THE FATE OF TRACE ELEMENTS IN OIL-POLLUTED GROUNDWATER UNDERGOING REMEDIATION: INSIGHTS FROM AL BATINAH, NORTHEAST OMAN

Abstract

Groundwater serves as a critical and often sole source of drinking water in arid regions such as Oman, necessitating vigilant monitoring to prevent contamination and depletion. Industrial activities and other anthropogenic sources pose significant threats to groundwater quality, leading to various forms of pollution. This study specifically addresses groundwater contamination by oil in the Al Batinah region of Northeast Oman, where untreated water samples exhibited oil concentrations below 0.5 mg/l, likely stemming from historical industrial discharges. The primary objective of this research was to investigate the mobility and decontamination levels of various trace elements as the polluted groundwater underwent a multi-step ex-situ treatment process. The treatment involved an initial air flotation step, followed by anthracite filtration, and finally, activated charcoal filtration. Approximately 15 water samples were collected from seven monitoring wells under air sparging treatment for oil contamination, as well as from various stages of the ex-situ treatment plant: raw water, water after air flotation, water after anthracite filtration, and water after activated carbon adsorption. The trace elements investigated included Na, Mg, Ca, K, Fe, Cr, Ni, Cu, Zn, Ag, Cd, Sr, Ba, Pb, and rare earth elements (REEs). Chemical analysis revealed distinct behavioral patterns for different trace elements during the remediation process. Notably, nickel (Ni), zinc (Zn), copper (Cu), and aluminum (Al) concentrations increased relative to untreated water, while silver (Ag) and total REEs showed a decrease. Major elements and other trace elements such as chromium (Cr), lead (Pb), and cadmium (Cd) generally remained unchanged throughout the treatment. The study highlights the complex interactions and mobility of trace elements during groundwater remediation, emphasizing the importance of detailed chemical investigations of treatment agents and the speciation of key trace elements at each procedural step to optimize decontamination efforts and ensure water quality [21, 22, 23].