In developing and rapidly urbanising regions, the expansion of fixed monitoring networks is often constrained by financial, technical, and logistical limitations. Conse-quently, monitoring coverage may remain insufficient to represent intra-urban varia-bility. Hybrid monitoring approaches that combine a limited number of fixed reference stations with mobile or low-cost calibrated sensors have been proposed as cost-effective and scalable alternatives (Snyder et al., 2013). These strategies enhance spatial resolu-tion while maintaining acceptable levels of measurement reliability. In Morocco, national air quality monitoring infrastructure is primarily based on fixed stations located in major metropolitan areas. Although these systems support regulatory reporting and environmental assessment, medium-sized industrial cities may experience limited spatial coverage. Mohammedia, characterised by significant industrial and petrochemical activities, represents a relevant case study where en-hanced spatial monitoring strategies could contribute to improved environmental management.

In regions experiencing rapid development and urbanization, expanding fixed monitoring networks faces significant challenges due to financial constraints, technical barriers, and logistical difficulties. As a result, monitoring coverage often fails to adequately capture the variations in air quality that occur within urban areas. Researchers have suggested hybrid monitoring strategies as practical and expandable solutions to address these limitations. These approaches use a small number of fixed reference stations alongside mobile or affordable calibrated sensors (Snyder et al., 2013). Such methods improve spatial coverage while keeping measurement accuracy at acceptable standards. Morocco's national air quality monitoring system relies mainly on fixed stations positioned in large metropolitan centers. While these installations fulfill regulatory requirements and support environmental evaluations, medium-sized industrial cities often lack comprehensive spatial monitoring. Mohammedia presents a compelling example of this issue, given its substantial industrial and petrochemical operations. This city demonstrates how improved spatial monitoring approaches could support better environmental management practices.