The NH₄⁺‐NO₃⁻‐Cl⁻‐SO₄²⁻‐H₂O aerosol system and its gas phase precursors at a pasture site in the Amazon Basin: How relevant are mineral cations and soluble organic acids?

Abstract

[1] Real-time measurements of ammonia, nitric acid, hydrochloric acid, sulfur dioxide and the water-soluble inorganic aerosol species, ammonium, nitrate, chloride, and sulfate were performed at a pasture site in the Amazon Basin (Rondônia, Brazil). The measurements were made during the late dry season (biomass burning), the transition period, and the onset of the wet season (clean conditions) using a wet-annular denuder (WAD) in combination with a Steam-Jet Aerosol Collector (SJAC). Measurements were conducted from 12 September to 14 November 2002 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). Real-time data were combined with measurements of sodium, potassium, calcium, magnesium, and low-molecular weight (LMW) polar organic acids determined on 12-, 24-, and 48-hours integrated filter samples. The contribution of inorganic species to the fine particulate mass (D p 2.5 mm) was frequently below 20% by mass, indicating the preponderance of organic matter. The measured concentration products of NH 3 Â HNO 3 and NH 3 Â HCl persistently remained below the theoretical equilibrium dissociation constants of the NH 3 /HNO 3 /NH 4 NO 3 and NH 3 /HCl/NH 4 Cl systems during daytime (RH < 90%). The application of four thermodynamic equilibrium models (EQMs) indicates that the fine mode aerosol anions NO 3 À , Cl À , and SO 4 2À were balanced predominantly by mineral cations (particularly pyrogenic K + ) during daytime. At nighttime (RH > 90%) fine-mode NH 4 NO 3 and NH 4 Cl are predicted to be formed in the aqueous aerosol phase. Probably, Cl À was driven out of the aerosol phase largely by reaction of pyrogenic KCl with HNO 3 and H 2 SO 4 . As shown by an updated version of the equilibrium simplified aerosol model (EQSAM2), which incorporates mineral aerosol species and lumped LMW polar organic acids, daytime aerosol NH 4 + was mainly balanced by organic compounds. -H 2 O aerosol system and its gas phase precursors at a pasture site in the Amazon Basin: How relevant are mineral cations and soluble organic acids?,

Importance of mineral cations and organics in gas-aerosol partitioning of reactive nitrogen compounds: case study based on MINOS results

“…Our main conclusion is that it is essential to consistently include inorganic and (lumped) organic acids together with (soluble) mineral cations and ammonium in order to correctly predict the observed aerosol composition and the associated aerosol precursor gas concentrations. This result is consistent with the findings of Trebs et al (2005) …”

“…Similar to the study by Trebs et al (2005) equivalent moles were calculated as a first approximation assuming that mono-, di-, and tricarboxylic acids form e.g. the respective mono-, di-, and tri-ammonium salts.…”

A systematic review of the physical and chemical characteristics of pollutants from biomass burning and combustion of fossil fuels and health effects in Brazil

“…Yamasoe et al 75 investigated the chemical composition of PM 2.5 relating to the burning phases or stages and detected that potassium (K), chlorine (Cl) and sulphate (SO 4 2-) were the dominant chemical elements. Ammonia (NH 3 ) was also found in fractions of PM 2.5 during the dry season in the Brazilian Amazon 77,81 . These same characteristics were observed in the Southeast Region of Brazil in areas of sugarcane burning 52,80,84 .…”

“…The Amazon biome was the most studied area in articles on the physical and chemical characteristics of PM 77,82 . Studies in this region show that PM 10 and PM 2.5 were predominantly composed of organic compounds 75,78,81,86 , and in the case of PM 2.5 these substances made up 70% to 92% of its composition 75 . Among the organic elements, Black Carbon (BC) made up between 5% and 15% of PM 2.5 , with values ranging from 5.5µg/m 3 to 16µg/m 3 during peak burning 76,77 .…”

Assessing the role of ammonia in sulfur transformation and deposition in China

“…In China, coal accounts for about 70% of the energy production (CESY, 2005), which leads to large emissions of SO 2 (SEPA, 2004). Part of SO 2 can be converted to SO 4 2− through gas phase or multiphase reactions in the atmosphere, and results in SO 4 2− as the predominant anion in aerosol and precipitation in China (Aas et al, 2007).…”