ELEVATED MASSIC ACTIVITIES OF 238U AND 226Ra IN SEDIMENT OF THE KAŠTELA BAY (, )

Ivanka Lovrenčić Mikelić Laboratory for Radioecology, Ruđer Bošković Institute, Zagreb, Croatia [email protected]

INTRODUCTION The area around the Kaštela Bay is intensively industrialized and urbanized and is the greatest urban agglomeration on the east Adriatic coast. The sources of contaminants for the bay were or still are numerous and include sewage system, industry, agriculture, and an airport. Sediment pollution with metals and the influence of the discharge of large amounts of nutrients of anthropogenic origin were intensively studied [1-5]. However, there are only few studies related to the radionuclides in the bay [6,7]. These studies indicated the presence of the TENORM (Technologically Enhanced Naturally Occurring Radioactive Material) in the bay. Its origin was attributed to the combustion of the coal with elevated 238U and 226Ra activities in the former chemical factory “Adriavinil” resulting with the bottom ash and slag enriched with 238U and 226Ra up to several times compared to the coal. By studying spatial distribution of 238U and 226Ra it is possible to determine the extent to which the bay is influenced by the deposition of the alochthonous material into the bay. The aim was to determine the areas or localized sites in the bay with elevated 238U and 226Ra massic activities and to assess the quality of the related sediments.

MATERIAL AND METHODS Samples were collected by gravity corer or by autonomous diving in a regular grid 1×1 km covering the whole bay, in a grid 500×500 m around the "Adriavinil" factory, and along the 300 m long profile in the vicinity of the "Adriavinil" fenced area (Figure 1). Total of 604 samples on 95 sampling stations were collected. Samples were taken up to a depth of 50 cm whenever possible. Sediment cores were sliced into eight segments of which the upper six were 5 cm long and two deepest ones were 10 cm long.

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K. 1 0 1 km K. Stari K. Lukšć i K. K. Su ć urac K. Novi Kambelovac K85 Gomilica K08 K71 K07 K74 K75 K. Šć tafili K84 K72 K09 Stream K73 K00 K01 K02 K03 K04 K05 K06 K77 K79 K23 K76 K80 KC K78 K11 K12 K19 K20 K21 K22 K10 K13 K14 K15 K16 K17 K18 K62 Divulje K61 K27 K24 K25 K26 K28 K29 K30 K31 K32 K33 K86 K60 K88 K a š t e l a Bay K45 K87 K70 K36 K43 K35 K37 K38 K39 K40 K41 K42 K44 Arbanija Split KV01 KK Marjan K50 K51 Fenced K90 K89 K46 K47 K48 K49 K67 K65 K64 K66 Adriavinil K69 K63 Slatine K68 area K82 KVC3 K91 Čiovo Island K52 K53 K54 K55 K56 K57 K58 K82a 100 m K92 K59 K08 K83 Brač Channel Figure 1. Sampling grid of the Kaštela Bay sediments

Prior to radiometric analysis sediments were dried overnight in a drier at 105 °C, ground, homogenized, put into plastic containers, weighed, sealed and stored for at least four weeks. Radiometric analysis was performed using HPGe detectors coupled with multichannel analyzers with 8,192 channels (Canberra Industries). Spectra were collected for 80,000 s and analyzed with Genie 2000 programme package (Canberra Industries). 226Ra activity was determined through 214Pb and 214Bi peaks at 295.21 keV and 351.92 keV and at 609.31 keV, 1120.28 keV, and 1764.49 keV, respectively. 238U activity was calculated through 234Th activity using 63.29 keV and 92.6 keV peaks. Elevated 238U and 226Ra activities were compared with the literature values for activities of Adriatic coastal sediments (AS) and with the experimentally obtained activities for the average, unpolluted Kaštela Bay sediment (KBS) calculated as the mean values of 238U and 226Ra activities in several samples in which no radionuclide contamination, i.e. anthropogenic influence was expected.

RESULTS Basic statistical parameters of 238U and 226Ra massic activities for all collected samples are given in Table 1. Very similar ranges of 238U and 226Ra massic activities in the Kaštela Bay sediments up to 55 cm depth were reported earlier (11.4 – 606 Bq/kg for 238U, 13.2 – 773 Bq/kg for 226Ra) [7]. Other authors also reported 130–750 Bq/kg of 238U and 130 – 810 Bq/kg of 226Ra in the Kaštela Bay sediments [6].

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Table 1. Descriptive statistics for 238U and 226Ra massic activities in the Kaštela Bay sediments for eight depth segments up to 50 cm depth; x – mean value, SD – standard deviation Statistical a (238U) a (226Ra) parameter (Bq/kg) (Bq/kg) 34 25 SD 46 48 Minimum 6.7 5.4 Maximum 603 685 Median 28 20

Elevated 238U and/or 226Ra massic activities were determined in 25 individual samples on five sampling stations (Figure 2). These samples can be divided in two groups: i) samples with moderately elevated activities, and ii) samples with significantly elevated activities. Significantly elevated 238U and 226Ra activities were determined only on the K90 station up to 30 cm depth (samples K9001–K9006).

700

600

500

400 U-238 Ra-226

(Bq/kg) 300

a 200

100

0

AS

KBS

K4302 K4303 K4304 K4305 K4306 K4307 K4308 K6303 K6304 K6305 K6306 K6307 K6308 K6402 K6403 K6404 K6503 K6504 K9001 K9002 K9003 K9004 K9005 K9006 K9007

Sample Figure 2. Samples with elevated 238U and/or 226Ra massic activities in the Kaštela Bay sediments; massic activities in the AS and KBS are given for comparison

The average 238U and 226Ra massic activities in the AS are 18.2 Bq/kg and 19.2 Bq/kg, respectively [7]. Moderately elevated 238U and 226Ra massic activities were 3 – 10 times higher than the average massic activities in the AS (Figure 3). Significantly elevated 238U and 226Ra massic activities were

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22 – 33 times and 20 – 36 times higher, respectively, than the corresponding average values of the AS (Figure 3).

40 35 30

(AS) 25

a U-238 20 Ra-226

15 (sample)/

a 10 5

0

K4302

K4303

K4304

K4305

K4306

K4307

K4308

K6303

K6304

K6305

K6306

K6307

K6308

K6402

K6403

K6404

K6503

K6504

K9001

K9002

K9003

K9004

K9005

K9006 K9007

Sample Figure 3. Elevated 238U and/or 226Ra massic activities in the Kaštela Bay sediments compared to massic activities in the Adriatic coastal sediments

25

20

(KBS) 15

a U-238 Ra-226

10 (sample)/ a 5

0

K4302

K4303

K4304

K4305

K4306

K4307

K4308

K6303

K6304

K6305

K6306

K6307

K6308

K6402

K6403

K6404

K6503

K6504

K9001

K9002

K9003

K9004

K9005

K9006 K9007

Sample Figure 4. Elevated 238U and/or 226Ra massic activities in the Kaštela Bay sediments compared to massic activities in the unpolluted Kaštela Bay sediment

Experimentally obtained 238U and 226Ra massic activities for unpolluted Kaštela Bay sediment were 38.8 ± 4.2 Bq/kg and 29.8 ± 1.7 Bq/kg, respectively. In the group with moderately elevated activities 238U massic activities were 1.5 – 5 times and 226Ra 2 – 6 times higher compared to these values while in the group with significantly elevated activities 238U

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massic activities were 10–16 times and 226Ra 13 – 23 times higher than the respective average massic activities in the KBS (Figure 4).

CONCLUSION Elevated 238U and/or 226Ra massic activities in the Kaštela Bay sediments are limited to local occurrences. All affected sampling stations are in the east part of the bay in the nearest vicinity of the industrial facilities or urban centre. Thus, anthropogenic influence is highly possible on these stations. The first 30 cm of the K90 sediment core is attributed to dumping of the alochthonous material into the sea. Taking into account very high radionuclides activities, this material can be considered as TENORM.

Acknowledgment This study was funded by the Ministry of Science, Education, and Sports of the Republic of Croatia through the "Radionuclides and trace elements in environmental systems" project (098-0982934-2713). Significant financial support from the Kaštela town is also greatly appreciated.

REFERENCES [1] Tudor M, Zvonarić T, Horvat M, Stegnar P. Vertical transport of mercury by settling particles in Kaštela Bay. Acta Adriat 1991;32(2):753-763. [2] Bogner D, Juračić M, Odžak N, Barić A. Trace metals in fine grained sediments of the Kaštela Bay, Adriatic Sea. Water Sci Technol 1998; 38(11):169-175. [3] Ujević I, Odžak N, Barić A. Trace metal accumulation in different grain size fractions of the sediments from a semi-enclosed bay heavily contaminated by urban and industrial wastewaters. Water Res 2000;34(11):3055-3061. [4] Kwokal Ž, Frančišković-Bilinski S, Bilinski H, Branica M. A comparison of anthropogenic mercury pollution in Kaštela Bay (Croatia) with pristine estuaries in Öre (Sweden) and (Croatia). Mar Pollut Bull 2002; 44(10):1152-1157. [5] Barić A, Marasović I, Gačić M. Eutrophication phenomenon with special reference to the Kaštela Bay. Chem Ecol 1992;6:51-68. [6] Mikac N, Foucher D, Kwokal Ž, Barišić D. Mercury and Radionuclides in Sediments of the Kaštela Bay (Croatia) – Evaluation of the Sediment Pollution History. Croat Chem Acta 2006;79(1):85-93. [7] Oreščanin V, Barišić D, Lovrenčić I, Mikelić L, Rožmarić-Mačefat M, Pavlović G, Lulić S. The influence of fly and bottom ash deposition on the quality of Kastela Bay sediments. Environ Geol 2005;49:53-64.

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ELEVATED MASSIC ACTIVITIES OF 238U AND 226Ra IN SEDIMENT OF THE KAŠTELA BAY (ADRIATIC SEA, CROATIA)

Ivanka Lovrenčić Mikelić Laboratory for Radioecology, Ruđer Bošković Institute, Zagreb, Croatia [email protected]

238U and 226Ra massic activities in the Kaštela Bay sediments were studied in order to determine the extent to which the bay is influenced by the deposition of the alochthonous material into the bay and to determine the areas or localized sites with elevated 238U and 226Ra massic activities. Total of 609 samples were collected on 95 sampling stations in a regular grid up to a depth of 50 cm whenever possible and sliced in eight segments. Radiometric analysis was performed on all samples and elevated 238U and 226Ra activities were detected and compared with the literature values for activities of the Adriatic coastal sediments (AS) and with the experimentally obtained activities for the average, unpolluted Kaštela Bay sediment (KBS). 238U massic activities were in the range 6.7 – 603 Bq/kg with the mean value 34 Bq/kg and median 28 Bq/kg. 226Ra massic activities were in the range 5.4 – 685 Bq/kg with the mean value 25 Bq/kg and median 20 Bq/kg. Elevated radionuclides activities were determined in 25 individual samples on five sampling stations. Significantly elevated 238U and 226Ra activities were determined only on one sampling station close to the former chemical factory up to 30 cm depth where 238U and 226Ra activities were 22 – 33 times and 20 – 36 times higher, respectively, than the respective average massic activities of the AS. Compared with the KBS, 238U activities were 10 – 16 times higher and 226Ra 13 – 23 times higher than the respective average values. In other samples activities were moderately elevated and 238U and 226Ra massic activities were 3 – 10 times higher than the average massic activities in the AS while compared to the KBS 238U activities were 1.5 – 5 times higher and 226Ra activities were 2 – 6 times higher. 238U and/or 226Ra massic activities in the Kaštela Bay sediments are elevated only locally in the east part of the bay. TENORM dumping into the sea in the vicinity of the chemical factory was documented.

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