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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  13 Jul 2020

13 Jul 2020

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This preprint is currently under review for the journal ACP.

Concentrations and biosphere–atmosphere fluxes of inorganic trace gases and associated ionic aerosol counterparts over the Amazon rainforest

Robbie Ramsay1,2, Chiara F. Di Marco1, Matthias Sörgel3,a, Mathew R. Heal2, Samara Carbone4, Paulo Artaxo5, Alessandro C. de Araùjo6, Marta Sá7, Christopher Pöhlker8, Jost Lavric9, Meinrat O. Andreae3,10, and Eiko Nemitz1 Robbie Ramsay et al.
  • 1UK Centre for Ecology and Hydrology (UKCEH), Bush Estate, Penicuik, EH26 0QB, UK
  • 2School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, UK
  • 3Biogeochemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
  • 4Federal University of Uberlândia, Agrarian Sciences Institute, Uberlândia, MG, Brazil
  • 5Instituto de Física, Universidade de São Paulo, São Paulo, Brazil
  • 6Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), Belèm-PA, CEP 66095-100, Brazil
  • 7Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), Instituto Nacional de Pesquisas da Amazonia (INPA), Manaus-AM, CEP 69067-375, Brazil
  • 8Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 9Department Biogeochemical Systems, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 10Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
  • anow at: Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany

Abstract. The Amazon rainforest presents a unique, natural laboratory for the study of surface-atmosphere interactions. Its alternation between a near-pristine, marine-influenced atmosphere during the wet season, and a vulnerable system affected by periodic intrusions of anthropogenic pollution during the dry season, provides an opportunity to investigate some fundamental aspects of boundary-layer chemical processes. This study presents the first simultaneous hourly measurements of concentrations, fluxes and deposition velocities of the inorganic trace gases NH3, HCl, HONO, HNO3 and SO2 and their water-soluble aerosol counterparts NH4+, Cl, NO2, NO3 and SO42− over the Amazon. Species concentrations were measured in the dry season (from 6 October to 5 November 2017), at the Amazon Tall Tower Observatory (ATTO) in Brazil, using a two-point gradient, wet-chemistry instrument (Gradient of Aerosols and Gases Online Registration, GRAEGOR) sampling at 42 m and 60 m. Fluxes and deposition velocities were derived from the concentration gradients using a modified form of the aerodynamic gradient method corrected for measurement within the roughness sub-layer. Findings from this campaign include observations of elevated concentrations of NH3 and SO2 partially driven by long-range transport (LRT) episodes of pollution, and the substantial influence of coarse Cl and NO3 particulate on overall aerosol mass burdens. From the flux measurements, the dry season budget of total reactive nitrogen dry deposition at the ATTO site was estimated as −2.9 kg N ha−1 a−1. HNO3 and HCl were deposited continuously at a rate close to the aerodynamic limit. SO2 was deposited with an average daytime surface resistance (Rc) of 28 s m−1, whilst aerosol components showed average surface deposition velocities of 2.8 and 2.7 mm s−1 for SO42− and NH4+. Deposition rates of NO3 and Cl were higher at 7.1 and 7.8 mm s−1, reflecting their larger average size. The exchange of NH3 and HONO was bi-directional, with NH3 showing emission episodes in the afternoon and HONO in the early morning hours. This work provides a unique dataset to test and improve dry deposition schemes for these compounds for tropical rain forest, which have typically been developed by interpolation from conditions in temperate environments. A future campaign should focus on making similar measurements in the wet season in order to provide a complete view of the annual pattern of inorganic trace gas and coarse aerosol biosphere-atmosphere exchange over tropical rainforest.

Robbie Ramsay et al.

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Robbie Ramsay et al.

Robbie Ramsay et al.


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Latest update: 29 Sep 2020
Publications Copernicus
Short summary
The Amazon Rainforest is a unique “laboratory” to study the processes which govern the exchange of gases and aerosols to and from the atmosphere. This study investigated these processes by measuring the atmospheric concentrations of trace gases and particles at the Amazon Tall Tower Observatory. We found that the long-range transport of pollutants can affect the atmospheric composition above the Amazon rainforest, and that the gases ammonia and nitrous acid can be emitted from the rainforest.
The Amazon Rainforest is a unique “laboratory” to study the processes which govern the...