Avaliação da composição mineral de material particulado atmosférico coletado na região geográfica intermediária de Salvador e de Amélia Rodrigues, Bahia, Brasil

Abstract

Air pollution has been a major focus of study in the scientific community, aiming to understand its implications for human health, ecosystems, and material heritage, identifying itself as a key element in the pursuit of sustainable development. The accelerated growth of urban areas, driven by industrialization and population increase, has significantly contributed to the current scenario. In this context, the present work aims to investigate, evaluate, and quantify samples of atmospheric particulate matter in the form of total suspended particles (TSP) and respirable particles (PM₂,₅), according to the limits established by Resolution No. 491/2018 of the National Environment Council (CONAMA), in addition to chemically characterizing the mineral composition. Sampling was conducted in the Intermediate Geographic Region of Salvador, encompassing the municipalities of Lauro de Freitas, Madre de Deus, São Sebastião do Passé, São Francisco do Conde, and Amélia Rodrigues, in the Metropolitan Region of Feira de Santana, in August, September, and December 2021, covering both the dry and rainy seasons in the region. Collections occurred during nominal 24-hour periods, using three portable samplers (HANDI-VOL) for PTS and one portable prototype for PM₂,₅, operating simultaneously. The geometric mean concentrations of PTS and PM₂,₅ were below the limits established by Resolution No. 491/2018 of the CONAMA. After the sampling procedures, the particulate matter deposited on the filters was subjected to acid extraction, followed by chemical analysis by inductively coupled plasma optical emission spectrometry (ICP OES) to determine Al, Ba, Cr, Cu, Fe, Ni, Mn, Mo, Pb, Sb, V, and Zn. Based on the results obtained, the trace metals were grouped in ascending order of concentration (Mo < V < Sb < Pb < Ni < Mn < Zn < Ba < Cr < Al < Cu < Fe) for PTS. The concentrations of the chemical elements in the PM2.5 samples were below the quantification limit of the analytical method. With the predominance of Fe concentration in the chemical composition of the atmospheric particulate matter (PTS), the results obtained clearly showed that in the study region, the chemical composition of atmospheric particulate matter is strongly associated with natural sources, but is directly influenced by anthropogenic sources such as the use of fossil fuels, vehicular traffic associated with brake system wear, maritime traffic, industrial, petrochemical and port activities through the presence of Cu, Mn, Pb, Sb and Zn. An investigation of pollution indices was carried out using the enrichment factor (EF) and the geoaccumulation index (Igeo), as geochemical indices, highlighting the need for extra attention to the concentrations of Cu, Cr and Sb. Multivariate data analysis was crucial in determining a possible anthropogenic contribution in the region. Principal component analysis (PCA) showed that Fe was the chemical element with the greatest contribution to the chemical composition of the PTS, mainly associated with natural sources, such as soil resuspension. Meanwhile, the concentration of Cu, Fe, Mn, and Pb indicated anthropogenic influence from traffic and industrial activities. During the dry and rainy seasons, PCA showed variation in the relative weight of the metals, but maintained the distinction between natural and anthropogenic sources. Hierarchical cluster analysis (HCA) consistently grouped the samples, separating sets influenced by industrial/port activities from those of natural origin. This analysis confirmed the correlation between Cu, Mn, and Sb as markers of anthropogenic impact. Together, PCA and HCA reinforced the identification of the main emission sources in the studied region. Finally, this work may assist the corresponding agencies in more effective air quality monitoring in the region.