Introduction

In the nature, radionuclides can be found as primordial, cosmogenic, and human-produced. Primordial radionuclides are present from the origin of the earth, cosmogenic radionuclides form as a result of cosmic ray interaction, and human-produced radionuclides come up with human activities such as nuclear weapon tests in the atmosphere, various applications of medicine, industries, and consumer products (Shouop et al. 2017; Khan et al. 2010). Natural environmental radioactivity develops principally from primordial radionuclides such as 232Th and 238U and their product of decay as well as 40K.

People are exposed to both external and internal radiation due to naturally occurring radionuclides that are present since the creation of the earth (Altunsoy et al. 2020; Al-Obaidi et al. 2020). Naturally occurring radionuclides are present in soil, rock, water, plant, sand, and air (SureshGandhi et al. 2014; Özseven et al. 2020; Akkurt et al. 2015; Albidhani et al. 2019). They are not uniformly distributed depending on the geographical conditions and geological formations in each region in the world. The activity of naturally existing radionuclides in sediment and also soil change depend on the type of rock from which they originate (Huang et al. 2015; Tzortzis et al. 2004; Agbalagba et al. 2014). Radionuclides in marine sediment dissolve in water over time and transfer to plants, animals, and human. The knowledge of concentration and distribution of natural radionuclides in sediment is crucial since the level of activity concentration influences human exposure to radiations. Many studies were performed on natural radioactivity in the literature (Kulalı et al. 2019; Günay et al. 2019; Günay et al. 2018a; Günay et al. 2018b; Külahçı et al. 2020; Günay and Eke 2019; Günay 2018; Mavi and Akkurt 2010; Nevinsky et al. 2018; Özseven et al. 2020).

In this study, sediment samples were collected from Aliaga Bay and analyzed to identify natural 226Ra, 232Th, and 40K gamma-emitting radionuclides. Aliaga Bay is located in the central Eastern Aegean Sea and has been contaminated by extensive domestic and industrial pollution load (Pazi et al. 2017). Aliaga region is located at about 50 km far from the north of Izmir in the western part of Turkey. The oldest rock unit of Aliaga is the Izmir flysch deposits of Cretaceous age. The main rocks that are exposed in the outcrop are volcano–sedimentary rocks including limestone, silicified limestone, marl, andesite, basalt, tuff, and tuffite of the Upper Miocene age and volcanic rocks of the Pliocene age (Sponza and Karaoğlu 2002). The town has a population of about 60,000 and the economy is mainly based on an oil refinery and also cultural tourism. Various industrial facilities are located in Aliaga Bay especially Tupras (the second largest oil refinery of Turkey), Petkim (a petro chemistry plant), iron–steel facilities, shipbreaking facilities, phosphate fertilizer plant, paper factory, and two thermal power plants based on natural gas. Industrial activities associated with these facilities cause environmental pollution in this region. In addition, the industrial plants in Aliaga cause marine pollution and change the natural balance of the sea (Arslan et al. 2015; Neşer et al. 2012). In several areas of Aliaga, rivers (especially Bakırçay River) and bays have been polluted by industrial and agricultural human activities, or waste disposal. Along its path, the Bakırçay River basin includes several agricultural lands where the farmers use often the fertilizers. Natural radionuclides are released to the environment in several industrial activities such as minerals mining, beneficiation and chemical processing of ores, phosphate fertilizer production and use, and fossil fuel combustion, causing enhanced natural radiation exposures etc. (Çam et al. 2013).

The objective of this study is to evaluate the radiological hazard in Aliaga Bay of Izmir district. Absorbed dose rate, annual effective dose equivalent, radium equivalent activity, external hazard index, and excess lifetime cancer risk were determined and compared to the limits given by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 2000). The parameters obtained in this investigation may contribute to the natural radioactivity level database, and give information about the activity distribution of natural radionuclides and the radiation doses to human beings in contact with this area.

Materials and methods

Sample collection and preparation

The sediment samples were collected manually from the surface layer sediment of 10-cm depth. The surface sediment samples were collected from 30 different locations (Fig. 1). The collected samples were then placed in labeled polythene bags and transferred to the laboratory for preparation and analysis. After that, the sediment samples were sieved through a 2-mm mesh. Then the samples were dried at 105 °C for 24 h and placed in polyethylene containers. Samples were stored in polyethylene containers for more than 4 weeks to reach secular equilibrium between 226Ra and its daughters/decay products (Ergül et al. 2013; Aközcan 2014).

Fig. 1
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Sample collection sites around Aliaga Bay (Eastern Aegean Sea) (Aydın et al. 2015)

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Activity measurements

The gamma spectra of the surface sediment samples were collected in the laboratory at the Central Research Laboratory of Kırklareli University by HPGe detector (Ortec, USA) with a 70% relative efficiency in multilayer shielding. The detector used was connected to a computer program MAESTRO window that matched the gamma energies to a library of possible isotopes and analyses were performed by GammaVision-32 software program. The gamma-ray peak of the 911.2 keV from 228Ac and the 583.1 keV from 208Tl was used to determine the activity concentration of 232Th in the sediment samples. The activity concentration of 226Ra was determined using gamma-ray lines at 351.9 keV for 214Pb and 609.3 keV for 214Bi, respectively. The activity concentration of 40K was evaluated using gamma-ray line at 1460.8 keV. The energy and efficiency calibrations of the detector were performed using multinuclide reference source (Isotope Products Laboratories, volume: 1.300 mL, density: 1.0 g cm−3) in 250-mL cylindrical geometry.

The mixed radionuclide, in the form of epoxy used for the calibration, contained 11 radionuclides in the energy range of 60–1836 keV as 210Pb, 241Am, 109Cd, 57Co, 139Ce, 203Hg, 113Sn, 85Sr, 137Cs, 88Y, and 60Co. The efficiency calibration of the HPGe detector was also carried out using the six different radionuclides (namely 241Am, 109Cd, 57Co, 137Cs, and 60Co) obtained in the spectrum. Out of the six radionuclides, four radionuclides reformed the fit of the data and the two discarded. The following radionuclides were used for the efficiency calibration: 57Co (122 keV), 137Cs (662 keV), 60Co (1173 keV), and 57Co (1333 keV). The resolution of the detector was determined by measuring a standard 137Cs source on the detector and a spectrum of the full energy peak located at 662 keV. Each sample and the background were counted for 160000 s (44 h). The activity concentration of 226Ra, 232Th, and 40K in the measured samples is calculated by the following relation (Aközcan et al. 2018);

$$ A\ \left(\mathrm{Bg}\ {\mathrm{kg}}^{-1}\right)=\frac{\mathrm{CPS}}{\varepsilon \times M\times {I}_{\gamma }} $$
(1)

where A represents the specific activity, CPS is the net gamma counting rate (counts per seconds), ε is the detector efficiency of a specific gamma ray, Iγ is the gamma-ray emission probability, and M is the mass of the sample (kg).

The minimum detectable activity (MDA) of the γ-ray measurement system was calculated using the following equation (Currie 1968):

$$ \mathrm{MDA}=\frac{2.71+4.65{B}^{1/2}}{\varepsilon \times t} $$
(2)

where B is the background counts, Ɛ is the counting efficiency, and t is the counting time in seconds (Aközcan et al. 2014).

The minimum detectable activities (MDAs) were 2.75 Bq kg−1 for 40K, 0.7 Bq kg−1 for 232Th, and 0.9 Bq kg−1 for 226Ra.

Evaluation of radiological parameters

Absorbed dose rate (D)

The absorbed dose rate, D (nGy h−1), due to terrestrial gamma radiations in air at 1 m above the ground level, was calculated using the Eq. (3) (Aközcan et al. 2018; UNSCEAR 2000; Alajeeli et al. 2019).

$$ D\ \left(\mathrm{nGy}{\mathrm{h}}^{-1}\right)=0.462{C}_{\mathrm{Ra}}+0.604{C}_{\mathrm{Th}}+0.0417{C}_{\mathrm{K}} $$
(3)

where CRa, CTh, and CK are the massic activities of 226Ra, 232Th, and 40K in the sediment samples, respectively. 0.462, 0.604, and 0.0417 are the conversion factors for 226Ra, 232Th, and 40K to evaluate the absorbed dose rate in air per unit specific activity in becquerels per kilogram (dry weight).

Annual effective dose equivalent

The annual effective dose equivalent received by human due to natural radioactivity in the sediment samples was calculated using the Eq. (4) (UNSCEAR 2000).

$$ \mathrm{AEDE}\ \left(\upmu \mathrm{Sv}\ {\mathrm{y}}^{-1}\right)=D\ \left(\mathrm{nGy}\ {\mathrm{h}}^{-1}\right)\times 8760\ \left(\mathrm{h}{\mathrm{y}}^{-1}\right)\times 0.2\times 0.7\ \left(\mathrm{Sv}{\mathrm{Gy}}^{-1}\right)\times {10}^{-3} $$
(4)

where D is the absorbed dose rate, 0.7 Sv Gy−1 is the dose convention factor, 0.2 (5/24) is the outdoor occupancy factor, and 8760 is the hour per a year.

Radium equivalent activity

The distribution of radionuclides such as 226Ra, 232Th, and 40K is not homogeneous in some area. Therefore, to compare the concentrations of these radionuclides and to evaluate the gamma radiation hazard to humans associated with the sediment samples, the radium equivalent activity (Raeq) in becquerels per kilogram was calculated according to the following relation given by Beretka and Mathew (Beretka and Mathew 1985):

$$ {\mathrm{Ra}}_{\mathrm{eq}}\left(\mathrm{Bq}\ {\mathrm{kg}}^{-1}\right)={C}_{\mathrm{Ra}}+1.43{C}_{\mathrm{Th}}+0.077{C}_{\mathrm{K}} $$
(5)

where CRa, CTh, and CK are the massic activities of 226Ra, 232Th, and 40K in the sediment samples, respectively. In this relation, it is assumed that 370 Bq kg−1 of 226Ra, 259 Bq kg−1of 232Th, and 4810 Bq kg−1 of 40K produce the same gamma dose rate.

External hazard index

The external hazard index gives an estimation the level of radiological risk of the samples and it must be less than unity to be free from the radiological hazards. The external hazard index was calculated for the sediment samples using the following formula which is proposed by Krieger (Krieger 1981; Al-Hamarneh and Awadallah 2009):

$$ {H}_{\mathrm{ex}}=\frac{C_{\mathrm{Ra}}}{370}+\frac{C_{\mathrm{Th}}}{259}+\frac{C_{\mathrm{K}}}{4810} $$
(6)

where CRa, CTh, and CK are the massic activities of 226Ra, 232Th, and 40K in the sediment samples, respectively. Krieger model assumes that the maximum value of the external hazard index is unity if the upper limit of Raeq equals to 370 Bq kg−1.

The excess life time cancer risk

The excess life time cancer risk (ELCR) gives the probability of the cancer risk to any population over a lifetime caused by exposure to ionizing radiation. It was calculated for sediment samples by the following equation (Taskin et al. 2009; Kolo et al. 2017):

$$ \mathrm{ELCR}=\mathrm{AEDE}\ \left(\upmu \mathrm{Sv}\ {\mathrm{y}}^{-1}\right)\times \mathrm{DL}\ (y)\times \mathrm{RF}\left({\mathrm{Sv}}^{-1}\right) $$
(7)

where DL is the average life time duration (70 years) and RF is the risk factor which gives the fatal cancer risk per sievert. For stochastic effects, International Commission on Radiological Protection (ICRP) suggests the value of 0.057 for the public exposure (ICRP 2007).

Results and discussion

Activity concentrations

The activity concentrations of 226Ra, 232Th, and 40K in the sediment samples collected from Aliaga Bay are given in Table 1. Figure 2, Fig. 3, and Fig. 4 show the activity concentration distribution maps of 226Ra, 232Th, and 40K in the sediment samples respectively. The activity concentration results are given in becquerels per kilogram of dry weight. As clearly seen, the lowest 226Ra activity concentration was found at location 1 (38° 48′ 51.4″ N, 26° 58′ 46.1″ E) whereas the highest was investigated at location 29 (38° 50′ 46.9″ N 26° 58′ 14.7″ E). The lowest 232Th activity concentration was observed at location 2 (38° 49′ 03.6″ N, 26° 58′ 54.3″ E) and the highest one was found 30 (38° 50′ 44.2″ N 26° 58′ 19.5″ E). In addition, the highest 40K activity was observed at location 27 (38° 50′ 33.5″ N 26° 58′ 09.9″ E) and the lowest value was at location 4 (38° 49′ 28.1″ N 26° 59′ 01.6″ E).

Table 1 The activity concentrations of 226Ra, 232Th, and 40K in the sediment samples from Aliaga Bay
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Fig. 2
figure 2

226Ra activity concentration distribution in Bq kg−1 of sediment samples

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Fig. 3
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232Th activity concentration distribution in Bq kg−1 of sediment samples

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Fig. 4
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40K activity concentration distribution in Bq kg−1 of sediment samples

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The results show that the mean activity of 226Ra, 232Th, and 40K in sediments of Aliaga Bay is higher than the world average as given in Table 1 (UNSCEAR 2000). The activity concentrations of radionuclides are compared with other studies for sediment samples in Table 2. As shown in the table, the range of activity concentration of 226Ra is much higher than the values reported for Spain (9–14 Bq kg−1) and Kuwait Bay (19–21 Bq kg−1) (Ligero et al. 2001; Zamel et al. 2005). The 232Th activity concentrations reported in Italy (31–37 Bq kg−1) and Spain (11–16 Bq kg−1) are lower than our values (Ligero et al. 2001; Doretti et al. 1992). The maximum value of 40K activity in the present study is much higher than the values reported for Albania (675 Bq kg−1), Egypt (487 Bq kg−1), Italy (475 Bq kg−1), Spain (460 Bq kg−1), Pakistan (825 Bq kg−1), and Kuwait Bay (683 Bq kg−1), but lower than Greece (1593 Bq kg−1), Rize/Turkey (1605 Bq kg−1), Bafa Lake/Turkey (1092 Bq kg−1), and Aqaba Gulf (1133 Bq kg−1).

Table 2 Comparison of natural radioactivity of Aliaga Bay sediments with other areas of the world
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Sediment samples have different physical, chemical, and geological structure and location characteristics; therefore, the obtained results vary. Natural radioactivity levels of sediments vary from place to place depending upon the concentration of 226Ra, 232Th, and 40K present in rock and soil (Lu et al. 2016). Moreover, some agricultural activities (e.g., phosphate fertilizer usage) and industrial activities (e.g., phosphate fertilizer manufacture, coal-fired power plants, and cement production) in the river and sea valley may affect the natural radioactivity level of the sediment. The use of agricultural raw materials and industrial plants may affect the results. The agricultural phosphate fertilizer industries use raw materials that consist of phosphate rocks, phosphoric acid, ammonium phosphate, ammonium sulfate, dolomite, limestone, potassium ores (potassium sulfate, potassium chloride), and nitrogen-based compounds (ammonium nitrate, nitric acid), as plant growth depends mainly on nitrogen, phosphorus, and potassium. Phosphate ores, especially sedimentary ores, can be significantly enriched with naturally occurring radionuclides, uranium (238U), and the daughter radionuclides coming from the radioactive decay of 238U. Phosphate fertilizers are one of the most used materials in the agricultural field all over the world. The use of potassium-rich fertilizers has enriched the potassium content of the soil. The transport of potassium-rich soils to the sea by erosion appears to increase 40K in the sediment. The use of fertilizers in large extent has affected radionuclide concentration, especially potassium-containing fertilizers are one of the causes of presence of high activity of 40K in soil. Evidence of high 40K activity in some sediment samples may indicate excessive use of phosphate fertilizer in agricultural lands and its transport to sediments (Yümün and Kam 2017; Boukhenfouf and Boucenna 2011; Ghosh et al. 2008). And also, the distributions of the natural radionuclides in the soils and sediments are closely related to the underlying geology. The Aliaga limestones form the sedimentary equivalents of the volcanic association (Çam et al. 2013). Although the distribution of 232Th massic activity in the studied area shows similarity to that of 226Ra, the relatively high values of 232Th correspond well with volcanic rocks.

Radiological parameters

Radiological parameters were used to assess the effects of radiation on the health of people exposed to the radiation and the environment. In Table 3, the results obtained for the absorbed dose rate in air due to gamma radiation (D), the outdoor annual effective dose rate (AEDE), the radium equivalent activity (Raeq), and the external hazard index (Hex), as well as the excess life time cancer risk (ELCR) assessment for sediment are presented. In addition, comparison of calculated absorbed dose rate, annual effective dose equivalent, radium equivalent activity, and excess lifetime cancer risk of sediment samples collected from Aliaga Bay with the World Standard Values is given in Fig. 3. As seen in Table 3, the absorbed dose rate ranged from 51.35 to 103.74 nGy h−1. The average absorbed dose rate was calculated as 81.64 nGy h−1 which is higher than the world average absorbed dose rate of 57 nGy h−1 (UNSCEAR 2000).

Table 3 Radiological parameters of sediment samples
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In the present work, the calculated values of annual effective dose due to natural radioactivity ranged from 62.98 to 127.23 μSv y−1 with a mean value of 100.13 μSv y−1, which is higher than the world average of 70 μSv y−1 (UNSCEAR 2000). It is observed that the values of D and AEDE for the studied sediment samples have higher values than world average value, except sample locations (1, 2, and 3) which have lower than world average (Fig. 5). The high absorbed dose rate in air and annual effective dose equivalent due to gamma radiation at collection sites were due to high level of 226Ra, 232Th, and 40K in the surface sediments.

Fig. 5
figure 5

Calculated a absorbed dose rate D (nGy h−1), b annual effective dose equivalent AEDE (μSv y−1), c radium equivalent activity Raeq (Bq kg−1), and d excess lifetime cancer risk ELCR of sediment samples collected from Aliaga Bay and comparison with the World Standard and Permissible Value

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The values of Raeq for the sediment samples varied from 110.31 to 219.28 Bq kg−1 and mean value of Raeq was found to be 173.31 Bq kg−1. The mean value of the radium equivalent activity due to the activities of 226Ra, 232Th, and 40K for the sediment samples is lower than the permissible value of 370 Bq kg−1 (UNSCEAR 2000). As seen in Fig. 3, all the Raeq values of samples are below the internationally accepted value 370 Bq kg−1 (UNSCEAR 2000).

The external hazard index varied from 0.29 to 0.59 with a mean value of 0.47. The calculated external hazard indices were less than the unity for all sampling locations which corresponds to the sediment samples which are free from the radiological hazards (Table 3).

The mean ELCR was found to be 0.40 × 10−3 and varied from 0.25 × 10−3 to 0.51 × 10−3. The mean ELCR value was found to be higher than the world average ELCR value of 0.29 × 10−3 according to UNSCEAR (UNSCEAR 2000). As given in Fig. 3, the ELCR values for the studied sediment samples have higher values than the world average value, except sample locations (1, 2, and 3) which have lower than the world average (Fig. 5).

Statistical approach

Statistical analysis of the activity concentrations of natural radionuclides was performed using statistical software (SPSS 25.0). Descriptive statistical data such as mean, median, kurtosis, skewness, and standard deviation for assessed parameters in sediment samples were calculated and are given in Table 4. Skewness of 226Ra (− 0.79) and 40K (− 0.51) was found to be negative while 232Th was positive with 0.33. The positive and negative skewness values give the information about the asymmetric distribution. Negative values for the skewness of 226Ra and 40K indicate that the peak of the distribution is left of the mean value, and positive values for the skewness of 232Th indicate that the peak of the distribution is right of the mean value. On the other hand, kurtosis values give information about the degree of peakedness of the probability distribution. In this study, kurtosis of 232Th (− 0.14) and 40K (− 0.33) were found negative which indicate relatively flat distribution while positive kurtosis of 226Ra (0.04) indicate relatively peaked distribution.

Table 4 Statistical data for assessed parameters in sediment samples
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Box plot of activity concentration of 226Ra, 232Th, and 40K in becquerels per kilogram is given in Fig. 6. Box plot of activity concentrations gives information about how the values in the data are spread out. As seen in Fig. 6, the median is near the middle of the box for 226Ra and 40K which means the distribution of the data set is normally distributed and symmetric. The median for box plot of 232Th is closer to the bottom of the box, and the distribution is positively skewed. The frequency distribution and Q-Q plots of activity concentrations of 226Ra, 232Th, and 40K were analyzed and are given in Fig. 7, Fig. 8, and Fig. 9, respectively. The graph of 232Th shows that radionuclides demonstrate a normal (bell-shaped) distribution. But 226Ra and 40K show log-normal distribution with some degree of multimodality. The multimodality characteristic shows the complexity of radionuclide in sediment samples. Quantile-quantile plot is another way to identify types of distributions. As can be seen in Figs. 7, 8, and 9, all points lie approximately along 45-degree reference line; it can be assumed that the distributions are normal.

Fig. 6
figure 6

Box plot of a 226Ra and 232Th, b 40K

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Fig. 7
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a Frequency distribution and b Q-Q plot of 226Ra in sediment samples

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Fig. 8
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a Frequency distribution and b Q-Q plot of 232Th in sediment samples

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Fig. 9
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a Frequency distribution and b Q-Q plot of 40K in sediment samples

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Linear Pearson’s correlation coefficients at alpha testing level of p < 0.05 were calculated among radiological parameters for soils around Aliağa Bay and the matrix between radioactive variables is given in Table 5. Strong correlation exists between 226Ra and 232Th (r = + 0.60), which can be based on their natural origin (Tanasković et al. 2012). Computed correlation between ELCR, D, AEDE, and Raeq has perfectly positive linearship (r ≥ 0.99) which means a perfect degree of association between these variables and also strong correlation (r ≥ 0.77) with 226Ra, 232Th, and 40K.

Table 5 Pearson’s correlation matrix between radioactive variables of sediment samples around Aliağa Bay
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Factor analysis was also performed on the studied variables by using varimax rotation with Kaiser Normalization method (Sivakumar et al. 2014). The rotated factor 1 and 2 values are listed in Table 6. Factor analysis provided two factors with eigenvalue < 1, explaining 96.74% of the total variance. The rotation space of component 1 and component 2 is given in Fig. 10. As seen in Table 6 and Fig. 10, the first factor accounted for 64.74% of the total variance and mainly characterized by high positive loading of concentrations of 232Th and 40K. The second factor accounted for 31.70% of the total variance and mainly consisted of positive loading of 226Ra. From the overall factor analysis, it can be indicated that 232Th and 40K dominantly increase the radioactivity in the sediments.

Table 6 Rotated factor loading of the variables
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Fig. 10
figure 10

Graphical representation of components 1 and 2

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In addition, cluster analysis (CA) was performed to understand the similarities between radiological parameters (Fig. 11). The dendrogram shows clusters with similar properties. In the present study, average linkage method was used to measure the distance between clusters. Average linkage method is based on the lowest value of the average distance between clusters in parallel with the single and full link technique. In the dendrogram, all 7 radiological parameters are classified into two clusters. Cluster 1 includes high similarity parameters (226Ra and 232Th) which means the radioactivity in sediment samples mainly depends on 226Ra and 232Th activity concentrations (Sivakumar et al. 2014). Cluster II consists of 40K at high Euclidean distance. ELCR, AEDE, D, and Raeq were primarily due to 40K as seen in the dendrogram.

Fig. 11
figure 11

Dendrogram shows the clustering of radiological parameters

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Conclusions

The activity concentrations have ranges from 23.54 to 59.46 Bq kg−1 dry weight for 226Ra, 37.54 to 64.37 Bq kg−1 dry weight for 232Th, and 354.71 to 978.35 Bq kg−1 dry weight for 40K, respectively. Clearly, the results show that the measured massic activity of 40K significantly exceeds the measured massic activity values of both 226Ra and 232Th. This is an indication that 40K is a more abundant radioactive element than the other elements in the soils under consideration.

The absorbed dose rates due to naturally occurring radionuclides in beaches range between 51.35 and 103.74 nGy h−1. The average absorbed dose rate was found as 81.64 nGy h−1 which is higher than the world average absorbed dose rate (UNSCEAR 2000). The annual effective dose ranges from 62.98 to 127.23 μSv y−1 with a mean value of 100.13 μSv y−1, which is calculated higher than the world average of 70 μSv y−1 (UNSCEAR 2000). The radium equivalent activities vary between 110.31 and 219.28 Bq kg−1 and average value of radium equivalent activity was calculated to be 173.31 Bq kg−1 which is lower than the international recommended maximum value of 370 Bq kg−1 (UNSCEAR 2000). The mean excess lifetime cancer risk of sediment samples was found to be 0.40 and changes between 0.25 and 0.51. The mean excess lifetime cancer risk value was found to be higher than the world average of 0.29 × 10−3 according to UNSCEAR (UNSCEAR 2000). From the statistical approach, log-normal distribution of 226Ra and 40K with multimodality shows the complexity characteristic of sediments. The Pearson’s correlation coefficient analysis suggested that strong correlation exists between 226Ra and 232Th and in good agreement with CA. CA indicates that ELCR, AEDE, D, and Raeq were primarily due to existence of 40K. From the factor analysis, it can be concluded that 232Th and 40K dominantly increase the radioactivity in the sediment.

This study can be used as a baseline for future researches and the data obtained in this study may be useful for radioactivity mapping. Information obtained from the study was intended to help in the determination of radionuclide sources and radionuclide distribution and potential public health hazard due to radionuclide contamination of the Aliaga Bay, Izmir (Aegean Sea, Turkey).