Comprehensive chemical characterization of PM2.5 in the large East Mediterranean-Middle East city of Beirut, Lebanon.

The chemical composition of PM2.5 at two sites in Lebanon, a country in the East Mediterranean - Middle East region, is investigated in the spring and summer seasons. The average PM2.5 concentrations were of (29 ± 16) µg/m3 for Beirut urban site and (32 ± 14) µg/m3 for Beirut suburban site. This study showed that the geographic location of the East Mediterranean region, such as its proximity to the Mediterranean Sea and the dust storm intrusion are a significant contributor to the high PM levels from natural sources, which cannot be mitigated, rendering the PM2.5 WHO annual Air Quality guideline unattainable due to high natural background, which also applies to the entire Middle East region. Turkey and Eastern Europe are the dominant origin of air masses throughout our sampling days, suggesting the long-range transport as an important potential contributor to the high observed concentrations of V, Ni, and sulfate in this region most probably in other East Mediterranean countries than Lebanon too. Main local sources determined through the chemical speciation including organics are road transport, resuspension of dust and diesel private generators. A health risk assessment of airborne metals was performed and the carcinogenic risk for all the metals exceeded by 42 (adults) and 14 (children) times the acceptable risk level (10-6) at both sites. Vanadium was the predominant carcinogenic metal, emphasizing the need to replace energy production with cleaner energy on a regional level and highlighting the severe impact of air pollution on the health of inhabitants in this region's main cities.

Source apportionment of PM2.5 using organic/inorganic markers and emission inventory evaluation in the East Mediterranean-Middle East city of Beirut.

Source contributions to PM2.5 concentrations were evaluated in Greater Beirut (Lebanon), a typical East Mediterranean-Middle East (EMME) city, using Positive Matrix Factorization with two approaches. The first approach included only inorganic species (PMF-trad) and the other approach added organic markers (PMF-org). PMF-org identified 4 additional sources, and large discrepancies in contributions were observed for some major sources found in both approaches, highlighting the importance of including organic markers. The traffic factor was underestimated in PMF-trad by 2 to 7 folds. Moreover, results showed that this city is prone to high desert dust concentrations originating from uncontrollable dust storm events, like all cities in the Middle East. A PM2.5 mitigation plan taking into account the potency of the identified sources was developed. Sources like diesel generators or traffic presented smaller contributions in term of mass compared to desert dust, however the health impact of the latter is relatively small and actions should target sources with the highest potency. Local emission inventories in the EMME region are scarce and studies typically rely on global emission inventories for local air quality management plans, but these inventories significantly underestimate Beirut's road transport emissions by more than an order of magnitude.