Methodologies for Estimating Emission Rates of Hazardous Gases from Single-Point Sources

Abstract

In the present study, a monitoring facility for hazardous gases was set up at Texas Tech University's Wind Engineering Research Field Site. The major objective of this study was to use the downwind experimental data acquired at the field site to develop a methodology for estimating point source emissions rates. Experiments were carried out by releasing controlled quantities of hydrogen sulfide (H2S) and ammonia (NH3) in the fields adjoining the field site. The downwind concentration of gases released during the studies was measured using a Single Point Monitor. The meteorological tower at the site was used to record meteorological data such as wind speed and direction, ambient temperature and relative humidity. An empirical correction to the Pasquill-Gifford model was determined which conservatively estimated emission rates. The estimation of atmospheric stability was studied using various methods published in literature. Terrain specific parameters such as friction velocity and surface roughness were determined. This approach was validated only for direct downwind sampling and neutral atmospheric stability. The dispersion parameters in the Gaussian model were then modified using experimental data. Finally, a novel method based on the use of artificial neural networks was also developed to model gaseous atmospheric dispersion. This approach offers significant potential because it does not require the accurate determination of the numerous variables which traditional models require. However, the neural network must be trained over the span of variables of interest.