Avaliação integrada de íons solúveis em MP10 e variáveis meteorológicas aplicada à qualidade do ar

Abstract

Inhalable particulate matter (PM₁₀) is an important indicator of air quality, particularly in coastal areas, where marine aerosols and anthropogenic activities contribute to its composition. The aim of this study was to evaluate the composition of water-soluble ions in inhalable particulate matter (PM₁₀) and its relationship with meteorological variables in the city of Aracaju, Sergipe, Brazil, in order to understand the processes influencing air quality and identify potential sources of atmospheric pollution. To ensure reliable determination of ion concentrations, the extraction method was optimized using a 2³ full factorial design, in which the effects of sample mass, extraction time, water volume, and their interactions were evaluated. The results showed that extraction time and sample mass had the most significant effects on ion extraction. The accuracy of the analytical method was evaluated using a certified reference material of urban particulate matter (NIST SRM 1648a), yielding agreement values ranging from 83.6% to 107.0%. Precision was expressed as relative standard deviation (RSD%), with values below 10%. The analytical method showed no lack of fit (ANOVA, p = 0.275) and exhibited a strong correlation between experimental and predicted values (r = 0.97). The method was considered green, with a sustainability score of 0.81 calculated using the Analytical GREEnness Metric (AGREE) software. The ionic composition was dominated by Na⁺, SO₄²⁻, Ca²⁺, and NO₃⁻, suggesting contributions from marine aerosols, secondary aerosol formation, and soil particle resuspension. The maximum daily concentration (53.87 μg m⁻³) and annual mean concentration (6.68 μg m⁻³) fully complied with the Intermediate Standard 2 (IS-2) limits established by CONAMA Resolution No. 506/2024. The enrichment factor (EF) indicated a marine contribution for Mg²⁺ (EF = 0.023), a crustal/construction-related origin for Ca²⁺ (EF = 28.64), and secondary and anthropogenic contributions for SO₄²⁻ (EF = 4.05) and K⁺ (EF = 2.14). The low EF value for Cl⁻ (EF = 0.13), together with its significant negative correlation with NO₃⁻ (r = −0.58), indicated the occurrence of chlorine depletion through ionic substitution in the particulate phase. Meteorological analysis showed that the rainy season favored particle removal through wet deposition, whereas the dry season and the influence of trade winds enhanced atmospheric dispersion and soil dust resuspension. Principal Component Analysis (PCA) explained 75.8% of the total cumulative variance through four components, confirming contributions from marine aerosols, mineral dust, vehicular traffic, and secondary atmospheric reactions. Overall, the results demonstrate the mixed and multifactorial nature of atmospheric pollution in Aracaju, providing essential scientific and methodological support for air quality management.