Geospatial Assessment of Ambient Air Quality Footprints in Relation to Urban Landuses in Nigeria

Abstract

Ambient air pollution is a global concern. It accounts for an estimated 4.2 million deaths yearly as a result of its ability to cause stroke, lung cancer, heart disease and chronic respiratory diseases. It has also been estimated that about 91 percent of the world’s population lives in places, mostly urban centres, where air quality levels exceed World Health Organization (WHO) limits. Fortunately, efforts are regularly made in most developed countries to monitor and reduce the level of air pollution and ameliorate its negative consequences. Unfortunately, the case is not the same in most developing countries of which Nigeria is a member, as air pollution status is rarely monitored religiously. This study geospatially assessed ambient air quality footprints vis-à-vis urban land uses in Calabar Metropolis, Nigeria. Data on emission level of CO, NO2, SO2, H2S, and SPM2.5 were collected for 6 months in both dry and wet seasons in the year 2020, using Crowcon Gasman, while point coordinates were collected using Garmin GPSMap 60CSx device. Geographic Information Systems (GIS) infrastructure was deployed to generate the ambient air quality maps for the metropolis. Descriptive and parametric analytical techniques were also deployed, based on the objectives of the study. From findings, F-ratio is significant for both season and land use for all the tested parameters (F-ratio for season is F(1,3224)=574.516, at p<0.05, while for land use, F(3,3224)=429.946, at p<0.05). The interaction between seasons and land use (season * land use) for all the parameters is also significant. It was concluded that there is a significant variation in air quality (CO, NO2, SO2, H2S, and SPM2.5) in Calabar Metropolis in relation to either land use types or seasons of the year. It was therefore recommended that there should be protection of residential land uses to avoid encroachment by incompatible uses that cause pollution.