Avaliação fitotoxicológica e físico-química de solos sob influência de lixão ativo no município de Crateús-CE utilizando allium cepa e lactuca sativa

Abstract

The inadequate disposal of municipal solid waste is one of the greatest environmental challenges in Brazil, especially in the northeast region, where the persistence of disposal in landfills compromises the quality of natural resources. Leachate, a polluting liquid that originates from decomposition of solid waste, can cause contamination by carrying heavy metals, salts, and organic compounds that infiltrate the soil. Given this scenario, the objective of this work was to investigate the environmental quality of the soil in the area of the active municipal landfill of Crateús, in Ceará, seeking to understand how the presence of these wastes alters the chemical characteristics of the soil and whether these changes can harm the initial development of plants and to evaluate the feasibility of phytotoxicological assays for monitoring the area. To perform this investigation, three collection sites were selected: two points located in the waste disposal area (P1 and P2) and a third point located about 500 meters away (P3), serving as a reference for soil in its natural state for comparison purposes. In the laboratory, physicochemical analyses of the soil were performed, and subsequently, the samples underwent an extraction process to remove the substances present, and the extracts obtained were tested on onion (Allium cepa) and lettuce (Lactuca sativa) seeds. The final extract was reconstituted with acetone, which is a solvent that can present toxicity in moderate to high concentrations; therefore, the ecotoxicological tests were performed with a 0.1% dilution of these extracts. Chemical analyses revealed that the landfill soil has some important alterations, such as the presence of arsenic at Point 1 at levels above the investigation value recommended by CONAMA Resolution No. 420, in addition to a high amount of salts and ammonium at Point 2, which is an older disposal area. However, when observing the behavior of the seeds, the results showed that the soil toxicity is low and does not affect the entire area equally. At Point 1, the seeds showed germination and initial root development. At Point 2, a difficulty in the growth of lettuce roots was noted, which seems to be more related to the excess of salts and soil salinity. The study concludes that, although there are warning signs in the chemical composition of the soil, such as arsenic and salinity, the potential to cause immediate damage to plants is small under the observed conditions.