M. A. Yamasoe

Chemical composition of aerosol particles from direct emissions of vegetation fires in the Amazon Basin: water-soluble species and trace elements

Biomass burning is an important global source of aerosol particles to the atmosphere. Aerosol particles were collected in plumes of tropical forest and cerrado biomass burning fires in the Amazon Basin during August–September, 1992. Fine (dp<2 μm, where dp is the aerodynamic diameter of the particle) and coarse (2 μm<dp<10 μm) aerosol particles were collected using stacked filter units. Up to 19 trace elements were determined using particle-induced X-ray emission analysis. Ion chromatography was used to determine up to 11 water-soluble ion components. The dominant species were black carbon, K+, Cl−, and SO42−. Organic matter represents in average 70–92% of the fine mode particle mass. The composition of the emitted particles in cerrado fires presents a well-defined pattern related to both the combustion phase and cerrado categories, which is not observed in the case of forest fires. Higher concentrations relative to the fine particulate mass were observed during the flaming emissions compared to the smoldering ones, for almost all experiments. Global emission flux estimates showed that biomass burning could be an important source of heavy metals and black carbon to the atmosphere. Estimates showed that savanna and tropical forest biomass burning could be responsible for the emission of about 1 Gg yr−1 of copper, 3 Gg yr−1 of zinc and 2.2 Tg yr−1 of black carbon to the atmosphere. In average, these values correspond to 2, 3 and 12%, respectively, of the global budget of these species.

High aerosol optical depth biomass burning events: A comparison of optical properties for different source regions

Received 29 May 2003; revised 8 September 2003; accepted 17 September 2003; published 21 October 2003. [1] The optical properties of aerosols such as smoke from biomass burning vary due to aging processes and these particles reach larger sizes at high concentrations. We compare the spectra of aerosol optical depth (ta), columnintegrated volume size distributions, refractive indices, and single scattering albedo retrieved from AERONET observations for four selected events of very high smoke optical depth (ta � 2 at 500 nm). Two case studies are from tropical biomass burning regions (Brazil and Zambia) and two are cases of boreal forest and peat fire smoke transported long distances to sites in the US and Moldova. Smoke properties for these extreme events can be significantly different from those reported in more typical plumes. In particular, large differences in smoke fine mode particle radius (� 0.17 to 0.25 mm) and single scattering albedo (� 0.88 to 0.99 at 440 nm) were observed as a result of differences in fuels burned, combustion phase, and aging. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation. Citation: Eck, T. F., B. N. Holben, J. S. Reid, N. T. O’Neill, J. S. Schafer, O. Dubovik, A. Smirnov, M. A. Yamasoe, and P. Artaxo, High aerosol optical depth biomass burning events: A comparison of optical properties for different source regions, Geophys. Res. Lett., 30(20), 2035, doi:10.1029/ 2003GL017861, 2003.

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.

Fine mode aerosol composition at three long-term atmospheric monitoring sites in the Amazon Basin

The Amazon Basin tropical rain forest is a key region to study processes that are changing the composition of the global atmosphere, including the large amount of fine mode aerosol particles emitted during biomass burning that might influence the global atmosphere. Three background monitoring stations, Alta Floresta, Cuiaba, and Serra do Navio, are operating continuously measuring aerosol composition. Fine (dp < 2.0 μm) and coarse (2.0 < dp < 10 μm) mode aerosol particles were collected using stacked filter units. Particle-induced X-ray emission was used to measure concentrations of up to 20 elements in the fine mode: Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr, and Pb. Soot carbon and gravimetric mass analysis were also performed. Absolute Principal Factor Analysis (APFA) has derived absolute elemental source profiles. APFA showed four aerosol particle components: soil dust (Al, Ca, Ti, Mn, Fe), biomass burning (soot, fine mode mass concentration, K, Cl), natural primary biogenic particles with gas-to-particle component (K, S, Ca, Mn, Zn), and marine aerosol (Cl). Biogenic and biomass burning aerosol particles dominate the fine mode mass concentration, with the presence of K, P, S, Cl, Zn, Br, and fine mode mass concentration (FPM). At the Alta Floresta and Cuiaba sites, during the dry season, a strong component of biomass burning is observed. Inhalable particulate matter (dp < 10 μm) mass concentration up to 700 μg/m3 was measured. Fine particle mass concentration alone can go as high as 400 μg/m3 for large regions. The fine mode biogenic and biomass burning components show remarkable similarities in the elemental composition, even though the sampling sites are more than 3000 km apart. Fine mode sulfur concentration is entirely associated with the primary biogenic aerosol particles, with gas-to-particle conversion and the biomass burning component. Large amounts of essential plant nutrients like P are mobilized into the atmosphere and possibly lost from the Amazon Basin ecosystem by long-range transport.

Single-scattering albedo of smoke retrieved from the sky radiance and solar transmittance measured from ground

A method of aerosol single-scattering albedo retrieval from diffuse radiance measured in the solar almucantar and direct solar measurements is proposed. The aerosol scattering optical thickness is derived from the diffuse radiance by applying a radiative transfer model driven by aerosol microstructure parameters and Mie theory. To improve the accuracy of the scattering optical thickness, the inversion results are acceptable only if the radiance is measured across the total almucantar and is accurately fitted by a theoretical model. The aerosol is assumed as an external mixture of purely scattering particles and soot particles, with the soot approximated as a pure absorber. The criterion for the acceptance of fit is determined from the analysis of the effects of random and systematic errors on the single-scattering albedo retrieval. The method was applied to measurements conducted during the Smoke, Clouds, and Radiation - Brazil (SCAR-B) campaign in August and September 1995. Aerosol radiance data were extensively collected by the Aerosol Robotic Network (AERONET) of ground-based Sun/sky radiometers. The analysis focuses on the studies of the time variability of the biomass burning aerosol in the local Cuiaba area, supplemented by measurements collected in Cuiaba in 1993-1994. The results show reasonable ranges of the aerosol single-scattering albedo variability (for example, single-scattering albedo averages 0.87 ±0.08 at 670 nm). The spectral dependence of the single-scattering albedo has both tendencies: decreasing and increasing with wavelength. The potential reasons causing different spectral behavior are analyzed theoretically.

Long-term monitoring of atmospheric aerosols in the Amazon Basin' Source identification and apportionment

Continuous sampling of atmospheric aerosols was carried out at two different sites in the Amazon Basin: Cuiabfi (16oS, 56oW), since July 1990, and Alta Floresta (09oS, 56oW), since August 1992. Aerosols were collected on polycarbonate filters mounted in stacked filter units (SFU). Particle-induced X ray emission (PIXE) was used to measure concentrations of up to 26 elements (Mg, A1, Si, P, S, C1, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Zr, Au, and Pb). Black carbon (BC) and gravimetric mass analyses were also performed. Inhalable particle ground concentrations showed a marked seasonality, with maxima of more than 100/zg m -3 in the dry season. The high aerosol optical thickness (AOT) values in this period (up to 4.0 at ;t = 0.440/zm) indicate that the whole air column has a significant aerosol load. Three main types of aerosol sources were identified: biomass burning, natural biogenic emissions, and soil dust resuspension. During the dry season the fine mode aerosol originated predominantly from biomass burning emissions (they were responsible for about 73% of fine aerosol mass), while the coarse mode was dominated by soil dust particles (50 to 60% of the aerosol mass). Crustal elements exhibited a unimodal coarse mode size distribution, while the pyrogenic elements showed a clear submicrometer mode. Black carbon had a submicrometer mode centered at 0.175/zm. During the wet season, biogenic aerosols were the dominant particle type and also the main source of atmospheric P in the region.

Atmospheric Mercury and Trace Elements in the Region of Alta Floresta in the Amazon Basin

In the early 1980’s the Amazon region in the North of Brazil was the scene of the most intense gold rush in the history of Brazil. Metallic mercury (Hg) in gold mining activities is used to amalgamate particulate gold. The other sources of Hg emissions in Amazonian are tailing deposits and biomass burning of tropical forests and savannas. Total Hg concentrations in the urban area of Alta Floresta ranged from 20 to 5800 ng/m3. Indoor total Hg concentration in gold shops ranged from 250 to 40600 ng/m3. Particulate Hg accounts for 5 to 20% of total Hg in Alta Floresta. Through Factor and cluster analysis it was obtained a pattern of relationships between total Hg, fine and coarse mode particulate Hg, Pt, Pb, Ag and several other trace elements associated with the amalgamation process. A clear correlation was also observed with the fine mode biomass burning aerosol and coarse mode soil dust.

Retrieval of the real part of the refractive index of smoke particles from Sun/sky measurements during SCAR‐B

A method is used to retrieve the real part of the refractive index of ambient aerosol particles in the entire vertical column using ground-based measurements of the angular dependence of the spectral sky radiance. The method is applied to smoke aerosol particles using spectral Sun/sky data measured by the AERONET (Aerosol Robotic Network) radiometers in Cuiaba, Brazil, during the SCAR-B (Smoke, Clouds, and Radiation-Brazil) experiment in 1995. The refractive index is retrieved from comparison between measurements taken in the solar almucantar and calculations using Mie theory. First the aerosol size distribution is derived from sky radiance at scattering angles less then 40°, then the refractive index is derived from sky radiances for angles of 20°–100°. Simulations and sensitivity studies are presented showing that the expected error is ±0.03, Application of the method to the Cuiaba region, which is dominated by smoke from cerrado vegetation burning, resulted in a mean value for the real part of the index of refraction of 1.53±0.04, 1.55±0.04, 1.59±0.02, and 1.58±0.01, respectively, for wavelengths of 438, 670, 870, and 1020 nm. Though we do not have independent verification of the results, we tested the effect of water vapor on the refractive index. The low humidification factors measured in Brazil and the lack of high relative humidities suggested a small effect of water vapor. In fact, as expected, a nonsignificant correlation was observed between the retrieved values of refractive index and total precipitable water vapor. Application to aerosol in the eastern United States (not reported here), with high humidity and high humidification factors, did show a strong reduction of the refractive index with increase of the total precipitable water vapor, thus generating confidence in the methodology.

Correlation between smoke and tropospheric ozone concentration in Cuiabá during Smoke, Clouds, and Radiation‐Brazil (SCAR‐B)

Ozone soundings launched from Cuiaba between August 16 and September 10, 1995, during the Smoke, Clouds, and Radiation-Brazil (SCAR-B) experiment show an enrichment of tropospheric ozone when compared with average wet season values and also present a great variability in concentrations depending on the dominant circulation pattern. Smoke tracers, such as aerosol optical thickness, measured from a Sun photometer installed at the Instituto Nacional de Pesquisas Espaciais-Cuiaba site, and black carbon ground measurements, also show an enhancement of smoke during the same period. Although there is a connection between the enrichment of the tropospheric ozone around Cuiaba during the dry season and smoke from biomass burning, the correlation between ozone and smoke indicates different behavior in different periods. Trajectory analyses suggest that the strong ozone peak measured in the period between August 26 and 29, 1995, may be associated not only with direct biomass-burning emissions but also with urban/industrial emissions from big cities on the coast of Brazil and recirculation of old smoke. This view is confirmed by measurements made from the Cloud Lidar System instrument aboard the ER-2 aircraft.

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...