SOIL QUALITY MONITORING IN OLIVE OIL MILL WASTE DISPOSAL SITES V. KAVVADIAS*, A. SARRIS**, M. DOULA*, D. ZAHARAKI, S. THEOCHAROPOULOS*, K. KOMNITSAS *Soil Science Institute of Athens, National Agricultural Research Foundation, 1 Sof. Venizelou str., 14124 Likovrisi, Greece **Laboratory of Geophysical-Satellite Remote Sensing & Archaeo-environment, Institute for Mediterranean Studies, Foundation for Research & Technology, Hellas, FORTH, Nik. Foka 130, Rethymno 74100, Crete, Greece.  Department of Mineral Resources Engineering, Technical University Crete, 73100 Chania, Greece e-mails: vkavvadias.kal@nagref.gr; asaris@ims.forth.gr; mdoula@otenet.gr; zaharaki@mred.tuc.gr; sid_theo@otnent.gr;komni@mred.tuc.gr. SUMMARY: The uncontrolled disposal of olive oil mill wastes in not properly designed evaporation ponds or directly on soil can cause severe damages to soil properties, affect its quality and subsequently deteriorate the quality of surface- and groundwater in neighboring areas. The aim of this work was to monitor the effects of wastes disposal on soil properties and to develop a soil information and monitoring system for olive oil mills wastes disposal sites with the use of GIS and parameters-indicators for soil quality. Five olive oil mills sites were selected in a pilot municipality in Rethymnon, Crete, South Greece, three of them are active for more than 10 years and two are inactive for the last 6 years. Periodical soil sampling campaigns reveal significant changes in soil properties. The sampling regions have been connected to map layers and an accompanying database of the measured parameters. On-the-fly diagrams that show the temporal fluctuations of the chemical parameters were formed and updated continuously following the corresponding analysis phase. At the same time, surfaces of the most critical parameter-indicators are formed based on kriging interpolation to define their spatial distribution in the wider waste disposal areas. The particular maps are superimposed on other available map layers (e.g. land use, vegetation, geology, erosion, a.o.) contributing to the study of the correlation and effects of the specific pollution parameters to the rest of the environmental attributes of the area. 1. INTRODUCTION The large quantities of Olive Mill Wastes (ΟȂW) generated in the area under study located in the municipality of Nikiforos Fokas, prefecture of Rethymnon, Crete, are disposed of in unprotected evaporation lagoons or directly on soil causing thus deterioration of the quality of soils as well as ground- and surface water. Lagooning is used widely despite the fact that only reduces the volume of wastes without treating the pollutants and a black foul-smelling sludge, difficult to remove and