Evaluation of Nitrogen Dioxide, Benzene, Toluene, Ethylbenzene and Xylene Concentrations in the Urban Environment of Meknes City, Morocco

Abstract

The present study focuses on the monitoring and the evaluation of air quality in the city of Meknes, based on the tracers of pollution of proximity cars (NO2 (nitrogen dioxide) and BTEX (Benzene, Toluene, Ethylbenzene, and Xylene). In the absence of a telemetric station and a mobile laboratory within the city, passive diffusion tubes, analyzed offline in the laboratory after exposure, were the most plausible solution. The low cost, ease of implementation of the technique, and the possibility of covering a large geographic area with many samplers all argue for adopting this approach.
 The coupling of the results of the measurement campaigns and counting sessions under a geographical information system allowed us to determine the most affected areas by automobile pollution and to carry out cartography at a large scale of spatial resolution of the prospected pollutants.
 The deployment of passive sensors at 14 measurement sites revealed the existence of spatio-temporal variability of the pollutants studied. This variability is due to the climatic conditions that prevailed during the measurement campaigns, notably wind and precipitation, the photochemical nature of the said markers, the proximity to the emission sources, the type of measurement site, and the topography and road infrastructure.
 The approach developed could be used as a decision-making tool for the competent authorities in this field and adapted for monitoring other types of pollutants (pesticides, tracers generated by industrial units, furan dioxins, etc.).