Assessing heavy metal contamination in oil and gas well drilling waste and soil in Pakistan

The contamination of soil and water with heavy metals is one of the major environmental problems in the world. Oil and gas exploration and production activities contaminate the environment with heavy metals. In this study, heavy metal concentration was assessed in drilling waste discharges of different oil and gas wells at Khyber Pakhtunkhwa (KP), Pakistan. Moreover, the concentration of heavy metals in the soil surrounding the drilling waste discharges was determined. The representative samples were collected from seven oil and gas drilling waste discharges and the surrounding soil. The collected samples were analyzed for selected heavy metals (Ba, Pb Cr, Cd, Zn, Mn, and Ni) by atomic absorption spectrometric standard methods. Analysis showed that oil and gas well drilling operation waste is enriched with determined heavy metals. The high concentration of heavy metals, particularly Ba and Pb, was also found in the surrounding soil samples. In particular, Ba concentration varied from 1050 to 4168 mg/kg soil. Statistical correlational analysis depicted a common origin of the heavy metals in the soil of the study area, potentially the drilling waste discharges from oil and gas wells. The concentration of heavy metals in oil and gas well drilling waste discharge high, and also affects surrounding soils.