f Contamination plume evaluation of two ditches using frequency domain electromagnetic method

The study site is located at 6 km NW of Coimbra, central Portugal, near two ditches: North ditch and the old Mondego river bed (Fig. 1). These ditches have been receiving sewage water from Coimbra municipality, causing severe environmental problems, such as ground-water contamination. This contamination is affecting agricultural and arboretum activities, which are the main use of the surroundings areas. In this area, the upper bedrock is of Cretaceous age and consist of siliciclastic sediments, limestones and marls, overlaid by recent sediments of the Mondego river. A geophysical survey, using electromagnetic method in frequency domain, was made near the two ditches with contaminated water. The purpose of this survey is to obtain information about the location of the conductive plume induced by organic and chemical pollution. This information will be used to locate fresh water aquifers, in order to provide the suitable location sites of water wells drilling.