Evaluación del riesgo geoquímico ambiental del Arsénico (As), Mercurio (Hg) y Plomo (Pb) en suelos mediante la cuantificación espacial de la incertidumbre usando Kriging Indicador (IK) en el sur de Ecuador

Abstract

Abstract: This Final Degree Project assesses the environmental geochemical risk associated with arsenic, mercury and lead in surface soils of a confidential domain in southern Ecuador, quantifying spatial uncertainty through Indicator Kriging. A database of 4060 samples was cleaned down to 3997 valid records, and thresholds were set according to TULSMA soil quality criteria for agricultural and residential use (As 12.0; Hg 0.10; Pb 19.0 ppm), with exceedance proportions of 60.0 %, 31.6 % and 39.6 %. Variographic modelling fitted spherical models with ranges of 2030, 1012 and 1774 m and nugget/sill ratios of 51.9 56.8 %. Estimation was performed over a 50 × 50 m grid (15093 nodes; 37.73 km²). The exceedance probability maps show the widest extent for As (57.9 % of the domain with P > 0.50), a focalized pattern for Hg (13.5 %) and an intermediate condition for Pb (33.0 %); 2.33 km² show simultaneous exceedance of the three potentially toxic elements. Cross-validation confirmed no systematic bias (|ME| < 0.005), with Brier Scores of 0.169 0.194 and accuracies of 70.2 77.2 %. The cartographic products support environmental monitoring prioritization.