Análise do potencial fitotóxico de lixiviado de lixão ativo no município de Crateús-CE

Abstract

One of the main contemporary environmental problems arises from the intense and accelerated generation of solid waste, as well as the inadequate form of final disposal of this waste. In landfills, there is a accumulation of waste without any control or protection and, consequently, generates significant environmental impacts. Leachate is composed of a complex mixture of several concentrated pollutants, with a high toxic potential capable of causing contamination of soil and water bodies in its area of influence. Thus, the objective of this study was to evaluate the toxicity of leachate produced by the active dump and raw water from the Riacho dos Cavalos reservoir, located in the municipality of Crateús/CE, based on physicochemical and ecotoxicological analyses, using the seeds of Allium cepa L. and Lactuca sativa L. as model organisms. To estimate the toxicity of leachate from the landfill, samples were collected from three different points of the landfill, and two points of the Riacho dos Cavalos reservoir. Physicochemical analysis were carried out to characterize leachate and water samples. To evaluate the phytotoxicity of the samples, tests were carried out with L. sativa (lettuce) and A. cepa (onion) seeds exposed to leachate and raw water samples from each point collected for an exposure period of 168h. The physical-chemical analyzes of the leachate revealed variations in the analyzed parameters, with non-compliance with CONAMA 430/2011. The pH varied between 7.98-8.23, close to neutrality, while conductivity and salinity were higher at point P3 (9.55 mS/cm and 5.46 ppt). COD varied between 2256.1-3891.9 mg/L and Ammonia Nitrogen (NH4-N) also presented values above the limit (20 mg/L), especially point P2 (126.82 mg/L). Raw water samples, on the other hand, demonstrated compliance with the standard.The leachate demonstrated the potential for a significant reduction (p<0.05) in the length of roots exposed to samples from points P2 and P3 for both seeds. The Germination Index (GI) demonstrated that the leachate is capable of causing mild, strong and severe inhibition for the species studied. The Normalized Residual Radical Elongation Percentage (IER) and Relative Growth Index (ICR) values classified the leachate from points P2 and P3 as moderate toxicity (-0.25<IER<-0.5) capable of causing inhibition in the radicle elongation (ICR<0.8). The results of toxicity tests with raw water from the Riacho dos Cavalos reservoir indicated low toxicity for the parameters evaluated for both seeds. The exposure of L. sativa L. seeds to the samples indicated low toxicity for P1 identified by the reduction in radicle length (IER<-0.25), while it showed induction of growth for the P2 point. The seeds of A. cepa L. showed induction of root growth for both points. The results demonstrated that the leachate presents potential toxicity when analyzing the effects on the different parameters studied. Therefore, toxicity tests with leachate allow a more realistic analysis of environmental risk, constituting an important monitoring and evaluation tool that makes it possible to estimate effective environmental damage.