Análise geoquímica de micronutrientes metálicos e aplicação de índices de risco ecológico em solos de áreas suscetíveis à desertificação no Jaguaribe, Ceará

Abstract

This study evaluated the availability of metals and the associated ecological risk in soils withdifferent degrees of degradation in a desertification-prone region in the municipality ofJaguaribe, Ceará State, Brazil. Three areas representing distinct stages of degradation wereselected: control area (CA), recovering area (RA), and degraded area (DA). In each area, threecomposite soil samples were collected at a depth of 0–20 cm, totaling nine samples. Eachsample was analyzed in triplicate in the laboratory to determine its physicochemical propertiesand the concentrations of B, Cu, Fe, Mn, Mo, Ni, and Zn. Metal concentrations were obtainedby partial acid digestion according to the EPA 3051A method and expressed as pseudo-totalconcentrations. Potential ecological risk was assessed using quantitative indices:Geoaccumulation Index (Igeo), Pollution Index (PI), Enrichment Factor (EF), and PollutionLoad Index (PLI). Statistical analyses were performed to evaluate the influence of independentvariables (soil degradation degree: DA, RA, and CA; and soil physicochemical attributes, suchas pH and organic matter) dependent variables corresponding to metal concentrations. Thisanalysis included normality tests, ANOVA, Kruskal-Wallis, and Spearman correlation. Ingeneral, soils from the degraded area showed lower concentrations of essential metals, exceptfor Fe, which presented higher levels in the degraded area, possibly due to the accumulation ofiron oxides in the clay fraction. Ecological risk indices indicated the absence of significantanthropogenic contamination, with values classified as non-polluted or minimally enriched.Significant correlations between Cu and B with organic matter, and between Ni and Zn withpH, suggest that the dynamics of these metals are strongly influenced by these soil attributes,affecting their availability and retention. The results obtained may support decision-makingregarding the management and recovery of degraded areas in semi-arid regions susceptible todesertification.