Estimación de secuestro de hidrocarburos en suelos: influencia de las características químicas de las sustancias húmicas

Abstract

Soil organic matter (SOM) is a key factor controlling the fate of hydrocarbons in soils; however, there are no standardized methods to accurately predict their sequestration. This study proposes an accessible analytical tool to predict the capacity of a soil to sequester hydrocarbons considering the chemical characteristics of humic (HA) and fulvic acids (FA) in SOM. The natural soil was modified by thermal treatments, obtaining five different soils. Their SOM was fractionated into HA and FA, and each fraction was characterized by UV-Vis and FTIR. The soils were contaminated with a hydrocarbon mixture (hexadecane [HXD], phenanthrene [PHE], and pyrene [PYR]), and the sequestered concentration of each hydrocarbon was quantified. The soil treated at 350 ºC presented seven times greater capacity to sequester polycyclic aromatic hydrocarbons (PAHs >100 mg∙[kg soil]-1) than that of the natural soil. The characteristics that significantly improved the sequestration of PAHs were: i) FA with low molecular weight and degree of condensation, and ii) HA with high molecular weight, aromaticity, aliphaticity, polarity and degree of condensation. Based on these results, two equations are proposed to predict, with more than 80% accuracy, the sequestration of PAHs in soils with different composition through UV-Vis and FTIR analysis of HA.