Assessment of radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia

Journal Pre-proof Assessment of radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia Fahad I. Almasoud, Zaid Q. Ababneh, Yousef J. Alanazi, Mayeen Uddin Khandaker, M.I. Sayyed PII:

S0045-6535(19)32420-8

DOI:

https://doi.org/10.1016/j.chemosphere.2019.125181

Reference:

CHEM 125181

To appear in:

ECSN

Received Date: 10 June 2019 Revised Date:

7 October 2019

Accepted Date: 20 October 2019

Please cite this article as: Almasoud, F.I., Ababneh, Z.Q., Alanazi, Y.J., Khandaker, M.U., Sayyed, M.I., Assessment of radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia, Chemosphere (2019), doi: https://doi.org/10.1016/j.chemosphere.2019.125181. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

Assessment of Radioactivity contents in bedrock groundwater samples from the northern region of Saudi Arabia

Fahad I. Almasoud1,2, Zaid Q. Ababneh3,4, Yousef J. Alanazi1, Mayeen Uddin Khandaker5, M.I. Sayyed6

1

Nuclear Science Research Institute (NSRI), King Abdulaziz City for Science and

Technology (KACST), P.O.Box 6086 Riyadh 11441, Saudi Arabia 2

Department of Soil Sciences, College of Food and Agricultural Sciences, King Saud

University, P.O. Box 2460, Riyadh 11451, Saudi Arabia 3

Physics Dept., Faculty of Science, Yarmouk University, Irbid 211-63, Jordan

4

College of Applied Medical Sciences, King Saud bin Abdulaziz University for

Health Sciences, Al-Ahsa, Saudi Arabia. 5

Center for Biomedical Physics, School of Healthcare and Medical Sciences, Sunway

University, 47500 Bandar Sunway, Selangor, Malaysia 6

Department of Physics, Faculty of Science, University of Tabuk, Tabuk, Saudi

Arabia

Corresponding Author: Fahad I. Almasoud Nuclear Science Research Institute (NSRI), King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh, 11441, Saudi Arabia Telephone : (+966) 504 129 330 Fax: +(966) 114 814 750 E-mail: [email protected]

Assessment of Naturally Occurring Radioactive Materials (NORM)

Th-232 Series Decay 228

Ra (Bq.L-1)

Gross Alpha and Beta

Max

3.09

Ave

1.09

Min

0.21

Gross Alpha (Bq.L-1)

Gross Beta (Bq.L-1)

Max

8.97

Max

6.63

Ave

3.51

Ave

3.48

Min

0.96

Min

1.26

U-238 Series Decay 238

U (Bq.L-1)

234

U (Bq.L-1)

226

Ra (Bq.L-1)

Max

0.11

Max

0.19

Max

0.82

Ave

0.06

Ave

0.09

Ave

0.31

Min

0.01

Min

0.02

Min

0.01

Assessment of Irrigation water Quality

1

Assessment of Radioactivity contents in bedrock groundwater samples from the northern

2

region of Saudi Arabia

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

1

24

Abstract

25

Recognizing the vast uses of water in human life, the presence of α and β particles

26

emitting radionuclides in groundwater of northern Saudi Arabia has been evaluated as a means of

27

water quality assessment of the region. A liquid scintillation counting technique was used to

28

determine the gross α/β, and

29

concentrations of

30

separation process.

234,238

228

U and

Ra radioactivities in water samples, while the radioactivity

226

Ra were determined using alpha spectrometry after the

31

Present results show that all water samples contain a higher level of gross α and β

32

radioactivity than the WHO recommended limits; the average gross α activity is about 7 times

33

greater than the limit value of 0.5 Bq L-1, while the average gross β activity value is about 3.5

34

times greater than the limit value of 1 Bq L-1. Correlations of TDS and pH with gross α and β

35

radioactivity in the studied samples were investigated. The activity ratio of the measured U and

36

Ra alpha emitters to the gross α radioactivity and the ratio of the measured β emitters to gross β

37

radioactivity were also discussed. Furthermore, interesting information on thorium abundance

38

and radioactive disequilibrium in U series were observed by studying the activity ratio of

39

228

40

being drinking, and mainly used in irrigation, the higher gross α/β radioactivity may cause health

41

risks to humans, since these radionuclides may enter the food chain through irrigation water.

42

Thus, further radioactive risk assessment is highly recommended.

Ra/226Ra,

226

Ra/238U, and

234

U/238U. Although these samples are not directly used for human

43 44

Keywords: Bedrock groundwater; Gross α/β radioactivity; NORM; Liquid scintillation counting;

45

Alpha spectrometry; Radioactive disequilibrium.

46

2

47 48

1. Introduction

49

Water, the primary natural resource of life on earth, is expected to contain radioactive

50

materials, this radioactivity in water resources of a country affects their food production and

51

public health (UNSCEAR, 2000; USEPA, 1991; WHO, 2011). The primary source of the

52

radioactivity that enters the water body comes from naturally occurring radioactive materials

53

(NORMs) of terrestrial origin, particularly 238U and 232Th progenies as well as 40K. However, the

54

concentration of such radionuclides in groundwater varies depending on the physicochemical

55

and geochemical conditions and the geological formation of the soil and bedrock of a particular

56

area (Osmond et al., 1983). Once the radionuclides present in the groundwater, it eventually

57

reaches the human body either indirectly through the food chain or directly through drinking

58

water, which could cause a health effect by elevation the ingestion dose. Thus, accurate

59

quantification, continuous monitoring and controlling the level of radioactivity in the water is

60

essential for public health. Therefore, several international organizations that are concerned

61

about the radioactivity content in drinking water published regulations limiting the radionuclides

62

concentrations in drinking water (EU, 1998; WHO, 2011).

63

Groundwater contains natural radionuclides in different concentrations; the process of

64

identifying each radionuclide concentration in water is considered time-consuming and

65

expensive. Thus, the World Health Organization (WHO) recommended the measurement of

66

gross α and β radioactivity in water samples as a convenient and fast screening test to ensure the

67

quality of water for human consumption (WHO, 2011). Consequently, the results of the

68

screening test determine whether further analysis is necessary for specific radionuclides. The

69

gross alpha activity refers to the total activity of all alpha emitters, such as

3

238

U,

234

U,

232

Th,

70

226

71

emitters, such as

72

et al., 2012). Generally, for natural radioactivity, the exposure effect due to gross alpha

73

radioactivity is of a more significant concern than that due to gross beta radioactivity (Bonotto

74

and Bueno, 2008).

Ra,

210

Po (excluding 40

222

Rn), while the gross beta activity is the total activity of all beta

K, 228Ra, and 210Pb excluding 3H, 14C and other weak beta emitters (Ferdous

75

The investigation of radioactivity in water and groundwater, in particular, has been reported

76

by many researchers worldwide, including Saudi Arabia (Al-Amir et al., 2012; Alkhomashi et

77

al., 2016; Bonotto et al., 2009; Condomines et al., 2010; Fasae et al., 2015; Forte et al., 2010;

78

Goldstein et al., 2010; Kleinschmidt, 2004; Korkmaz et al., 2016; Kumar et al., 2016; Labidi et

79

al., 2010; Shabana and Kinsara, 2014; Vesterbacka, 2005). Most of these reports focused on

80

measuring the natural radioactivity content, as well as the associated health hazard from the

81

radioactivity in the groundwater. Moreover, these reports showed that the radioactivity in

82

groundwater varies significantly depending on the geochemical conditions and in the bedrock of

83

the study area.

84

In Saudi Arabia, only two studies were performed concerning the radioactivity content in

85

groundwater in different parts of the country (Alkhomashi et al., 2016; Shabana and Kinsara,

86

2014). Therefore, continued and systemic monitoring of the radioactivity in water is essential for

87

the environment and public health since Saudi Arabia relies substantially on the groundwater for

88

drinking and agricultural purposes. The present work investigated the radioactivity content in

89

groundwater utilized mainly for irrigation. These groundwater wells lie in the northern part of

90

Saudi Arabia, which forms one the most suitable places for crops; it includes large scale

91

agricultural activities, such as the production of beans, vegetation especially potato, tomato,

92

cucumber and onions, fruits, such as pomegranate, figs, grape and citrus fruits. In this study,

4

93

several approaches were performed to measure the radioactivity in groundwater based on a

94

radio-chemical process using LSC and alpha spectrometer. It is expected that this study may help

95

to prepare baseline data for radioactivity content in the bedrock groundwater samples in the

96

northern region of Saudi Arabia, which will be used as a fingerprint for the evaluation of future

97

changes in the natural radioactivity profile.

98

2. Experimental

99

2.1 Study area

100

The study area lies in the northern part of the Arabian Peninsula. It is covering about 32.624

101

km2 with coordinate point A (lat 27.06888, long 40.34797), point B (lat 28.25760, long

102

40.36937), point C (lat 28.21702, long 42.82862), and point D (lat 27.00849, long 42.93865). It

103

located on a sedimentary plateau of elevation between 650 m and 1000 m above the sea level. It

104

has a continental climate with an average temperature of 36 o C in summer and 15 o C in winter.

105

The area receives about 100 mm average annual precipitation, which occurs mostly between

106

November and March (Almazroui, 2011).

107

The study area is characterized by relatively a flat landscape hosting the most urban and

108

agricultural land, which has a general slope towards the South-East (Ahmed et al., 2017). In this

109

region, several wells were drilled into the Saq sandstone aquifer, and the extracted groundwater

110

mostly used for agricultural purposes. The Saq is dominated by the sedimentary formation of

111

age range from Cambrian to Ordovician and is composed of medium to coarse-grained

112

sandstones, which extends north to Jordanian borders (Hussein et al., 1992). The thickness of

113

aquifers is varied from one place to another, depending on the geological formation. The depth

114

of the aquifer in the study area ranged from 400 to 1200 m (Burdon, 1982; MAW, 1984).

115 5

116 117

2.2. Sample collection and preparation

118

A total of thirty-six groundwater samples were collected from drilled wells distributed

119

randomly in eighteen farms that lie in the northern part of Saudi Arabia.. Sampling sites are

120

listed in Table 1 and shown in Figure 1. The groundwater samples were collected from each well

121

and placed in 5 L plastic containers. The water samples were acidified to reduce the absorption

122

on the container walls. Then the collected samples were sealed and transferred to the laboratory

123

of King Abdulaziz City for Science and Technology (KACST), Saudi Arabia for further

124

radioactive investigation. Furthermore, an approximately 100 mL water sample from each well

125

was collected to determine the characteristics of groundwater samples: pH and total dissolved

126

solids TDS. The parameters pH and TDS were measured using Ultrameter (II) (Model # 6P,

127

Myronl Company, Carlsbad, USA. The measured values of pH and TDS are given in Table 1.

128

2.3. Gross α and β activities measurements

129

The gross α and β activities in the groundwater samples were measured by a low-

130

background liquid scintillation spectrometer LCS using a Quantulus 1220™ spectrometer. The

131

detector can detect α and β at the same time in two different channels by using pulse shape

132

analyzer (PSA). Following the method of Sanchez-Cabeza et al. (1993), the samples were

133

prepared by choosing 100 mL aliquot of each water sample, then evaporated at 50 oC for pre-

134

concentration. After cooling to room temperature, 8 mL of the concentrated solution was taken to

135

a liquid scintillation vial, and 12 mL of (Opti-Phase “HiSafe” 3) cocktail was added. Then

136

samples were counted for gross α and β activities. The MDA for gross α and β was calculated as

137

0.1 Bq L-1 and 0.3 Bq L-1, respectively. The calibration of the detector was carried out using a

138

mixed standard solution containing

139

Technology (NIST)) from the USA. The stability study of the detector is done by using high

241

Am and

6

90

Sr/90Y (National Institute Standards and

140

energy beta, carbon fourteen (14C) (99500 dpm/std ± 1.30%) and low energy beta, tritium 3H

141

(202900 dpm/std ± 1.6%) from PerkinElmer, (1215-111) August 3, 2012. The detection

142

efficiency was evaluated and found to be almost 98% for both gross α/β activity.

143

2.4. Radioactivity Measurement of 228Ra

The radioactivity of

144

228

Ra in water samples was determined using the Radiochemical

145

analysis described by Chalupnik and Lebecka (1990). Briefly, the procedure involved radium

146

extraction from the sample by co-precipitation with barium sulfate Ba(Ra)SO4. The precipitate

147

was treated with EDTA and re-precipitation attained by adjusting the pH of the solution to 4.5 by

148

adding glacial acetic acid. Then, the precipitation was mixed with a scintillation cocktail, and

149

228

150

function. The MDA for 228Ra was found to be 7 mBq L-1 for a counting period of 64,800 s.

151

2.5 Radioactivity Measurement of 226Ra

152

The activity concentration of

Ra was counted on a low background beta counting system LSC using α/β discrimination

226

Ra in water samples was performed using an alpha

153

spectrometer, which is based on radiochemical separation procedure described by Medley et al.

154

(2005). A brief outline of this method, radium from the sample was co-precipitated with barium

155

sulfate in the presence of lead sulfate. The precipitate is dissolved in DTPA, then the solution

156

precipitates by adding barium carrier and acetic acid which adjust the pH to 4.8. The precipitate

157

is filtered through 1mm polypropylene membranes and radium counted by the alpha

158

spectrometer.

159

226

160

2.6. Radioactivity measurements of 234U and 238U

161

133

Ba is used as a yield tracer to determine the radium isotopes. The MDA for

Ra isotopes was found to be 6 mBq L-1 for a one day count.

The activity concentrations of

238,234

U in water samples were performed using an alpha

162

spectrometer. Briefly, the procedure involved radiochemical separation of U by ion exchange

163

and preparing the counting alpha source by micro co-precipitation technique. Following the 7

164

method of (Lally, 1982), briefly, 200 mL of the water sample was filtered, spiked with 200 µL of

165

232

166

mL was obtained. The U is separated by passing the solution through a Bio-Rad AG 1-X8 anion

167

exchange column, preconditioned with 10 M HCl solution. Finally, the uranium adsorbed on the

168

column was washed off using 0.1 M HCl. The U obtained from the column was prepared for

169

alpha spectroscopy after the separation using micro co-precipitation method as described by

170

Jiang et al. (1986). Then the prepared source mounted on a stainless steel disc, and the

171

measurement of U isotopes was performed using an ORTEC octet alpha spectrometer. The

172

detector has an efficiency between 25.1 and 27.9%. The MDA for U isotopes was found to be <

173

4 mBq L-1.

U radiotracer and evaporated. Then the sample was treated with 10 M HCl until the final 20

174 175

3. Results and discussion

176

3.1. The activity concentrations of the gross alpha and beta

177

Table 2 lists the activity concentrations of gross α and β as well as 226,228Ra and 234,238U in

178

the groundwater samples analyzed in this work. All activity measurements were presented in (Bq

179

L-1), and the uncertainties expressed in terms of 1σ. Gross α activity concentration for all

180

samples varied over a wide range from 0.96 ± 0.17 to 8.97 ± 0.71 Bq L-1 with an average of

181

3.51± 0.33 Bq L-1, while gross β activity ranges from 1.26 ± 0.23 to 6.63 ± 0.57 Bq L-1with an

182

average of 3.48 ±0.36 Bq L-1. From Table 2, we can see that all the sampling wells exhibit

183

considerable variations in gross α and β radioactivity, which might be due to the geological

184

variations in the studied region. The results showed that the mean values of gross α and β activity

185

concentrations were almost identical, although, they came from a different origin, where

186

and

228

226

Ra

Ra are the main contributors for gross α and β, respectively (Ferdous et al., 2012). It is

8

187

worth mentioning here that the exposure risk due to gross alpha in water is higher than that of

188

gross beta (Bonotto and Bueno, 2008; Semkow and Parekh, 2001). Therefore, the WHO

189

recommended different limits for gross alpha and gross beta in drinking water (WHO, 2011). In

190

this context, the obtained results showed that both gross α and β activities in all groundwater

191

samples were higher than the recommended limits proposed by WHO, for drinking water (WHO,

192

2011). The average gross α activity is about 7 times greater than the recommended limit of 0.5

193

Bq L-1, while the average gross β activity value is about 3.5 times greater than the recommended

194

limit of 1 Bq L-1. Although these groundwater wells are not directly used for human being

195

drinking, and mainly used in agricultural irrigation of crops, the relatively higher concentrations

196

may cause health risks to humans, since these radionuclides may enter the food chain through

197

irrigation water. Thus, a further radioactive risk assessment should be done.

198

Natural radioactivity in water was studied extensively by several researchers worldwide

199

to assess the drinking and irrigation water quality following its vast use in human life. Table 3

200

presents a comparative study of the measured gross α and β radioactivity in groundwater samples

201

with other regions of Saudi Arabia, as well as different countries around the world. It is observed

202

from Table 3 that gross α and β radioactivities in well waters from the northern region of Saudi

203

Arabia are in line with the results of other similar studies conducted in other regions of Saudi

204

Arabia (Alkhomashi et al., 2016; Shabana and Kinsara, 2014). Also, our results are comparable

205

with the groundwater in the United Arab Emirates (Murad et al., 2014), drilled well water in

206

Finland (Salonen, 1994), and drinking water in Australia (Kleinschmidt, 2004), while our results

207

are relatively higher than the underground and drinking water samples of other studies conducted

208

by Al-Amir et al. (2012) from Jordan, Fasae et al. (2015) from Nigeria, Beyermann et al. (2010)

209

from Germany, Jia et al. (2009) from Italy, Todorović et al. (2012) from Serbia, Turhan et al.

9

210

(2013) from Turkey, Bonotto et al. (2009) from Brazil, Agbalagba et al. (2013) from Nigeria,

211

Darko et al. (2015) from Ghana, and Jowzaee (2013) from Southwestern Caspian. This

212

comparison indicates a clear difference in the underground geology of Saudi Arabia with other

213

countries. Such high activity concentrations might be due to the reservoir rock, which may

214

contain elevated levels of uranium and thorium. It may also be worth noting that the groundwater

215

in Saudi Arabia, especially the northern region, contains relatively higher levels of radioactivity

216

than other studies. Therefore, a comprehensive survey and continuous efforts should be carried

217

out to monitor the radioactivity content in Saudi Arabian water. Moreover, Table 3 shows that

218

drinking water has less gross alpha and beta radioactivities than that of groundwater, which

219

means the purification and the water treatment before it becomes ready for drinking reduces a

220

large fraction of the radioactivity from the water.

221

3.1.1. Correlation analyses between TDS and pH with gross radioactivity

222

The effect of the chemical parameters such as TDS and pH on gross radioactivity in the

223

studied groundwater samples were investigated because such information is required for making

224

a correct assumption of radiation dose via the use of water (Al-Kharouf et al., 2008).TDS in

225

groundwater samples were varied between 263 and 2098 mgL-1(Table 1). However, in all

226

investigated wells, except well number 7, TDS values were below the WHO drinking water

227

standard of 1000 mgL-1 (WHO, 2011). Figure 2, shows a weak correlation exists between the

228

gross α and β radioactivity with TDS (rα = 0.073; rβ = -0.265). This indicated other parameters

229

might affect the distribution of the radionuclides in the groundwater such as the irregular

230

distribution of the mineral in the surface of the bedrock due to the differences in the

231

characteristic of the rocks (Bonotto et al., 2009).

10

232

Meanwhile, the pH values in groundwater samples varied within a narrow range between

233

7.11 and 8.20 with a mean value of 7.43, which tends to be alkaline. Figure 3 shows a weak

234

negative correlation between pH and the gross α and β (rα = -0.115; rβ = -0.246) in the studied

235

water samples. This finding of weak correlation is similar to the groundwater study reported by

236

Murad et al. (2014)

237

3.1.2. Correlation analyses of 226,228Ra and gross α and β radioactivities

238

Groundwater contains, to a large extent, higher levels of radium concentration than

239

surface water or wells dug in soil, depending on the geology and the composition of the aquifer

240

rocks. Due to the similar chemical behavior of radium and calcium, it can be quickly

241

accumulated in the bone, and hence the ingestion of water containing radium may lead to

242

possible hazards to human health via the emission of high LET alpha particles that may damage

243

surrounding tissue (USEPA, 1991).

244

Gross alpha and beta are considered a simple and reliable screening method to estimate

245

the level of all alpha and beta emitters in water. However, this method cannot provide

246

information on particular radionuclides in water. Therefore, it is essential to assay the

247

contribution of particular α emitters such as 226Ra, and β emitters such as 228Ra in the gross α and

248

β radioactivities in the studied water sample.

249

According to Pearson correlation analysis,

226

Ra has a weak correlation (r = 0.178) with 226

250

the gross α radioactivity. The mean value of the activity ratio of

251

found to be 0.11. This ratio reflects significant contributions of other nuclides to the level of gross

252

α radioactivity in the studied water ( Table 4). It should be noted here that the sum of the

253

activities of all principle alpha-emitting radionuclides (226Ra,

254

context is still lower than the level of measured gross α radioactivity, which means the sources of

11

234

Ra to gross α radioactivity was

U, and

238

U) measured in this

255

gross α radioactivity in groundwater comes from all decay of U and Th series and their

256

progenies. It is worth mentioning here that the elapsed time between the sample preparation and

257

measurements has a significant influence on the gross alpha counts (Arndt and West, 2004).

258

On the other hand, a moderate correlation exists between

259

correlation factor (r = 0.57), and the mean ratio of

260

relatively higher value of 0.32 (Table 4). However, the gross β radioactivity is still exceeding the

261

activity of 228Ra for all water samples. This result reveals that the measured gross β radioactivity

262

is largely contributed to the presence of 40K besides 228Ra in the studied water.

263

3.2. Radionuclides concentration

228

Ra and gross β radioactivity with a

228

Ra to gross β radioactivity showed a

264

The activities of radium and uranium isotopes in groundwater samples are listed in Table

265

2. A clear enrichment in radium activities is observed in most of the samples compared to

266

uranium activities. The high radium concentration in groundwater might be attributed to its

267

prolonged contact with the radioactive crystalline of the bedrocks of the well. Also, other factors

268

affect the radium concentration such as physiochemical parameters of water, the leaching

269

process of rocks and alpha recoil effect of the daughter product during the decay process

270

(Ivanovich and Harmon, 1992). For radium isotopes, the results showed an overall lower activity concentration for

271 272

226

Ra (range 0.095 ± 0.009 - 0.82 ± 0.05Bq L-1, average 0.31± 0.02 Bq L-1 ) than the 228Ra (range

273

0.21 ± 0.03 - 3.09 ± 0.17 Bq L-1, average 1.09 ± 0.07 Bq L-1). This could be attributed to the fact

274

that the radioisotopes

275

respectively, which reflects the enrichment of 232Th in the bedrock of the Saq sandstone aquifers

276

relative to

277

reported in groundwater samples extracted from sandstone aquifer rocks (Dickson et al., 1987;

238

226

Ra and

228

Ra belong to different natural decay series of

U. A similar observation of a higher

12

228

Ra concentration than

238

226

U and

232

Th,

Ra has been

278

Lively et al., 1992). On the other hand, the groundwater hosted in granitic aquifer rocks shows

279

higher

280

bedrock structure and its interaction with the groundwater are considered essential parameters

281

that influence the existence of the radionuclides in the groundwater. It can be seen from Table 2,

282

that all values of 226Ra activity concentrations are lower than the WHO recommended limit value

283

of 0.1 Bq L-1, while the mean value of

284

than the recommended limit value of 0.1 Bq L-1, for drinking water (WHO, 2011). According to

285

the risk estimation of radionuclides in groundwater, it is evident that 228Ra is the most significant

286

dose contributor in drinking water. This is because it has relatively higher concentrations than

287

other detected radionuclides of uranium-series; also 228Ra ingestion dose conversion coefficients

288

for all age groups is 2-6 times higher than that of 226Ra, and about one order of magnitude higher

289

than that of

290

activity concentration of 228Ra.

291

226

Ra concentrations than 228Ra (Condomines et al., 2010; Moise et al., 2000). Thus, the

234

U and

238

228

Ra activity concentration is about 10 times higher

U (ICRP, 1996). Thus, special attention should be taken for the higher

For uranium isotopes, the results showed that the activity concentrations of 238

234

U in most

292

of the studied groundwater samples were higher than its parent

293

preferential leaching of

294

alpha recoil effect (Banks et al., 1995; Fleischer, 1980). However, the measured

295

activity concentrations are found to be below the WHO recommended limits of 1 Bq L-1 and 10

296

Bq L-1, respectively, for drinking water (WHO, 2011). Moreover, the present results show

297

relatively lower concentrations for 238U and 234U while compared with a similar study conducted

298

by Shabana and Kinsara (2014) in Saudi Arabia. The relatively high uranium concentration

299

found in their study was justified to the granite rocks of the aquifers from which the groundwater

300

samples were extracted.

234

U. This occurs due to the

U from the host rock into adjacent groundwater, which results due to

13

234

U and

238

U

301 302 303

3.3. Isotopic Ratio

304

Studying the isotopic ratios between the radionuclides may provide valuable information about

305

the origin, chemical behavior, and activities associated with any variation of the radionuclides in

306

the environment (Kumar et al., 2016; Yanase et al., 1995). For

307

varied between 0.3 and 10.7, with an average value of 4.7, and 84% of the ratios are higher than

308

unity in groundwater samples (Table 4). This variation is relatively related to the difference of

309

their parents’ 232Th/238U ratios in host aquifer rocks, in addition to other geochemical factors that

310

control the solubility and desorption/adsorption properties of the groundwater (Al-Kharouf et al.,

311

2008; Asikainen, 1981; Fleischer, 1980). The variations of 228Ra/226Ra ratio in groundwater samples

312

have been reported by many authors; Grabowski et al. (2015) have reported that

313

groundwater samples vary from 0.4 to 2.5. Alkhomashi et al. (2016) have obtained the mean value of

314

228

315

0.21 to 0.80 as reported by Sturchio et al. (2001). Moreover, literature has found that the variation of

316

228

317

observed that the activity ratio of

318

1987; Lively et al., 1992), and <1 in granitic aquifer rocks (Condomines et al., 2010; Moise et

319

al., 2000). However, other debates have attributed the enrichment of

320

228

321

al., 1987; Rihs and Condomines, 2002).

322 323

228

Ra/226Ra, the activity ratios

228

Ra/226Ra in Poland

Ra/226Ra to be 4.25 in groundwater from aquifers in Saudi Arabia. In USA, this ratio is ranged from

Ra/226Ra is attributed to the differences of the groundwater aquifer rocks;

it has been

228

Ra/226Ra is > 1 in sandstone aquifer rocks (Dickson et al.,

226

Ra in groundwater

Ra/226Ra <1 to the preferential solubility of uranium with respect to the thorium (Dickson et

The activity ratios of

226

Ra/238U in groundwater samples were found to be alwaysgreater

than unity and ranged from 1.25 to 20.4, with an average value of 6.4. Thus, the data presented

14

238

U and 226Ra even though they belong to the same series.

324

here suggest disequilibrium between

325

Also, the values indicate that

326

could be attributed to the differences in the geochemical properties of radium and uranium in

327

groundwater resulting in different mobility of the radionuclides from the same series. The

328

enrichment of 226Ra in groundwater is also seen in similar studies; Gascoyne (1989) reported the

329

226

330

reported in Konnngara Australian groundwater the ratio of

331

Pen˜a Blanca region of Mexico the groundwater

332

113 (Goldstein et al., 2010). In contrast, other studies reported the enrichment of

333

groundwater, where the 226Ra/238U ratio is less than unity; Kumar et al. (2016) reported that this

334

ratio in southwestern Punjab in India is ranged 0.08 to 0.22. Also, Asikainen (1981) reported that

335

the ratio is 0.05-1 in Finland groundwater. The differences in the

336

attributed to the oxidation state of uranium in groundwater. Uranium exists in groundwater in

337

two states either U( IV) or (VI), under reducing condition, uranium present in U( IV) oxidation

338

state which is immobile and insoluble, thus

339

uranium present in U(VI) state, which enhances the mobility and the dissolving in a solution,

340

thus 226Ra/238U <1 (Durrance, 1986).

341

226

Ra is always enriched compared to

238

U. This disequilibrium

Ra/238U ratios of Canadian groundwater ranged between 0.026-5300, Yanase et al. (1995)

For

234

226

226

226

Ra/238U ranged 0.02-89, also in

Ra/238U activity ratios ranged from 0.006 to 238

U in

226

Ra/238U ratios may be

Ra/238U >1. However, under oxidizing condition

U/238U, the activity ratios of the studied groundwater samples were found to vary

342

from 0.9 to 3.2 with almost all values above unity (Table 4). These values imply that no

343

equilibrium exists between

344

leaching of 234U from the bedrock of the groundwater causes the disequilibrium between the two

345

radionuclides, which may result from the recoil effects during the decay process of

346

process, when

238

234

U and

238

U which is always in favor of

234

U. The preferential

238

U. In this

U undergoes decay via alpha decay, the released daughter Th gain kinetic

15

347

energy via alpha recoil, which enhances its mobility in the crystal lattice or to the surrounding

348

groundwater. This daughter is subsequently decayed to 234mPa and 234U, thus leading to an excess

349

of

350

Osmond et al., 1983); In the literature, the enrichment of

351

groundwater; in Pen˜a Blanca region of Mexico, the activity ratios of 234U/238U varied between

352

0.9 to 1.5 (Goldstein et al., 2010), in Finland Asikainen (1981) reported the

353

ratio varied between 0.76 and 4.67. In the southern United States, Kronfeld and Adams (1974)

354

reported that

355

that the ratio could reach up 27.88 in South American groundwater. To a lesser extent, some

356

literature has reported the

357

Yanase et al., 1995). They attributed the lower activity ratio to the elevation of

358

concentrations in the groundwater. However, the mechanisms that lead this ratio to be less than

359

unity are still under debate and need further investigation. Meanwhile, other studies have

360

reported that secular equilibrium exists between

361

unity (Alkhomashi et al., 2016; Kumar et al., 2016).

234

U in the groundwater relative to

234

238

U (Bonotto and Andrews, 1993; Fleischer, 1982; 234

U

is commonly seen in the

234

U/238U activity

U/238U activity ratios ranged from 0.5 to > 12, whereas Bonotto (1999) reported

234

U/238U to be less than unity in groundwater (Osmond et al., 1983;

238

U and

234

U, where the

234

238

U

U/238U is almost

362 363

4. Conclusions

364

The present study determined the radioactivity concentrations in groundwater samples

365

collected from wells distributed in the northern region of Saudi Arabia. The obtained results

366

showed that both gross α and β activity in all groundwater samples are higher than the

367

recommended limits proposed by WHO for drinking water (WHO, 2011). Further analysis was done for these groundwater samples. The activities of 226,228Ra and

368 369

234,238

U isotopes in groundwater samples and their contribution to gross α and β radioactivities

16

228

370

were investigated. The results showed that

Ra activity concentration is higher than that of

371

226

372

finding is attributed to the abundance of

373

ratio of radium to uranium concentrations indicates the U-series disequilibrium in all

374

groundwater samples.

Ra and about 10 times higher than the recommended limit by WHO for drinking water. This 232

Th over

238

U in the bedrock structure. The isotopic

375

Although these groundwater wells are not directly used for human being drinking, and

376

mainly used for irrigation and animal drinking, the relatively higher concentrations may cause

377

health risks to human, since these radionuclides may enter the food chain through irrigation

378

water. Thus, continuous monitoring of radioactivity in flora and fauna that use the studied well

379

waters is highly recommended.

380 381

Acknowledgment

382

The authors would like to express their sincere appreciation to the technical staff of the Nuclear

383

Science Research Institute (NSRI)) at the King Abdulaziz City for Science and Technology

384

(KACST) in Riyadh, Kingdom of Saudi Arabia for their help to complete this study.

385 386

References

387

Agbalagba, E.O., Avwiri, G.O., Chadumoren, Y.E., 2013. Gross α and β activity concentration

388

and estimation of adults and infants dose intake in surface and ground water of ten oil fields

389

environment in Western Niger Delta of Nigeria. Journal of Applied Sciences and Environmental

390

Management 17, 267-277.

17

391

Ahmed, I., Nazzal, Y., Zaidi, F., 2017. Groundwater pollution risk mapping using modified

392

DRASTIC model in parts of Hail region of Saudi Arabia. Environmental Engineering Research

393

23, 84-91.

394

Al-Amir, S.M., Al-Hamarneh, I.F., Al-Abed, T., Awadallah, M., 2012. Natural radioactivity in

395

tap water and associated age-dependent dose and lifetime risk assessment in Amman, Jordan.

396

Applied radiation and isotopes 70, 692-698.

397

Al-Kharouf, S.J., Al-Hamarneh, I.F., Dababneh, M., 2008. Natural radioactivity, dose

398

assessment and uranium uptake by agricultural crops at Khan Al-Zabeeb, Jordan. Journal of

399

environmental radioactivity 99, 1192-1199.

400

Alkhomashi, N., Al-Hamarneh, I.F., Almasoud, F.I., 2016. Determination of natural radioactivity

401

in irrigation water of drilled wells in northwestern Saudi Arabia. Chemosphere 144, 1928-1936.

402

Almazroui, M., 2011. Calibration of TRMM rainfall climatology over Saudi Arabia during

403

1998–2009. Atmospheric Research 99, 400-414.

404

Arndt, M.F., West, L., 2004. A study of the factors affecting the gross alpha measurement, and a

405

radiochemical analysis of some groundwater samples from the state of Wisconsin exhibiting an

406

elevated gross alpha activity. Wisconsin State Laboratory of Hygiene http://dnr. wi.

407

gov/org/water/dwg/gw/research/reports/176. pdf.

408

Asikainen, M., 1981. State of disequilibrium between 238U, 234U, 226Ra and 222Rn in

409

groundwater from bedrock. Geochimica et Cosmochimica Acta 45, 201-206.

410

Banks, D., Røyset, O., Strand, T., Skarphagen, H., 1995. Radioelement (U, Th, Rn)

411

concentrations in Norwegian bedrock groundwaters. Environmental Geology 25, 165-180.

18

412

Beyermann, M., Bünger, T., Schmidt, K., Obrikat, D., 2010. Occurrence of natural radioactivity

413

in public water supplies in Germany: 238U, 234U, 235U, 228Ra, 226Ra, 222Rn, 210Pb, 210Po

414

and gross α activity concentrations. Radiation protection dosimetry 141, 72-81.

415

Bonotto, D., 1999. Applicability of the Uranium-Isotopic Model as a Prospecting Technique in

416

Guarany Aquifer, South America, In: Ninth Annual VM Goldschmidt Conference, Abstract no

417

7021, LPI Contribution no 971, Lunar and Planetary Institue, Houston.

418

Bonotto, D.M., Andrews, J., 1993. The mechanism of 234U238U activity ratio enhancement in

419

karstic limestone groundwater. Chemical geology 103, 193-206.

420

Bonotto, D.M., Bueno, T., 2008. The natural radioactivity in Guarani aquifer groundwater,

421

Brazil. Applied radiation and isotopes 66, 1507-1522.

422

Bonotto, D.M., Bueno, T., Tessari, B., Silva, A., 2009. The natural radioactivity in water by

423

gross alpha and beta measurements. Radiation Measurements 44, 92-101.

424

Burdon, D., 1982. Hydrogeological conditions in the Middle East. Quarterly Journal of

425

Engineering Geology and Hydrogeology 15, 71-82.

426

Chalupnik, S., Lebecka, J., 1990. Determination of radium isotopes in water samples by means

427

of a low background liquid scintillation spectrometer Quantulus, Proceedings of the Fourth

428

Europhysics Conference on Nuclear Physics, Bratislava, Czech Republic, World Scientific,

429

Singapore, pp. 327-336.

430

Condomines, M., Rihs, S., Lloret, E., Seidel, J., 2010. Determination of the four natural Ra

431

isotopes in thermal waters by gamma-ray spectrometry. Applied Radiation and Isotopes 68, 384-

432

391.

19

433

Darko, G., Faanu, A., Akoto, O., Atta-Agyeman, F., Aikins, M.A., Agyemang, B., Ibrahim, A.,

434

2015. Assessment of the activity of radionuclides and radiological impacts of consuming

435

underground water in Kumasi, Ghana. Environmental earth sciences 73, 399-404.

436

Dickson, B., Giblin, A., Snelling, A., 1987. The source of radium in anomalous accumulations

437

near sandstone escarpments, Australia. Applied Geochemistry 2, 385-398.

438

Durrance, E.M., 1986. Radioactivity in geology: principles and applications.

439

EU, 1998. EUROPEAN UNION, Council Directive 98/83/EC of 3 November 1998 on the

440

quality of water intended for human consumption, Official Journal L330 (05/12/98).

441

Fasae, K., Ibikunle, K., Akinkuade, S., 2015. Gross alpha and beta activity concentrations in

442

portable drinking water in Ado-Ekiti metropolis and the committed effective dose. International

443

Journal of Advanced Research in Physical Science (IJARPS) 2, 1-6.

444

Ferdous, M., Rahman, M., Begum, A., 2012. Gross alpha and gross beta activities of tap water

445

samples from different locations of Dhaka City. Sri Lankan Journal of Physics 13(12),01-08.

446

Fleischer, R.L., 1980. Isotopic disequilibrium of uranium: alpha-recoil damage and preferential

447

solution effects. Science 207, 979-981.

448

Fleischer, R.L., 1982. Alpha-recoil damage and solution effects in minerals: uranium isotopic

449

disequilibrium and radon release. Geochimica et Cosmochimica Acta 46, 2191-2201.

450

Forte, M., Bagnato, L., Caldognetto, E., Risica, S., Trotti, F., Rusconi, R., 2010. Radium isotopes

451

in Estonian groundwater: measurements, analytical correlations, population dose and a proposal

452

for a monitoring strategy. Journal of Radiological Protection 30, 761.

453

Gascoyne, M., 1989. High levels of uranium and radium in groundwaters at Canada's

454

Underground Research Laboratory, Lac du Bonnet, Manitoba, Canada. Applied Geochemistry 4,

455

577-591.

20

456

Goldstein, S.J., Abdel-Fattah, A.I., Murrell, M.T., Dobson, P.F., Norman, D.E., Amato, R.S.,

457

Nunn, A.J., 2010. Uranium-series constraints on radionuclide transport and groundwater flow at

458

the Nopal I uranium deposit, Sierra Pena Blanca, Mexico. Environmental science & technology

459

44, 1579-1586.

460

Grabowski, P., Bem, H., Romer, R., 2015. Use of radiometric (234/238 U and 228/226 Ra) and

461

mass spectrometry (87/86 Sr) methods for studies of the stability of groundwater reservoirs in

462

Central Poland. Journal of radioanalytical and nuclear chemistry 303, 663-669.

463

Hussein, M., Bazuhair, A., Ageeb, A., 1992. Hydrogeology of the Saq formation east of Hail,

464

northern Saudi Arabia. Quarterly Journal of Engineering Geology and Hydrogeology 25, 57-64.

465

ICRP, 1996. Age-dependent Doses to Members of the Public from intake of Radionuclides: Part

466

5 Compilation of Ingestion and Inhalation Dose Coefficients (ICRP Publication 72). IOP

467

Publishing.

468

Ivanovich, M., Harmon, R.S., 1992. Uranium-series disequilibrium: applications to earth,

469

marine, and environmental sciences. 2.

470

Jia, G., Torri, G., Magro, L., 2009. Concentrations of 238U, 234U, 235U, 232Th, 230Th, 228Th,

471

226Ra, 228Ra, 224Ra, 210Po, 210Pb and 212Pb in drinking water in Italy: reconciling safety

472

standards based on measurements of gross α and β. Journal of environmental radioactivity 100,

473

941-949.

474

Jiang, F., Lee, S., Bakhtiar, S., Kuroda, R., 1986. Determination of thorium, uranium and

475

plutonium isotopes in atmospheric samples. Journal of radioanalytical and nuclear chemistry

476

100, 65-72.

21

477

Jowzaee, S., 2013. Determination of selected natural radionuclide concentrations in southwestern

478

Caspian groundwater using liquid scintillation counting. Radiation protection dosimetry 157,

479

234-241.

480

Kleinschmidt, R.I., 2004. Gross alpha and beta activity analysis in water—a routine laboratory

481

method using liquid scintillation analysis. Applied Radiation and Isotopes 61, 333-338.

482

Korkmaz, M.E., Agar, O., Şahin, M., 2016. Gross α and β activity concentrations in various

483

water from Karaman, Turkey. Environmental Earth Sciences 75, 14.

484

Kronfeld, J., Adams, J.A., 1974. Hydrologic investigations of the groundwaters of central Texas

485

using U-234U-238 disequilibrium. Journal of Hydrology 22, 77-88.

486

Kumar, A., Karpe, R., Rout, S., Gautam, Y., Mishra, M., Ravi, P., Tripathi, R., 2016. Activity

487

ratios of 234U/238U and 226Ra/228Ra for transport mechanisms of elevated uranium in alluvial

488

aquifers of groundwater in south-western (SW) Punjab, India. Journal of environmental

489

radioactivity 151, 311-320.

490

Labidi, S., Mahjoubi, H., Essafi, F., Salah, R.B., 2010. Natural radioactivity levels in mineral,

491

therapeutic and spring waters in Tunisia. Radiation Physics and Chemistry 79, 1196-1202.

492

Lally, A., 1982. Chemical procedures, Uranium series disequilibrium: applications to

493

environmental problems, pp. 79-106. Oxford Univ. Press. London/New York.

494

Lively, R.S., Jameson, R., Alexander Jr, E.C., Morey, G., 1992. Radium in the Mt. Simon-

495

Hinckley Aquifer, East-Central and Southeastern Minnesota, Minnesota Information Circular 36.

496

MAW, 1984. Ministry of Agriculture and Water. Water Atlas of Saudi Arabia cooperation with

497

the Saudi Arabian-United sates joint commission on economic cooperation, Page-119. .

22

498

Medley, P., Bollhöfer, A., Iles, M., Ryan, B., Martin, P., 2005. Barium sulphate method for

499

radium-226 analysis by alpha spectrometry. Environmental Research Institute of the Supervising

500

Scinetist, internal report 501.

501

Moise, T., Starinsky, A., Katz, A., Kolodny, Y., 2000. Ra isotopes and Rn in brines and ground

502

waters of the Jordan-Dead Sea Rift Valley: enrichment, retardation, and mixing. Geochimica et

503

Cosmochimica Acta 64, 2371-2388.

504

Murad, A., Zhou, X., Yi, P., Alshamsi, D., Aldahan, A., Hou, X., Yu, Z., 2014. Natural

505

radioactivity in groundwater from the south-eastern Arabian Peninsula and environmental

506

implications. Environmental monitoring and assessment 186, 6157-6167.

507

Osmond, J., Cowart, J., Ivanovich, M., 1983. Uranium isotopic disequilibrium in ground water as

508

an indicator of anomalies. The International Journal of Applied Radiation and Isotopes 34, 283-

509

308.

510

Rihs, S., Condomines, M., 2002. An improved method for Ra isotope (226Ra, 228Ra, 224Ra)

511

measurements by gamma spectrometry in natural waters: application to CO2-rich thermal waters

512

from the French Massif Central. Chemical Geology 182, 409-421.

513

Salonen, L., 1994. 238U series radionuclides as a source of increased radioactivity in

514

groundwater originating from Finnish bedrock. IAHS Publications-Series of Proceedings and

515

Reports-Intern Assoc Hydrological Sciences 222, 71-84.

516

Sanchez-Cabeza, J., PUJOL, J.M., LUIS LEON, J.M., VIDAL-QUADRAS, A., MITCHELL, P.,

517

1993. Optimization and calibration of a low-background liquid scintillation counter for the

518

simultaneous determination of alpha and beta emitters in aqueous samples. In: Noakes, J.E.,

519

Schonhofer, F., Polach, H.A. (Eds.), Liquid Scintillation Spectrometry 1992. Radiocarbon, 43 -

520

50.

23

521

Semkow, T.M., Parekh, P.P., 2001. Principles of gross alpha and beta radioactivity detection in

522

water. Health physics 81, 567-574.

523

Shabana, E., Kinsara, A., 2014. Radioactivity in the groundwater of a high background radiation

524

area. Journal of environmental radioactivity 137, 181-189.

525

Sturchio, N., Banner, J., Binz, C., Heraty, L., Musgrove, M., 2001. Radium geochemistry of

526

ground waters in Paleozoic carbonate aquifers, midcontinent, USA. Applied Geochemistry 16,

527

109-122.

528

Todorović, N., Nikolov, J., Tenjović, B., Bikit, I., Veskovic, M., 2012. Establishment of a

529

method for measurement of gross alpha/beta activities in water from Vojvodina region.

530

Radiation Measurements 47, 1053-1059.

531

Turhan, Ş., Özçıtak, E., Taşkın, H., Varinlioğlu, A., 2013. Determination of natural radioactivity

532

by gross alpha and beta measurements in ground water samples. Water research 47, 3103-3108.

533

UNSCEAR, 2000. Sources and effects of ionizing radiation: sources. United Nations

534

Publications.

535

USEPA, 1991. Guidelines for Developmental Toxicity Risk Assessment. United Nations,

536

Washington.

537

Vesterbacka, P., 2005. 238U-series radionuclides in Finnish groundwater-based drinking water

538

and effective doses. STUK-A213, Helsinki.

539

WHO, 2011. Guidelines for Drinking-water Quality. Chapter 9 Radiological Aspects, fourth ed.

540

WHO, Geneva.

541

Yanase, N., Payne, T.E., Sekine, K., 1995. Groundwater geochemistry in the Koongarra ore

542

deposit, Australia (II): activity ratios and migration mechanisms of uranium series radionuclides.

543

Geochemical Journal 29, 31-54.

24

544

545

List of Figures

546

Figure 1: Sampling locations of drilled wells in Saudi Arabia

547

Figure 2: Correlation between TDS of waters and gross α and β radioactivities

548

Figure 3: Correlation between pH of waters and gross α and β radioactivities

549

550

List of Tables

551

Table 1: Information on specific sampling locations together with the physical parameters of the

552

studied water

553

554

Table 2: The determined activity concentrations of gross α/β, Uranium and Radium radionuclides

555

contents in the investigated water samples

556 557

Table 3: Comparison of gross α/β radioactivities in the studied water sample with similar data

558

available in the literature.

559

560

Table 4: The contribution of radium (Ra) and uranium (U) radionuclides to the gross α/β

561

radioactivities, an abundance of thorium (Th) compared to uranium and uranium series

562

disequilibrium information

25

Table 1: Information on specific sampling locations together with the physical parameters of the studied water Well no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

pH 7.18 7.38 7.33 7.42 7.19 7.37 7.20 7.58 7.11 7.71 7.28 8.20 7.66 7.38 7.31 7.70 7.42 7.38

TDS (mg L-1) 637 958 888 347 452 428 2098 276 263 862 863 420 902 647 466 440 500 760

Latitude (Decimal. Degrees) 27.87750 27.88132 27.86366 27.67418 27.69151 27.98424 27.84305 27.41418 27.30178 27.85994 27.87255 27.83683 27.84982 27.87366 27.86213 27.95367 27.69688 27.82146

Longitude (Decimal. Degrees) 41.96588 41.92442 41.92731 42.17273 42.16905 41.64799 41.73964 41.54700 41.22178 41.92137 41.91261 41.57846 41.60556 42.10783 41.76735 42.05000 42.16602 41.62333

Table 2: The determined activity concentrations of gross α/β, Uranium and Radium radionuclides contents in the investigated water samples

Well No.

Activity concentration (Bq L-1)

1

Gross α ±1σ 2.87±0.28

Gross β ±1σ 2.47±0.29

Ra-228 ±1σ 0.90±0.06

Ra-226 ±1σ 0.120±0.011

U-238 ±1σ 0.077±0.009

U-234 ±1σ 0.174±0.015

Ra+U contents 0.37 0.44

2

2.29±0.25

2.19±0.28

1.28±0.08

0.211±0.015

0.054±0.007

0.175±0.015

3 4

5.75±0.49 3.27±0.32

5.39±0.49 2.59±0.32

1.74±0.10 0.43±0.04

0.373±0.024 0.230±0.017

0.061±0.008 0.037±0.006

0.063±0.008 0.040±0.006

5

5.27±0.44

3.25±0.34

0.65±0.04

0.194±0.014

0.044±0.006

0.077±0.009

6 7

6.39±0.52 2.92±0.28

4.40±0.42 1.57±0.26

0.70±0.05 0.28±0.03

0.095±0.009 0.662±0.038

0.076±0.009 0.079±0.009

0.111±0.011 0.097±0.010

8

3.17±0.30

6.63±0.57

1.15±0.06

0.130±0.004

0.101±0.012

0.117±0.013

0.35

9

2.48±0.26

6.28±0.54

1.32±0.07

0.170±0.004

0.041±0.006

0.048±0.007

0.26

10

3.89±0.36

4.88±0.44

3.09±0.17

0.615±0.038

0.077±0.009

0.128±0.013

11 12

3.65±0.33 3.03±0.28

4.81±0.44 1.31±0.24

2.26±0.13 0.23±0.03

0.404±0.026 0.531±0.033

0.061±0.008 0.074±0.008

0.141±0.013 0.079±0.009

0.82 0.61

13

3.58±0.32

1.26±0.23

0.21±0.03

0.816±0.047

0.080±0.010

0.090±0.011

14 15

2.29±0.25 1.32±0.19

3.89±0.38 1.54±0.24

1.99±0.12 0.91±0.06

0.186±0.014 0.149±0.013

0.015±0.004 0.044±0.007

0.021±0.005 0.062±0.009

16

1.11±0.18

2.68±0.30

1.21±0.07

0.286±0.021

0.014±0.004

0.022±0.005

17 18

0.96±0.17 8.97±0.71

2.06±0.27 5.49±0.49

0.36±0.03 0.88±0.06

0.187±0.015 0.455±0.028

0.029±0.005 0.112±0.011

0.025±0.005 0.193±0.016

Average

3.51±0.33

3.48±0.36

1.09±0.07

0.308±0.021

0.060±0.008

0.092±0.010

0.50 0.31 0.32 0.28 0.84

0.68 0.99 0.22 0.26 0.32 0.24 0.76 0.48

Table 3: Comparison of gross α/β radioactivities in the studied water sample with the similar data available in the literature.

Origin

Type

Nigeria Australia Germany Italy Serbia (Vojvodina) Finland Turkey (Nevsehir) Brazil (Sao Paulo) Nigeria Ghana Southwestern Caspian United Arab Emirates (UAE) Aqaba, Jordan Saudi Arabia, Hail Saudi Arabia, North-western Saudi Arabia, Northern region World average

Drinking water Drinking water Drinking water Drinking water Drinking water Drilled well water Groundwater Groundwater Groundwater Groundwater Groundwater Groundwater Ground water Groundwater Groundwater Drilled well water Drinking water

Gross alpha (Bq L-1) 0.0058 – 0.174 1.40 0.013 – 0.97 0.01- 0.25 0.029 – 0.21 2.4 0.192 0.001-0.4 0.15 ± 0.003 0.0157 – 0.198 0.016 - 1 1.4 ± 4.1 0.64 2.15 3.15 ± 0.26 3.51± 0.33 0.5

Gross beta (Bq L-1) 0.0147 – 0.2225 1.15

MDC – 0.4 1.5 0.579 0.12-0.86 6.0 ± 0.1 0.122 – 0.28 0.022 – 0.63 1.5 ± 1.52 0.71 2.60 5.39 ± 0.44 3.48± 0.36 1.0

References Fasae et al., 2015 Kleinschmidt (2004) (Beyermann et al., 2010) (Jia et al., 2009) (Todorović et al., 2012) Salonen (1994) Turhan et al. (2013) Bonotto et al. (2009) Agbalagba et al. (2013) (Darko et al., 2015) (Jowzaee, 2013) Murad et al. (2014) Al-Amir et al., 2012 Shabana and Kinsara (2014) Alkhomashi et al. (2016) Present work WHO, 2011

Table 4: The contribution of radium (Ra) and uranium (U) radionuclides to the gross α/β radioactivities, an abundance of thorium (Th) compared to uranium and uranium series disequilibrium information.

Well no.

Contribution of 226Raα emitter to Gross α

Contribution of Ra+Uα emitters to Gross α

Contribution of 228Raβ emitter to Gross β

Abundance of Th compared to U

U series disequilibrium

226

(Ra+U) / gross α

228

228

226

0.13 0.19 0.09 0.09 0.06 0.04 0.29 0.11 0.10 0.21 0.17 0.23 0.28 0.10 0.19 0.29 0.25 0.08 0.16

0.37 0.59 0.32 0.16 0.20 0.16 0.18 0.17 0.21 0.63 0.47 0.18 0.17 0.51 0.59 0.45 0.17 0.16

7.53 6.10 4.67 1.85 3.36 7.37 0.42 8.8 7.8 5.02 5.59 0.44 0.25 10.67 6.06 4.23 1.90 1.93

1.56 3.91 6.11 6.22 4.41 1.25 8.38 1.29 4.15 8.00 6.62 7.18 10.20 12.40 3.39 20.43 6.45 4.06

2.26 3.21 1.04 1.09 1.76 1.46 1.23 1.15 1.17 1.66 2.30 1.06 1.12 1.42 1.40 1.51 0.86 1.71

0.32

4.67

6.44

1.53

Ra/ gross α

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

0.04 0.09 0.06 0.07 0.04 0.01 0.23 0.04 0.07 0.16 0.11 0.18 0.23 0.08 0.11 0.26 0.19 0.05

Average

0.11

Ra/gross β

Ra/ 226Ra

Ra/238U

234

U/ 238U

Highlights

•

Gross α and β radioactivity in groundwater samples has been investigated in northern part in KSA.

•

The contributions of U and Ra alpha emitters to gross α radioactivity were discussed.

•

The ratios of the measured β emitters to gross β radioactivity were discussed.

•

The ratios of 228Ra/226Ra, 226Ra/238U, and 234U/238U in groundwater were investigated.

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: