Browsing by Author "Jorquera, Hector"
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- ItemAnalysis of urban pollution episodes by inverse modeling(PERGAMON-ELSEVIER SCIENCE LTD, 2010) Jorquera, Hector; Castro, JulioUrban pollution episodes pose two relevant issues: a) was the episode controlled by specific meteorology, a rise of emissions or both? b) Were mitigation measures effective in curbing down pollution? A methodology for answering those questions comes from an inverse modeling approach. In this work we have applied the methodology to the city of Santiago, Chile for which the required input data are available. We use a Kalman filter and ambient observations to constrain sources of tracers such as CO, elemental carbon and suspended street dust. The period analyzed is the week from May 20th till May 26th 2005. We find that a posteriori CO emissions were 76% of the a priori estimates. For suspended street dust a posteriori values are 36% and 21% of the prior values for coarse and fine fractions, respectively. Elemental carbon emissions are underestimated in the prior inventory - we find a correction factor of 1.53 for the whole week. Sensitivity analyses tested the robustness of a posteriori estimates, generating ensembles of simulations for different modeling options. For different initial prior estimates, the ratio of standard deviation to mean values was below 0.20 for 75% of the a posteriori, estimated emissions. For different choices of the error covariance matrices and model errors those ratios were below 0.30 for 75% of a posteriori emissions, which shows the robustness of results for different parameter choices - only a small fraction of results were not significant. The high pollution peaks on May 21st are due to specific meteorological conditions and increased traffic emissions as well. Contingency measures taken on Sunday May 22nd and better dispersion conditions on Monday May 23rd stopped the accumulation of those pollutants, showing the effectiveness of short term strategies such as traffic bans and street sweeping operations in curbing down traffic pollution at Santiago. (C) 2009 Elsevier Ltd. All rights reserved.
- ItemEnvironmental signature and health risk assessment of polybrominated diphenyl ethers (PBDEs) emitted from a landfill fire in Santiago de Chile(2023) Pozo, Karla; Oyola, Germán; Jorquera, Hector; Gomez, Victoria; Galbán-Malagón, Cristobal; Mena-Carrasco, Marcelo; Audy, Ondřej; Příbylová, Petra; Guida, Yago; Estellano, Victor Hugo; Lammel, Gerhard; Klánová, Jana; CEDEUS (Chile)Polybrominated diphenyl ethers (PBDEs) have been used as flame retardants in building materials, electronics, furnishings, vehicles, airplanes, plastics, polyurethane foams, and textiles for many years. Currently, the primary commercial mixtures, penta-, octa-, and deca-BDE, are globally restricted. Still, products containing PBDEs are expected to impact waste management and the environment for many years. In January 2016, an open fire in the Santa Marta landfill close to Santiago de Chile affected the city and surroundings. The fire caused several acute health effects and an increase in emergency hospitalizations. We measured PBDE levels in the areas affected by the fire in the air (gaseous and particulate) and soil, and PBDE emissions were estimated using a dispersion model. The results showed an increase in PBDE concentrations by a factor of 2–4 one day after the start of the fire. However, PBDE concentrations measured after the fire in PM10 and the gas phase were considered low compared to other regions. Interestingly, PBDEs’ patterns differed across the sites; however, BDE209 was the dominant congener for all environmental matrices. A preliminary risk assessment was conducted using the daily exposure dose (DED) by air inhalation estimation. The results showed low DED values for adults and children and suggested no direct health risk due to PBDE exposure. This study brings new data useful for future solid waste management initiatives in the country
- ItemFast and reliable calibration of solid substrate fermentation kinetic models using advanced non-linear programming techniques(UNIV CATOLICA DE VALPARAISO, 2007) Macarena Araya, M.; Arrieta, Juan J.; Ricardo Perez Correa, J.; Biegler, Lorenz T.; Jorquera, HectorCalibration of mechanistic kinetic models describing microorganism growth and secondary metabolite production on solid substrates is difficult due to model complexity given the sheer number of parameters needing to be estimated and violation of standard conditions of numerical regularity. We show how advanced non-linear programming techniques can be applied to achieve fast and reliable calibration of a complex kinetic model describing growth of Gibberella fujikuroi and production of gibberellic acid on an inert solid support in glass columns. Experimental culture data was obtained under different temperature and water activity conditions. Model differential equations were discretized using orthogonal collocations on finite elements while model calibration was formulated as a simultaneous solution/optimization problem. A special purpose optimization code (IPOPT) was used to solve the resulting large-scale non-linear program. Convergence proved much faster and a better fitting model was achieved in comparison with the standard sequential solution/optimization approach. Furthermore, statistical analysis showed that most parameter estimates were reliable and accurate.
- ItemSource apportionment of ambient PM2.5 in Santiago, Chile: 1999 and 2004 results(ELSEVIER SCIENCE BV, 2012) Jorquera, Hector; Barraza, FranciscoA receptor model analysis has been applied to ambient PM2.5 measurements taken at Santiago, Chile (33.5 degrees S, 70.7 degrees W) in 2004 (117 samples) and in 1999 (95 samples) on a receptor site on the eastern side of the city. For both campaigns, six sources have been identified at Santiago and their contributions in 1999/2004 are: motor vehicles: 28 +/- 2.5/31.2 +/- 3.4%, wood burning: 24.8 +/- 2.3/28.9 +/- 3.3%, sulfates: 18.8 +/- 1.7/16.2 +/- 2.5%, marine aerosol: 13 +/- 2.1/9.9 +/- 1.5%, copper smelters: 11.5 +/- 1.4/9.7 +/- 3.3% and soil dust: 3.9 +/- 1.5/4.0 +/- 2.4%. Hence relative contributions are statistically the same but the absolute contributions have been reduced because ambient PM2.5 has decreased from 34.2 to 25.1 mu g/m(3) between 1999 and 2004 at Santiago. Similarity of results for both data sets - analyzed with different techniques at different laboratory facilities - shows that the analysis performed here is robust.
- ItemSource apportionment of PM10 and PM2.5 at Tocopilla, Chile (22A degrees 05' S, 70A degrees 12' W)(SPRINGER, 2009) Jorquera, HectorTocopilla is located on the coast of Northern Chile, within an arid region that extends from 30A degrees S to the border with PerA(o). The major industrial activities are related to the copper mining industry. A measurement campaign was conducted during March and April 2006 to determine ambient PM10 and PM2.5 concentrations in the city. The results showed significantly higher PM10 concentrations in the southern part of the city (117 mu g/m(3)) compared with 79 and 80 (mu g/m(3)) in the central and northern sites. By contrast, ambient PM2.5 concentrations had a more uniform spatial distribution across the city, around 20 (mu g/m(3)). In order to conduct a source apportionment, daily PM10 and PM2.5 samples were analyzed for elements by XRF. EPA's Positive Matrix Factorization software was used to interpret the results of the chemical compositions. The major source contributing to PM2.5 at sites 1, 2 and 3, respectively are: (a) sulfates, with similar to 50% of PM2.5 concentrations at the three sites; (b) fugitive emissions from fertilizer storage and handling, with 16%, 21% and 10%; (c) Coal and residual oil combustion, with 15%, 15% and 4%; (d) Sea salt, 5%, 6% and 16%; (e) Copper ore processing, 4%, 5% and 15%; and (f) a mixed dust source with 11%, 7% and 4%. Results for PM10-at sites 1, 2 and 3, respectively-show that the major contributors are: (a) sea salt source with 36%, 32% and 36% of the PM10 concentration; (b) copper processing emissions mixed with airborne soil dust with 6.6%, 11.5% and 41%; (c) sulfates with 31%, 31% and 12%; (d) a mixed dust source with 16%, 12% and 10%, and (e) the fertilizer stockpile emissions, with 11%, 14% and 2% of the PM10 concentration. The high natural background of PM10 implies that major reductions in anthropogenic emissions of PM10 and SO2 would be required to attain ambient air quality standards for PM10; those reductions would curb down ambient PM2.5 concentrations as well.