Simulação numérica da dispersão dos poluentes H2S e NH3 provenientes do lixão de Maceió-AL nas épocas seca e chuvosa: estudo de casos

Abstract

The city of Maceió, due to the almost non-existence of pollutant industries, has its landfill, located at Cruz das Almas (LAT 09°33’ S; LON 35°46’ W), as one of the main sources of atmospheric pollutants emission. There are two main reasons of complaint by the inhabitants of its surroundings: the ashes resultant from the spontaneous combustion of the garbage, mainly during the dry period of the region (October, November, December and January), and the emission of gases produced by the bacterial activity, which occurs essentially throughout the whole year, being most noticed by the inhabitants in the wet period (April, May, June and July). The main pollutants emitted are Ammonium (NH3) and Hydrogen Sulfide (H2S), due to their smell. The main objective of this work is to simulate the dispersion of the pollutants mentioned, through two models: HYSPLIT_4 (HYSPLIT_4 MODELING SYSTEM – Hybrid Single-Particle Lagrangian Integrated Trajectory) – installed at the Air Research Laboratory / NOAA, available on-line, and a gaussian model adapted for the landfill’s condition. For an input of the second model, 3 seasons of measurements were made, with two being in the dry period and one being in the wet period, for several meteorological variables; also, 5 levels of soil temperature were measured, to estimate the level of highest gas emission from the garbage, with the installation of na Automatic Meteorological Station. It was also noticed the importance of atmospheric stability, wind velocity, air and soil temperature for the pollutants dispersion. The ratio of maximum concentration in the HYSPLIT_4 simulations were between 2-11km, while the simulations through the Gaussian model showed a higher concentration up to 3km, in the wind direction, of the pollutant source. Due to the predominant Wind direction the most affected districts are: Cruz das Almas, Sâo Jorge, Serraria, Barro Duro e Feitosa in the dry period, and Jacarecica in the wet period, predominant Wind direction East and South, respectively.