Browsing by Author "Jorquera, Héctor"

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    A kinetic theory of suspensions. II. The steady flow of a hard-sphere suspension
    (1994) Jorquera, Héctor; Dahler, John S.
    Calculations are reported of the steady-state shear and bulk viscosity coefficients of a suspension of freely rotating, hard spheres dispersed in a continuous Newtonian solvent. These calculations are based on a theory recently reported in this journal. Our theoretical predictions are compared with those of other theories, with the results of computer simulations, and with experimental data.
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    A kinetic theory of suspensions. III. Hard spheres and lubrication dynamics
    (1995) Jorquera, Héctor; Dahler, John S.
    Numerical estimates are presented for the shear viscosity coefficient of a hard-sphere suspension. Our calculations are based on a previously reported theory which uses a Fokker-Planck equation to describe the evolution of the solute many-body distribution function. The hydrodynamic interactions of the solute particles are modeled by two-body forces which include the short-ranged, singular contributions due to lubrication. This produces estimates of the viscosity that agree significantly better with experiment than did our earlier calculations which neglected the effects of lubrication. Our predictions are compared with those of other theories, with results of computer simulations, and with experimental data.
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    A new methodology for source apportionment of gaseous industrial emissions
    (2023) Jorquera, Héctor; Villalobos, Ana María; CEDEUS (Chile)
    Air quality modeling (AQM) is often used to investigate gaseous pollution around industrial zones. However, this methodology requires accurate emission inventories, unbiased AQM algorithms and realistic boundary conditions. We introduce a new methodology for source apportionment of industrial gaseous emissions, which is based on a fuzzy clustering of ambient concentrations, along with a standard AQM approach. First, by applying fuzzy clustering, ambient concentration is expressed as a sum of non-negative contributions — each corresponding to a specific spatiotemporal pattern (STP); we denote this method as FUSTA (FUzzy SpatioTemporal Apportionment). Second, AQM of the major industrial emissions in the study zone generates another set of STP. By comparing both STP sets, all major source contributions resolved by FUSTA are identified, so a source apportionment is achieved. The uncertainty in FUSTA results may be estimated by comparing results for different numbers of clusters. We have applied FUSTA in an industrial zone in central Chile, obtaining the contributions from major sources of ambient SO2: a thermal power plant complex and a copper smelter, and other contributions from local and regional sources (outside the AQM domain). The methodology also identifies SO2 episodes associated to emissions from the copper smelter.
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    A new methodology to assess the performance and uncertainty of source apportionment models II : The results of two European intercomparison exercises
    (2015) Belis, C. A.; Karagulian, F.; Amato, F.; Almeida, M.; Artaxo, P.; Jorquera, Héctor
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    Air quality at Santiago, Chile: A box modeling approach - I. Carbon monoxide, nitrogen oxides and sulfur dioxide
    (2002) Jorquera, Héctor
    Ambient monitored data at Santiago, Chile, are analyzed using box models with the goal of assessing contributions of different economic activities to air pollution levels. The period analyzed is 1990-2000, characterized by the introduction of air pollution emissions standards, shift to unleaded gasoline and compressed natural gas, and steady growth of the private and public fleet and the associated fuel consumption growth. The box models explicitly include the seasonal behavior of meteorological variables; the results show that dispersion conditions in fall and winter seasons are 20-30% of the summertime values. This result explains the poor air quality in those seasons and shows that significant emissions reductions are required in order to improve air quality in wintertime. Emissions of CO, NOx and SO2 are estimated from data on fuel consumption in the city; the estimated parameters are thus fleet-average or industry-average emission factors. In terms of contributions to ambient concentrations, older cars and diesel vehicles are the major contributors to CO and NOx impacts, with more than 60% and 50%, respectively. Ambient concentrations of SO2 are largely dominated by stationary sources, although long range contributions are not negligible. By contrast, CO and NOx pollution is dominated by local sources within the city boundaries. The box models can be used for forecasting purposes, and they can predict annual average concentrations within 20% of the observed values. The methodology requires data on ambient air quality measurements and fuel consumption statistics, and produces quantitative results, which can be combined with economic models to analyze environmental regulation and public policies.
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    Air quality management in Chile : effectiveness of PM2.5 regulations
    (2021) Jorquera, Héctor; CEDEUS (Chile)
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    Ambient PM10 impacts brought by the extreme flooding event of March 24-26, 2015, in Copiapo, Chile
    (2018) Jorquera, Héctor; Maria Villalobos, Ana; Barraza Saavedra, Francisco Javier; CEDEUS (Chile)
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    Application of MM5/CALMET/CAMx in Santiago, Chile
    (2003) Jorquera, Héctor; Castro, Julio; Escobar, Jaime; Jakobs, Hermann
    The Comprehensive Air Quality Model with Extensions (CAMx) has been applied to two summer photochemical episodes in the greater metro area of Santiago, Chile. It is shown that the CAMx model predicts reasonably well the spatial gradients of gaseous pollutants and the weekly cycle of variation for CO and NOx. The emission estimates for CO seem to be quite on agreement with actual emissions in 2000. NOx emissions are more appropriate for the 1998 scenario, whereas for 2000 they seem to overestimate actual emissions, so the mobile sources emission factors need to be verified. The SO2 simulations indicate that there relevant sources not accounted for in the inventory. There are problems with the VOC emissions for the area sources, because the model predictions for ozone are quite below what is being observed, for all network stations in 1998, a scenario with reliable NOx simulated levels. For the 2000 scenario, this problem is worsened because of excessive ozone scavenging. When we use the results of a comprehensive VOC campaign to produce a synthetic VOC profile of emissions for the whole city, simulated ozone gets closer to ambient measurements for the 1998 scenario. For the 2000 scenario, the overestimation in the simulated NOx levels is large enough to prevent any significant ozone sensitivity with respect to VOC increases. All things considered, CAMx has passed the "proof of the concept" for studying photochemical episodes at Santiago, Chile. The major sources of uncertainty are the emission inventory estimates for NOx and VOC. As a second source of uncertainty, meteorology was not properly represented on the second half of the January 1998 episode, and there are some problems with the stations closer to the Andes foothills overnight, particularly regarding ozone nocturnal profiles, that deserve further research.
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    Association of Kawasaki disease with tropospheric winds in Central Chile : Is wind-borne desert dust a risk factor?
    (2015) Jorquera, Héctor; Borzutzky Schachter, Arturo; Hoyos Bachiloglu, Rodrigo Andrés; García A.; CEDEUS (Chile)
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    Carbon monoxide concentrations in Santiago City at street levels and their vertical gradient
    (2008) Rubio, María A.; Lissi, Eduardo; Jorquera, Héctor; Salinas, Elizabeth; Castro, Julio; Cádiz, Marcela
    Carbon monoxide concentrations were measured at ground level (1 m) near heavy traffic streets in downtown Santiago de Chile in periods of low (November and December), intermediate (April) and high (May) ambient concentrations. Also, measurements were carried out at several heights (from 1 to 127 m) in Santiago's main street during winter time. Measurements carried out at ground level show maximum values during the morning rush hour, with values considerably higher than those reported by the urban air quality network, particularly in summer time. However, the measured values are below air quality standards. Vertical CO profiles were measured in a tower located in the center of downtown. Below 40 m (average altitude of neighboring buildings), the profiles do not show a consistent vertical gradient, with CO concentrations increasing or decreasing with height, regardless of atmospheric stability. In this low altitude range, the observed vertical profiles are poorly predicted by a street canyon model, and the measured concentrations can not be described by a simple exponential decay. At higher altitudes (40 and 127 m) a negative gradient in CO concentrations is observed, both for stable and unstable atmospheric conditions. The values of CO measured at 127 m are relatively well described by an Eulerian dispersion model running with current CO emission inventories for Santiago, although this model tends to predict stepper CO gradients than the observed ones.
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    Chemical speciation and source apportionment of fine particulate matter in Santiago, Chile, 2013
    (2015) Villalobos, A.; Barraza Saavedra, Francisco Javier; Jorquera, Héctor; Schauer, J.; CEDEUS (Chile)
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    Combining Cluster Analysis of Air Pollution and Meteorological Data with Receptor Model Results for Ambient PM2.5 and PM10
    (2020) Jorquera, Héctor; Villalobos, Ana María; CEDEUS (Chile)
    Air pollution regulation requires knowing major sources on any given zone, setting specific controls, and assessing how health risks evolve in response to those controls. Receptor models (RM) can identify major sources: transport, industry, residential, etc. However, RM results are typically available for short term periods, and there is a paucity of RM results for developing countries. We propose to combine a cluster analysis (CA) of air pollution and meteorological measurements with a short-term RM analysis to estimate a long-term, hourly source apportionment of ambient PM2.5 and PM10. We have developed a proof of the concept for this proposed methodology in three case studies: a large metropolitan zone, a city with dominant residential wood burning (RWB) emissions, and a city in the middle of a desert region. We have found it feasible to identify the major sources in the CA results and obtain hourly time series of their contributions, effectively extending short-term RM results to the whole ambient monitoring period. This methodology adds value to existing ambient data. The hourly time series results would allow researchers to apportion health benefits associated with specific air pollution regulations, estimate source-specific trends, improve emission inventories, and conduct environmental justice studies, among several potential applications.
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    Comparison of indoor and outdoor air quality in latino communities in Peru, Chile, and USA
    (International Society of Indoor Air Quality and Climate, 2015) Champion, Wyatt M.; Barraza Saavedra, Francisco Javier; Jorquera, Héctor; Montoya, Lupita D.
    The air quality inside and outside the homes of three Latino communities (rural Peru, urban Chile and suburban USA) was compared in this study. Filter samples were collected and analysed for fine mass (PM2.5) and elemental and organic carbon (ECOC). An optical particle sensor was used in lieu of filter samples for PM2.5 mass in Peru. Results indicated that rural Peruvian homes burning dung for heating and cooking had the highest average level of PM2.5 indoors (140 μg/m3) and relatively clean outdoor air. Urban Chilean homes had a lower average indoor PM2.5 concentration (22 μg/m3), while suburban USA homes showed elevated concentrations of PM2.5 indoors (7.0 μg/m3) compared to outdoors, but lower indoor levels than the other two communities studied.
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    Dispersión del MP10 en Temuco : construcción del escenario base y análisis del cumplimiento de la normativa ambiental
    (2010) Stocker Tolosa, Daniela Soledad; Jorquera, Héctor; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    En la zona urbana de las comunas de Temuco y Padre las Casas, actualmente se exceden las normas primarias diaria y anual para el material particulado respirable MP10, principalmente por el uso de leña para calefacción, por lo que la zona ha sido declarada saturada por la autoridad. El objetivo de la presente Tesis consistió en: a) modelar la dispersión de las emisiones atmosféricas en Temuco para el año 2006, usando un inventario estimado para el año 2005; b) evaluar cuantitativamente el desempeño del modelo de dispersión CALPUFF (EPA-EEUU) para el año 2006 y diagnosticar las deficiencias de dicho inventario; c) calibrar el inventario de emisiones para el año 2006, por medio de la metodología de modelación inversa, específicamente del filtro de Kalman; d) construir un escenario de emisiones modificado para el año 2006, y con él estimar cuales serían las reducciones de emisiones necesarias para cumplir con las normas, considerando diversos escenarios y verificando su factibilidad tecnológica.
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    Effects of biodiversity in green roofs and walls on the capture of fine particulate matter
    (2021) Vera Araya, Sergio Eduardo; Viecco Márquez, Margareth Indira; Jorquera, Héctor; CEDEUS (Chile)
    Exposure to ambient PM2.5 poses serious threats to human health. In such cases, the presence of green roofs (GRs) and green walls (GWs) has several environmental benefits, including the capture of pollutants. Choosing appropriate designs of GWs and GRs to improve urban air quality is challenging because their performances depend on their constituent species and environmental characteristics of the particular locality. Capture of PM2.5 by different plant species of GRs and GWs has been measured only on monocultures. The impact of planting different species together (polycultures) on capturing PM2.5 remains unexplored. This paper aims to evaluate the impact of biodiverse GRs and GWs on PM2.5 capture. Seven species were analyzed as polycultures: Sedum album, Lampranthus spectabillis, Sedum spurium P, Lavandula angustifolia, Erigeron karvinskianus, Aptenia cordifolia, and Sedum palmeri. PM2.5 capture was measured by two methods: gravimetric determination and decay curve. Gravimetric results suggest that higher the biodiversity of plants in GRs and GWs, higher the PM2.5 capture, particularly for species with relatively low capture when used as monocultures. The ability to capture PM2.5 is dependent on the plant species, relative position of plants within the polyculture, and horizontal (GRs) or vertical (GWs) layout. Decay method results suggest that polycultures could be more effective in long-term reduction of high PM2.5 concentrations.
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    Estimación de la exposición a la contaminación atmosférica del transporte en ciudades chilenas: contribuciones por emisión de tubo de escape y polvo de calle en suspensión
    (2023) Standen Benítez, Francisca; Jorquera, Héctor; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Una de las principales fuentes de material particulado en la atmósfera es el transporte. Los sitios con tráfico cercano son responsables de la mayoría de las superaciones de los valores de PM10 que se registran en ciudades. De esta fuente, se pueden distinguir dos aportes: exhaust emissions, provenientes del tubo de escape, y non-exhaust emissons, es decir, todo lo que no se deriva del tubo de escape y proviene principalmente del polvo de calle en resuspensión. En este contexto, el objetivo de este trabajo fue cuantificar el aporte del sector transporte: tubo de escape escape y polvo de calle, a las concentraciones ambientales de material particulado (MP10 y MP2.5) en ocho ciudades chilenas con diferentes condiciones climáticas (Calama, Viña del Mar, Santiago, Curicó, Talca, Concepción, Osorno y Coyhaique). Para lograr esto, se utilizó una metodología de agrupamiento difuso de las concentraciones ambientales de MP10 y MP2.5 de estaciones de monitoreo para así aislar aporte del sector transporte; y mediante un balance de masas a ambas fracciones de tamaño se determinó cuatro aportes: MP2.5ex (MP2.5 de tubo de escape), MP10ex (MP10 de tubo de escape), MP2.5nex (MP2.5 de polvo de calle), MP10nex (MP10 de polvo de calle). La contribución de estos aportes a la atmosfera cambia a lo largo del país principalmente por su variabilidad climática. Esto se puede ver en los resultados, donde en las ciudades ubicadas entre el norte y centro de Chile predomina el polvo de calle en el MP10. En la zona centro existe un aporte similar entre polvo de calle y tubo de escape. Mientras que, en las ciudades más al sur predomina el aporte del tubo de escape. En términos generales, estas contribuciones han disminuido con el paso de los años, gracias a la influencia de programas de limpieza y aspirado de calles en algunas ciudades, así como el reforzamiento de normas de emisión a nivel nacional.
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    Evaluation of receptor and chemical transport models for PM10 source apportionment
    (2020) Belis, C.A.; Pernigotti, D.; Pirovano, G.; Favez, O.; Jaffrezo, J.L.; Kuenen, J.; Denier van Der Gon, H.; Reizer, M.; Riffault, V.; Alleman, L.Y.; Almeida, M.; Amato, F.; Angyal, A.; Argyropoulos, G.; Bande, S.; Beslic, I.; Besombes, J.-L.; Bove, M.C.; Brotto, P.; Calori, G.; Cesari, D.; Colombi, C.; Contini, D.; De Gennaro, G.; Di Gilio, A.; Diapouli, E.; El Haddad, I.; Elbern, H.; Eleftheriadis, K.; Ferreira, J.; Garcia Vivanco, M.; Gilardoni, S.; Golly, B.; Hellebust, S.; Hopke, P.K.; Izadmanesh, Y.; Jorquera, Héctor; Krajsek, K.; Kranenburg, R.; Lazzeri, P.; Lenartz, F.; Lucarelli, F.; Maciejewska, K.; Manders, A.; Manousakas, M.; Masiol, M.; Mircea, M.; Mooibroek, D.; Nava, S.; Oliveira, D.; Paglione, M.; Pandolfi, M.; Perrone, M.; Petralia, E.; Pietrodangelo, A.; Pillon, S.; Pokorna, P.; Prati, P.; Salameh, D.; Samara, C.; Samek, L.; Saraga, D.; Sauvage, S.; Schaap, M.; Scotto, F.; Sega, K.; Siour, G.; Tauler, R.; Valli, G.; Vecchi, R.; Venturini, E.; Vestenius, M.; Waked, A.; Yubero, E.
    In this study, the performance of two types of source apportionment models was evaluated by assessing the results provided by 40 different groups in the framework of an intercomparison organised by FAIRMODE WG3 (Forum for air quality modelling in Europe, Working Group 3). The evaluation was based on two performance indicators: z-scores and the root mean square error weighted by the reference uncertainty (RMSEu), with pre-established acceptability criteria. By involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), the intercomparison provided a unique opportunity for their cross-validation. In addition, comparing the CTM chemical profiles with those measured directly at the source contributed to corroborate the consistency of the tested model results. The most commonly used RM was the US EPA- PMF version 5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) while more difficulties were observed with the source contribution time series (72% of RMSEu accepted). Industrial activities proved to be the most difficult sources to be quantified by RMs, with high variability in the estimated contributions. In the CTMs, the sum of computed source contributions was lower than the measured gravimetric PM10 mass concentrations. The performance tests pointed out the differences between the two CTM approaches used for source apportionment in this study: brute force (or emission reduction impact) and tagged species methods. The sources meeting the z-score and RMSEu acceptability criteria tests were 50% and 86%, respectively. The CTM source contributions to PM10 were in the majority of cases lower than the RM averages for the corresponding source. The CTMs and RMs source contributions for the overall dataset were more comparable (83% of the z-scores accepted) than their time series (successful RMSEu in the range 25% - 34%). The comparability between CTMs and RMs varied depending on the source: traffic/exhaust and industry were the source categories with the best results in the RMSEu tests while the most critical ones were soil dust and road dust. The differences between RMs and CTMs source reconstructions confirmed the importance of cross validating the results of these two families of models.
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    Fine particulate matter : indoor and outdoor source apportionment at Santiago, Chile
    (2015) Barraza Saavedra, Francisco Javier; Jorquera, Héctor; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Los habitantes de Santiago han estado expuestos a altas concentraciones de material particulado fino (PM2.5) por décadas. La mejoría de los niveles ambientales del MP2.5 en Santiago ha ido frenándose en los últimos años. Para poder solucionar esta problemática, es necesario identificar y cuantificar claramente los agentes que contribuyen al aumento de niveles de PM2.5. El objetivo de esta Tesis es obtener una evaluación mejorada de la calidad del aire existente para Santiago, mediante la identificación y cuantificación de las principales fuentes que contribuyen al PM2.5 en Santiago, diferenciando entre el ambiente intradomiciliario y el exterior. Para cumplir con este objetivo se aplicó un modelo fuente-receptor mediante la utilización del programa computacional PMFv3.0 el cual fue aplicado sobre: a) bases de datos históricos, b) nuevos datos interior/exterior generados por esta tesis y c) nueva base de datos colectados en conjunto con investigadores de la University of Wisconsin-Madison.
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    First measurement of human exposure to current use pesticides (CUPs) in the atmosphere of central Chile: The case study of Mauco cohort
    (2020) Cortés Arancibia, Sandra; Pozo, K.; Llanos Castillo, Yasna Jovita; Martínez, N.; Foerster, C.; Leiva, C.; Ustáriz Lucena, Javier Ernesto; Pribylova, P.; Klanova, J.; Jorquera, Héctor; CEDEUS (Chile)