Avaliação preliminar da poluição do solo e da água subterrânea da área de um lixão desativado

Abstract

The deposition of solid waste on soil is one of the oldest methods of waste final disposal. Dumpsites presents direct contact between waste and soil, therefore the components of the leachate can migrate through it, contaminating it and possibly reaching the local groundwater. The objective of this study is to evaluate the contamination of soil and groundwater in the area of influence of an open dump operated for approximately 25 years, through physico-chemical analysis of soil, groundwater and 3 leachate lagoons. For this purpose, monitoring wells were installed, the local potentiometric map was prepared, the local subsoil assessment was carried out and physico-chemical analysis of groundwater, soil in depth, leachate accumulation lagoons and outcrops were performed. Three contaminants that generally presents high concentrations in waste leachate were selected: chloride, ammoniacal nitrogen and total organic carbon. The analysis of the local soil profile shows mostly clayey soil, also occurring a region of sandy predominance, and great variation in the depth of rocky outcrops. The soil in depth showed concentrations of chloride between 17 - 1270 mg.L-1, ammonia nitrogen 0.2 - 1.9 mg.L-1and total organic carbon 10 - 982 mg.L-1. The local groundwater had chloride concentrations between 843 - 3252 mg.L-1, maximum concentration of ammoniacal nitrogen of 2 mg.L-1 and 132 mg.L-1 of organic carbon. The leachate accumulation lagoon located closest to the waste showed the highest concentrations of all the contaminants studied. The results show the migration of the leachate components through the local soil and its influence on the local groundwater. The underground water flow occurs from the solid masses towards the leachate accumulation ponds and the equipotential lines demonstrate a possible advance of the contamination plume beyond the limits of the landfill area.