Multivariate Analysis of the Environmental Impact of Traffic Density on Air Quality in Lagos, Nigeria
Creators: name: OSHO, BABATUNDE YUSUF
Publisher: name: University of Surrey
Year: 2022

description: Urban air pollution is a major global challenge. Industrial activities, vehicular
description: emissions, frequent use of private power-generating sets, and indiscriminate and
description: open burning of solid waste have contributed to air pollution. In Nigeria, there is a
description: paucity of research and data on air pollution studies that incorporate either singly or
description: jointly the effects of land use, road density, road intersection density, and elevation.
description: Furthermore, available data on ambient air quality are concentrated around major
description: roads and industrial establishments. In contrast, traffic-related air pollution monitoring
description: and modelling in developed countries employ different sampling strategies and
description: statistical analysis based on the availability of air monitoring networks; however, the
description: influence of land-use diversity, road density, road intersection density, and elevation
description: in moderating not only the spatiotemporal dynamics of air pollution emanating from
description: vehicular movement but also in siting such monitoring stations has not been
description: adequately addressed. This study, therefore, was designed to investigate the
description: influence of land-use diversity, road density, road intersection density, and elevation
description: on selected air pollutants in the Lagos metropolis, to understand the spatiotemporal
description: dynamics of the air pollution emanating from the vehicular movement in the Lagos
description: metropolis.
description: An existing land-use map of the area of study was obtained from the Ministry of
description: Physical Planning, Lagos State, while a contemporary land-use map was developed
description: from an extremely high-resolution satellite image of the study area. Road network
description: data was obtained from OpenStreetMap.org, while elevation data was obtained from
description: Shuttle Radar Topographical Mapping (SRTM). Data from OpenStreetMap.org
description: provided information on road length, road density, and road intersections. A grid of
description: 100 x 100 metres was overlaid on the road network to obtain the road density and
description: intersection (node) density, while the SRTM was processed to obtain elevations as
description: percentages. A weighted linear combination method was used to combine all these
description: data layers and subsequently classify the resulting map into three categories. This
description: classified map was subsequently overlaid on the land-use map. Eighty-five percent of
description: each grid within the different land-use types were selected. The centre (centroid) of
description: each grid was a location where air quality data were obtained. Ambient air quality
description: parameters collected at these locations were CO, NO2, and PM2.5. Sample readings
description: were taken using air quality monitoring equipment from 08:00 to 20:00 hrs over a
description: period for 30 days, in both wet and dry seasons, in two selected local government
description: areas (LGAs), namely Ikeja LGA and Lagos Mainland LGA. Vehicular counts were
description: conducted simultaneously.
description: A Pearson correlation analysis was used assess the correlation of the daily average
description: pollutant concentrations compare to traffic density. CO and NO2 concentrations
description: showed positive correlations (p&lt;0.05) with traffic density in the sampling zones. A
description: Wilcoxon test was used to analyse regional variations in the observed measurements
description: across different land uses and seasons in the two selected LGAs. On the whole,
description: significant variations in the air quality parameters were recorded at different times of
description: the day and in different land-use areas within the two LGAs of the Lagos metropolis.
description: In some cases, pollutant concentrations, i.e. PM2.5, were higher for the wet than for
description: the dry season, which is attributed to excessive delays of vehicles due primarily to
description: traffic congestion associated with poor physical planning, lock-up shops along the
description: highways and arterial roads, and a poor road maintenance culture. Combined
description: vehicular traffic density analysis revealed its contribution to the seasonal variations
description: (p&lt;0.05). Lastly, a land-use regression model was used to estimate the levels of
description: ambient air pollutants and determine the possible predictors of the air pollutants,
description: especially land use, within the two LGAs of the Lagos metropolis. The result confirms
description: that land use is an important independent variable in the determination of PM2.5
description: concentrations, especially during the wet season.
description: The results underscore the need to consider land use and time of day when
description: assessing the impact of traffic on ambient air quality. Furthermore, there is a need to
description: regularly monitor the micro-variations and dynamics of ambient air quality parameters
description: in the Lagos metropolis.