Mobility of Trace Elements During Remediation of Oil Polluted Groundwater: A Case Study of Al Batinah Region, Northeast Oman

A study was carried on an area polluted by oil in Oman to determine the mobility of trace elements during each step of an ex-situ treatment process. Quality of groundwater following an air flotation treatment was investigated and discussed. About 15 water samples were collected from 7 monitoring wells which are under air sparging treatment for remediation of oil contamination in Al Batinah region (Northeast of Oman). Chemical composition of groundwater during and after the treatment was compared with chemical composition of groundwater before any treatment. Water samples were also collected from different monitoring wells in the same area. The investigated elements consist in Na, Mg, Ca, K, Fe, Cr, Ni, Cu, Zn, Ag, Cd, Sr, Ba, Pb and rare earth elements (REEs). Chemical composition of trace and major elements during each step of treatment revealed that Ni, Zn, Cu and Al have been increased relative to untreated water contrary to Ag which decreased. Major elements and Cr, Pb, and Cd remain unchanged during the treatment process. The REEs were significantly depleted during the last step of treatment relative to the raw water but their distribution did not reveal any fractionation. Trace elements such as Zn, Cu, Ni show an increase and Ag and REES a decrease relative to raw water before any treatment. For treatment of groundwater, chemical investigation of different agents used during the treatment and the speciation of each key trace elements should be investigated at each step of treatment procedure.