Spatio-temporal analysis of the geochemical state of the surface waters and active sediments of the Huasco River

This thesis aims to analyze the spatiotemporal geochemical condition of surface waters and active sediments in the Huasco River. A database was developed from samples collected in April 2007 and January 2008, supplemented by geochemical data from published studies and public agencies, covering 2015 and 2016. Data sets were filtered to exclude parameters where more than 70% of observations were below detection limits, and only matching parameters across matrices were selected. To determine whether the observed concentrations were of natural or anthropogenic origin, the isometric log-ratio transformation (Egozcue et al., 2003) was applied to the variables, and statistical methods like box plots, principal component analysis, and factor analysis were used, alongside concentration profiles by distance to the sea and enrichment factor calculations. Data from various years was used to build concentration profiles versus distance to the sea and evaluate environmental quality through specific parameters. Primary sources of elements in both matrices include mineral deposits from the ferriferrous belt, while surface waters showed the influence of marine aerosols up to 40 km inland. A year-on-year comparison between 2007 and 2008 indicated rising concentrations in surface waters and decreasing levels in sediments. A similar trend was observed when comparing 2007-2008 data with that of 2015-2016, likely due to climate events mobilizing material and redistributing elements in the river. Surface water quality showed elevated levels of NO₃ and Fe, where NO₃ may enter through soil fertilization, warranting further isotopic analysis, and Fe levels exceeded standards throughout the valley