RESUMO

Samples of soil, iron ore, and airborne particulate matter (size <10 µm) were analyzed with the main goal of investigating the differentiating physicochemical properties of their ferruginous compounds. These data were used to identify whether the sources of airborne particulate matter in the metropolitan area of Belo Horizonte, Minas Gerais, Brazil, are either from natural origin, as, for instance, re-suspension of particles from soil, or due to anthropogenic activities, meaning that it would be originated from the many iron ore minings surrounding the metropolitan area. Numerical simulations were used to model the atmospheric dispersion of the airborne particulate matter emitted by iron mining located at the Iron Quadrangle geodomain, Minas Gerais. Results from these numerical simulations supported identifying the sites with the highest concentrations of airborne particulate matter in the metropolitan area. Samples of these suspended materials were collected at the selected sites by using high-volume air samplers. The physicochemical features of the solid materials were assessed by X-ray fluorescence, X-ray diffraction, magnetometry, and 57Fe Mössbauer spectroscopy. The soil materials were found to be rich in quartz, aluminum, organic matter, and low contents of iron, mainly as low crystalline iron oxides. The samples of the iron ores, on the other hand, contain high concentration of iron, dominantly as relatively pure and crystalline hematite (α-Fe2O3). The samples of the airborne particulate matter are rich in iron, mainly as hematite, but contained also quartz, aluminum, and calcium. Mössbauer spectroscopy was used to evaluate the hyperfine structure of 57Fe of the hematite both from the iron ore and the soil samples. The structural characteristics of the hematite of these particulate materials were further explored. The direct influence of the iron ore mining on the composition of the airborne particulate matter was clearly evidenced based on the trace ability of hematite to its source of emission. Even the atmospheric air on regions relatively far away from the mining activities is also significantly influenced.

Assuntos

RESUMO

O modelo CAL3QHCR (California Line Source for Queuing & Hot Spot Calculations Refined) foi utilizado para avaliar a contribuição das emissões de material particulado (MP10 e MP2,5) de origem veicular na qualidade do ar de uma microrregião do centro de Belo Horizonte (MG). Os resultados de concentração obtidos nas simulações foram comparados com dados experimentais de concentração de MP10 e MP2,5, obtidos a partir da amostragem desses poluentes em uma estação de monitoramento da qualidade do ar localizada na área de estudo. Para todos os cenários, os valores de concentração previstos pelo modelo foram menores do que os observados. Uma análise de sensibilidade revelou que o fator de emissão veicular é o parâmetro que mais influencia os resultados das simulações, indicando a necessidade de realização de um maior número de pesquisas sobre o tema no Brasil.

The CAL3QHCR (California Line Source for Queuing & Hot Spot Calculations Refined) model was used to assess the contribution of particulate matter (PM10 and PM2.5) from vehicular exhausts to the air quality of a specific site downtown Belo Horizonte (MG), Brazil. Concentration results obtained through simulations were compared to the experimental data of concentrations of PM10 and PM2.5 which consisted of collected samples of these pollutants from a monitoring station for air quality located in the area of the study. For all scenarios, the concentration values predicted by the model were lower than the experimental concentrations. The sensitivity analysis showed that the vehicular emission factor influenced the simulation results more than the other parameters, which points out to the need of more researches in this area in Brazil.

RESUMO

Este estudo se iniciou com a realização de um inventário das fontes de emissão de material particulado existentes no município de Sete Lagoas (MG). Com base nessas informações e nos parâmetros meteorológicos e topográficos da região, foi feita a seleção dos pontos de maior concentração de material particulado inalável (MP10) usando o modelo ISC3. Um dos pontos identificados se situa na área central do município. Nesse local foram coletadas várias amostras de material particulado (MP) para determinação das composições mineralógica e elementar das partículas de aerossol (MP10). A calcita foi o mineral mais abundante (> 30 por cento) e o Na, Ba e o Fe foram os elementos-traço presentes em maior proporção no material coletado. A análise de fatores principais mostrou que a ressuspensão de poeira de solo e as atividades industriais são os maiores contribuintes de emissão do MP naquela área.

This study started with the inventory of the main particulate emission sources of Sete Lagoas city, Minas Gerais, Brazil. Based on this data and on local meteorological and topographic parameters, the selection of the highest points of inhalable particulate (PM10) concentrations was carried out using the ISC3 model. One of the identified points is situated on the central area of the city. Several samples of particulate matter (PM) were collected in that site for the determination of the mineralogical and elemental composition of the aerosol particles (PM10). Calcite was the most abundant mineral (> 30 percent), and Na, Ba and Fe were the trace elements presented in larger proportion in the collected material. The analysis of the main factors showed that resuspension of soil dust and industrial sources were the largest contributors of PM emissions in that area.