Approach into the influence of Saharan dust on the physicochemical properties of PM2.5 in Monterrey, México.

In this work, the influence of Saharan dust (S.D.) on the physicochemical properties of the PM_2.5 in the Monterrey Metropolitan Area in Mexico is studied. PM_2.5 sampling was carried out in a strategic sampling point during the alert peak of Saharan dust in July 2021. Additional samples were taken during the same weather season for comparison purposes. The characterization of the elemental composition in PM_2.5 was carried out by FRX and EDS. The crystalline phases and the morphology were investigated by XRD and SEM, respectively. Organic matter was analyzed by TGA. Results revealed that S.D. contributes to the increase of > 22% of PM_2.5 of the MMA. This increase in PM_2.5concentration comes together with the increase of the elemental concentration of S and Al in 13 and 35 wt% (FRX) respectively, as calcium sulfates and aluminum oxides. A decrease in the Fe content of S.D. is attributed to the warm season and/or the long distance from the original source. In addition, the arrival of the Saharan dust decreases approximately 10% the amount of organic matter in PM_2.5 samples as well as the particle size distribution from 0.660 to 0.469 μm with significant changes in the particle morphology and in the crystalline compounds. During the free days of Saharan dust in the MMA, the chemical composition of PM_2.5 is associated with crustal suspended particles as well as burning fuels and industrial activities emissions located near the sampling point. Zn could require more attention due to its possible inhalation risk. [ABSTRACT FROM AUTHOR]