Ernesto V. Gramsch This email address is being protected from spambots. You need JavaScript enabled to view it.1, Cristian R. Soto1, Pedro P. Oyola2, Felipe A. Reyes2, Yeanice Vasquez2, María A. Rubio3, Patricio A. Pérez1, Matías Tagle2

1 Physics Department, University of Santiago de Chile, Santiago, Chile
2 Mario Molina Center for Environmental Studies, Santiago, Chile
3 Facultad de Química y Biología and CEDENNA, Universidad de Santiago de Chile, Santiago, Chile


Received: November 2, 2018
Revised: April 22, 2020
Accepted: July 12, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

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Gramsch, E.V., Soto, C.R., Oyola, P.P., Reyes, F.A., Vasquez, Y., Rubio, M.A., Pérez, P.A. and Tagle, M. (2020). Relationship between UV Energy and Formation of Secondary Particles in Santiago de Chile. Aerosol Air Qual. Res.



  • New particles are formed primarily in summer.
  • There is a linear relationship between UV and new particles in summer
  • In megacities, existing particles inhibit creation of new secondary particles.


Over the last few years there has been a leveling off and even a small increase of PM2.5 in Santiago, Chile. This increase may not be due to primary emissions, but to an increase in the formation of new secondary particles. Therefore, the size distribution of particle matter has been studied at several sites in the metropolitan area of Santiago in 2013 and 2018 in order to study the formation of secondary ultrafine particles. Measurements were made with an electric low-pressure impactor (ELPI Dekati) in all sites. During winter, little formation of new ultrafine particles was detected, more formation of ultrafine particles during fall and the highest number during summer. A clear peak in the number of particles between 10 and 20 nm was found in the afternoon when solar radiation was high during summer. The correlation plot between new particles and UV radiation has two trends: for energies greater than ~ 4.5 kJ m-2 there is an almost linear relationship between the number of new particles and UV energy (R2 = 0.739). For lower energies there is no clear relationship between new particle formation and energy. For total solar energy, a much lower correlation was found, indicating that UV solar radiation rather than total solar energy plays a role in the formation of ultrafine particles. This two-trend characteristic may only exist in polluted cities, with large numbers of pre-existing particles. Formation of new ultrafine particles occurs mainly in summer; when PM2.5 concentration is low and confirms that in megacities the large number of existing particles inhibit creation of new particles.

Keywords: Ultrafine particles; New particle formation; UV radiation.

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