Physical, chemical, and optical properties of regional hazes dominated by smoke in Brazil

Abstract

Abstract. Gas and particle measurements are described for optically thick regional hazes, dominated by aged smoke from biomass buming, in the cermdo and rain forested regions of Brazil. The hazes tended to be evenly mixed from the surface to the trade wind inversion at 34 km in altitude. The properties of aged gases and particles in the regional hazes were significantly different from those of young smoke (<4 min old). As the smoke aged, the total amount of carbon in non-methane hydrocarbon species (C<I 1) was depleted by about one third due to transformations into CO 2, CO, and reactive molecules, and removed by dry deposition and/or by conversion to particulate matter. As the smoke particles aged, their sizes increased significantly due to coagulation and mass growth by secondary species (e.g., ammonium, organic acids and sulfate). During aging, condensation and gas-to-particle conversion of inorganic and organic vapors increased the aerosol mass by -20-40%. One third to one half of this mass growth likely occurred in the first few hours of aging due to the condensation of large organic molecules. The remaining mass growth was probably associated with photochemical and cloud-processing mechanisms operating over several days. Changes in particle sizes and compositions during aging had a large impact on the optical properties of the aerosol. Over a 2 to 4 day period, the fine particle mass-scattering efficiency and single-scattering albedo increased by 1 m 2 g-I, and 4).06, respectively. Conversely, the Angstrom coefficient, backscatter ratio, and mass absorption efficiency decreased significantly with age.

Biomass burning emissions disturbances on the isoprene oxidation in a tropical forest

“…Our results showed higher values for O3 mixing ratios, ranging from 10 to 75 ppbv in FP and 20 to 70 ppbv in AP. Agreeing with SAMBBA results, Reid et al (1998) found O3 mixing ratios ranging from 60 to 100 ppbv during SCAR-B experiment in the 1995 dry season, and Kaufman et al (1992) found similar levels of O3 in a forest site in Amazonia during BASE A (Table 3). …”

Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols

“…In practice, a value of about 10 m 2 g −1 is typically used to derive BC e from absorption measurements. However, the range of values for α ATN reported in the literature is between about 1 to 30 m 2 g −1 (Liousse et al, 1993;Chylek et al, 1995;Liousse et al, 1995;Colbeck et al, 1997;Petzold et al, 1997;Martins et al, 1998a;Moosmüller et al, 1998;Reid et al, 1998a;Fuller et al, 1999;Kopp et al, 1999;Lavanchy et al, 1999;Dillner et al, 2001;Sharma et al, 2002;Lim et al, 2003;Schnaiter et al, 2003). This range is so large because, in addition to the inherent variability of α abs , α ATN is affected by experimental bias.…”

Chemical composition of boundary layer aerosol over the Atlantic Ocean and at an Antarctic site

“…Biomass burning is not the only source of oxalate but it is clearly the dominating one. In biomass burning aerosols concentrations may be in the order of several µg m −3 (e.g., Reid et al, 1998) whereas in clean marine aerosols concentrations are some ng m −3 . It is not clear whether they oxalate is emitted directly or produced photochemically in the atmosphere from gaseous precursors (Neusüβ et al, 2002).…”