Isotopic Signatures of Neodymium and Strontium in PM10 from the Distrito Federal, Central Brazil

Changes in urban air quality are widely documented, with atmospheric particulate matter (PM₁₀) being a critical parameter due to its effects on health and ecosystems. Strontium (Sr) and Neodymium (Nd) isotopes serve as tracers to identify aerosol provenance and transport pathways. Despite advances globally, such isotopic data remain scarce in Brazil. This study aims to determine Nd and Sr isotopic compositions in PM₁₀ collected in the Distrito Federal to identify emission sources, providing the first isotopic data for this region. PM₁₀ samples were collected using High-Vol samplers between January 2018 and September 2019 at two sites: Fercal (cement industry area; n = 11) and Rodoviária (bus terminal; n = 9). Twenty samples with the highest PM₁₀ masses (80.71 ± 28.88 μg/m³) were selected. Analytical procedures followed Goia and Pimentel (2015). Isotopic ratios were measured via MC-ICP-MS (Neptune) at IG/UnB, with accuracy confirmed by international standards (NBS1, BHVO-2, and SRM 1648a). Average PM₁₀ concentrations peaked during the dry season at both sites—Fercal (90.98 ± 19.60 µg/m³) and Rodoviária (106.88 ± 39.14 µg/m³)—exceeding the WHO daily limit of 50 µg/m³.

The εNd(0) values showed no significant variation between sites (Fercal: –9.68 ± 2.12, n = 7; Rodoviária: –9.45 ± 1.12, n = 8) but individual ranges indicate distinct PM₁₀ sources. εNd(0) values from –13 to –11 at Fercal are consistent with local lithology (Bambuí Group), whereas values from -10 to -8 at both sites reflect a mixture of vehicular emissions, cement industry inputs, and potentially long-range transport of Amazonian aerosols. The ⁸⁷Sr/⁸⁶Sr range (0.708828–0.721402, n = 6) supports these mixed-source interpretations.