and is calculated through four modules. The Eulerian Grid Module solves prognostic equations for concentration and for cross-correlation of concentration and virtual potential temperature. The Lagrangian Particle Module can be used to represent near-source dispersion more accurately. The Plume Rise Module is used to account for plume momentum and buoyancy effects for point sources (chimneys). Finally, the Building Wake Module, that includes wake effects on the emitted pollutants, uses both the Eulerian Grid and the Lagrangian Modules.

(The Air Pollution Model (TAPM) version 2. Part 1: Technical Description. Author: Peter Hurley. CSIRO Atmospheric Research Technical Paper No. 55, 2002).