Mapping leachates and subsurface structures using different geophysical methods.

Sammanfattning: The enrichment of ore produces large amounts of sulfur and metal-rich residual waste called tailings, which need to be deposited and stored for a long time. When the tailing is oxidized, large amounts of protons and metals are dissolved and diffuse to the groundwater. This poses a major environmental threat to biological life forms in the downstream ecosystem (Karltorp, 2008). In this study, leachate plumes and geological structures surrounding the tailings impoundment at the Kringelgruvan mine in northern Sweden have been successfully mapped using geophysical methods. Three methods have been used in parallel, slingram, ground penetrating radar (GPR) and electrical resistivity measurements, known as continuous vertical electrical sounding (CVES). The resulting data from GPR and CVES have been co-analyzed using Matlab. Algorithms have been produced that plots underground structures from CVES and compares them with interpreted structures from GPR. Studies have shown that the GPR is more sensitive than CVES to local variations of substructures when used in shallow soil cover, while CVES gives considerably more information regarding localization of the leachates and other electrically conductive materials, such as ore. Slingram EM31 has been shown to be the most time-efficient method to localize groundwater flow.