Cl-SO4 Mass Ratio as an Indicator of Contamination of Freshwater Resources in Kuwait by Seawater and Oilfield Brine

Amitabha Mukhopadhyay
The mass ratio of chloride to sulphate in different samples of groundwater from the Raudhatain - Umm AL-Aish area of Kuwait was investigated to assess the extent of contamination of the groundwater by the seawater used for extinguishing the oil fire ignited by the Iraqi Army during the 1991 Gulf War and by the brine that gushed out with oil from the damaged wells. Previous investigations indicated that the seawater from the Arabian Gulf, which was used for fire fighting, had the total dissolved solids (TDS) contents of 45,000 mg/l and a Cl/SO4 mass ratio of 7.19. The brines produced with oil from the Sabriya and the Raudhatain oil fields adjacent to the freshwater fields of Umm Al-Aish and Raudhatain were characterized by TDS in the range of 172,000 to 256,000 mg/l and Cl/SO4mass ratio in the range of 118 to 267. In contrast, unpolluted (with no petroleum hydrocarbon) groundwater in the water fields had TDS in the range of 320 to 5,500 mg/l and Cl/SO4 mass ratio below 1.3. It was, therefore, surmised that wherever groundwater in the study area had Cl/SO4 mass ratio values higher than about 1.5, contamination by seawater and/or oilfield brine could be suspected; and when this value exceeded 7.5, contamination by oilfield brine could be inferred. The current investigation observed Cl/SO4 mass ratio as high as 23.5 in areas where groundwater had high (>0.05 soil oil equivalent [SOE] units) hydrocarbon content. Positive correlations between TDS, hydrocarbon content and Cl/SO4 mass ratio in such areas suggested that hydrocarbons and salts from seawater and oilfield brine moved together and did contaminate the groundwater in some parts of the study area.
Groundwater; Pollution; Raudhatain; Umm Al-Aish; Petroleum Hydrocarbon
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