Andrea D. A. Castanho

Wintertime and summertime São Paulo aerosol source apportionment study

A detailed aerosol source apportionment study was performed with two sampling campaigns, during wintertime and summertime in the heavily polluted metropolitan area of S* ao Paulo, Brazil. In addition to 12 h fine and coarse mode filter sampling, several real time aerosol and trace gas monitors were used. PM10 was sampled using stacked filter units that collects fine (do2.5mm) and coarse (2.5odo10mm) particulate matter, providing mass, black carbon (BC) and elemental concentration for each aerosol mode. The concentration of about 20 elements was determined using the particle induce X-ray emission technique. Real time aerosol monitors provided PM10 aerosolmass (TEOM), organic and elemental carbon (Carbon Monitor 5400, R&P) and BC concentration (Aethalometer). A complex system of sources and meteorological conditions modulates the heavy air pollution of the urban area of S* ao Paulo. The boundary layer height and the primary emissions by motor vehicles controls the strong pattern of diurnal cycles obtained for PM10, BC, CO, NOx, and SO2. Absolute principal factor analysis results showed a very similar source pattern between winter and summer field campaigns, despite the different locations of the sampling sites of both campaigns, pointing that there are no significant change in the main air pollution sources. The source identified as motor vehicle represented 28% and 24% of the PM2.5 for winter and summer, respectively. Resuspended soil dust accounted for 25% and 30%. The oil combustion source represented 18% and 21%. Sulfates accounts for 23% and 17% and finally industrial emissions contributed with 5% and 6% of PM2.5, for winter and summer, respectively. The resuspended soil dust accounted for a large fraction (75–78%) of the coarse mode aerosol mass. Certainly automobile traffic and soil dust are the main air pollution sources in S* Paulo. The sampling and analytical procedures applied in this study showed that it is possible to perform a quantitative aerosol source apportionment in a complex urban area such as S* ao Paulo. r 2001

Large‐scale aerosol source apportionment in Amazonia

Aerosol particles were collected aboard two Brazilian Bandeirante EMB 110 planes, and the University of Washington Convair C-131A aircraft during the Smoke, Clouds, and Radiation-Brazil (SCAR-B) field project in the Amazon Basin in August and September 1995. Aerosols were collected on Nuclepore and Teflon filters. Aerosol size distribution was measured with a MOUDI cascade impactor. Sampling was performed mostly over areas heavily influenced by biomass burning smoke. Particle-induced X ray emission (PIXE) was used to measure concentrations of up to 20 elements (Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr, and Pb). Black carbon (BC) and gravimetric mass analysis were also performed. Instrumental neutron activation analysis (INAA) determined the concentrations of about 15 elements on the Teflon filters. Electron probe X ray microanalysis (EPMA) was used to analyze individual aerosol particles. The average aerosol mass concentration was 105 μg m−3, with a maximum of 297 μg m−3. Black carbon (BC) averaged 5.49 μg m−3, or 1–7% of the aerosol mass load. Five aerosol components were revealed by absolute principal factor analysis: (1) a biomass burning component (responsible for 54% of the aerosol mass and associated with BC, K, Cl, Zn, I, S, Br, Rb, aerosol mass concentration, and other elements); (2) a soil dust aerosol component (15.6% of the aerosol mass); (3) a natural biogenic component (18.7% of the aerosol mass and associated with P, K, S, Ca, Sr, Mg, Mn, Cu and Zn); (4) a second soil dust (5.7% of the aerosol mass and enriched in Si, Ti, and Fe); and (5) a NaCl aerosol component (5.9% of the aerosol mass with Na, Cl, Br, and iodine). Electron microscopy analysis of individual aerosol particles confirmed these five aerosol types. Organic material dominated the aerosol mass and the number concentration of airborne particles. Aerosol size distributions show that the fine mode accounts for 78% of the aerosol mass, centered at 0.33 μm aerodynamic diameter. The coarse mode accounts for 22% of the mass, centered at about 3.2 μm. Black carbon size distributions show a consistent picture, with a mass median diameter centered at about 0.175-0.33 μm aerodynamic diameter. This study suggests that for modeling the optical properties of aerosol in the Amazon Basin, it is essential to use a model that includes the optical and physical properties of at least two aerosol components other than the biomass burning aerosol, namely, natural biogenic aerosol and soil dust.

Spectral absorption properties of aerosol particles from 350-2500nm

forcing of non-absorbing aerosols of about –1.3 W/m 2 and theforcingduetoblackcarbonof+0.8W/m 2 .Theabsorption properties of aerosol particles are still one of the largest uncertainties in estimating aerosol forcing of the climate. Global measurements of BC are not available and are badly needed. In situ aerosol absorption measurements are often inaccurate,andusually cover anarrow spectral range missing significant absorption features. This work presents spectral measurements of aerosol absorption efficiency in a broad spectral range (350–2500 nm) highlighting some characteristics of BC and other aerosol absorbers. We also discuss implications of these results to atmospheric studies. BC is the main absorbing material present in atmospheric aerosols, but it is not the only one. Soil dust absorbs light in the UV and visible, some organic materials absorb in the UV,

Tropospheric aerosol observations in São Paulo, Brazil using a compact lidar system

A backscattering light detection and ranging (lidar) system, the first of this kind in the country, has been set up in a suburban area in the city of São Paulo, Brazil (23°33′ S, 46°44′ W) to provide the vertical profile of the aerosol backscatter and extinction coefficients at 532 nm and up to 4–5 km height above sea level (asl). The measurements have been carried out during the second half of the so‐called Brazilian dry season, September and October in the year of 2001. When possible, the lidar measurements were complemented with aerosol optical thickness measurements obtained by a CIMEL Sun‐tracking photometer in the visible spectral region, not only to validate the lidar data, but also to provide an input value of the so‐called extinction‐to‐backscatter ratio (lidar ratio). The lidar data were also used to retrieve the Planetary Boundary Layer (PBL) height and low troposphere structural features over the city of São Paulo. Three‐dimensional air mass back trajectory analysis was also conducted to determine the source regions of aerosols observed during this study. These first lidar measurements over the city of São Paulo during the second half of the dry season showed a significant variability of the aerosol optical thickness (AOT) in the lower troposphere (0.5–5 km) at 532 nm. It was also found that the aerosol load is maximized in the 1–3 km height region and this load represents about 20–25% of the lower tropospheric aerosol.

Chemical Characterization of Aerosols on the East Coast of the United States Using Aircraft and Ground-Based Stations during the CLAMS Experiment

Abstract The Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) experiment was carried out off the central East Coast of the United States in July 2001. During CLAMS, aerosol particle mass was measured at two ground stations and on the University of Washington’s Convair 580 research aircraft. Physical and chemical characteristics of the aerosols were identified and quantified. Three main aerosol regimes were identified in the region and are discussed in this work: local pollution/sea salt background, long-range transported dust, and long-range transported pollution. The major component measured in the fine mode of the aerosol on the ground at Wallops Island, Virginia, was sulfate, estimated as NH4HSO4, which accounted for 55% ± 9% on average of the fine particle mass (FPM) during the experiment period. Black carbon concentrations accounted for 3% ± 1% of FPM; soil dust was also present, representing on average 6% ± 8% of FPM. The difference between the sum of the masses of the measured...

Analysis of atmospheric aerosols by PIXE: the importance of real time and complementary measurements

Abstract Particle-Induced X-ray Emission (PIXE) has been used for more than 30 yr in many urban and background air pollution studies. The technique has certainly contributed to the understanding of source-receptor relationship for aerosol particles as well as to aerosol physics and chemistry. In the last few years, where aerosol issues were strongly linked to global climate change through the relationship between aerosol and atmospheric radiation points to new challenges in atmospheric sciences, where PIXE could play an important role. Also the recognition for the inter-relationship between aerosol and liquid and gas phases in the atmosphere makes important to integrate PIXE aerosol analysis with other complementary measurements. The use of Nephelometers and Aethalometers to measure scattering and absorption of radiation by aerosol particles can be done in parallel with particle filter collection for PIXE analysis. Parallel measurements of trace gases using traditional monitors as well as with new techniques such as Differential Optical Absorption Spectroscopy (DOAS) that can provide concentration of O3, SO2, NO3, NO2, HCHO, HNO3, Benzene, Toluene, and Xylene, is also important for both urban and remote aerosol studies. They provide information that allows a much richer interpretation of PIXE data. Recently developed instruments that provide real time aerosol data such as the Tapered Element Oscillating Microbalance (TEOM) PM10 monitor and automatic real time organic and elemental carbon analyzers provide extremely useful data to complement PIXE aerosol analysis. The concentrations of trace elements measured by PIXE comprise only 10–30% of the aerosol mass, leaving the organic aerosol characterization and measurement with an important role. The aerosol source apportionment provided by PIXE analysis can be extended with other aerosol measurements such as scattering and absorption, estimating for example, the radiative impact of each discriminated aerosol source. The aerosol bulk PIXE measurements can be complemented with soluble concentrations provided by Ion Chromatography (IC) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Recent developments in remote sensing techniques and products also enhance significantly regional aerosol studies. Three-dimensional air mass trajectories should be integrated in aerosol studies for urban and remote areas. The applications of these techniques to study urban aerosols from Sao Paulo and Santiago de Chile have broadened extensively the scientific scope of these studies.

A Study of the Spatial Distribution of Aerosol Optical Thickness in Rio de Janeiro

The Rio de Janeiro Metropolitan Region (RJMR) has the second largest concentration of people, vehicles, industries and other air pollutant sources of Brazil, suffering from chronic air pollution problems. A high resolution (1×1 km) spatial distribution of aerosols over the RJMR was obtained based on reflectance measured by MODIS (Moderate Resolution Spectrometer) sensors, on board of EOS‐Terra platform, operated by NASA/GSFC. Aerosol optical thicknesses were retrieved from these measurements using the software SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer Model) and an algorithm developed in a previous study.