The Impact of Bitumen Deposits on Groundwater Quality

Physico-chemical and elemental characteristics of groundwaters from a bitumen deposit area in Nigeria were determined with a view to assessing their levels of accumulation by the waters from the bitumen deposit and to provide a framework for the establishment of relationships between the chemistry of the mineral deposit and the groundwaters of the area. Physico-chemical parameters were measured using standard analytical procedures, while the elemental contents were determined by total reflection x-ray fluorescence spectroscopy technique. The results showed that the groundwaters have higher concentrations of elements (V, Cr, Mn, Cu, and Zn), which are known to be associated with hydrocarbon formation, than regular Nigerian groundwaters, apparently due to leaching of the elements from the bitumen deposit into the waters. Comparison of the analyzed parameters with their standard permissible values indicated that the waters were not potable. This was also corroborated by the values of their pollution index. Strong and significant positive correlations existed between some of the analyzed elements (K/Fe, K/Cu, Ca/Cr, V/Pb, Ni/Zn, Ni/Pb, Ca/Zn, V/Cr, V/Mn, V/Ni, V/Zn, Cr/Mn, Mn/Ni, and Ni/Cu), indicating a common source, chemical similarity, and/or common natural background levels in the waters. Elemental clustering results indicated that analyzed transition metals showed the closest inter-element clustering and were corroborated with their Pearson correlation matrices results, indicating chemical affinity and/or similar genetic origin. Strong positive correlations were shown by the results of the cross-plot analysis of the groundwater/oil sand water fraction and groundwater/bitumen suggesting inter-element correlations between them, and also establishing relationships between the groundwaters and the bitumen deposit in the area and that contamination of any components of the ecosystem would easily affect other ecosystems. These results could be used as a fingerprint for bitumen exploration elsewhere and also for similar mineral deposit settings, such as crude oil and coal deposits.