Percorrer por autor "Silva, Alan Victor da"
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- First long-term air quality assessment in Luanda, Angola: Performance evaluation of a low-cost monitoring station against reference equipmentPublication . Silva, Alan Victor da; Furst, Leonardo; Cipoli, Yago A.; Soares, Marlene J.S.; Leitão, Anabela G.A.; Feliciano, Manuel; Alves, Célia A.Low-cost air quality monitoring stations (LCMS), which integrate sensors for gases and particulate matter (PM), offer an economical solution for expanding monitoring networks. However, their reliability requires validation, particularly in rapidly urbanising regions with limited infrastructure. This study presents the first long-term, continuous, multi-pollutant air quality assessment in Luanda, Angola - where no monitoring stations currently exist - by evaluating the performance of an LCMS against reference-grade equipment. Daily averages, correlation metrics (R-2, RMSE), and a hybrid Bland-Altman/regression analyses were used to evaluate the agreement. Results indicated strong correlation for CO (R-2 = 0.96; RMSE = 0.24 ppm) and good for NO2 (R-2 = 0.81; RMSE = 6.35 ppb), although limitations near detection limits were noted. Significant challenges were identified in O-3 measurements (R-2 = 0.77, RMSE = 7.13 ppb), primarily due to strong cross-sensitivity to high ambient NO2 levels and potential sensor ageing. For PM10 and PM2.5, although good linear correlations (R-2 similar to 0.82) were observed with reference methods, the LCMS exhibited considerable systematic bias (RMSE over 46 mu g/m(-3)) and consistently underestimate concentrations. The study also registered frequent and severe exceedances of WHO AQG and EU standards for PM10, PM2.5, and NO2, underscoring significant public health risks. Despite limitations, particularly for O-3 measurements and biases in PM data, the LCMS demonstrates potential as a cost-effective tool to complement reference networks, enhance spatial monitoring coverage, identify pollution hotspots, and support air quality management in resource-constrained settings, since continuous calibration and validation procedures are implemented to mitigate measurement uncertainties.
- PM10-bound elements in Luanda's urban atmosphere: Concentrations, sources, and their environmental and health impactsPublication . Alves, Célia A.; Campa, Ana Sanchez de la; Cipoli, Yago; Furst, Leonardo; Higawa, Gustavo; Leitão, Anabela; Silva, Alan Victor da; Feliciano, ManuelAn unprecedented study was carried out in the megacity of Luanda, Angola, involving daily sampling of particulate matter (PM10) from June to November 2023. The analysis was focused on the detection of 56 metal(loid)s and complemented by the application of several contamination and health risk indices. PM10 levels ranged from 23.6 to 108 μg/m3, averaging 59.3 μg/m3, exceeding WHO’s 24-h guideline on 83% of days. In addition to crustal elements, the most abundant constituents were Zn (159 ng/m3), Ba (43.2 ng/m3), Pb (17.8 ng/m3), Cu (10.5 ng/m3), Sr (7.0 ng/m3), Ni (4.5 ng/m3), Sb (3.7 ng/m3) and Cr (3.5 ng/m3). Mineral dust, primarily from unpaved roads and local soils, accounted for 31 wt% of PM10, while sea salt contributed 6%. Geochemical markers (e.g., Ce-La-V relationships) suggest that vanadium originates predominantly from upper crust weathering. Elemental ratios such as Fe/Cu, Cu/Sb, and Zn/Sb indicate significant contributions from traffic-related emissions (e.g., brake and tyre wear) and industrial sources. Sulphur, an important PM10 component, likely stems from fossil fuel combustion and petroleum refining. Luanda experiences severe air pollution, with high inputs from Sb, Cd, Zn, and other elements linked to traffic, industrial emissions, and biomass burning. The extremely high ecological risk (RI = 4360 ± 2440) highlights critical contamination, driven primarily by Cd and Sb, while the Nemerow risk index (1990 ± 1530) underscores urgent public health concerns. Non-cancer hazard indices (HI) exceeded safe thresholds for children (2.29) and adults (2.18), with Fe, Mn, Be, Pb, Ni, Co, and Sb identified as key contributors. Carcinogenic risks from PM10 inhalation (2.34 × 10 3 for children and 1.36 ×10 3 for adults) also exceeded acceptable levels, emphasising the need for targeted pollution mitigation strategies.