1 23 Environmental Earth Sciences ISSN 1866-6280 Volume 75 Number 4 Environ Earth Sci (2016) 75:1-9 DOI 10.1007/s12665-015-5145-5 Heavy metal pollution and ecological geochemistry of soil impacted by activities of oil industry in the Niger Delta, Nigeria P. O. Fatoba, C. O. Ogunkunle, O. O. Folarin & F. A. Oladele