Rn , 226 Ra and 238 U concentration in water samples for some marshes in Dhi-Qar governorate , Iraq

Radon (Rn), radium (Ra) and uranium (U) concentration in the samples of marshes’ water have been measured. The samples were collected from various places at the marshes, in Dhi-Qar governorate. The method that used in the present study is the can technique by Solid State Nuclear Track Detectors (SSNTDs) with CR-39 detectors. Also, it was determined the average internal effective dose risk (AED), with lifetime cancer risk due to ingestion of Rn and Ra in drinking water. The average values of Rn, Ra and uranium U concentration in water samples were found to be 288.02+ 31.21 Bq/m, 0.45+ 0.04 Bq/L, and 0.60+ 0.06 ppm, respectively. The average values of AED (in mSv/y unit) caused by ingestion of Rn and Ra in the samples of the study were found to be 0.019+ 0.002 and, 0.093+ 0.01, respectively. The average values of total AED and lifetime cancer risk values were calculated to be 0.11+ 0.01 mSv/y and (4.34+ 0.47) 10 , respectively. The average concentration values of Rn and Ra were found to be within the global average limitations (0.4 Bq/L), and (1 Bq/L) that are recommended by World Health Organization (WHO) in 1993 and 2011, while the average of U concentrations were higher than that of the global average limitation (0.566 ppm) that was recommended by Environmental Protection Agency (EPA). When some results of AED due to Rn and Ra concentrations, in the samples under study, were compared with the worldwide median value it was found that the lifetime cancer risk in all samples of the present study were higher than the safety limit for the healthy drinking water. Therefore, consuming the water of marshes in the Dhi-Qar Governorate, Iraq, for cooking and drinking (which is contaminated with alpha emitters like Rn, Ra, and U) may lead to a considerable variation in the internal effective dose.


INTRODUCTION
It has been reported that naturally originated radiation is among the biggest contributors to the accumulative radiation dose that the world population receives. A persistent population exposure to radiation at a specific location, and for some period of time, may be one cause of the hazards of radiation to the exposed population (L'annunzia 2016; Mirdoraghi et al. 2020). The most common forms of ionization radiation are alpha particles such as 222 Rn, 226 Ra, and 238 U. These three elements occur naturally in the environment and are found in very trace amounts in rocks, soil, water and plants (L'annunzia 2012). Water is indispensable for life; therefore, it is supposed to be radioactive contamination free. The water has two important closely related measures, they are: quantity and quality. Naturally, the water is known to have certain impurities: water quality is a matter of the utmost priority when the environment is considered. The resources of water, in any country, would impact food production process, public health, development of industries, and consequently its economy (Murray 1981). The water people drink can also contain amount radionuclides: the common radionuclides are 40 K, 226 Ra and 238 U and their associated progeny (Charles et al. 2010). Examples of the radioactive nuclides include uranium, radium, and radon can be existed in the air, soil, food, and water. Inhaling and/or ingesting of these radionuclides in larger amounts than that of the safe levels, can be turned into health hazards (Attix 2008). The levels of radon concentrations in groundwater is 11 kBq/ m 3 (11Bq/L) set by United States Environmental Protection Agency (USEPA) (Raymond et al. 2007), while in drinking water is 400 Bq/m 3 (0.4 Bq/L) that are the recommended levels by WHO Guidelines for drinking water quality (WHO 1993(WHO , 2011. In this regard, the priority of the health system in any developing country is a profound supply of clean water. Geographic information system (GIS) technology has been widely used in various fields, such as agriculture, business, geography, ecology, electricity and gas, emergency management and public safety, environmental management, forestry, health care, education, mining and geosciences, real estate, remote sensing, telecommunications, and transportation as well as water distribution and resources (Abojassim & Rasheed 2019;Saleh et al. 2019;Kiani et al. 2021). The study of natural radioactivity (alpha emitters) was carried out by many investigators in different countries around Iraq and others throughout the world (Abbasi & Bashiry 2016;Abojassim & Mohammed 2017;Abojassim et al. 2017aAbojassim et al. , 2017bEl-Taher et al. 2020). Many regions in the Dhi-Qar governorate have been bombarded in the recent wars that Iraq was exposed to in the previous period. Water marshes and their direct impact on the lives of people, animals, and agricultural crops are important. As well, there is no comprehensive study of alpha emitters like 222 Rn, 226 Ra, and 238 U, lifetime cancer risk water, and radiation mapping marshes in the Dhi-Qar Governorate. Indeed, the present study is the first attempt to evaluate the risk related to radon presence in water samples of marshes (Ahwar) at Dhi-Qar Governorate. Therefore, the aim of this work was to estimate the concentrations of radon, radium, and uranium in water samples from marshes in Dhi-Qar Governorate, Iraq, using CR-39 detector. Also, evaluation of the AED and lifetime cancer risk due to consumption of 222 Rn and 226 Ra in the drinking water is estimated. GIS techniques were used to draw a map that depicts all alpha emitters found in the present study.

Study area and collection samples
Dhi-Qar is one of the Iraqi governorates; it has the greatest history in the world: it is the place where the first writing letters were invented, so one can proudly say that what you see of human prosperity and development, in fact is owed to that great city and its marshes. It lies on the banks of the Euphrates River, 370 km southeast of Baghdad, capital of Iraq. It is located 31°05 0 388.8″N latitudes, 46°26 0 66.7″E 32.05 longitudes. It rises about 9 m above the sea level (Jassim & Goff 2006). The marshes of the south of Iraq are known to include areas suitable for the growth and reproduction of algae. Furthermore, they are famous in their biodiversity and cultural richness. The two rivers of Iraq (i.e. Tigris and Euphrates) have created about 15,000 km 2 of wetlands known as Mesopotamian marshes in Iraq. These wetlands include complicated inter-connected shallow freshwater lakes and marshlands. These lakes and marshlands are considered as the most extensive wetland of the ecosystem of the middle east (Brasington 2002). Twenty water samples were collected from different marshes at Dhi-Qar Governorate for the study: the period of collection from 1/1/2020 to 1/3/2020 to measure the 222 Rn, 226 Ra, and 238 U levels. Sample locations were determined by coordinates using the Global Positioning System (GPS) which is a satellite navigation system used to determine the ground position of any object. The locations of the samples and name of marshes (Ahwar) at the Dhi-Qar governorate are shown in Figure 1 drawn using GIS technique by ArcGIS 10.7.1. Water samples were measured directly without any preparation. The collected samples were stored for about one month prior to counting. The storage is done in order that the secular equilibrium is reached between 222 Rn and its parent 226 Ra within the uranium chain (Alaboodi et al. 2020).

Samples measurement
0.25 L samples were collected in plastic cups with radius of 3.5 cm and length of 18 cm. Solid state nuclear track detector was used in this study as shown in Figure 2. The detector name CR-39 (C 12 H 18 O 7 ) and it was purchased from TASTRAK Analysis System Ltd, UK: TASTRACK. A sheet of CR-39 detector was cut into pieces which of 2 cm Â 2 cm dimensions, thickness 1 mm, and density of 1.3 gm/cm 3 . A piece of the CR-39 detector was positioned at the bottom of each cover of the cylinders. The samples were set at the bottom of the cylinders, then the cylinders were sealed, and stored at room temperature for 90 days (exposure time). At the end of the exposure time, the CR-39 detectors were etched of sodium hydroxide (NaOH) solution at 70°C temperature for 5 h, with 6.25 normality solution (Abojassim & Mohammed 2017;Abojassim et al. 2017aAbojassim et al. , 2017b. Following this step, the detectors were washed using distilled water. Then, a microscopic treatment was performed to calculate the concentrations of radon using the optical microscope (Novel, China). The magnifying power of the microscope used to count tracks of 400X, where the object piece is 40X. The detector surface dividing into 10 areas of view to count the alpha particles and taking multiple pictures of each region by using a digital camera connecting with computer via cable USB after installing the camera program on the computer to measure a number of tracks. The background correction was done via the subtraction of the background level from the counted alpha track density.  2.3. The calculations 222 Rn concentrations in the air of the tube (C a Rn ) was calculated using the following formula (Mayya et al. 1998): where ρ is the track density on the detector (Tr/cm 2 ), t is the exposure time (90 days), and K is the calibration factor. The calibration factor for the detector had a range of 0.5-3 days for the Radium-226 (Radon source) whose activity of 3.3 kBq was calculated to be (0.2217 + 0.033) (track/cm 2 )/(Bq.day/m 3 ). These values agreed well with the reported values in many works (Abojassim 2013;Subber et al. 2015;Mohammed 2016;Alkhafaji et al. 2019).
The concentration of the radon in the sample (C s Rn ), can be calculated using the following Equation (2) (Elzain 2014): where λ Rn is the decay constant of 222 Rn (0.1814 d À1 ), h is the distance from the surface of the sample to the detector, t is the exposure time, and l is the thickness of the sample in the tube. The activity concentration of radon inside sample (C s,ac Rn ) was determined using the relation (3) where A s is the surface area of the sample and M s is the mass of the investigated sample. Radium activity concentration ( 226 Ra) within the sample (C s,ac Ra ) was determined using the relationship (4) (Azam et al. 1995): The concentration of uranium (C s U ) in ppm is given by Equation (5) where M s U is the mass of uranium in the sample. The annual effective dose (AED) due to the ingestion of 222 Rn and 226 Ra through drinking water for adults was calculated using Equation (6) (Sajo et al. 1997): where C is the radionuclide activity concentration ( 222 Rn and 226 Ra), WC is the annual water consumption for a person (2 L/d) (El-Taher et al. 2020) and DCF is the ingestion dose conversion factor for the corresponding radionuclide, which it is equal for radon-222, and radium-226 ingestion by people as 0.0035 μSv/Bq and 0.28 μSv/Bq (ICRP 1995;Eckerman et al. 1988;UNSCEAR 2001

RESULTS AND DISCUSSION
To achieve the aim of this study, alpha emitters ( 222 Rn, 226 Ra, and 238 U) concentrations in water samples from marshes in Dhi-Qar Governorate were studied using SSNTDs with CR-39. The results of 222 Rn (C a Rn , C s Rn , and C s,ac Rn ), 226 Ra, and 238 U concentrations in water samples for selected marshes in Dhi-Qar Governorate are shown in Table 1 WHO in 1993(WHO 1993Pfister 2000): 0.4 Bq/L (400 Bq/m 3 ), except samples M6, M9, M10 and M11. Variations in concentration values of radon in the water samples, in the present study, were given. These variations were resulted from several factors such as the geological nature of the area where the samples were collected, their geochemistry and their components (that may vary from one area to another). It should be noted that the pollution that resulted from the radiation may be directly caused by the absorption of radionuclides of the atmosphere. When we compared the values of (C a Rn ) and (C s Rn ) of the investigated metrics (Table 1), it was clear that the radon concentration of the samples itself was much higher than that of the airspace of the tube. This clear difference between the two values can be attributed to the known fact that most the radon atoms of the sample were disintegrated before entering the space of the tube as they had a short decay time of 3.82 d (Sajo et al. 1997). In addition to this, the existence of the radium (i.e. radon parent) inside the sample is not in the airspace of the tube. It can be concluded from Table 2 that the activities of alpha due to radium in water samples were found to be lower than those caused by radon. These observations can be clarified by the fact that radon has the shorter halflife (3.82 d) than that of radium (1,600 y) (Elzain 2014;Abojassim & Mohammed 2017;Abojassim et al. 2017aAbojassim et al. , 2017b. The results of C s,ac Ra for samples of water in the present study were found to be within the global average limitations (1 Bq/L) that are recommended by WHO (2011), except sample M6 was larger than global average limitations.
The values of C s,ac U for most water specimens of Marshes in Dhi-Qar Governorate are higher than the global average limitations (0.566 ppm) in the drinking water according to EPA organization (Raymond et al. 2007). Figures 3-5 show the maps of C a Rn , C s,ac Ra , and C s,ac U respectively in the water samples of marshes (Ahwar) at Dhi-Qar Governorate that was drawn by GIS technique with ArcGIS 10.7.1. Where different colors were used to distinguish between high, medium, and low quantities.
AED due to activity of 222 Rn, 226 Ra, and the total of AED in water samples in the present study are shown in Table 2. It was found that the AED in mSv/y for 222 Rn, 226 Ra, and total of AED were ranged from 0.007 to 0.043, with an average value of 0.019 + 0.002, from 0.035 to 0.210, with an average value of 0.093 + 0.01 respectively. While the values of the total AED ranged from 0.04 mSv/y to 0.25 mSv/y, with an average value of 0.11 + 0.01 mSv/y. Ingestion of radioactive contaminated food or drinks (contaminated water, juices, tea, coffee, etc.) contribute to around 0.3 mSv/y of the average human exposure to radiation from natural sources. The total suggestive radiation dose is restricted to about 0.1 mSv/y through the intake of radionuclides via drinking of the water (WHO 2011). If these radionuclides have resulted in more than 0.1 mSv/y dose limit, then the resulting AED will be the summation of AED equivalents from each of the radioelements present in the food or drink. The mean of the total AED in the present study was 0.11 mSv/y for two radionuclides ( 222 Rn and 226 Ra), which is lower than an action limit of 1.0 mSv/y (excluding 222 Rn). The average AED from ingested 222 Rn in drinking water was calculated to be as low as 0.002 mSv/y (UNSCEAR 2001;Somlai et al. 2007). The lifetime cancer risk due to water intake was also evaluated. The biggest lifetime risk resulted from water intake, seen in the sample M6, while the lowest lifetime risk was found in the sample M15. The lifetime risk from ingestion of 222 Rn and 226 Ra in water samples for the inhabitants of some marshes in Dhi-Qar Governorate, Iraq, was found ranging from 1.61 Â 10 À4 to 9.74 Â 10 À4 with an average value of (4.34 + 0.47) Â 10 À4 , which exceeds the admissible limit of 10 À4 (Alomari et al. 2019). Figures 6 and 7 show the maps of total AED and lifetime cancer risk respectively in the water samples of marshes (Ahwar) at Dhi-Qar Governorate, that were drawn by GIS technique, with ArcGIS 10.7.1, where different colors were used to distinguish between high, medium, and low quantities of these radioactive elements in drinking water. These findings of alpha emissions were varied across all water samples that were studied, due to the radioactivity in origin, or natural materials that compose the contents of the samples such as chemical material, and from one another important factor which is the geology. Indeed, the present study is the first attempt to evaluate the risk related to radon presence in water samples of marshes (Ahwar) at Dhi-Qar Governorate. The results of the current study were compared with the results of other local and international studies, which were conducted to measure the concentration of radon gas in water, as shown in Table 3. Through these studies, it is of note that the average of 222 Rn concentration in the waters of the present study were within the other studies in Table 3. The total number of locations measured should be increased in future studies. It was found that the radon concentration in most of the samples under study was not high    and not significant to represent a health hazard from the point of view of this study. Certainly, this study was conducted to provide a health-oriented radon assessment of marshes in the Dhi-Qar Governorate, address long-term management goals, especially from the environmental point of view. The results provide a framework for future studies that should include a large and broader survey of radon concentration of water as well as other natural radioactivity in Iraq.

CONCLUSIONS
The concentrations of radon-222, radium-226, and uranium-238 in water samples of marshes (Ahwar) at Dhi-Qar Governorate were studied. Most results of radon concentrations in the present samples are within that recommended WHO (400 Bq/m 3 ). Also, it was found that the values of 226 Ra in all samples were lower than that of the global average limits (1Bq/L) recommended by WHO, except sample M6, where the 238 U concentrations were higher than global average limitations (0.566 ppm) which is recommended by the EPA in healthy drinking water. The average value of total AED from radon-222 and radium-226 in water for drinking for all samples under study were lower than an effective limit of 1.0 mSv/y, and were very close to the radiation dose limit of 0.1 mSv/y acceptable level of radionuclides to be ingested via drinking water, as recommended by WHO. It is also found that the lifetime cancer risk in most samples exceeds the allowed maximum level of (10 À4 ). Consequently, measurement of alpha emitters and radiological risks due to radon-222 and radium-226 of water samples collected from some marshes (Ahwar) at Dhi-Qar Governorate, revealed that some water samples do not comply with the global average limitation standards. Therefore, the water of the study area is not suitable for human drinking but suitable for other activities.

RECOMMENDATIONS
Through the present study and according to the obtained results and the conclusions, many ideas for the suggestion concerning the works and important recommendations can be outlined.