A critique of industrial air dispersion modelling in Trinidad and Tobago

Abstract

Air dispersion modelling (ADM) was required by the Environmental Management Authority (EMA) of Trinidad and Tobago for an aluminium smelter complex, an iron and steel plant, and a chlor-alkali plant. This article critiques the outputs of the modelling. For the aluminium smelter complex, wind roses which were produced by the MM5 model, and then used in the CALPUFF ADM, underestimated calm periods 20-fold compared with actual observations. For the iron and steel plant and for the chlor-alkali plant, the ADMs (ISC3 and AERMOD) produced apparently unjustifiable bicycle-spoke patterns for airborne emission concentrations instead of concentric loops of iso-concentration around the source. It is concluded that the predictions of airborne emission concentrations were erroneous and that the Certificates of Environmental Clearance (CECs) for the plants must be withdrawn.