Overview and Seasonality of PM10 and PM2.5 in Guayaquil, Ecuador

Julio Cáceres,Daniel Moran-Zuloaga,Emilio Rodríguez-Caballero,Mauricio H Cornejo,Wilson Merchan-Merchan,Philip Hernick

doi:10.1007/s41810-021-00117-2

Abstract

The focus of this study is the assessment of total suspended particles (TSP) and particulate matter (PM) with various aerodynamic diameters in ambient air in Guayaquil, a city in Ecuador that features a tropical climate. The urban annual mean concentrations of TSP (Total Suspended Particles), and particle matter (PM) with various aerodynamic diameters such as: PM10, PM2.5 and PM1 are 31 ± 14 µg m−3, 21 ± 9 µg m−3, 7 ± 2 µg m−3 and 1 ± 1 µg m−3, respectively. Air mass studies reveal that the city receives a clean Southern Ocean breeze. Backward trajectory analysis show differences between wet and dry seasons. During the dry season, most winds come from the south and southwest, while air masses from the peri urban may contribute as pollutant sources during the wet season. Although mean values of PM10 and PM2.5 were below dangerous levels, our year-round continuous monitoring study reveals that maximum values often surpassed those permissible limits allowed by the Ecuadorian norms. A cluster analysis shows four main paths in which west and southwest clusters account for more than 93% of the pollution. Total vertical column of NO2 shows the pollution footprint is strongest during the dry season, as opposed to the wet season. A microscopic morphological characterization of ambient particles within the city during the wet and the dry season reveals coarse mode particles with irregular and rounded shapes. Particle analysis reveals that samples are composed of urban dust, anthropogenic and organic debris during the dry season while mainly urban dust during the wet season.

Highlights

Aerosols originate both naturally or anthropogenically, and their composition, their effect on atmospheric processes and their physical and chemical properties are key components to understanding interactions with biogeochemical cycles that could affect rain and drought (Andreae 1995)
Meteorological data were collected using the Escuela Superior Politécnica del Litoral (ESPOL) LabFREE project (2008–2015) which consist on HOBO weather station with the following items: Temperature/relative humidity (RH) smart sensor (S-THB-M00x, temperature working range − 40° to 75° C with ± 2.5% °C, RH > 95% increased 1% error), rain gauge smart sensor (S-RGA-M002, accuracy ± 1% at up to 20 mm/h, wind direction smart sensor (S-WDA-M003, accuracy ± 5°), wind speed smart sensor (S-WSA-M003, accuracy ± 1.1 m/s) and a HOBO U30 cellular data logger U30-GSM
Average temperatures during the wet season and mean relative humidity (RH) of 27 °C and 78% occurred, while during the dry season, temperatures dropped to 24 °C with a mean RH of 73%, refer to Fig. 1b, c

Summary

Introduction

Aerosols originate both naturally or anthropogenically, and their composition, their effect on atmospheric processes and their physical and chemical properties are key components to understanding interactions with biogeochemical cycles that could affect rain and drought (Andreae 1995). Aerosol can be classified by sizing as: (a) fine mode particles corresponding to those with sizes < 1 μm, and (b) coarse mode particles with aerodynamic diameters > 2.5 μm and < 10 μm (PM2.5–10) that vary from natural origin e.g., fungus, bacteria, pollen, or sea salt. Fine particles, corresponding to the cloud condensation nuclei and ice nuclei, are suspended in the clouds and they may precipitate to the Earth’s surface through raindrops in a process known as wet deposition (Seinfeld and Pandis 1998; Pöschl 2005). If no precipitation is present the concentration of airborne particle increases (Després et al 2012; FröhlichNowoisky et al 2012). These airborne particles reach the Earth’s surface through convective transport, diffusion, etc. Trade winds assist air masses to transport airborne particles longer distances, known as long range transport, which can occur through natural causes such as volcanic eruptions (Kahn and Limbacher 2012) and dust transport (Abdelkader et al 2017; Di Biagio et al 2017)

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