Arsenic and mercury groundwater contamination caused by oil and gas production wastewaters in the Niger Delta Region

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Arsenic and mercury are two highly toxic elements that compromise groundwater as a source of drinking water globally. According to the World Health Organization, at least 140 million people in 50 countries have been drinking arsenic-contaminated water. While both elements have been studied extensively in Asia, South and North America and Europe, there has been little attention on the African continent.The Niger Delta is the heart of the petroleum industry in Nigeria. Nigeria is the largest natural gas producer in Africa, the sixth-largest crude oil exporter globally, and has the second-largest oil reserves on the African continent. Over the past 50 years, an estimated 13 million crude oil barrels have been spilled in the Niger Delta region. Since both As and Hg are known to occur in crude oil or are released into groundwater during oil spills, we propose the first study concerning As and Hg in Nigeria's oil-producing region, intending to provide crucial information for sustainable and safe use of groundwater. This presents a unique opportunity to study the groundwater contamination related to extensive hydrocarbon production, which can be extrapolated to other locations with a similar incidence.The main goal will be to understand the processes that control the source, transport and fate of As and Hg in groundwater. To reach this goal, field and laboratory studies will be carried out to predict the possibility of elevated As and Hg concentrations in groundwater. Furthermore, we will evaluate removal techniques that are simple but efficient and can be deployed at the household scale.Four hypotheses drive the study:1. Introduction of oil and gas production wastewater into the aquifer potentially elevates the concentration of As and Hg in groundwater2. A concentration increase of Hg and As in groundwater is possible if the aquifer matrix contains geogenic Hg and As.3. Mobilization of geogenic Hg and As from sulfide minerals (e.g., pyrite) and natural organic matter due to oxidation by oxygen introduced into the aquifer by either natural or anthropogenic processes.4. Manual filters of brass granule and iron oxide remove As and Hg from groundwater.