Physical and chemical properties of aerosols in the wet and dry seasons in Rondônia, Amazonia

Abstract

[1] As part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), a large study of aerosol and trace gas properties was conducted in Amazonia during the dry and wet seasons and for pasture and primary forest sites. Aerosol mass and elemental composition were measured on filters for both fine (d p < 2.0 mm) and coarse (2.0 < d p < 10 mm) modes using polycarbonate filters mounted in stacked filter units (SFU). Measurements with real-time aerosol and trace gas monitors were made, parallel to the collection of filter samples to obtain high time resolution (1-30 min). Black carbon equivalent (BCE) was determined with a multiwavelength Aethalometer as well as by reflectance in the fine-mode SFU samples. Elemental carbon as well as total and organic carbon was measured using an R&P 5400 real-time carbon monitor. PM 10 aerosol mass concentrations were determined with a Tapered Element Oscillating Monitor (TEOM) monitor every 5 min. CO, O 3 , NO, and NO 2 were analyzed with Thermo Environment monitors with trace level capabilities for NO x . A TSI 3010 particle counter measured the total particle number concentration (d p > 10 nm) every minute. A 55-m tower in a primary forest in Rondônia and a facility built on a pasture site were used to operate the instrumentation for 4 months in the wet season and 3 months in the dry season of 1999. Particle-Induced X-Ray Emission (PIXE) was used to measure the concentration of 22 trace elements for fine-and coarse-mode aerosol. During the wet season, very clean atmospheric conditions were observed at both sites. Particle concentration averaged 900 cm À3 , black carbon averaged 250 ng m À3 , and mean fine-mode mass concentration was 2.9 mg m À3 . In sharp contrast, very high concentrations were observed in the dry season for all the parameters at both sampling sites. Aerosol mass concentrations up to 250 mg m À3 and particle number concentrations of more than 40,000 cm À3 were observed, while the CO peaked at 8 ppm and NO 2 reached 16 ppb. High correlation was observed between BCE, NO 2 , CO, aerosol particle number, mass, aerosol optical thickness, and other properties linked to biomass-burning emissions. Relatively large concentrations of phosphorus in the coarse-mode particles were observed, especially at nighttime. The emission of biogenic particulate P could have an effect in the nutrient cycling of this essential and key nutrient, which is present almost exclusively in the form of aerosol particles. Phosphorus is exchanged in the aerosol phase and mostly for coarse-mode particles and during nighttime.

Elemental Mixing State of Aerosol Particles Collected in Central Amazonia during GoAmazon2014/15

“…Here, systematic error in the calculated mass fractions of specific particles can be introduced in particles where elements not considered represent a significant portion of that particle's mass (e.g., mineral dust and Si or Al). During the Amazonian dry season, Al and Si represent 0.3% and 0.4% of the average fine mode particle mass [48]. This mass fraction error becomes negligible, however, when the ensemble diversity values or mixing state index is considered due to the overwhelming mass of C, N, and O in each particle.…”

Fingerprinting the impacts of global change on tropical forests

“…A further increase in the extent and load of N deposition is expected in the future as biomass burning continues, and industrialization and more intensive farming spread further across the tropics. It is likely that deposition of other nutrients, notably P, may have also increased near biomass-burning sites (Artaxo et al 2002), but global-scale estimates of increases in P and other nutrient depositions are, to our knowledge, unavailable.…”

“…However, if N is not limiting, extra N inputs may lead to soil acidification, the depletion of base cations and the mobilizing of aluminium ions, the net effects of which may be a decrease in soil-nutrient availability and plant growth rates (Matson et al , 2002Martinelli et al 1999;Asner et al 2001). If P is limiting and P deposition increases (Artaxo et al 2002), then growth may increase. Likewise if other micro-nutrients increase and they are limiting, growth may increase.…”

Comparing parameterized versus measured microphysical properties of tropical convective cloud bases during the ACRIDICON–CHUVA campaign

“…2 (from . This region was chosen for documenting cloud microstructure and precipitation-forming processes during the dry season with high concentrations of CCN and to contrast these measurements with cleaner conditions that could be found within flight range, as documented previously (Andreae et al, 2004;Artaxo et al, 2002). Additionally, we made use of the fact that Manaus is located in the central Amazon (3.11 • S, 60.02 • W), and the aerosol perturbation from the Manaus urban plume may therefore increase CCN concentrations by 1 to 2 orders of magnitude above the pristine conditions in the background air (Kuhn et al, 2010).…”