Browsing by Author "Atiaga, Oliva"
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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.
- Effect of cooking on arsenic concentration in ricePublication . Atiaga, Oliva; Nunes, Luís; Otero, Xosé L.This study assessed the effect of rinsing and boiling on total content of As (tAs) and of its inorganic and organic forms in different types of rice (polished and brown) from Spain and Ecuador. Rice was subjected to five different treatments. The results showed that the treatment consisting of three grain rinsing cycles followed by boiling in excess water showed a significant decrease in tAs content compared with raw rice. Regarding As species, it is worth noting that the different treatments significantly reduced the content of the most toxic forms of As. The estimated lifetime health risks indicate that pre-rinsing alone can reduce the risk by 50%, while combining it with discarding excess water can reduce the risk by 83%; therefore, the latter would be the preferable method.
- Toxic elements in soil and rice in EcuadorPublication . Atiaga, Oliva; Ruales, Jenny; Nunes, L.; Otero, Xosé LuisThe concentration of trace toxic metals (Cr, Zn, As, Pb, Cd, Cu, and Ni) in soil and rice plants, including the stems, leaves, and grain, from the main rice-producing provinces in Ecuador, was determined. Additionally, the soils were analyzed to determine their properties, composition, total content, bioavailable fraction, and geochemical fractions of toxic elements. Approximately 30% of soil samples in the case of Cr and Cu and 10% of samples in the case of Ni exceeded the legal thresholds for Ecuador. Moreover, for Cr and Cu, approximately 4% and 13% of samples, respectively, exceeded the threshold value of 100 mg kg−1 proposed for these two elements in several international regulations. Concentrations of As, Pb, and Cd in the soils were below the threshold values established both by Ecuadorian laws and by other countries. The concentrations of metals in rice plants did not correlate linearly with the total metal concentrations in the soil, nor with their bioavailability. However, the bioconcentration factors for As, Cd, Cu, Ni, and Zn could be predicted from bioavailability by a power law with exponents ranging from −0.724 to −1.625, which is typical of accumulator plants, where trace metal homeostasis plays an important role.