Geophysical assessment of contamination due to explosives in an abandoned facility towards its hydrogeological characterization

摘要

This paper discusses a case study concerning the application of geophysical methods in long-term contaminated areas with explosive compounds and their input to the environmental assessment and hydrogeological characterization. The study is focused on the old factory of Sociedade Portuguesa de Explosivos, located in Seixal, Portugal, that produced explosives for almost 50 years and was closed about 15 years ago. The remains of the activity consist on the production of poly-nitroaromatic compounds that were deposited inside the facilities perimeter and caused negative environmental impacts in the soils and groundwater of the area. Although several studies have been conducted in the Sociedade Portuguesa de Explosivos facilities area and focused on the aquifers to assess the environmental impact of contaminated areas, they were mostly restricted to borehole studies and hydrochemical organic and inorganic compounds analysis of groundwater sampled in the numerous boreholes existing in the area. In the present study, this information is complemented with geophysical surveys that comprised several methods, namely electrical resistivity tomography and both time and frequency domains electromagnetics. Geoelectrical parameters determined with the geophysical surveys and laboratory determinations were related with physical and chemical parameters from soil samples collected in two shallow investigation boreholes located in a poly-nitroaromatic deposition area. These surveys allowed not only an important input to the general assessment of the Sociedade Portuguesa de Explosivos environmental situation but also the evaluation of its effects in the surrounding area and constitute an important input towards its hydrogeological and environmental characterization. They also give information about in situ geoelectrical characteristics of poly-nitroaromatic compounds in long-term attenuation process.