Characterisation and evolution of a soil affected by olive oil mill wastewater disposal

A location used for 10 years as an uncontrolled olive oil mill wastewater d isposal site is studied in this work. Once it was closed the sedimented sol id waste on the soil surface was removed. In order to evaluate the influenc e upon soil characteristics, morphological aspects and analytical parameter s of a soil profile from the affected zone are compared to those of a contr ol soil located near the landfill. The residual contamination levels in the underlying soil are determined. The results show that the wastewater infil tration in the soil has caused carbonate dissolution and redistribution and modifications in pH values, electrical conductivity, nutrient contents, ph enolic compounds and biological activity of the horizons. Removal of waste, natural leaching and biological activity, in time, led to an effective dec rease in electrical conductivity and phenolic compounds, although residual levels can be important even 2 years later. (C) 2001 Elsevier Science B.V. All rights reserved.