Atmospheric ventilation corridors and coefficients for pollution plume released from an Industrial Facility in Ile-Ife Suburb, Nigeria

Abstract

This study presents a comparative investigation of atmospheric ventilation corridors and coefficients for gaseous pollution plume released from an isolated industrial facility into the ambient air of the host community in Ile-Ife suburb, southwest Nigeria. For the months of September to December in the year 2012 and 2013, measurement of surface layer atmospheric parameters made from an instrumented mast located near the industrial facility were used to parameterize for mixing layer height (MLH). Estimates of ventilation coefficients were obtained as well as in-depth analysis of the ventilation corridors performed. With an estimated carbon monoxide (CO) emission rate of 3.37 gs^-1 from the industrial facility, AERMOD regulatory dispersion model was executed within a domain covering 8 km × 6 km around the host community. Effect of monthly changes in local ventilation corridors on pollutants dispersal at the study location was analyzed. Observed speed wind at the study location was weak (monthly mean value is ~ 1.5 m-s^-1). The wind direction was predominantly southwesterly, indicating ventilation corridors were towards the north-east of the region. Characteristic values of the atmospheric ventilation coefficients varied from month to month and from daytime (08:00 to 19:00, GMT+1) to nighttime (20:00 to 07:00, GMT+1) with daily maximum values occurring in the late afternoon between (13:00 to 17: 00, GMT+1). The maximum values obtained were 1216 m²s^-1and 1156 m²s^-1, 1760 m²s^-1 and 1038 m²s^-1, 1225 m²s^-1 and 691m²s^-1, and 1334 and 436 m²s^-1 for September to December, 2012 and 2013 respectively. Nighttime values were generally low, mostly less than 200 m²s^-1. The study reveals that locations SE and NE of the scrap-iron recycling factory are prevalently exposed to high concentration of gaseous pollutants and the populace in those corridors is potentially susceptible to long-term adverse effects.

Key words: Air pollution, ventilation coefficient, ventilation corridors, dispersion, AERMOD.