Radioactivity in the Kuwait marine environment — Baseline measurements and review

Abstract

The Arabian Gulf region is moving towards a nuclear energy option with the first nuclear power plant now operational in Bushehr, Iran, and others soon to be constructed in Abu Dhabi and Saudi Arabia. Radiological safety is becoming a prime concern in the region. This study compiles available data and presents recent radionuclide data for the northern Gulf waters, considered as pre-nuclear which will be a valuable dataset for future monitoring work in this region. Radionuclide monitoring in the marine environment is a matter of prime concern for Kuwait, and an assessment of the potential impact of radionuclides requires the establishment and regular updating of baseline levels of artificial and natural radionuclides in various environmental compartments. Here we present baseline measurements for 210Po, 210Pb, 137Cs, 90Sr, and 3H in Kuwait waters. The seawater concentration of 3H, 210Po, 210Pb, 137Cs, and 90Sr vary between 130–146, 0.48–0.68, 0.75–0.89, 1.25–1.38 and 0.57–0.78mBqL−1, respectively. The 40K concentration in seawater varies between 8.9–9.3BqL−1. The concentration of 40K, total 210Pb, 137Cs, 90Sr, 226Ra, 228Ra, 238U, 235U, 234U, 239+240Pu and 238Pu were determined in sediments and range, respectively, between 353–445, 23.6–44.3, 1.0–3.1, 4.8–5.29, 17.3–20.5, 15–16.4, 28.7–31.4, 1.26–1.30, 29.7–30.0, 0.045–0.21 and 0.028–0.03Bqkg−1 dry weight. Since, radionuclides are concentrated in marine biota, a large number of marine biota samples covering several trophic levels, from microalgae to sharks, were analyzed. The whole fish concentration of 40K, 226Ra, 224Ra, 228Ra, 137Cs, 210Po and 90Sr range between 230–447, 0.7–7.3, <0.5–6.6, <0.5–15.80, <0.17, 0.88–4.26 and 1.86–5.34Bqkg−1 dry weight, respectively. 210Po was found to be highly concentrated in several marine organisms with the highest 210Po concentration found in Marica marmorata (193.5–215.6Bqkg−1 dry weight). 210Po in most dissected fish samples shows increasing concentrations in the following order: edible tissue, gills, digestive system, liver and fecal matter. Fish fecal pellets had 210Po concentrations several orders of magnitude higher than the seawater, fish muscle, and the fishes' ingested food. The high 210Po concentration in fish fecal matter, suggest that the bulk of 210Po content in fish was eventually excreted back into the environment as fecal pellets. In most fish high concentrations were noted in liver, with the highest 210Po concentration recorded in shark liver (126.2–141.5Bqkg−1 wet). Moreover, 210Po concentration in the soft tissue of molluscs (10.36–215.60Bqkg−1 dry weight) was far higher than that in fish muscle (0.05–7.49Bqkg−1 wet weight). A seasonal drop in 210Po concentration in seawater was observed to vary with the abundance of phytoplankton and macroalgae due possibly to biological dilution. 137Cs concentration in all the fish sampled was below the detection limit, and the concentration in seawater was also low; hence such low levels provide an opportunity to use this radionuclide as an indicator for any future radiocesium releases in this region.