Elemental composition of airborne dust samples retained by internal filters of air condition units (ACUs) was determined at 12 locations of Doha city, state of Qatar. Twenty-four elements: Al, Ca, Mg, Fe, Na, K, Ti, Zn, P, Sr, Mn, Ba, Cu, Cr, Ni, Pb, V, Mo, Li, Co, Sb, As, Cd, Be, were analysed by ICP-OES technique after acid digestion of the samples. The analysed components reflect 20.6% of the total sample mass. Similar or lower concentration values have been found for As, Cd, Cr, Cu, Mn, Ni, Pb, V, Zn, Al, and Fe compared to the international context of upper crust concentrations, NIST SRM (urban dust), published local dust information of outdoor, and surface terrestrial deposit (STD) counted for 7.2, 0.7, 91.8, 192.8, 369.7, 68.6, 65.3, 52.1, 824.3, 19,791, 20,508 mg/kg, respectively. The coefficient of correlation (p ≤ 0.05) showed significant association of ACUs dust elemental compositions with the main components of the local earth crust and surface deposits, ranging from the lowest 0.77 (Mg–Fe) to the highest 0.98 (Al–Fe), while Ni and V, typical anthropogenic pollutants, are also strongly correlated (0.86). These strong correlation relationships can be interpreted as the contribution of outdoor particulate to the indoor dust. Dendrogram of metal/Al ratios, based on Euclidean distance calculation and average linkage clustering method, distinguished three typical groups. Studying the enrichment factors of the three groups indicated elevated levels of Zn (131), Pb (49), Cu (32), Cd (8) and Ni (5) found indoors compared to the background composition of STD especially at locations in the industrial zone. The major elemental composition of the samples reflects the typical mineral composition of the local dust, while the trace composition demonstrates the influence of indoor sources. The collected ACU filter dust samples show significant contribution of outdoor mineral particles, non-exhaust traffic emission, industrial sources, as well as the influence of indoor activity such as smoking.

The Eastern Arabian Peninsula experiences elevated atmospheric particle loads due to anthropogenic emissions from the extraction and use of fossil fuels, as well as natural dust events, resulting in significant aerosol optical thickness (AOT). However, despite the region's significance, there is a lack of studies focusing on the optical and microphysical characterization of aerosols, leaving critical gaps in understanding their radiative effects. This study examines the optical properties of atmospheric particles over Qatar using more than one-year sun photometer data, with an emphasis on temporal variations and source origins. Measurements of direct sunlight were recorded every 5 minutes across wavelengths from 340 to 1020 nm between March 2023 and November 2024. Aerosol optical thickness (AOT) was calculated from these measurements using the Beer-Lambert-Bouguer law, while the Angstrom Exponent (AE) was derived to assess particle size. The results revealed notable daily variability, with average AOT values at 440 nm of 0.41 ± 0.21 and AE values averaging 0.87 ± 0.35. Seasonal patterns showed higher AOT during the summer months and a transition from dust-dominated to anthropogenic aerosols between March and December. Aerosols were classified into three categories: mineral dust-dominated (AE < 0.5), mixed (0.5 < AE < 1), and anthropogenic (AE > 1), accounting for 18%, 44%, and 38% of the total observations, respectively. These findings provide new insights into the aerosol composition over the region and emphasize the need for further research using radiative transfer models to evaluate aerosol-induced changes to the radiation budget.

Polyaromatic Hydrocarbons (PAHs) concentrations in dust trapped on air conditioning unit filters operating in residential and workplace locations in Doha, Qatar were sampled and measured. Fourteen samples were collected and their PAH congener profile were quantified using gas chromatography–mass spectrometry (GC-MS). The results showed that the medians of ΣPAH ₁₆ , which include seven carcinogenic components (ΣPAH ₇ ), were 214.7 ng g ^− 1 and 129.2 ng g ^− 1 of dust respectively for the residential samples, and 224.4 ng g ^− 1 and 137.9 ng g ^− 1 respectively for dust samples collected in an office workplace environment. Among all samples, benzo (b) fluoranthene (BBF) and benzo (a) pyrene (BAP) were the dominant congeners in both the residential and workplace samples, representing 18.2% and 16.9% of the ΣPAH _16, respectively. Factors of correlation were calculated for various PAHs, and showed that lighter molecular weight PAHs have a significant positive correlation with heavier congeners within the residential samples, while workplace samples showed a negative correlation with BAP, Indeno (1,2,3-cd) pyrene (IND), and Dibenz (a,h) anthracene (DBA). Benzo (a) pyrene equivalent (BAPe) was used to assess the risk of human exposure to PAH inhalation. BAPe estimates for residences sampled averaged 0.019 μg g ^− 1 , with a maximum of 0.063 μg g ^− 1 of dust, while workplace estimates averaged at 0.056 μg g ^− 1 with a maximum of 0.148 μg g ^− 1 . Source apportionment assessment indicated that most residential and workplace PAHs samples have a pyrogenic origin with few showing evidence of petrogenic origins. All quantified PAHs concentrations and estimated BAPe in Qatar indoor dust samples are well below reported values elsewhere in the world.