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 (dp 10 nm) every minute. A 55-m tower in a primary forest in Rond¿nia 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-3, black carbon averaged 250 ng m-3, and mean fine-mode mass concentration was 2.9 ¿g m-3. 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 ¿g m-3 and particle number concentrations of more than 40,000 cm-3 were observed, while the CO peaked at 8 ppm and NO2 reached 16 ppb. High correlation was observed between BCE, NO2, 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.