Source apportionment of ambient pollution levels in Guayaquil, Ecuador

Abstract

In this study, the relative contributions of main emission sources to the typical ambient concentrations of key pollutants, such as sulfur dioxide (SO ₂), nitrogen dioxide (NO ₂), carbon monoxide (CO), and particulate matter (PM ₁₀ and PM _2.5) in Guayaquil, Ecuador, were investigated. A previous urban emissions inventory for mobile sources was expanded to include other transportation means and main industrial activities using the EMEP/EEA methodology to achieve this objective. The WRF/CALMET/CALPUFF modeling system was used to simulate the annual spatiotemporal distribution of air pollution in the city. According to the model, NO ₂ concentrations exceed the yearly value and 1-h Ecuadorian standards (40 and 200 μg/m ³) in 1 % and 6 % of the cells of the modeling domain, respectively. These hotspots related to local sources were located in the northwest center of the city. The contributions of the manufacturing sector, thermal power plants, ports, airports, and road traffic were assessed individually, and the results indicated that air quality in the study area was strongly dominated by road traffic. The contributions of NO ₂, CO, PM ₁₀, and PM _2.5 at the city level reached 76 %, 96 %, 90 %, and 92 % of the annual mean, respectively. In the case of SO ₂, the manufacturing sector made the most significant contribution (75 %), followed by thermal power plants (16 %). Furthermore, an analysis at 14 specific locations across Guayaquil identified spatial variations that may support the design and development of an air quality monitoring network for the city.

Highlights

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  Emissions estimated for mobile sources, power plants, and industry in Guayaquil.

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  Road traffic is the most important emission source in the city.

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  Pollution dispersion modeled with the WRF/CALMET/CALPUFF over 1-yr period.

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  Road traffic responsible of 92 % of PM _2.5 and 76 % of NO ₂ ambient concentration.

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  91 % of SO ₂ concentration attributed to manufacturing sector and power plants.