DEVELOPMENT OF A CIRCUIT MODEL TO DESCRIBE THE ADVECTION-DIFFUSION EQUATION FOR AIR-POLLUTION

A circuit model for calculating pollutant concentration from an area s ource is derived. This model includes various loss, production and tra nsfer terms and can be used by grid modellers seeking to build a more sophisticated description of the PBL. After analysis of exchange/remov al processes operating in the PBL by using the circuit model, we find that the near ground steady-state concentration is close to max(q(0)l/ 2ul(e), C-b) where q(0) is emission rate, l the length of an area sour ce, u wind speed, l(e) an effective mixing length, and C, upwind conce ntration. The value of q(0)l/2ul(e) increases proportionally with the length of an area source and inversely with wind speed until it reache s q(0)/V-d during rainless time and q(0)/Lambda l(e) during raining ti me. V-d is dry deposition rate, and Lambda scavenging coefficient. The worst air quality occurs under stable atmosphere with low wind speed and rainless conditions. However, it might take more than a day to rea ch such a high concentration in a stable atmosphere. Copyright (C) 199 6 Elsevier Science Ltd