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Advancing Molecular Level Understanding of Aerosol Processes in the Amazon and Integration with Modeling

Active Dates 8/15/2019-8/14/2024
Program Area Atmospheric System Research
Project Description
Advancing Molecular Level Understanding of Aerosol Processes in the Amazon and Integration with Modeling
A. Goldstein, University of California at Berkeley (Principal Investigator)
L. Yee, University of California at Berkeley (Co-Principal Investigator)

The Amazon forest is being converted to urban and agricultural uses through land clearing including large scale burning. It is also the dominant source of biogenic hydrocarbons globally, which can chemically transform in the atmosphere to form secondary organic aerosol (SOA). Aerosols, solid or liquid particles suspended in air, form naturally and under anthropogenic influence and are fundamental to cloud formation, the hydrologic cycle, and radiative balance in this region. The 2014 GoAmazon field campaign at the DOE/ARM facility at T3 afforded study of chemical transformations in the region downwind of Manaus. Local biogenic hydrocarbons emissions are high, and their chemical oxidation can be studied with varying degrees of influence by the urban plume. We collected filter samples and made time-resolved molecular level measurements by deploying a sequential filter sampler and a Semi-Volatile Thermal desorption Aerosol Gas Chromatograph (SV-TAG) during Jan-Mar 2014 (wet season) and Aug-Oct 2014 (dry season). Contrasting both seasons allows study of varying chemical and atmospheric states (i.e. clean, background biogenic SOA with regular wet deposition vs higher biogenic hydrocarbons and biomass burning emissions with decreased wet deposition).

Critical science questions remain regarding source contributions and processes of SOA formation in this region. While oxidation of monoterpenes and biomass burning emissions (during the dry season) are assumed to be the largest contributors to SOA, substantial uncertainties remain regarding fundamental processes controlling their formation and their magnitudes. Here we propose to provide new measurements of molecular tracers for each of these sources (from existing samples and raw data) to 1) constrain their contribution to SOA, and 2) provide insight into the chemical mechanisms behind their formation as influenced by anthropogenic pollution. We intend to hone in on those tracers that participate in heterogeneous and aqueous chemical pathways that lead to new particle formation, growth, and cloud formation in the region, as current modeling schemes for SOA formation lack the necessary process level understanding and observational constraints to improve atmospheric system predictability.

The proposed research will advance integration of modeling and measurements, leading to improved predictability of Earth’s radiative balance and hydrologic cycle. We propose to complete five objectives. Objective 1) Complete comprehensive analysis of filter samples using state-of-the-art two dimensional gas chromatography with mass spectrometry; Objective 2) To the extent possible, confirm the identity/sources of all observed compounds (with a focus on oxidation products of monoterpenes and biomass burning emissions); Objective 3) Quantify known and potential tracers from filters and SV-TAG data, identify novel tracers of aqueous and heterogeneous chemical processes, and elucidate differences in SOA formation under varying anthropogenic influence; Objective 4) Using results from Objectives 1, 2, and 3, iteratively discuss and provide measurements of tracers data to modelers to test and update mechanistic processes affecting aerosol and cloud formation in the Amazon region; Objective 5) Update the UCB GLOBES mass spectral library with newly observed compounds based on Objectives 1, 2, and 3, and make it available to the scientific community.
Award Recipient(s)
  • University of California, Berkeley (PI: Goldstein, Allen)