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La presente memoria de Trabajo Fin de Máster trata de aplicar todos los conocimientos adquiridos durante el año para desarrollar la mejora del diseño de una unidad didáctica sobre el estudio de las reacciones químicas, impartida en la asignatura de Física y Química de 3º de ESO. Con este objetivo, se ha considerado tanto el marco normativo del currículo, como el desarrollo de los referentes teóricos, donde se ha analizado la evolución histórica de los contenidos tratados, las principales dificultades de aprendizaje asociadas al tema, y algunos aspectos relacionados con la estrategia basada en la construcción de modelos, propia del método constructivista, que será aplicada en el desarrollo de la unidad. Finalmente, se describen algunas conclusiones sobre las principales mejoras que han sido aplicadas, implicaciones educativas, y la futura formación docente necesaria., The purpose of this Master´s Thesis is to apply all knowledge acquired during the present year in order to develop the improvement of the design of a didactic unit on chemical reactions, taught in Physics and Chemistry subject for the 3rd year of Secondary Education (Spanish Education System). Both the normative framework of the curriculum and theoretical references, including historical evolution of treated contents, main learning difficulties related to the topic, and some aspects about modelization, typical of the constructivist method, which will be applied in the unit, have been considered. Finally, some conclusions about main improvements, educational implications, and future teacher training needed, are showed.

In this work we have monitored the seasonal inputs, occurrence and distribution of the world’s most widely used surfactants (linear alkylbenzene sulfonates, LAS, nonylphenol polyethoxylates, NPEOs, and alcohol polyethoxylates, AEOs) in Mar Menor lagoon (SE Spain) and its main tributary (El Albujón) for the first time. Concentration of target compounds was determined in both surface waters and sediments after solid phase extraction and pressurized liquid extraction, respectively, followed by liquid chromatography-mass spectrometry (LC-MS). There were significant differences in surfactant fluxes from El Albujón towards Mar Menor depending on the season and the day of the week, with maximum estimated annual inputs being detected for LAS (406 kg) and their metabolites, sulfophenyl carboxylic acids (482 kg). Average concentrations of surfactants in the lagoon were between 44 and 1665 µg/kg in sediment, and between 0.3 and 63 µg/L in water. These levels were significantly higher for samples collected near the shore than for those measured inside the lagoon itself. Overall, the occurrence and distribution of surfactants in the system could be explained due to a combination of different sources (surface and groundwater inputs, treated and untreated wastewater effluents, towns, ports, etc.) and simultaneous in-situ physicochemical and biological processes, with an special emphasis on degradation during warmer months.

Synthetic surfactants are among the chemicals that are produced and consumed in the largest volumes in the world (more than 10 million tons per year), due to their variety of applications, mainly as key ingredients in detergents and cleaners but also as additives in paints, pesticides, personal care products, etc. In spite of the high removal efficiences of surfactant residues in sewage treatment plants (STP), significant amounts of these chemicals reach aquatic ecosystems via direct discharges of treated or non-treated wastewaters, or indirect discharges through rivers, where they are present dissolved or associated with particulate material. Therefore, particular attention has been given to the environmental analysis of anionic and non-ionic surfactants (90% of the overall production. Our main objective in this work was to detect the presence and compare the distribution of the most world-wide used non-ionic (alcohol polyethoxylates, AEOs, and nonylphenol polyethoxylates, NPEOs) surfactants, and an important group of nonionic synthetic water-soluble polymers of ethylene oxide, polyethylene glycols (PEGs), which are also used in a wide range of applications (e.g., antifreeze agents, cosmetics) as well as the main precursors / degradation products of AEOs, in waters and sediments from Mar Menor Lagoon (SE Spain). Under our knowledge, some of the data shown here are among the first even reported on the environmental distribution of PEGs in aquatic systems.