Submissões Recentes
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Sedimentation and growth of volcanic aerosols within the Hunga plume
2025 - SOUZA, GIOVANNI; VERNIER, JEAN PAUL; QUINTÃO, DEMILSON; BIAZON, BRUNO; LOPES, FABIO; RICARDO, JHONATHA; PANDIT, AMIT K.; CHANDRA, RUBEL das; LIU, HONGYU; KNEPP, TRAVIS N. N.; VERNIER, HAZEL; LANDULFO, EDUARDO
The Hunga eruption was an unprecedented event which influenced stratospheric aerosols. This study analyzes the unique dynamics of aerosol plumes using balloon measurements from the Brazil Volcano campaign in Bauru (22.36° S, 49.03 °W) and the Stratospheric Aerosol and Gas Experiment III/ISS along with theoretical calculations. They revealed consistent trends in particle sedimentation and spreading. Temporal analysis showed that smaller particles (<225 nm) experienced slower sedimentation rates, with a larger influence by the Brewer-Dobson circulation. Larger particles (>400 nm) exhibited faster sedimentation, descending approximately 3 km by the end of 2022. The descent of the plume into the Upper Troposphere and Lower Stratosphere (UTLS) by February-March 2023 is accompanied by an increase of effective radius from 400 nm to 450 nm due to hygroscopic growth from moist convection. These unique observations suggest that Hunga could have impacted cirrus cloud formation by re-entering the UTLS.
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Recognizing microplastic deposits on sandy beaches by altimetric positioning, Μ-Raman spectroscopy, and multivariate statistical models
2024 - FERREIRA, ANDERSON S.; WETTER, NIKLAUS U.; RIBEIRO, MARIA C. H.; ESTEVES, LUCIANA S.; DIAS, ANTÓNIO G.; GROHMANN, CARLOS H.; KUZNETSOVA, MARIA; OLIVEIRA, REGINA C. de; FREITAS, ANDERSON Z. de; SIEGLE, EDUARDO
This study examines microplastic (MP) pollution along São Paulo State's coast, southeastern Brazil, using geodetic surveys, beach morphometric analyses, sediment collection, µ-RAMAN spectrometry, and multivariate statistical models. The coastline was divided into six compartments (C1 to C6) for sampling. Higher MP concentrations were found in C3 and C2, influenced by industrial and port activities. MP types, including pellets, fragments, and fibers, showed distinct distribution patterns based on their sources and properties. Fragments and foams were most common, constituting 42% and 35% of the 1,026 MPs found. Statistical tests linked MP types to beach morphometric characteristics, with higher elevations correlating with higher MP concentrations, especially pellets and foams. Beaches with intermediate profiles and those facing south accumulated more MPs. The study highlights the complexity of MP dynamics in coastal environments and the need for developing specific monitoring and environmental remediation strategies, supporting Sustainable Development Goal 14 (Life Below Water).
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Development of a fast simulator for GEM-based neutron detectors
2022 - SANTOS, RENAN F. dos; MUNHOZ, MARCELO G.; MORALLES, MAURICIO; SERRA FILHO, LUCAS de A.; BREGANT, MARCO; SOUZA, FERNANDO A. de
Gas Electron Multiplier (GEM)-based detectors using a layer of 10B as a neutron converter is becoming popular for thermal neutron detection. A common strategy to simulate this kind of detector is based on two frameworks: Geant4 and Garfield++. The first one provides the simulation of the nuclear interaction between neutrons and the 10B layer, while the second allows the simulation of the interaction of the reaction products with the detector gas leading to the ionization and excitation of the gas molecules. Given the high ionizing power of these nuclear reaction products, a full simulation is very time consuming and must be optimized to become viable. In this work, we present a strategy to develop a fast simulator based on these two frameworks that will allow us to generate enough data for a proper evaluation of the expected performance and optimization of this kind of detector. We will show the first results obtained with this tool concentrating on its validation and performance.
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Increase in the platinum group elements content in road dust from São Paulo city, Brazil, due to exhaust emissions from vehicle catalytic converter, over a 10-year period
2023 - HORTELLANI, MARCOS; SARKIS, JORGE J.E.S.
Platinum Group Elements (PGEs) are widely used as catalysts in vehicle emission reduction, and road dust is a primary receptor for PGE releases. However, the determination of PGEs in these samples by ICP-MS is affected by matrix interferences, and measurement and sampling uncertainties are often overlooked. This study presents the first PGEs measurements in road dust samples from São Paulo city avenues, including matrix separation and estimation of measurement uncertainty includes analytical and sampling uncertainties. Measurement uncertainties for PGEs ranged from 12.3% to 19.5%, and analytical uncertainty ranged from 2.25% to 5.64%. PGEs concentrations: Pt (2.6 - 227 ng g-1), Pd (16.3 - 1875 ng g-1), Rh (2.02 - 257 ng g-1). Three methodologies were applied to evaluate the PGEs and other metals contamination in 54 road dust samples (< 100 µm fraction) collected in 2008, 2016 and 2018 at 18 sites with high (17 sites) and low (1 site) volumes of traffic. Metal pollution index (MPI), enrichment factor (EF) and statistical analyses. These evaluations suggested that PGEs and Mo contamination were originated from automobile exhaust emissions. Cu and Zn contamination seemed to have been caused by tires and brakes vehicular sources (non-exhaust emissions), but Ni and Pb contamination seemed from non-vehicular sources. Only rare earth elements are mostly associated with crustal source. The changes in PGE ratios stemmed from decreased Pt and increased Pd concentrations. A considerable portion of these metals in road dust is bioaccessible and poses health risks to the population near high-traffic density avenues, through ingestion, dermal contact, and inhalation pathways.