Evaluation of the contamination on organic soil of Gramacho M.S.W. Landfill, Brazil

摘要

The Metropolitan Gramacho Landfill, was considered the largest landfill in Latin America. Its activities of waste disposal ended in June 2012. The disposal of waste at the site was carried out directly on the foundation soil since the beginning of its operation (1978). Taking into consideration that contaminants present in leachate can migrate by diffusion through the landfill organo-saline clay and reach the surroundings, an investigation of the soil contamination on the landfill perimeter was performed. Such investigation was conducted in the soil pore water in two types of contaminants: ammonium and total organic carbon (TOC), to assess organic compounds. Moreover, acute toxicity tests with the species Vibrio fischeri were performed to evaluate the toxicity in the soil. Batch tests and diffusion tests were executed in order to better understand the behaviour of the investigated contaminants. The results showed low values of ammonium and soil TOC. Ammonium values are considered low, as even in samples of lateral barrier soil, situated next to where there was a leachate drainage ditch, which are smaller than 1% of the one found in the leachate. The acute toxicity tests pointed to the Hormesis effect in the samples of pore water, indicating the possible presence of chronic toxicity.