Background 

During the 2^nd and 3^rd Gulf war, Basrah as a part of Southern Iraq exposed to a radiation attacks due to the usage of DU weapon against military troops and vehicles. Radiological results were detected within Basrah Governorate (Saadon et al., 2016). Moreover, Soils and Sediments from Southern part of Iraq is characterized by the existence of natural occurring radioactive materials (NORM), mostly are ⁴⁰K, ²¹²Pb,²¹⁴Pb, ²¹⁴Bi, and ²²⁸Ac (Bashar et al., 2015).

Radioactive pollutants were spread over all Basrah Land (Al-Imarah and Ali, 2009). The radioactive materials are transferee from land towards waterways from where they move towards oceans and seas and accumulated in the water column, then they undergoes sedimentation to the bottom of the waterways, once they reach bottom bed they became a part of the ecosystem, water, sediments, and biota (Akram, 2005).

Radium is a decay product of uranium within the naturally occurring uranium series. When radium decays in soil, the resulting atoms of radon isotopes first escape from the mineral to air-filled pores. The rate at which radon escapes from soil into the surrounding air is known as radon exhalation rate of the soil. This may be measured by either per unit area or per unit mass of the soil. The measurement of radon exhalation rate in soil and building materials is helpful to study radon health hazard (Al-Yani, 2008; Pressyanov, 2012). Among many factors affecting radon exhalation, one of the most important is radium content of the bedrock or soil (Singh and Singh, 2006). Being aware of the hazardous effects of radon exhalation on human health, it was necessary to conduct measurements of radium content in the soil. Higher values of Ra-226 in soil contribute significantly in the enhancement of environmental radon. However, radon exposure shows an extreme variation from location to location and depends primarily on the exhalation rate of radon from the soil. Since radium present in the soil is the main source of indoor radon, the estimation of radium content along with the radon exhalation rate in the soil was carried out.

Radon arises from trace concentrations of radium in the earth's crust. It exists in three isotopes ²¹⁹Rn, ²²⁰Rn, and ²²²Rn with different half-lives, 4 s, 56 s, and 3.8 days respectively, the largest and most important isotope is ²²²Rn. It is formed in the decay of ²²⁶Ra within the decay chain of ²³⁸U, it is an α emitter, and due to its relative high solubility in water it makes radon existence in all types of water (Al-Shamsi, 2014). Typical activity concentrations of ²²²Rare n 2-20 Bq/m³ in outdoor air, 10-100 Bq/m³ in indoor air, 1-10 Bq/m³ in underground cavities, and 5-50 k Bq/m³ in soil gas (USEPA, 2013).

Radon is decays to relatively short lived (less than 30 min) radionuclides ²¹⁸Po, 3-11 min, ²¹⁴Pb, 26.8 min, ²¹⁴B, 19.9 min, and ²¹⁴Po, 164 µs. They all likely to decay to the stable isotope ²¹⁰Pb with half-life 22.3 y (USEPA, 2013). Concentrations of indoor radon gas have been measured by using time independant passive radon dosimeter solid state nuclear track CR-39 technique detection (Al-Alawy and Fadhil, 2016). ²²²Ra was estimated as an average value of 1386, 36 Bq/m³ in soil samples from Al-Nasiriah Province /southern Iraq to the north of Basrah Governorate, by using the CR-39 technique (Kadhim, 2014).

Concentrations of radon gas in samples of soil from Ras Tanurah and Saudi Arabia were measured by can technique containing CR-39 and found as an average to be 120 Bq/m3 (Al-Shahri et al., 2017).

Recent studies conducted for determination of radon concentrations in the marine sediments from nearby sites, measurements were done for Khor Abdullah the extended water way of Khor Al-Zubair, and Jaber et al. (2015) adopted two techniques, the SSMTDs and RAD7 and reported values were in the range 78 to 606 Bq/m³ and 97 to 301 Bq/m³ respectively.

Scientists overall the world are still probing the earth’s crust and continuing to measure the radiation levels and quantify the hazards and doses affecting people, animals, plants and all kinds of life (Darwish et al., 2015).

1 Aim of the Study

In the present study investigations have been carried out to measure the radiological parameters in sadiment samples collected from water ways around Hajjam island by using can technique containing SSNTDs of type CR-39.

2 The Study Area

Khor Al-Zubair is one of the main outlet water ways from Iraq to the Arabian Gulf, it is an estuarine lagoon environment (Emery and Stevenson, 1957; Al-Ramadan, 1986) situated south west of Basrah (Figure 1), which is connected to Al-Hammar marsh through Shatt Al-Basrah canal. Hajjam Island is located in the lower part of Khor Al-Zubair as a unity island in the beach of Iraq with locations (N: 30°00'54''. 3, E: 47°57'02''. 1), as shown in Figure 2, Hajjam Island has a length of 3.5 km and a width of 0.45 km, water and sediments around the island are effected heavily by the discharge from Khor Al-Zubair which is covered with fine muddy sediments where sandy deposits is restricted to the narrow zone of the shallow part near the shore and around the island slopes (Afaj, 2004).

3 Materials and Methods

Sediment were collected by means of Van veen Grab sampler from 15 sites around the island (Figure 2). Samples dried overnight, grinded, and powdered. For the determination of Radon concentrations two methods were adopted, passive and active.

3.1 Passive method

Within the passive method, can Technique was adopted (Abu-Jarad, 1988). About150-250 gm of the sample is kept inside the can as shown in Figure 3.

Equation 1 was used for the estimation of radon concentration (Khan et al., 1992; Al-Zoubi et al., 2013; Mansour et al., 2014):

Most of the emanation radon produced from marine sediment remains within the grain under water and many of fraction of radon escapes to the pore spaces and water, so it dissolves through the water which is depending on the grain size and location of its parent in grain (Duenas et al., 1997). The ²²⁶Ra decays to ²²²Rn by emitting an Alpha particle, the main mechanism of escape turns back energy of its atoms during the decay of ²²⁶Ra and diffusion through grain or water as shown in Figure 4.The exhalation rate is defined as the rate at which radon escapes from soil into the surrounding air. This may be measured by either per unit area or per unit mass of sample.

The surface exhalation rate from the sample inside the dosimeter is calculated by equation 2 (Imma et al., 2014):

The exhalation rate per unit mass is calculated by equation 3:

While the effective radium content in the sample is calculated by equation 4 (Sharma et al., 2003):

3.2 Active method

RAD7, Durridge Company USA analyzer as shown in Figure 5 was used which has a measurement chamber containing an electrostatic field overnight. When radon atoms enter the RAD7 from sample and decay, polonium-218 (²¹⁸Po) atoms are deposited onto the surface of the RAD7’s Canberra Passivity Ion-implanted Planar Silicon Alpha Detector. Alpha particles from subsequent steps along the decay chain are counted and their energy recorded to memory. The spectrum of the RAD7 can allow for energies from 0-10 MeV. Specific interest is shown in the 5-9 MeV region, since most of the radon and thoron decay produce alpha particles in that range. The first window has the energy range 5.00 MeV, hence, alpha particle with energy 5.23 MeV from the ²¹⁰Po decay will fall in this region. Window A covers the energy range of 5.40-6.40 MeV, so clearly the alpha particle with energy 6.00 MeV from the ²¹⁸Po decay will fall in this region. All the counts detected in the region divided by the lifetime (duration of the time that it took to collect the data), give the count rate.

4 Results and Discussion

During this study results were obtained through short term measurements using the RAD7 accessories and long term measurement using the SSNTDs. Hence, the values of radon, radium concentrations and radon exhalation rates per unit area and mass were determined in 15 sediment samples collected from different locations around of Hajjam island. Results are listed in Table 1.

In the present work, the results show that radon concentrations calculated by passive method varies from 132±34 Bq/m³ to 414±108 Bq/m³ with arithmetic mean value 287±45 Bq/m³. The offshore sample 9 reported the highest value due to geological nature, while in the active method radon concentrations varies from 145±9 Bq/m³ to 401±26 Bq/m³ with average 263±20 Bq/m³. The difference between the values estimated by the two methods could be due to the different measurements time. The positively correlation between passive and active method R²=0.7947 which explain in Figure 6.

The E_A in B/m²/h is range from 0.1 to 0.31, with mean value of 0.22, while E_M in unit of mBq/kg/h ranged from 0.002 to 0.006, with arithmetic mean value of 0.004.

Sediments samples has an effective radium varies from 0.0013 Bq/kg to 0.0049 Bq/kg with an average value of 0.0028 Bq/kg. The radium distribution of the soil is one important parameter governing radon emanation. Radon emanation from mineral grain or matter depends on where the atoms are situated in the grain, the texture and the size of grain, the permeability of the grains and the temperature and pressure. The emanation of radon from the measured soil samples indicates an important point in which the radon emanation from samples should be taken into consideration when measuring radium or uranium content with gamma spectroscopy, by using gamma lines emitted from radon daughters. Figure 7 explains the relation between effective radium in Bq/kg and radon concentration in Bq/m³.

For comparison the levels of radon concentrations recorded for sediments within this study were lower or comparable to values recorded for soil/sediments over all the world as well as to standard levels as shown in Table 2.

5 Conclusion

The specific activity of radon in the study area (Hajjam island) is acceptable, and there are a positive correlation has been observed between effective radium contents and radon, as well as positive correlation between the passive and active which are acceptable.

Authors’ contributions

FJM is the team leader analysis of results and paper writing. MQJ is responsible for field investigations, processing, seating the experimental dosimeter and conducting the radiological measurements. AJB is responsible for sample collection.

Acknowledgments

The authors of the present work would like to thank physics department/Marine Science Center/Basrah University for their support.

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