Heavy Metal Concentration In a Degraded Soil After Sewage Sludge Application.

The objective of this study was to assess possible contamination by heavy metals in a degraded area of sandy soil after application of increasing doses of sewage sludge in order to recover it. The experiment was conducted at Entre Rios Farm from Suzano Bahia Sul Company, in Itatinga, São Paulo State, Brazil. The treatments were: doses of sewage sludge on a dry basis (2.5, 5, 10, 15 and 20 Mg ha^-1 + K supplementation), conventional fertilization (NPK) and control. Nine species of the Atlantic Forest were tested: Croton floribundus, Schinus terebinthifolius, Peltophorum dubium, Cedrella fissilis, Guazuma ulmifolia, Anadenanthera macrocarpa, Copaifera langsdorffii, Hymenaea courbaril and Cariniana estrellensis. Higher doses of sludge increased the total and available heavy metals in soil. However, until the dose of 20 Mg ha^-1, the presence of metals was not detected in foliar analysis carried out up to 18 months after sludge application. The levels of heavy metals available to the soil remained below the limit allowed by Brazilian, which allows the use of this waste in the recovery of degraded areas.