Importance of soil horizons in gasohol distribution in the unsaturated zone of a tropical soil

• Main Authors: Thomás Gerdulo Bodelão, Everton de Oliveira, Juliana Gardenalli Freitas, Miguel Alfaro Soto, Sheila A.C. Furquim
• Format: Article
• Language: English
• Published: Associação Brasileira de Águas Subterrâneas 2017-12-01
• Series: Revista Águas Subterrâneas
• Subjects: Solo tropical. Zona não saturada. Gasolina. Etanol.
• Online Access: https://aguassubterraneas.abas.org/asubterraneas/article/view/28924

The main goal of this research was to evaluate the infiltration in the unsaturated zone of a mixture simulating gasoline with ethanol (gasohol) in a typical tropical soil. To achieve that, a field test was performed in the Rio Claro/SP experimental area, simulating a shallow superficial gasohol spill. Twenty-seven liters of a mixture consisting of 60% hexane, 11% of xylene, 11% of benzene and 18% of ethanol were spilled in a 0.3 m deep trench, 2.63 m above the water table. Seven days after the spill, the area was excavated in blocks of 0.2 x 0.2 x 0.15 m and samples were collected from each block. The soil samples were analyzed for the four compounds present in the mixture. Based on the concentrations found in the soil samples, most of the hydrocarbons and the ethanol were accumulated in the shallow horizons, not reaching the water table. The amount of mass found relative to the total mass of hydrocarbons spilled was low, while for the ethanol the mass recovery was complete. Contaminants accumulated mainly in the interface between horizons due to contrasts in water saturation (for ethanol) and in hydraulic conductivity (for hydrocarbons). Therefore, the soil horizons characterization is important to understand contaminants distribution in the unsaturated zone