(385b) IMPACT MAPS of Immission for AIR Contaminants FROM PROCESS PLANTS: Modelling and Validation RESULTS USING Chemical ANALYSIS

Chemical substances emitted to the atmosphere by industrial installations could have certain impacts in people and environment. The atmospheric air acts as a dispersive media with several circumstances that makes very difficult to assign the focus of a contaminant if there are different possible candidates. In addition to that, the trajectory of the contaminants in air depends on the wind, on the atmosphere stratification, on the half period of live, etc. (Gallego et al, 2008), so it can travel long distances or it can impact in the nearby zone of the emission area. On the other hand, the evaluation of the immission levels, the concentration that is breathed by population, deposited in soil, water, etc., is usually not accurate. Generally, qualitative and quantitative data of emission is not well known, not only for regulators but also for the industrial responsible. The emission of chemical substances to the atmosphere occurs mainly from stacks, from the process itself by fugitive emissions and from tank ventilation systems. Only for a very few number of substances (e.g. NOx, SO2, CO, O3, PM, BTEX, PAHs and some metals) continuous or discontinuous measurement data is available. However, there are plenty of substances not controlled at all, partially due to the fact that the capture and analysis methods of air are more complex than in other media, as water or soil. There can be hundreds of compounds found in an air sample by qualitative analysis. Hence, the quantification of the concentration of these compounds is also difficult, because the calibration must be done specifically for all of them, or for a group of them using response factor assigned to a typical substance (Ribes et al, 2007). All these aspects make the control of air emissions and the assessment of the impact produced in people and environment more difficult than in any other media. What is proposed in this presentation is the conjunction of modeling and analytical methods in order to achieve a reliable method to evaluate the impact of a process plant, which can be very useful in all the life phases of the industrial installation: from the design of the plant, the selection of the location where this plant could be deployed causing minimum environmental impact, and the optimization of the emissions during the normal operation. This can be done using accurate modeling which allows obtaining impact maps that can be validated lately by chemical analysis. Examples of this methodology are presented in case studies done at our research laboratory. In figure 1 there is an impact maps of existing chemical plants which indicate clearly the zone when the air samples must be taken in order to obtain samples of gas with contaminants coming with the biggest probability from the simulated focuses. Figure 1. Average 1-hour concentration of a tracer gas emitted by the chimneys of a group of chemical plants for the years 2005, 2006, 2007, 2008 and 2009. Refs. 1- Gallego E. , Soriano C., Roca F.X., Perales J.F., Alarcón M., Guardino X. Identification of the origin of odour episodes through social participation, chemical control and numerical modeling. Atmospheric Environment 42 (2008) 8150?8160 2- Ribes A., Carrera G., Gallego E., Roca F.X., Berenguer M.J., Guardino X. Development and validation of a method for air quality and nuisance odours monitoring of volatile organic compounds using multisorbent adsorption and GC/MS thermal desorption system. J. Chromatogr. A 2007;1140:44?55.