Publication - Journal Article High concentration of ultrafine particles in the Amazon free troposphere produced by organic new particle formation

Proceedings of the National Academy of Sciences, vol. 117, iss. 41, pp. 25344-25351, 2020

Bin Zhao, Manish Shrivastava, Neil M. Donahue, Hamish Gordon, Meredith Schervish, John E. Shilling, Rahul A. Zaveri, Jian Wang, Meinrat O. Andreae, Chun Zhao, Brian Gaudet, Ying Liu, Jiwen Fan, Jerome D. Fast

Significance The high-altitude tropics constitute one of the world’s largest aerosol reservoirs, which may significantly affect clouds, radiation, and hydrological cycle by delivering the seeds on which clouds form to lower altitudes and maintaining the stratospheric aerosol background. However, the formation mechanisms of these aerosols remain a scientific mystery. Through a systematic experiment-based model representation of organic chemistry and new particle formation (NPF) combined with constraints from field measurements, we demonstrate that the NPF driven by extremely low volatility organics formed from biogenic emissions plays a key role in producing the large number of aerosols observed in the high-altitude Amazon. This organic NPF mechanism likely also prevailed during preindustrial times and hence may modulate anthropogenic aerosol forcing above the preindustrial baseline.