Browsing by Author "Castro, Rafael"
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- Assessment of variations in air quality in cities of Ecuador in relation to the lockdown due to the COVID-19 pandemicPublication . Atiaga, Oliva; Guerrero, Fernanda; Páez, Fernando; Castro, Rafael; Collahuazo, Edison; Nunes, Luís; Grijalva, Marcelo; Grijalva, Iván; Otero, Xosé LuisThis study analyzes the effect of lockdown due to COVID-19 on the spatiotemporal variability of ozone (O3), sulfur dioxide (SO2), and nitrogen dioxide (NO2) concentrations in different provinces of continental Ecuador using satellite information from Sentinel - 5P. The statistical analysis includes data from 2018 to March 2021 and was performed based on three periods defined a priori: before, during, and after lockdown due to COVID-19, focusing on the provinces with the highest concentrations of the studied gases (hotspots). The results showed a significant decrease in NO2 concentrations during the COVID-19 lockdown period in all the study areas: the Metropolitan District of Quito (DMQ) and the provinces of Guayas and Santo Domingo de los Ts & PRIME;achilas. In the period after lockdown, NO2 concentrations increased by over 20% when compared to the pre-lockdown period, which may be attributable to a shift towards private transportation due to health concerns. On the other hand, SO2 concentrations during the lockdown period showed irregular, non-significant variations; however, increases were observed in the provinces of Chimborazo, Guayas, Santa Elena, and Morona Santiago, which could be partly attributed to the eruptive activity of the Sangay volcano during 2019-2020. Conversely, O3 concentrations increased by 2-3% in the study areas; this anomalous behavior could be attributed to decreased levels of NOx, which react with ozone, reducing its concentration. Finally, satellite data validation using the corresponding data from monitoring stations in the DMQ showed correlation values of 0.9 for O3 data and 0.7 for NO2 data, while no significant correlation was found for SO2.
- COVID-19 pandemic impacted differently air quality in Latin American citiesPublication . Atiaga, Oliva; Páez, Fernando; Jácome, Wilson; Castro, Rafael; Collaguazo, Edison; Nunes, LuísThis research explores the spatial and temporal variations of nitrogen dioxide (NO2), sulphur dioxide (SO2), and ozone (O-3) levels in four Latin American cities, namely Mexico City, Santiago de Chile, Lima, and the Metropolitan District of Quito, utilizing Sentinel-5P satellite data alongside ground-based monitoring stations. The period covers pre-lockdown, lockdown, and post-lockdown phases of the COVID-19 pandemic, providing insights into pollutant behaviour across different levels of human activity. Findings show notable spatial variability in pollutant levels, with Santiago de Chile repeatedly presenting the highest concentrations of NO2 and SO2, linked to urban development and local weather patterns, whereas Quito showed the lowest levels. The lockdowns typically resulted in decreased NO2 concentrations, yet their effects on SO2 and O-3 levels were inconsistent, highlighting the complexity of pollutant interactions. The research confirms that satellite data serves as an affordable addition to conventional monitoring, especially in areas with limited resources. These results emphasize the necessity for customized, city-oriented strategies to reduce urban air pollution and safeguard public health.