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- PublicaciónLong-term airborne particle pollution assessment in the city of Coyhaique, Patagonia, Chile(2022) Solís, Rafael; Toro A., Richard; Gómez, Luis; Vélez-Pereira, Andrés M.; López, Manuela; Fleming, Zöe; Fierro, Nicolás; Leiva G., ManuelAn air pollution assessment in a small city located in the heart of Chilean Patagonia is presented. Seven years (2014–2020) of PM concentration levels retrieved from two monitoring stations permits an evaluation of the city’s pollution variability, the effect of meteorological variables and long-term trends of air pollution. The highest PM concentration levels observed during the coldest months are mainly related to an increasing emission associated with the intensive use of firewood for residential heating and cooking. The most polluted days are associated with low temperatures, low wind speed and high PM2.5/PM10 ratios, which is consistent with the predominance of local firewood sources over background emissions. A decrease in both PM fractions over time has been estimated (PM10: -4.1, CI99%: − 5.7 to − 2.9 and PM2.5: -2.2, CI99%: − 3.5 to − 1.3 μg m− 3 year− 1 ). However, the annual average PM mass concentrations in Coyhaique exceeded both national and international air quality thresholds. The city reported a percent of annual exceedances of the daily WHO guidelines of 57% for PM10 and 77% for PM2.5. These numbers highlight the serious air pollution problem of the city of Coyhaique, which exhibits air pollution levels comparable to those of many polluted megacities in the world.
- PublicaciónPhotochemical sensitivity to emissions and local meteorology in Bogotá, Santiago, and São Paulo: An analysis of the initial COVID-19 lockdowns(2022) Seguel, Rodrigo J.; Gallardo, Laura; Osses, Mauricio; Rojas, Néstor Y.; Nogueira, Thiago; Menares, Cmilo; Andrade, María Fátima; Belalcázar, Luis C.; Carrasco, Paula; Eskes, Henk; Fleming, Zöe; Huneeus, Nicolás; Ibarra-Espinosa, Sergio; Landulfo, Eduardo; Leiva, Manuel; Mangones, Sonia C.; ernando G. Morais8 , Gregori A. Moreira11, Nicola´ s Pantoja3 , Santiago Parraguez1,12, Jhojan P. Rojas13, Roberto Rondanelli1,2, Izabel da Silva Andrade8 , Richard Toro9 ,; Moreira, Gregori A.; Pantoja, Nicolás; Parraguez, Santiago; Rojas, Jhojan P.; Rondanelli, Roberto; Silva Andrade, Izabel da; Toro, Richard; Yoshida, Alexandre C.This study delves into the photochemical atmospheric changes reported globally during the pandemic by analyzing the change in emissions from mobile sources and the contribution of local meteorology to ozone (O3) and particle formation in Bogotá (Colombia), Santiago (Chile), and São Paulo (Brazil). The impact of mobility reductions (50%–80%) produced by the early coronavirus-imposed lockdown was assessed through high-resolution vehicular emission inventories, surface measurements, aerosol optical depth and size, and satellite observations of tropospheric nitrogen dioxide (NO2) columns. A generalized additive model (GAM) technique was also used to separate the local meteorology and urban patterns from other drivers relevant for O3 and NO2 formation. Volatile organic compounds, nitrogen oxides (NOx), and fine particulate matter (PM2.5) decreased significantly due to motorized trip reductions. In situ nitrogen oxide median surface mixing ratios declined by 70%, 67%, and 67% in Bogotá, Santiago, and São Paulo, respectively. NO2 column medians from satellite observations decreased by 40%, 35%, and 47%, respectively, which was consistent with the changes in mobility and surface mixing ratio reductions of 34%, 25%, and 34%. However, the ambient NO2 to NOx ratio increased, denoting a shift of the O3 formation regime that led to a 51%, 36%, and 30% increase in the median O3 surface mixing ratios in the 3 respective cities. O3 showed high sensitivity to slight temperature changes during the pandemic lockdown period analyzed. However, the GAM results indicate that O3 increases were mainly caused by emission changes. The lockdown led to an increase in the median of the maximum daily 8-h average O3 of between 56% and 90% in these cities.
- PublicaciónImpact of mining on the metal content of dust in indigenous villages of northern Chile(2022) Zanetta-Colombo, Nicolás; Fleming, Zöe; Gayo, Eugenia M.; Manzano, Carlos A.; Panagi, Marios; Valdés, Jorge; Siegmund, AlexanderIndigenous communities from northern Chile have historically been exposed to the impacts of massive copper industrial activities conducted in the region. Some of the communities belonging to the Alto El Loa Indigenous Development Area are located less than 10 km from the “Talabre'' tailings dam, which contains residues from copper production and other metals that can be toxic to human health (e.g., As, Sb, Cd, Mo, Pb). Given the increasing demand of copper production to achieve net-zero emission scenarios and concomitant expansions of the tailings, the exposure to toxic metals is a latent risk to local communities. Despite the impact that copper production could generate on ancestral communities from northern Chile, studies and monitoring are limited and the results are often not made accessible for local communities. Here, we evaluate such risks by characterizing metal concentrations in dust collected from roofs and windows of houses from the Alto El Loa area. Our results showed that As, Sb, Cd, Cu, Mo, Ag, S, and Pb concentrations in these matrices can be connected to local copper mining activities. Additionally, air transport models indicate that high concentrations of toxic elements (As, Sb, and Cd) can be explained by the atmospheric transport of particles from the tailings in a NE direction up to 50 km away. Pollution indices and Health Risk Assessment suggested a highly contaminated region with a health risk for its inhabitants. Our analysis on a local scale seeks to make visible the case of northern Chile as a critical territory where actions should be taken to mitigate the effects of mining in the face of this new scenario of international demand for the raw materials necessary for the transition to a net-zero carbon global society.
- PublicaciónEffects of Using High-Strength Reinforcement in the Seismic Performance of a Tall RC Shear Wall Building(2023) Puentes, Juan; Parra, Pablo F.; Magna-Verdugo, Carolina; Cendoya, Patricio; Avudaiappan, SivaChile’s reinforced concrete (RC) design is based on ACI 318-08, where high-strength reinforcement is not allowed in seismic force-resistant members. In 2019, new requirements adopted by ACI 318 permitted the incorporation of high-strength reinforcement in walls. This study compared the seismic performance of two Chilean 20-story residential buildings on soft soil, one designed with traditional Grade 60 and the other with high-strength Grade 80 reinforcement. The performance was assessed in terms of the probability of exceeding the ASCE 41 limit states during a 50-year lifecycle. Analyses showed that both buildings had similar seismic performance. However, the reduction in reinforcement in the Grade 80 building was close to 18%. It is concluded that using high-strength reinforcement in a typical wall building implies a significant reduction in the reinforcement used without affecting the seismic performance.
- PublicaciónReciprocity heightens academic performance(2022) Candia, Cristián; Oyarzún, Melanie; Landaeta, Víctor; Yaikin, T.; Monge, Cecilia; Hidalgo, Cesar; Rodríguez-Sickert, CarlosSocial relationships are pivotal for human beings. Yet, we still lack a complete understanding of the types and conditions of social relationships that facilitate learning among children. Here, we present the results of a study involving 855 elementary school children from 14 different public schools in Chile designed to understand their social learning strategies in classrooms. We mapped students' social relationships using a behavioral experiment–a non-anonymous social dilemma–that allows us to measure cooperation and infer reciprocal and asymmetrical relationships between peers. We implemented the experiment synchronously in each classroom using networked tablets and a friendly user interface to mitigate cognitive barriers and boost students' engagement. Using regression models, we found a positive and significant association between reciprocity and academic performance. This result holds after controlling for class attendance, sex, parents’ education, social status, individual cooperative dispositions, and fixed effects per class group. Finally, using a difference-in-difference framework, we found robust evidence that reciprocity heightens academic performance by comparing two consecutive academic semesters. This effect is heterogeneous and is considerably more prominent for the top 20% students experiencing higher levels of reciprocity in their social relationships. We expect these results to inform cooperative learning interventions in elementary education.