PM\(_2\)\(_.\)\(_5\) source apportionment and mass closure study in Doha city, Qatar

This study aims to identify key sources that contribute to fine particulate matter (PM2.5) mass concentrations in Doha city, Qatar. Specifically, to determine the increase in PM2.5 mass caused by dust events, by comparing abundance and composition between the dust events season ‘the summer season’ and non-dust event season ‘the winter season’. Knowing PM2.5 sources in Doha will help to 1) identify the predominant (natural or anthropogenic) sources responsible for particulate matter (PM) exceedances of the daily and annual air quality standards, 2) ensure an appropriate focus on controlling major anthropogenic sources, and 3) evaluate the current air quality standards and potential improvements to the allowable margin of tolerance for PM limit and the number of allowed exceedances to take appropriate account of natural sources. Two parallel sampling campaigns at two urban sites in Doha, namely Al-Corniche (AC) and Qatar University (QU) were conducted during the winter of 2014/2015 and the summer of 2015 using low volume samplers. Chemical analysis of minerals, trace metals, soluble inorganic ions, organic and elemental carbon was carried out on PM2.5 samples. Subsequently, a mass closure analysis, and a source apportionment by means of positive matrix factorisation (PMF-5) were performed. The mass closure solution found a good closure between the samples’ gravimetric mass and the reconstructed mass of the chemical constituents determined on those samples. However, mass discrepancies ranged between -5 and +12% were found between reconstructed mass and gravimetric measured mass as a result of using different filters substances (Teflon & Quartz) to collect PM2.5 samples with contradictory behavior in retaining and releasing organic carbon and ammonium nitrate. Then comparing the sum of chemical constituents from both filters to the mass collected on the Teflon filters