Ecotoxicidade de resíduos sólidos urbanos e de lixiviado gerado em aterro sanitário.

Abstract

The study of ecotoxicity in sanitary landfills aims to measure the potential that Urban Solid Waste (USW), and the leachate, have to cause adverse effects to the environment and human health. Thus, in this work aimed to determine the ecotoxic effects of USW and leachate generated in a sanitary landfill, using test organisms of different trophic levels. The methodology was divided into two general steps: the first comprised the sampling of the USW newly grounded, with 1 and 2 years of grounding, collected at the Sanitary Landfill in Campina Grande (SLCG), Paraíba, Brazil, in which the gravimetric composition, physicochemical characterization and classification, phytotoxicity tests using Relative Seed Germination (RSG), Relative Root Growth (RRG) and analysis of Effective Concentration (EC50.5days) in tomato (Solanum lycopersicum) and cabbage Brassica oleraceae) seeds was determined; in the second stage, physical-chemical and ecotoxicological tests were carried out on tomato seeds, cabbage, microcrustaceans (Daphnia magna) and earthworms (Eisenia andrei), using the in natura leachate of the SLCG. For the phytotoxicity of the USW, at a concentration of 1%, the RSG was equal to 300, 20 and 7% (tomato seeds) and 117, 600 and 47% (cabbage seeds) for newly grounded residues, with 1 and 2 years, in respective. The RRG of tomato and cabbage seeds, for residues with 1 year of grounding, was of 105.4, 74.6 and 87.56% and 84.94, 75.86 and 61.15%, respectively, at the dilutions of 1, 5 and 10%. For residues of 2 years, the RRG was of 170, 171, 94, 70 and 60%, in the dilutions of 1, 5, 10, 25 and 50% and of 18, 15.92, 34 and 49.61% at the concentrations of 1, 5, 10 and 25% in tomato and cabbage seeds, in sequence. An EC50.5days of 20.85 and 47.91% were observed in tomato seeds and an EC50.5days of 40 and 32% in cabbage seeds, for residues with 1 and 2 years, in this order. Tomato and cabbage seeds exposed to leachate showed EC50.5days of 12.75 and 16.78%, respectively. In the toxicity assessment of the leachate, an EC50.48h of 1.22% to Daphnia magna, and a Lethal Concentration (LC50.14days) of 56%, to Eisenia andrei, were obtained. The behavioral escape test showed that exposure to concentrations between 10.38 and 39.86 mL.kg-1 of leachate resulted to the escape of earthworms and habitat loss was observed at a concentration of 55.80 mL.kg-1, in which the źscape (Ż) ≥ 80% was obtained. It was concluded that the toxicity of residues in tomato and cabbage seeds reduced with increasing of the grounding time. The leachate of SLCG proved to be very toxic to seeds, to Daphnia magna and to Eisenia andrei and, between the test organisms evaluated, the microcrustacean was the most sensitive. However, the other organisms proved to be adequate for the ecotoxicological assessment of the leachate generated in the SLCG.