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High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation.

ABSTRACT: The large concentrations of ultrafine particles consistently observed at high altitudes over the tropics represent one of the world's largest aerosol reservoirs, which may be providing a globally important source of cloud condensation nuclei. However, the sources and chemical processes contributing to the formation of these particles remain unclear. Here we investigate new particle formation (NPF) mechanisms in the Amazon free troposphere by integrating insights from laboratory measurements, chemical transport modeling, and field measurements. To account for organic NPF, we develop a comprehensive model representation of the temperature-dependent formation chemistry and thermodynamics of extremely low volatility organic compounds as well as their roles in NPF processes. We find that pure-organic NPF driven by natural biogenic emissions dominates in the uppermost troposphere above 13 km and accounts for 65 to 83% of the column total NPF rate under relatively pristine conditions, while ternary NPF involving organics and sulfuric acid dominates between 8 and 13 km. The large organic NPF rates at high altitudes mainly result from decreased volatility of organics and increased NPF efficiency at low temperatures, somewhat counterbalanced by a reduced chemical formation rate of extremely low volatility organic compounds. These findings imply a key role of naturally occurring organic NPF in high-altitude preindustrial environments and will help better quantify anthropogenic aerosol forcing from preindustrial times to the present day.

SUBMITTER: Zhao B

PROVIDER: S-EPMC7568247 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation.

Zhao Bin B Shrivastava Manish M Donahue Neil M NM Gordon Hamish H Schervish Meredith M Shilling John E JE Zaveri Rahul A RA Wang Jian J Andreae Meinrat O MO Zhao Chun C Gaudet Brian B Liu Ying Y Fan Jiwen J Fast Jerome D JD

Proceedings of the National Academy of Sciences of the United States of America 20200928 41

The large concentrations of ultrafine particles consistently observed at high altitudes over the tropics represent one of the world's largest aerosol reservoirs, which may be providing a globally important source of cloud condensation nuclei. However, the sources and chemical processes contributing to the formation of these particles remain unclear. Here we investigate new particle formation (NPF) mechanisms in the Amazon free troposphere by integrating insights from laboratory measurements, che ...[more]

PMID: 32989149

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High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation.

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High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation.

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