EGU23-16945, updated on 15 Jul 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Wet deposition of sub-micron aerosol particles in an urban area of the Amazon central

Glauber Cirino1, Márcio Matheus2, Henrique Barbosa3, Courtney Schumacher4, Aaron Funk4, Joel Brito5, Luciana Rizzo6, Rafael Palácios1, Simone Silva1, Breno Imbiriba1, Jost Lavric7, Scot Martin8, and Paulo Artaxo6
Glauber Cirino et al.
  • 1Federal University of Pará, Geosciences Institute, Belém, Brazil (,,,
  • 2Institute of Astronomy, Geophysics and Atmospheric Sciences, São Paulo University, São Paulo, Brazil (
  • 3Physics Department, University of Maryland, Baltimore County (
  • 4Department of Atmospheric Sciences, Texas A&M University, Texas, United States (,
  • 5Atmospheric Sciences and Environmental Engineering, IMT Nord Europe, Douai, France (
  • 6Physics Institute, São Paulo University, São Paulo, Brazil (,
  • 7Max Planck Institute for Biogeochemistry, Jena, Alemanha (
  • 8School of Engineering and Applied Science, Havard University, Cambridge, United States (

Aerosol particles impact health, ecosystems, and climate, especially when in high concentrations in urban environments. Wet deposition is one of the most critical limiting mechanisms of particulate matter in the atmosphere.  This mechanism captures particles inside clouds (rain-out) or below the cloud due to precipitation (washout). In the Amazon basin, the physical mechanisms and scavenging rates remain unknown in many regions. Several studies over the last decades have empirically ascertained the impact of wet deposition to develop local atmospheric models or to estimate the contribution of its effects. Here, we analyzed some of the physical and chemical properties of aerosols: nucleation mode (NU, 10-30 nm), Aitken (30-100 nm), accumulation mode (AC, 100-430 nm), total particle number (10-430 nm), Black Carbon equivalent (BCe), and chemical properties, such as organic aerosols (OA), sulfate (SO42−) and nitrate (NO3). We obtained the data set from the Intensive Observation Periods (IOPs) of the GoAmazon2014 experiment, Iranduba-AM (T2 sampling site), ~ 9 km NE of Manaus city. We conducted three analyzes from these data: (I) daily cycles on dry and rainy days; (II) scavenging rates (TS), i.e., the difference in the concentration of aerosol one hour before and the first hour of rainfall events, generally, during local thunderstorms or Mesoscale Convective Systems - MCS; and (III) scavenging coefficients (λ). We verified significant statistics decreases at both NU and AIT modes, as well SO42− and NO3. In TS analysis, we observed a similar decline (NU: -21%, AIT: -17%, AC: -22%), contributing to an overall removal of up to -13% (on average). The soluble fractions were removed easily (OA: -21%, SO42−: -16%, and NO3: -16%) compared to insoluble fractions (BCe: -11%). In λ analysis, a substantial decrease in all size classes (NU: 2.0 × 10−4 s−1, AIT: 7.8 × 10−4 s−1, AC: 1.3 × 10−4 s−1, CN: 5.4 × 10−4 s−1) was also observed, with unexpected prominence to the AIT. We've attributed this result to introducing aerosol particles of 10-50 nm by deep convection, which may counteract the washout. Measurements of cloud properties might help confirm this hypothesis. Our preliminary findings are helpful for the local modeling of pollutant dynamics and provide evidence that wet deposition substantially removes sub-micron particles in the Amazon region. The wet deposition rates for other storms and clouds in the atmosphere, however, remain unknown.

How to cite: Cirino, G., Matheus, M., Barbosa, H., Schumacher, C., Funk, A., Brito, J., Rizzo, L., Palácios, R., Silva, S., Imbiriba, B., Lavric, J., Martin, S., and Artaxo, P.: Wet deposition of sub-micron aerosol particles in an urban area of the Amazon central, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16945,, 2023.