| Point
source algorithm For point sources, IMMISnet uses the stationary Gaussian smoke plume equation, according to the definition in Appendix C of the German Technical Directive on Air Pollution Control (TA Luft, 1986). Smoke plumes are reflected at a mixture layer height in addition to the Technical Directive's model. Line source algorithm Traffic emissions are treated as finite line sources. An analytic solution of the diffusion equation is used. The solution takes varying distance to the receptor along the line source into account, i.e. emissions from parts of the line source located further from the receptor reach the receptor with a greater degree of dilution than the emissions of nearer sections. The line source algorithm can thus be used for all angles between the line source and wind direction. Areal source algorithm Area sources are represented by a varying number of line sources. A numerical procedure that successively divides the area source - beginning with one division (represented by one line source) and proceeding to ever-smaller areas (represented by several line sources) - is used for determining the concentration contribution of an area source at one receptor. The division of the area source into a growing number of line sources continues until the concentration at the receptor shows only negligible alteration. Area sources far from a receptor can thus be represented by one or few line sources, while area sources close to the receptor are resolved using many line sources. |
