Acevedo, Alessandro Araújo 3, Paulo Artaxo 4, Cybelli G. HONO exhibited a characteristic diel cycle with high mixing ratios at nighttime and was not completely depleted by photolysis during daylight hours.read more read less This is attributed to strong relative humidity and temperature variations between day and night as well as to changing photochemistry and stability conditions of the planetary boundary layer. Additionally, N-containing gas and aerosol species featured pronounced diel variations. During the wet season, mixing ratios decreased by nearly a factor of 3 for all compounds compared to those observed when intensive biomass burning took place. Accordingly, mixing ratios of NH4+ exceeded those of other inorganic aerosol contributors by a factor of 4 to 10. Mixing ratios of acidic trace gases remained below 1ppb throughout the measurement period, while NH3 levels were an order of magnitude higher. Median LOD values (3σ-definition) were ≤0.015ppb for acidic trace gases and aerosol anions and ≤0.118ppb for NH3 and aerosol NH4+. The limit of detection (LOD) was determined for each single data point measured during the field experiment. Overall measurement uncertainties of the ambient mixing ratios usually remained below 15%. A detailed description and verification of the inlet system for simultaneous sampling of soluble gases and aerosol compounds is presented. Measurements were made continuously using a wet-annular denuder (WAD) in combination with a Steam-Jet Aerosol Collector (SJAC) followed by suitable on-line analysis. Sampling was performed from 12 September to 14 November 2002, extending from the dry season (extensive biomass burning activity), through the transition period to the wet season (background conditions). This study was conducted within the framework of LBA-SMOCC (Large Scale Biosphere Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate: Aerosols from Biomass Burning Perturb Global and Regional Climate). We measured the mixing ratios of ammonia (NH3), nitric acid (HNO3), nitrous acid (HONO), hydrochloric acid (HCl), sulfur dioxide (SO2 and the corresponding water-soluble inorganic aerosol species, ammonium (NH4+), nitrate (NO3-), nitrite (NO2-), chloride (Cl- and sulfate (SO42-), and their diel and seasonal variations at a pasture site in the Amazon Basin (Rondonia, Brazil). This review is intended to facilitate an understanding of the current state of knowledge on Amazonian aerosol particles specifically and tropical continental aerosol particles in general and thereby to enhance future research in this area.read more read lessĪbstract. The review presents Amazonian aerosol particles in the context of natural compared to anthropogenic sources as well as variability with season and meteorology. These properties include number and mass concentrations and distributions, chemical composition, hygroscopicity, and cloud nucleation ability. It begins with a discussion of the primary and secondary sources relevant to the Amazonian particle burden, followed by a presentation of the particle properties that characterize the mixed populations present over the Amazon Basin at different times and places. The review is organized to follow the life cycle of Amazonian aerosol particles. Abstract: This review provides a comprehensive account of what is known presently about Amazonian aerosol particles and concludes by formulating outlook and priorities for further research.
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