Chemical composition and sources of particulate matter across urban and rural sites in the Caribbean region of Cienfuegos (Cuba)
Palabras clave : 
atmospheric particulate material
Materias Investigacion::Ciencias medioambientales::Atmósfera
Materias Investigacion::Ciencias medioambientales::Contaminación y su control
Fecha de publicación: 
10-ene-2019
Fecha de la defensa: 
10-sep-2018
Cita: 
MORERA-GÓMEZ, Y. "Chemical composition and sources of particulate matter across urban and rural sites in the Caribbean region of Cienfuegos (Cuba)". Santamaría, J.M., Elustondo, D. y Alonso, C.M. Tesis doctoral. Universidad de Navarra, 2018.
Resumen
Particulate matter (PM) is a complex mixture of small particles and liquid droplets suspended in the atmosphere originated from a wide range of natural and anthropogenic sources that has been related with many adverse effects on human health, ecosystems and climate. Consequently, the deterioration of air quality caused by the release of PM is one of the main environmental concerns in the world and has resulted in many resources being invested in monitoring and controlling air pollution. In Cuba, the study of atmospheric PM pollution constitutes one of the most challenging issues in environmental research because there are still technical and¡ analytical limitations that prevent its correct monitoring. Therefore, conducting studies on PM are of paramount importance to fill the existing gap, providing useful information to develop effective strategies to improve air quality in this region. The general objective of this thesis is to investigate the levels and chemical composition of atmospheric particulate material present in rural and urban areas of Cuba. More specifically, the work aims to identify the main sources of emission of PM, evaluating its possible effects on air quality and the environment. For this purpose, during a period of one year (January 2015 to January 2016) samples of PM10 were simultaneously collected in a rural and an urban site of Cienfuegos by means of highvolume samplers. Likewise, in the rural site monthly samples of bulk depositions were collected between March 2014 and November 2016. In order to improve the process of identification of sources, several samples from aerosol emitters were also collected during 2015 and 2016 in the region studied. The samples thus collected were later analyzed by applying various analytical techniques, determining a high number of chemical elements and the stable carbon and nitrogen isotope signatures. The different research works carried out in this thesis have been presented in five chapters. In the first one it is shown that concentrations of PM10 reached annual averages of 35.4 and 24.8 μg m-3 in the rural and urban sites respectively. The highest concentrations of PM were observed between March and August, coinciding with a strong advection of Saharan dust clouds. The PM10 daily limit (50 μg m-3) established in the Cuban legislation for air quality was exceeded 3 and 8 times in the rural and urban sites, respectively. Chemical characterization of PM10 showed important contributions of mineral matter, total carbon and secondary inorganic compounds in the region, detecting higher concentrations in the urban site. A source apportionment analysis using Positive Matrix Factorization (PMF) model identified 5 main sources in the studied sites (Saharan intrusions, marine aerosol, combustion, road traffic and cement plant). Saharan dust contribution was quantified for the first time in Cuba, proving to be one of the most important pollution sources in the region. In the second chapter the content, pattern and sources of lanthanoid elements (La to Lu) in PM10 are investigated. Lanthanoid elements concentrations were distributed unevenly throughout the year, showing higher values in the period between April and August when Saharan dust intrusions are more frequent. According to the results, most lanthanoid elements exhibited a dominant crustal origin, but the influence of anthropogenic emissions was also demonstrated by the strong fractionation of lanthanoid ratios as well as the higher enrichment factors of heavier lanthanoids. By using different approaches, including the application of the conditional bivariate probability function (CBPF) and the concentration-weighted trajectory (CWT), four pollution sources were identified: crustal matter (driven by Saharan dust and local soils), oil combustion (power plant and shipping emissions), petroleum-coke combustion (cement plant) and urban road traffic. Chapter 3 reports on the study of the stable isotope compositions (13C and 15N) of total carbon (TC) and nitrogen (TN) in both PM10 and emissions from potential sources of contamination. 13C isotope signatures revealed that air quality was degraded by the mixed contributions from two main emitters: combustion of fossil fuel and cement plant and quarries, with this last source impacting more air quality at the urban site. In addition, TN and 15N values from the urban site demonstrated that nitrogen in PM10 was generated by secondary processes through the formation of (NH4)2SO4 and that the corresponding 15N enrichment is controlled by exchange between gaseous NH3 and particle NH4 + in the (NH4)2SO4 molecule under stoichiometric equilibrium. By comparing15N values in PM10 at lower nitrogen concentrations with those measured in samples from potential sources of pollution it was concluded that emissions from diesel cars and the power plant may represent the major vectors of primary nitrogen. The fourth research study carried out in this thesis describes exhaustively the major and trace elements analyzed in monthly bulk depositions. Bulk depositions and fluxes of the elements studied showed a high variability, without exhibiting any evident pattern between dry and wet periods, result that was attributed to fluctuations in emissions from their main sources. However, stronger correlations were found between typical crustal elements, which showed a marked seasonality related to the presence of Saharan clouds dust in the Caribbean. Most of the analyzed elements were found in the variation range of those reported in rural environments around the world but the elements V, Ni, As and Sb presented higher levels, typically founded in urban and industrial areas. The elements Zn, Sb, Pb, W, Sn, S, Cu, Mo, Nb and P were significantly enriched, revealing their anthropogenic origin. Finally, the application of Principal Components, Multilinear Regression and Cluster statistical analyses led the identification of 5 main sources contributing to bulk deposition: crustal matter (39.5%), marine aerosol (38.2%), combustion processes (6.7%), industries (8.7%) and road traffic (1.4%). In the last chapter, the implications of the results obtained in the air quality and the environment of the studied area are evaluated. It should be noted that the results obtained in this work can contribute to significantly improve the understanding of the properties of aerosols in the atmosphere and the potential impacts of air pollutants on terrestrial and aquatic ecosystems. Moreover, this thesis is a valuable source of information to expand the existing datasets in Cuba, thus providing a very useful information to environmental managers and policy makers to take sound decisions that contribute to improving air quality in Cuba.

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