Identificação de fontes de contaminação atmosférica que contribuem para o MP2,5 em Belo Horizonte – MG, aplicando a técnica de ativação neutrônica e ferramentas estatísticas

Abstract

Air pollution has been the subject of growing studies in recent years due to the impacts caused to the environment and human health. One of the most critical pollutants is particulate matter (PM), which comes from natural sources such as pollen, marine spray, and soil dust, as well as anthropogenic sources, mainly from vehicles and industries. Among the PM classes, we highlight the fine particulate material, which corresponds to atmospheric particles with an aerodynamic diameter less than or equal to 2.5 micrometers (PM2.5), whose effects are related to impacts on climate and human health. According to the official inventory of sources of emissions base year 2015, about 90% of all PM issued in the city of Belo Horizonte is of vehicular origin, followed by approximately 6% originated by fires and 2% by industries. Due to the dynamics of the atmosphere, it is known that emissions launched in other municipalities in the Metropolitan Region of Belo Horizonte may be influencing the air quality of Belo Horizonte. Therefore, this work aimed to collect and determine the chemical composition of the MP2.5 samples, as well as to identify the potential sources of PM2.5 emissions. The PM2.5 samplings were performed using a large volume sampler (AGV) with a quartz filter during 2017 in a region of heavy traffic of vehicles and people in the city of Belo Horizonte. The sampled filters were analysed by neutron activation, k0 method applied to large samples, which determines the elemental composition present in the PM without the need to dissolve and destroy the sample. To identify the primary sources of PM, the Positive Matrix Factory (PMF) mathematical model was used, which was developed by the United States Environmental Protection Agency (US-EPA) and is recommended to estimate the participation of the primary sources of air pollution. The majority of the 112 PM2.5 samples collected showed average concentrations of particulate airborne matter (24 hours, short exposure standard) of 25 g/m3, value above the national standard and the recommendations of the World Health Organization (WHO). Twenty-three elements (As, Au, Ba, Br, Ce, Co, Cr, Cs, Fe, Hf, La, Mo, Na, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn) were identified by neutron activation analysis. Based on the determined elemental concentration, it was verified what the possible sources of particulate matter would be through the enrichment factor in the PMF. The results obtained in this study point out the contribution of geogenic source to PM2.5 due to presence of U. The outcomes confirm previous studies that the sources of additives used in vehicles are the ones that most contribute to the formation of PM2.5 in Belo Horizonte, highlighting the presence of chemical elements As, Au, Ba, Ce, Cs, La, Na, Rb, Sm, Ta, Tb, Th, Yb, Zn. The second source identified by the PMF was fuel exhaust characterized by the presence of the elements Br, Cr, Fe, Sb, Sc. Finally, it was possible to identify vehicle emissions, such as Co, Hf and Mo.