Evaluation of particulate matter emissions from non-passenger diesel vehicles in Qatar

Road traffic is one of the main sources of particulate matter (PM) in the atmosphere. Despite its importance, there are significant challenges in the quantitative evaluation of its contribution to airborne concentrations. To propose effective mitigation scenarios, the proportions of PM traffic emissions, whether they are exhaust or non-exhaust emissions, should be evaluated for any given geographical location. Particulate matter emissions from all registered heavy duty diesel vehicles in Qatar were assessed in an active traffic zone in urban Doha. Dust samples were collected and characterized for their shape and size distribution. The observed particle size ranged from few to 600 Μm with the dominance of small size fraction (less than 100 Μm). In-situ elemental composition analysis was conducted for side and main roads traffic dust, and compared with non-traffic PM. The enrichment factor of anthropogenic elements amounted to 350. The traffic source based on sulfur elemental fingerprint was almost five times higher in main roads compared with the samples from non-traffic locations. Also, evaluation of PM exhaust and non-exhaust emissions (tyre wear, brake wear and road dust resuspension) revealed that the majority of the dust was generated from tyre wear with 33% followed by road dust resuspension (31%), brake wear (19%) and then exhaust emissions with 17%. The low contribution of exhaust PM₁₀ emissions was due to the fact that the majority of the registered vehicle models were recently made and equipped with efficient exhaust PM reduction technologies.