Abstract: In the Metropolitan Area of Belo Horizonte (MABH) wind-blown dust resuspension, dust emissions by mining activities, industrial activities, and vehicular emissions have a high contribution to air pollution in mining regions being the particulate matter the main air pollutant in open pit mining areas. Experimental campaigns identified significant proportions of crustal elements, featuring a robust presence of natural iron enrichment alongside contamination from local urban-industrial pollution in the range of particulate matter with 2.5 microns or less in diameter (PM2.5). With this, the main objective of the study was to identify the spatiotemporal variations in PM2.5/PM10 ratio in the MABH. The MABH comprises 34 cities in 15,000 km2 and approximately 6 million people in the Minas Gerais state, being referenced in iron ore mining and processing. Along this area, there are seventeen air quality stations supported by the Fundação Estadual do Meio Ambiente do Estado de Minas Gerais (FEAM), which obtain hourly data. In this context, daily averages were computed based on hourly data spanning from 2016 to 2021, being calculated when more than 3⁄4 of the daily hourly data were available. Then, the daily average PM2.5/PM10 ratio was calculated. Following, in the computer software “R” by using the package “openair”, which is an open-source tool for analyzing air pollution data, polar plots were elaborated to identify the relationship between wind direction and PM2.5/PM10 ratios and to analyze the ratios behaviors in a specific day which registered dust storm event in the MABH, splitting the air quality stations into vehicular, industrial, and mining classes. The analysis of the PM2.5/PM10 ratio indicates high values in air quality stations near human activity-related pollutant sources, conversely, when moving away from the air pollutants sources air quality stations near mining activities exhibited low ratios, attributed to wind-blown emissions dominated by particle sizes in the PM10 range, and the dust storms. On 2021 September 26th, a dust storm in the MABH was identified, and the average PM2.5/PM10 ratio for each air quality station class were 0.36 < 0.60 < 0.70 for mining, vehicular, and industrial classes. In this regard, the PM2.5/PM10 ratio serves as a valuable indicator of the sources of PM emissions, whether they are caused by human activity (greater ratio) or by natural processes (lower ratio).

Keywords: Dust storm, air quality data, mining activities.