SOIL CONTAMINATION Total Mercury Distribution in Sediment Cores from Kuwait Bay A. Al-Zamel 1, F. Bou-Rabee 1, E. Lesniewska 2, M. Szynkowska 2, M. Dlugosz 3, H. Bem 3 1Faculty of Sciences, Department of Earth and Environmental Sciences, Kuwait University, P.O. Box 5969, Safat, Kuwait, 2Institute of General and Ecological Chemistry, Department of Chemistry, Technical University of Lodz, Poland 3Institute of Applied Radiation Chemistry, Department of Chemistry, Technical University of Lodz, Poland

Abstract Five sediment cores from Kuwait Bay were taken in order to study the present distribu- tion of the total mercury (THg) in the vicinity of the Salt and Chlorine Plant (SCP) operated in the 1963-1985 period. The THg concentration profiles were determined also in four sed- iments cores from the northern part of Kuwait Bay as well as the THg average contents were measured in the surface layer (40 cm) of five sediment samples in the entrance of Kuwait Bay, in order to compare the present Hg levels in the other parts of this reservoir. The cores were dated by 210 Pb method. The observed contents of mercury were in the range of 35 to 2000 µg/kg dry weight (ppb). It indicates that the bottom sediments in these three areas of the Kuwait Bay are still contaminated by Hg. In a few cases, the depth concentration profiles of THg were disturbed as an effect of partial mixing of the sediment layers especially in the shallow, northern part of Kuwait Bay. This suggestion was supported by the results of addi- tional measurements of the anthropogenic 137 Cs profiles in the same cores. Keywords: Kuwait Bay, sediments, mercury pollution, radionuclide dating

Introduction 20 tons of mercury was discharged to the Extensive anthropogenic use of Hg has coastal zone in the vicinity of the SCP led to the contamination of various ecosys- [Szucs, F.K., and Oostdam, B.L. 1977]. The tems by this highly toxic pollutant. There- distribution of Hg in the bottom sediments fore, the transport of mercury and its com- of Kuwait Bay (at a total of 103 locations) pounds to and within aquatic systems, as was determined during the 1996-1998 sam- well as the biochemical transformations of ple collection campaigns, e.g. about ten years mercury, are still the subject of abundant after the closure of the factory [Al-Mayed, research [Delongchamp, T.M et. all , 2009; N.B., and Preston, M.R., 2004]. The highest Li P., 2009; Merritt, K.A. and Amirbahman, contents of the total mercury (THg) in the A. 2009]. Vast amounts of discharged mercu- bottom sediments were observed in the ry to aquatic reservoirs is finally accumulated vicinity of the SCP (Shuwaikh Port) with an in the bottom sediments [US EPA. 1997]. average value of 36,500 ppb. The measured Inorganic Hg(II) is usually the dominant contents decreased toward the northern species in the bottom sediments but it can be coastline to values of around 50 ppb, which partially transformed into the more toxic and were still at least twice the background base- bioavailable compound methyl mercury lines of 15 - 20 ppb for these sediments [Al- [Hammerschmidt, C.R,et all. 2004; Sunder- Mayed, N.B., and Preston, M.R., 2004]. The land, E.M. et. all, 2004; Bełdowski, J. and determination of THg content profiles in the Pempkowiak, J. 2007]. For these reasons bottom sediment cores allows, the history of many studies are focused on the observation mercury pollution can be traced. Recently, of the spatial and vertical distributions of the sedimentation rates, and consequently mercury species in the bottom sediments (for the dates of the deposition of particular lay- example: [Bełdowski, J. and Pempkowiak, J. ers for several bottom sediment cores in this 2003; Castelle, S. et. All., 2008]). area, were measured by 210 Pb and 137 Cs Kuwait Bay, a semi-enclosed area of methods [Al-Zamel, A.Z. et. All, 2006]. approximately 720 km 2 in the northern part Therefore, it was interesting to compare the of the Persian Gulf, is an example of the present THg levels in those dated cores, as point source of anthropogenic mercury pol- well as in a few newly collected samples, lution from the Salt and Chlorine Plant from the northern part of Kuwait Bay. (SCP), which operated from 1963 to 1985. It was estimated that during this period at least

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Figure 1. Location map of sampling sites In the Kuwait Bay. *Resuspension and sediment transport directions taken from: Al-Ghadban, A.N. and El- Sammak A. 2005.

Methods The details of these procedures, as well The locations of all the 14 sampling as 210 Pb and 137 Cs radioactivity measure- sites are presented in Fig.1. ments by γ-spectrometry and quality assur- The sediment core samples (# 1, 2, 3, ance of the radiometric procedure, were 4, 5 and S2, S3, T1, T2) were collected using described elsewhere [Al-Zamel, A.Z. et. All, a 7.5 cm diameter aluminium tube. The core 2006]. samples were divided into 5 cm or 10 cm increments through the length of core, up to Results and Discussion 40 cm. For THg determination the samples Distribution of THg in previously col- were dried in the ambient temperature lected cores in the SCP area is shown in Fig. 2. (~25 oC) for ~ 48 h to allow a constant Presently observed total mercury con- weight to be reached, then carefully mixed in tents are still high, up to 1,700 ppb, close to plastic polypropylene dishes. A portion of the average value previously determined. the samples was taken for mercury analysis, The historical THg records for these sedi- while the remaining part was oven-dried for ments show basically the same shapes. 12 h at 105 oC before radionuclide measure- The dates were calculated for the aver- ment [Al-Zamel, A.Z. et. All, 2006]. age sediment deposition rate of 0.27 The content of THg in 10 to 20 mg cm/year. As expected, the highest contents, samples was determined using a Mercury covering the ten-year period 1975-1985, cor- SP-3D (Nippon Inst. Comp.) cold respond to the peak activity of the SCP. vapour atomic absorption analyser. For each However, high THg contents for the well-homogenized sediment layer, three deeper sediment layers, beneath 15 cm, are samples were taken for analysis. The accura- observed and only for one core does the mer- cy of the THg analysis was checked by deter- cury content fall to a level of around of 50 ppb. mining THg content in the standard refer- The elevated THg concentrations in the ence materials obtained from the IAEA in sediment layers below 15 cm, which accumu- Vienna: IAEA-405. The determined value lated before 1960 when the SCP did not yet for the IAEA sample was 804.4 ± 25 o, while exist, suggest a partial but continuous Hg the certified value was 810 ppb, which remobilisation and its vertical, probably means that accuracy was better than 99%. mainly diffusive transport. As expected, the The 210 Pb method was applied for observed mercury contents in the northern determining the age of each sediment layer Kuwait Bay sediments are much lower, in the in the examined cores. range of 20 to 250 ppb.

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Figure 2. THg concentration profiles for sediment cores from SCP area.

The higher values occur for sites S2 tents (up to 1700 ppb) of the mercury were and S3, lying in the middle of the northern found in the upper layers of the sediments coastline. Lower THg contents in the range near to the pollution source (SCP), even 23 of 20 to 100 ppb are observed for sites T1 and years after its closure. However, with time, T2. However, the historical trend in mercu- according to the conceptual model for the ry pollution is not clearly evident for the S1, suspended sediment transport pattern in S2, T1 or T2 concentration profiles taken Kuwait Bay [Al-Ghadban, A.N. and El-Sam- from the northern Kuwait Bay coastline. mak A. 2005], the slow spreading of mercu- At that time (10 years after the SCP ry pollution to the northern part of Kuwait closure) no increase in the THg content for Bay may take place. Therefore, presently sediments from the northern part of Kuwait slightly higher contents of THg (50-280 ppb) Bay was observed. in comparison to the values determined dur- Similar levels of the THg content in the ing the 1996-1998 sampling campaigns are sediment samples from the border of Kuwait observed. Bay and those samples collected outside Failaka Island (Table 1) were determined. References These values are presently still higher Agah, H., Elskens,M., Fatemi, R., than those recently determined for the sedi- Owfi, F., Baeyens, W. and Leermarkers, M. ment samples collected along the Iranian 2009, Mercury speciation in the Persian coastline (10 to 56 ppb) [Agah, H. et. all, Gulf sediments. Environmental Monitoring 2009] but much lower than the average and Assessment 157, 363-373. measured content of THg ~ 540 ppb in the Al-Ghadban, A.N. and El-Sammak A. southern part of the Persian Gulf [Al-Madfa, 2005. Source, distribution and composition H., et. Al 1994]. of the suspended sediments, Kuwait Bay, Northern Arabian Gulf. Journal of Arid Conclusions Environments. 60, 647-641. The observed mercury contents in the Al-Madfa, H., Dahab, A.O. and Holail, surface sediments of Kuwait Bay exceed the H. 1994, Mercury pollution in Doha (Qatar) threshold effect levels (TEL) proposed in sev- coastal environment. Environmental Toxi- eral national sediment quality guidelines cology and Chemistry 13, 725-735. [Hőbner , R et. all, 2009]. The highest con-

Table 1. Total mercury concentration in the surface layer (0-30 cm) of the bottom sediments nearby Failaka Island.

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Al-Mayed, N.B., and Preston, M.R., Hőbner , R., Astin B.K., and Herbert 2004, The distribution and inventory of R.J.H. 2009. Comparison of sediment qual- total and methylmercury in Kuwait Bay. ity guidelines (SQGs) for the assessment of Marine Pollution Bulletin 49, 930-937. metal contamination in marine and estuar- Al-Zamel, A.Z., Bou-Rabee, F., Al- ine environments. Journal of Enviromental Sarawi, M.A., Olszewski, M., and Bem, H. Monioring. 11, 713-722. 2006, Determination of the sediment depo- Hammerschmidt, C.R., Fitzgerald, sition rates in the Kuwait Bay using 137 Cs W.F., Lamborg, C.H., Balcom, P.H., and and 210 Pb. Nukleonika. 51(S2), 39-44. Visscher, P.T. 2004, Biogeochemistry of Bełdowski, J. and Pempkowiak, J. methylmercury in sediments of Long Island 2007, Mercury transformations in marine Sound. Marine Chemistry 90, 31-52. coastal sediments as derived from mercury Li, P., Feng, X,B., Qiu, G.L., Shang, concentration and speciation changes along L.H. and Li, Z.G. 2009, Mercury pollution in source/sink transport pathway (Southern Asia: A review of the contaminated sites. Baltic). Estuarine, Coastal and Shelf Science Journal of Hazardous Materials 168, 591- 72, 370-378. 601. Bełdowski, J. and Pempkowiak, J. Merritt, K.A. and Amirbahman, A. 2003, Horizontal and vertical variabilities of 2009, Mercury methylation dynamics in mercury concentration and speciation in estuarine and coastal marine environments- sediments of the Gdansk Basin, Southern A critical review. Earth-Science Review 96, Baltic Sea. Chemosphere 52, 645-654 54-66. Castelle, S., Schäfer, J., Blanc, G., Sunderland, E.M., Gobas, F.A., Heyes, Audry, S., Etcheber, H., and Lissalde J.P. A., Branfireun, B.A., Bayer, A.K., Cranston, 2008, 50-year record and solid state specia- R.E., and Parsons, M.B. 2004, Speciation tion of mercury in natural and contaminated and bioavailability of mercury in well-mixed reservoir sediment. Applied Geochemistry estuarine sediments. Marine Chemistry 90, 22, 1359-1370. 91-105. Delongchamp, T.M., Lean, D.R.S., Szucs, F.K., and Oostdam, B.L. 1977, Ridal, J.J. and Blais J.M. 2009, Sediment Kuwait Institute for Scientific Research, mercury dynamics and historical trends of Technical Report No: KISR/PPI/EES-R-RT- mercury deposition in the St. Lawrence 7701, Kuwait River area of concern near Cornwall, US EPA. 1997, The Incidence and Ontario, Canada. Science of the Total Envi- Severity of Sediment Contamination in Sur- ronment 407, 4095-4104. face Waters of the United States. EPA-823- R-007, US EPA, Washington, D.C

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