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Understanding and modelling land use and land cover (LULC) change have become one of the major subjects of interest for environmental management due to the negative effects that human activities generate on the normal functioning and dynamics of freshwater resources. Remote sensing and geographic information systems (GIS) are essential tools for assessing the drivers that cause LULC change and its relationship with lake and reservoir water quality. The objective of this study was to assess the spatial and temporal dynamics of LULC change in the watershed of Los Molinos reservoir (Argentina), and to investigate its relationship with the reservoir's water quality. Four Landsat imagery was used to analyse the LULC change in the studied watershed and in different buffer zones from 1990 to 2020. Further, the Normalized Difference Vegetation Index (NDVI) derived from a MODIS time-series dataset (2001–2020) was used to explain the effects of LULC change on the status of the reservoir. Results showed that the most significant LULC change started two decades ago and it has intensified during the last ten years. This change is related to the intensification of agriculture activities, and to the increasing conversion into urban areas, mainly on the shores of Los Molinos reservoir. During the period 2010–2020, urbanization located in the 1 km buffer zone defined from the shore of the reservoir increased at an annual rate of 18.02%. The degradation trend of LULC in Los Molinos watershed significantly contributed to the degradation of water quality of the reservoir. This was corroborated by analysing the MODIS NDVI time-series, which showed that since 2014 the NDVI trend-line presented an increasing behaviour and extreme values of NDVI, related to algal blooms, were more frequently observed. Fil: Bonansea, Matias. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria; Argentina Fil: Bazán, Raquel del Valle. Comisión Nacional de Actividades Espaciales. Instituto de Altos Estudios Espaciales "Mario Gulich"; Argentina Fil: German, Alba. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Actividades Espaciales. Instituto de Altos Estudios Espaciales "Mario Gulich"; Argentina Fil: Ferral, Anabella. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Actividades Espaciales. Instituto de Altos Estudios Espaciales "Mario Gulich"; Argentina Fil: Beltramone, Giuliana Beatriz. Comisión Nacional de Actividades Espaciales. Instituto de Altos Estudios Espaciales "Mario Gulich"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cossavella, Ana Maria. Universidad Nacional de Córdoba; Argentina Fil: Pinotti, Lucio Pedro. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina

Water bodies eutrophication is a worldwide environmental problem characterized by excessive phytoplankton growth which often includes occurrence of harmful algal blooms events. Chlorophyll-a concentration is widely used as an indicator of biomass and can be quantified by optic sensors. In this work, we use a satellite derived Chlorophyll-a concentration time series for the period 2001–2014 obtained from MODIS/TERRA data to detect and characterize algal bloom events in an eutrophic reservoir. Our results demonstrate that fixed threshold methods identify too many bloom dates but a dynamic method based on frequencies analysis and statistical approach, performed better because it represents the normal phytoplankton mass and a bloom is identified like a deviation from it. This approach was tested in San Roque reservoir which supplies fresh water to Cordoba city, one of the most populated of Argentina. According to Carlson index values, this is an eutrophic to hypereutrophic water body. Validation of log10 (Chlorophyll-a concentration) derived from satellite model concentration with ground-based measurements data of Chlorophyll-a concentration demonstrates an acceptable error (RMSE = 0.59) considering data distribution. The implementation of the proposed method to identify blooms over a control data set and validated with LANDSAT 8 - OLI images, demonstrates that the approach described is robust and stable over time.

The adsorption of n-alkanethiols on the 1 1 1 surface of copper was studied by means of quantum mechanical calculations. Charge transfer processes between the adsorbates and the metal were investigated in order to elucidate the nature of the adsorbed species. The electronic structure of the adsorbates in the proximity of the Fermi level was also investigated to obtain a better understanding of the electronic states which contribute to scanning tunneling microscopy (STM) images. We found that the bonding of the n-alkanethiols is independent of the chain length when the adsorbates are perpendicular to the surface. This bonding mainly involved the sulfur p-orbitals and, to a lesser extent, the orbitals of the first methyl group. From the analysis of dipole moment curves and Mulliken populations, a charge transfer of 0.6 electrons from the metal towards the adsorbate was obtained, thus confirming the anionic nature of the adsorbate. A depletion of electron density was observed in the metal atoms of the primary chemisorption site as well as a net accumulation of charge around the sulfur atom. Constant current STM images of thiols adsorbed flat on the surface showed a pronounced protrusion on the position of sulfur due to the accumulation of electron density around this atom in the proximity of the Fermi level. However, for thiols adsorbed perpendicular to the surface, the STM images were found to be sensitive to the position of the terminal methyl group. A corrugation of 1.5 A was obtained for a methyl radical adsorbed perpendicular to the surface.