Autores: L. Caudillo, D.Salcedo, O. Peralta*, T. Castro*, H. Alvarez-Ospina

* Departamento de Ciencias Ambientales | Aerosoles Atmosféricos

Abstract

article size distributions in the 10–400 nm diameter size range were measured at a site south of Mexico City, during 30 non-consecutive days from October to December 2016 using a Scanning Mobility Particle Sizer, together with meteorological parameters and criteria pollutants concentration. Particles were classified into three modes depending on their diameter: D‾p ≤ 20 nm (M₁, nucleation mode), 20 > D‾p > 100 nm (M₂, Aitken mode), and D‾p ≥ 100 nm (M₃, accumulation mode) to describe their concentration variability and discuss its connection with meteorology and atmospheric chemistry. In general, M₁ and M₃ concentrations showed maximum variability during the sampling period and were linearly anticorrelated. Concentrations of M₃, black carbon, and PM_2.5 showed a similar trend, which indicates that M₃ represents the largest fraction of the particle mass concentration. The concentration fraction of M₂ was relatively constant. The three modes showed a primary character during peak traffic hours in the morning; M₂ also showed an important secondary character during the hours of highest photochemical activity. We only observed one nucleation event, which coincided with an unusually high concentration of SO₂. On the other hand, we identified several days with typical condensational growth behavior at noon, and sometimes in the afternoon, associated with the highest values of O₃, SO₂, NO₂, and PM_2.5 concentrations, as well as of radiation and temperature.