Concentration of selected radionuclides in seawater from Kuwait

Marine Pollution Bulletin 64 (2012) 1261–1264

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Baseline

Concentration of selected radionuclides in seawater from Kuwait Saif Uddin ⇑, Abdul Nabi Al Ghadban, Abdulaziz Aba, Montaha Behbehani Kuwait Institute for Scientific Research, P.O. Box 24885, 13109 Safat, Kuwait

a r t i c l e

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Keywords: 3 H 90 Sr 210 Po 137 Cs

a b s t r a c t No baseline existed for the radionuclides in Kuwait territorial water. With changing trend in the region to embrace nuclear energy, the baseline study is imperative to create a reference and to record the influence-functioning of upcoming power plants. The first one in Bushehr, Iran is ready to start and several more are likely to come-up in UAE, Saudi Arabia and Kuwait. The present baseline concentration of the four considered radionuclide’s show low concentration of tritium, polonium, strontium and cesium; their concentration is comparable to most oceanic waters. Ó 2012 Elsevier Ltd. All rights reserved.

Kuwait lies at the northwest of the Arabian Gulf (AG). The AG is a shallow water body located in a subtropical, hyper arid region (Sheppard et al., 2010). Many of the oil producing Gulf countries are considering nuclear energy option to meet their growing energy demand. Currently, there is only a single nonoperational nuclear plant in the region at Bushehr, Iran; while the entire northern, western, and southern coastline is without any nuclear infrastructure. The decision of the United Arab Emirates (UAE) to have its nuclear plant by 2020 and other countries, like Saudi Arabia and Kuwait (Huber, 2007) having nuclear aspirations is likely to influence the radionuclide levels in the Gulf water, which is extremely important to sustenance in the region. The information on radiochemistry of Gulf water is very limited. There have been few studies done on surface sediment concentration (ROPME, 2000) and core sediments (Al-Zamel et al., 2005) in Kuwait. Few studies from Oman and UAE have reported radionuclide concentration in seaweeds and seagrasses (Goddard and Jupp, 2001) and in Omani fishes (Goddard et al., 2003). Radionuclide concentration in local foodstuff was also screened in an earlier study in Kuwait (Husain et al., 2003). However, to the best of the authors knowledge, there is yet no published information available on radionuclides levels in seawater for Kuwait territorial water. This study, therefore, provides baseline concentrations of 3H, 210Po, 90Sr and 137 Cs, in coastal waters of Kuwait for future local and regional studies. The importance of the Gulf waters is further strengthened by the fact that most of the freshwater needs of the region are met by desalination, with a cumulative desalination capacity of the countries in the Arabian Gulf, being around 11 m3/d (Lattemann and Höpner, 2008) including, Kuwait, Saudi Arabia, Bahrain, Qatar, UAE and Iran.

⇑ Corresponding author. E-mail address: [email protected] (S. Uddin). 0025-326X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marpolbul.2012.02.025

The study was carried out in the territorial waters of Kuwait, much of the area being <30 m deep. With very low annual precipitation of <80 mm, over the past 4 years. The Shatt Al-Arab river and the Third River drains into the northwestern AG supplying limited quantities of freshwater to the Gulf and lots of sediment, making a large portion of the northern Arabian Gulf turbid. The sea surface temperature fluctuates between 10 and 35 °C. Based on multi-criterion evaluation using bathymetric condition, hydrodynamic flow regime, sediment transport and accessibility, a number of stations were identified for sample collection (Plate 1). Water samples were collected at a depth of 1 m below the water surface using 5-l Niskin bottles. The water sampler was mounted on a winch, lowered to the sampling depth, and released. The sampler was pulled and sample transferred into appropriate sample bottles, preserved and stored. One hundred litres of sample was collected from each location into 5 containers of 20 l each. The container was labeled with date time, and GPS location and a sample ID was assigned. The container was closed and sealed. The standard procedures were used for measurement of radionuclides. The tritium (3H) was measured by liquid scintillation spectrometry using Quantalus 1210 after electrolytic enrichment using the procedure developed by Ostlund and Werner (1962). The method is precise and useful for environmental samples with low 3H concentrations. The lower detection limit for this method is 0.2 tritium unit (TU), corresponding to 0.025 Bq/l for a 100-min count (Al Ghadban et al., 2010). Polonium (210Po) determination was done in water samples, by electrodeposition on a 0.064-cm thick silver disk of 1.2-cm diameter using the method proposed by Fisenne (1997). Reagent blanks were analyzed along with the samples. The 5.305-MeV energy line was used for quantification. A six-chamber alpha spectrometry system from Canberra was used. Strontium (90Sr) was determined by yitrium in growth and beta-ray spectrometry (La Rosa et al., 2001). Cesium (137Cs) concentration in water was determined

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Plate 1. Identified sampling locations.

using ammonium phosphomolybdate (AMP) method (Yamagata, 1963); Molero et al., 1993). The water samples were not filtered, for the reason that total radionuclide concentration was determined rather than by soluble fraction. The radionuclide concentration in seawater samples collected on 10 May 2010 were determined for tritium (3H), strontium (90Sr), polonium (210Po) and cesium (137Cs). The results are presented in Table 1. Tritium, requires special consideration because of its high mobility in the environment and its importance in the hydrological cycle in the biosphere. Tritium occurs naturally and in very small quantities, being produced in the upper atmosphere by cosmic rays. Natural (pre-nuclear age) levels of tritium in precipitation are 1– 5 TU (EPA, 2006). Nuclear weapon testings during the 1950s and

Table 1 Radionuclide concentration in seawater samples. Station

3

90

1 2 3 4 5 6 S Z

1.26 ± 0.01 1.04 ± 0.01 1.36 ± 0.01 1.22 ± 0.01 1.10 ± 0.01 1.01 ± 0.01 1.12 ± 0.01 0.92 ± 0.01

0.68 ± 0.08 0.73 ± 0.05 0.65 ± 0.05 0.78 ± 0.10 0.77 ± 0.08 0.61 ± 0.08 0.57 ± 0.05 0.68 ± 0.10

H (TU)

Sr (mBq/l)

210

137

0.50 ± 0.06 0.68 ± 0.08 0.54 ± 0.08 0.63 ± 0.02 0.68 ± 0.02 0.64 ± 0.20 0.48 ± 0.07 0.49 ± 0.08

1.06 ± 0.01 1.06 ± 0.01 1.06 ± 0.01 1.04 ± 0.01 1.01 ± 0.01 1.04 ± 0.01 1.06 ± 0.01 1.04 ± 0.01

Po (mBq/l)

Cs (mBq/l)

1960s created large amounts of tritium which reached the environment in addition to discharge from nuclear power plants.

S. Uddin et al. / Marine Pollution Bulletin 64 (2012) 1261–1264

The low baseline level of tritium in 0.92–1.36 TU range in the region can be attributed to very limited atmospheric tritium fall out due to scanty precipitation. The major source of tritium discharge are nuclear power plant, and there is none operational in the area. The likely fall out from atmospheric nuclear testing in the 1950s and 1960s decayed significantly due to the short half-life of tritium (12.32 year) resulting in this low baseline. Strontium-90 concentration in Kuwait territorial water ranges between 0.57 ± 0.05 and 0.78 ± 0.10 mBq/l. Stable strontium naturally occurs in seawater along with sodium, magnesium, calcium, and potassium. The concentration of stable strontium in seawater is strongly influenced by changes in the rates of continental weathering relative to oceanic crust alteration over geologic past (Shields, 2007; Spooner, 1976). The average oceanic concentration of strontium is considered to be 8 ppm, although it is not fixed and varies with salinity. The seawater samples analyzed for strontium showed a range of 8.94–9.60 ppm. The 87Sr/86Sr ratio were also determined (Table 2). The seawater in the study area gives 87 Sr/86Sr ratios in range between 0.709128 and 0.709157. The 87 Sr/86Sr ratio is a firm indicator of geochemical process (Shields, 2007) with modern day seawater having a ratio of 0.709. There are two major sources of strontium such as the submarine, chemical alteration with a characteristic 87Sr/86Sr ratio of 0.703 (Hofmann, 1997) and the subaerial chemical weathering of the continental crust and sedimentary cover, with 87Sr/86Sr ratio of 0.712 (Palmer and Edmond, 1989; Peucker-Ehrenbrink and Miller, 2006). It had been reported that the bulk of strontium is contributed by river runoff rather than the hydrothermal exchange. The 87Sr/86Sr ratio of continental input can be viewed as a function of the ratio between carbonate and silicate weathering rates with respect to strontium. In areas where the strontium contribution is dominated by silicates its reported to have an 87Sr/86Sr ratio of 0.7077; whereas, the areas where strontium is derived from carbonates it showed to have a higher ratio of 0.7090 (Shields, 2007). The 87Sr/86Sr ratio in the region suggested that the strontium originates from carbonate rock dissolution, possibly due to excessive sediment input from northern rivers and also due to acidification of Gulf water (Uddin et al., 2010, 2009, 2008). Polonium arises as a naturally occurring radioactive element in the earth’s crust. The concentration is in traces and is quite frequently associated with phosphates. There are many elemental forms of polonium, but in this study 210Po was considered, because bulk of Po takes in this form, and the half-life is 138 d, and specific activity is quite high (4500 ci/g). Another factor of considering 210 Po was that it comes about as a decay product of radon-222 gas. Radon concentration in Kuwait is reasonably high, and the decay product is expected to land on terrestrial and marine environment. The baseline concentration of 210Po in seawater ranges between 0.48 and 0.68 mBq/l. Cesium occurs in nature as a low melting point metal, that reacts violently with cold water. The bulk of the radioactive cesium occurring as 134CS, 135CS and 137Cs is a fission product of 235U. Most of the radiocesium found in the environment comes from spent nu-

Table 2 87 Sr/86Sr concentration ratios in seawater samples. Station

87

Uncertainty

1 2 3 4 5 6 Z S

0.709143 0.709151 0.709128 0.709138 0.709157 0.709140 0.709154 0.709153

Sr/86Sr

0.000006 0.000013 0.000010 0.000009 0.000011 0.000013 0.000007 0.000013

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clear fuel, radioactive waste, and soil erosion. In principle, radiocesium adheres to sediment and its concentration in interstitial waters is extremely low. The baseline 137Cs concentrations in seawater samples from Kuwait range between 1.01 and 1.06 mBq/l. The 90Sr concentration ranges between 0.57 ± 0.05 and 0.78 ± 0.10 mBq/l, which is comparable to the observations made under International Atomic Energy Agency (IAEA) coordinated, Worldwide Marine Radioactivity Studies (WOMARS) in the Pacific and Indian Oceans. Their Observations reported the estimated average during the year 2000 to be 0.1–1.5 mBq/l (Povinec et al., 2005). The 90Sr concentration in the Arabian Gulf is far less as compared to the Caspian Sea, where the mean 90Sr concentration during 1995 was 8.0 ± 1.6 mBq/l (Povinec et al., 2003). This concentration appeared to be higher than that expected from global fall out in this latitude belt (IAEA, 2001). It was mainly attributed to river input, suggesting remobilization of 90Sr from the catchment. The 137Cs concentration in Kuwait marine water ranges between 1.01 and 1.06 mBq/l. This concentration is comparable to the range reported from Pacific and Indian Oceans where the 137 Cs concentration during year 2000 ranged between 0.1 and 2.8 mBq/l (Povinec et al., 2005). The current baseline data generated suggested that the levels of different radionuclides in the Kuwait marine environment proved to be comparable to other marine waters in the northern hemisphere. Acknowledgements The authors wish to thank the Kuwait Foundation for the Advancement of Sciences (KFAS) for their financial support. Thanks are due to Dr. Naji M. Al-Mutairi, Director General and Mohammad J. Salman, Deputy Director General, Kuwait Institute for Scientific Research for their support. Appreciation is due to Dr. Nader AlAwadhi, National Liaison Officer, Kuwait, for his excellent support in coordinating with the IAEA. Thanks are due to Dr. A. Shamsi, Head of Technical Cooperation, Asia – Pacific, IAEA; Dr. Hartmut Nies, Head Radiometrics Laboratory, Marine Environmental Laboratory, IAEA, Monaco; and Dr. Mats Eriksson, Technical Officer, Marine Environmental Laboratory, IAEA, Monaco, for their valuable guidance. Authors are extremely thankful to Dr. Scott Fowler for critically reviewing the manuscript and for suggesting significant modifications towards improvement of the manuscript. References Al Ghadban, A., Uddin, S., Aba, A., L.N., A., Al Shamroukh, D., Al Mutairi, A., Al Khabbaz, A., Behbehani, M., 2010. Measurement and Assessment of Radionuclide Concentration in the Coastal Marine Environment. Kuwait Institute for Scientific Research, Kuwait, pp. 1–49. Al-Zamel, A.Z., Bou-Rabee, F., Olszewski, M., Bem, H., 2005. Natural radionuclides and 137Cs activity concentration in the bottom sediment cores from Kuwait Bay. Journal of Radioanalytical and Nuclear Chemistry 266, 269–276. EPA, U., 2006. . Fisenne, I.M., 1997. Polonium in water and urine, Method Po-01-R C Environment Measurement Laboratory, US Department of Energy Report, 28th Ed. vol. 1, USA. Goddard, C.C., Jupp, B.P., 2001. The Radionuclide Content of Seaweeds and Seagrass Around tthe Coast of Oman and the United Arab Emirates. Marine Pollution Bulletin 42, 1411–1416. Goddard, C.C., Mathews, C.P., Al Mamry, J., 2003. Baseline radionuclide concentrations in Omani Fish. Marine Pollution Bulletin 46, 903–917. Hofmann, A.W., 1997. Mantle geochemistry: the message from ocean volcanism. Nature 385, 219–229. Huber, N.D., 2007. Nuclear Gulf Cooperation Council, Energy Publisher. Energy Publisher. Husain, A., Sawaya, W., Al-Sayegh, A., Al-Amiri, H., Al-Sager, J., Al-Sharrah, T., AlKandari, R., Al-Foudari, M., 2003. Screening Level Assessment of Risks Associated with Dietary Exposure to Selected Heavy Metals, Polucyclic Aromatic Hydrocarbons and Radionuclides in Kuwait. Human and Ecological Risk Assessment 9, 1075–1087. IAEA, 2001. Worldwide marine radioactivity studies (WOMARS). IAEA-MEL, Monaco.

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