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GammaEmittingRadionuclidesinSoilsfromSelectedAreasinDouala-BassaZoneLittoralRegionofCameroon

ARTICLEmiddotJANUARY2014

DOI1011552014245125

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5AUTHORSINCLUDING

MauriceMoyoNdontchueng

UniversityofDouala

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EricNguelem

UniversityofGhana


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RLNjinga

IbrahimBadamasiBabangidaUniversity


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GuembouShouopCeacutebastienJoeumll

UniversityofDouala

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Research ArticleGamma Emitting Radionuclides in Soils from Selected Areas inDouala-Bassa Zone Littoral Region of Cameroon

Maurice Moyo Ndontchueng12 Eric Jilbert Mekongtso Nguelem12 Augustin Simo1

Raymond Limen Njinga34 and Gembou Shouop Ceacutebastien Joeumll2

1 National Radiation Protection Agency PO Box 33732 Yaounde Cameroon2Department of Physics Faculty of Science University of Douala PO Box 24157 Douala Cameroon3Department of Physics Ibrahim Badamasi Babangida University Lapai Niger State Nigeria4 Radioanalysis and Spectrometry Service National Radiation and Protection Agency Yaounde Cameroon

Correspondence should be addressed to Maurice Moyo Ndontchueng ndomomauyahoofr

Received 12 November 2013 Accepted 10 December 2013 Published 22 January 2014

Academic Editors B Liu and T Stafilov

Copyright copy 2014 Maurice Moyo Ndontchueng et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

A study of natural radioactivity levels in some composites of eighteen soil samples selected within Douala-Bassa zone of LittoralRegion has been evaluatedThe samples were analysed using gamma spectrometry based broad energy germanium detector (BEGe6350) The activity profile of radionuclide shows low activity across the studied areas The obtained mean values of 226Ra 232Thand 40K in the two campuses were 2548 Bqkg 6596 Bqkg and 3914 Bqkg for Campus 1 and 2450 Bqkg 6671 Bqkg and2819 Bqkg for Campus 2 respectively In terms of health analysis some radiation health hazard parameters were calculated withinthe two campuses The mean values of radium equivalent activity were 12281 Bqkg and 12208 Bqkg absorbed dose rate in airwas 9913 nGyh and 9818 nGyy annual outdoor effective dose was 012mSvy and 012mSvy and external health hazard indexwas 034 and 033 in Campus 1 and Campus 2 respectively These health hazard parameters were seen to be below the safe limit ofUNSCEAR 2000 except the absorbed dose rate in air and the annual outdoor effective doses which are relatively high comparedto the values of 60 nGyh and 007mSvy These results reveal no significant radiological health hazards for inhabitance within thestudy areas

1 Introduction

Gamma radiation emitted from naturally occurring radioiso-topes also called terrestrial background radiation representsthemain source of radiation of the humanbodyNatural envi-ronmental radioactivity and the associated external exposuredue to gamma radiation depend primarily on the geologicaland geographical conditions and appear at different levels inthe soils of each region in the world [1 2] Only radionuclideswith half-lives comparable with the age of the earth ortheir corresponding decay products existing in terrestrialmaterials such as 232Th 238U and 40K are of great interestAbnormal occurrences of uranium and its decay productsin rocks and soils and thorium in monazite sands are themain sources of high natural background areas that have

been identified in several areas of the world [3] Outdoorsexposure to this radiation originates predominantly from theupper 30 cm of the soil [1] According to the literature ofnatural radioactivity in soil there is lack of information onnatural radioactivity levels in soils from various living sitesin Cameroon Radionuclides in soil generate a significantcomponent of the background radiation exposure to thepopulation [3]

The knowledge of specific activities or concentrations anddistributions of the radionuclides in soil is of great interestfor many researchers throughout the world and serves asthe reference in documenting changes to environmentalradioactivity due anthropogenic activities or any releaseof radioactive elements [4 5] Monitoring of radioactivematerials is therefore of primary importance to humans

Hindawi Publishing CorporationISRN SpectroscopyVolume 2014 Article ID 245125 8 pageshttpdxdoiorg1011552014245125

2 ISRN Spectroscopy

organisms and environmental protectionThe accumulationof such radioactivity may substantially contribute to collec-tive radiation dose received by the local population livingwithin this particular environment Radiation exposure candamage living cells causing death in some of them andmodifying others

There have been many surveys to determine the back-ground levels of radionuclides in soils which can in turnbe related to the absorbed dose rates in air All of thesespectrometric measurements indicate that the three com-ponents of external radiation field namely from the 120574-emitting radionuclides in the 238U and 232Th series and 40Kmade approximately equal contributions to the externallyincident 120574-radiation dose to individuals in typical situationsboth outdoors and indoors Since 985 of the radiologicaleffects of the uranium series are produced by radium and itsdaughter products the contribution from the 238U and othercontributions of 226Ra precursors are normally ignored

The aim of the present study tends to assess the specificactivity and examine radiation hazard indices of the natu-rally occurring radionuclides (226Ra 232Th and 40K) in soilsamples from the two campuses of the University of Douala-Cameroon using broad energy gamma-ray spectrometrybased high purity germanium detector

11 Overview of the Study Area The field experimentwas carried out at the two campuses of the Univer-sity of Douala-Cameroon (04∘03101584014810158401015840ndash04∘03101584029710158401015840N and09∘44101584000110158401015840ndash09∘44101584045210158401015840W) The studied sites are locatedwithin the Douala-Bassa zone where the geology of theregion is compromised by the sedimentary rocks namelyby the tertiary to quaternary sediments as seen in Figure 1These sedimentary rocks found in the Douala-Bassa zone(within the Douala basin) consist of poorly consolidated gritsand sandstones that occasionally display bedding with a fewintercalations of limestone and shale Soils in Douala-Bassazone vary from yellow through brown to back freely drainedsandy ferralitic [6]

12 Samples Collection and Preparation Techniques Com-posites of eighteen soil samples were randomly chosen fromthe two campuses of University of Douala (seven fromsmall area coverage of Campus 1 ESSEC situated at Angel-Raphael and eleven from large area coverage of Campus 2located at Ndong-Bong Douala-Bassa) The vertical or nearvertical surfacewas dressed (scraped) to remove smeared soilThis was necessary to minimize the effects of contaminantmigration interferences due to smearing of material fromother levels Each composite sample was a mixture of fivesamples collected within an area of 5m2 separated from eachother by a distance of 300m to cover the study site andto observe a significant local spatial variation in terrestrialradioactivity Each sampling point was marked using a globalpositioning system (GPS) Four samples were collected atthe edges (end corners) and one at the centre These fivesamples collected at a depth of approximately 20 cm fromthe top surface layer were mixed thoroughly to form acomposite sample and packed into a polyethylene bag to

Bassa zone

Tertiary to quaternary sedimentsA riverPonds

0 200 400 600 800

Figure 1 Map indicating the study area

prevent contaminationThe samples were transferred into thelaboratory after they were labelled accordingly

At the laboratory the samples were air-dried for a weekthen oven-dried at 105∘C for 24 hours The dried sampleswere grinded into powder and sieved through a 2mm wiremesh to obtain a uniform particles size In order to maintainradioactive equilibrium between 226Ra and its daughtersthe soil samples were then packed in a 360mL air tightpolyethylene cylindrical container dry-weighed and storedfor a period of 32 days for equilibrium between the long-livedparent and daughter nuclides

2 Experimental

Each sample was subjected to a coaxial gamma-ray spec-trometer consisting of broad energy germanium detector(BE6530) manufactured by Canberra Industries The resolu-tion of this detector is 05 keV at 59 keV for 55Fe 075 keVat 122 keV for 57Co and 22 keV at 1332 keV for 60Co Thedetector is placed in a low-level Canberra Model 747 leadshield with thickness of 10 cm

The energy distributions of the radioactive samples weregenerated by the computer inbuilt Multiport II MultichannelAnalyzer (MCA) Each sample was counted for 86400 sec-onds for effective peak area statistics of above 01

Following the sample analysis process the specific activityconcentration in Becquerel per kilogram (Bqsdotkgminus1) for eachradionuclide was calculated after background separationusing the Genie-2000 software incorporated with cascadesumming correction coefficient

Assuming a state of secular equilibrium between 238Uand 232Th and their respective decay daughter productsthe following relatively intense gamma-ray transitions wereused to measure the activity concentrations for the above-mentioned radionuclides

(a) 226Ra concentration was calculated as a weightedmean of the activity concentrations of the gamma-rays of 214Pb (2951 keV 3519 keV) 214Bi (6093 keVand 112029 keV) and its specific gamma-ray at

ISRN Spectroscopy 3

1862 keV Interference correction due to the presenceof 1857 keV energy peak of 235U has been taken intoaccount and subtracted accordingly

(b) The gamma-ray photopeaks used for the determina-tion of the 232Th contents were 3384 keV 9112 keVand 96911 keV of 228Ac and 2386 keV of 212Pb

(c) 40K was directly determined by using 14608 (107)gamma-ray

21 Health Hazard Parameters

211 Absorbed Dose Rate in Air (119863) A direct connectionbetween radioactivity concentrations of natural radionu-clides and their exposure is known as the absorbed dose ratein the air at 1 metre above the ground surface The meanactivity concentrations of 226Ra (of the 238U series) 232Thand 40K (Bqsdotkgminus1) in the soil samples were used to calculatethe absorbed dose rate using the following formula providedby UNSCEAR [7] and European Commission [8]

119863(nGysdothminus1) = 092119860Ra + 11119860Th + 008119860K (1)

where 119863 is the absorbed dose rate in nGysdothminus1 and 119860Ra 119860Thand 119860K are the activity concentrations of 226Ra (238U) 232Thand 40K respectivelyThedose coefficients in units of nGysdothminus1per Bqsdotkgminus1 were taken from the UNSCEAR (2000) report[7ndash9]

212 Annual Effective Dose Equivalent The absorbed doserate in air at 1 metre above the ground surface does notdirectly provide the radiological risk to which an individualis exposed [10] The absorbed dose can be considered interms of the annual effective dose equivalent from outdoorterrestrial gamma radiation which is converted from theabsorbed dose by taking into account two factors namely theconversion coefficient from absorbed dose in air to effectivedose and the outdoor occupancy factor The annual effectivedose equivalent can be estimated using the following formula[7 11]AEDE (120583Svsdoty minus 1)

= 119863 (nGysdothminus1) times 8760 h times 02 times 07 SvsdotGyminus1 times 10minus3(2)

The values of those parameters used in the UNSCEARreport (2000) are 070 SvsdotGyminus1 for the conversion coefficientfrom absorbed dose in air to effective dose received by adultsand 020 for the outdoor occupancy factor [7]

213 Radium Equivalent Activity As a result of nonuniformdistribution of natural radionuclides in the soil samples theactual activity levels of 226Ra 232Th and 40K in the samplescan be evaluated by means of a common radiological indexcalled radium equivalent activity (Raeq) [10 12] It is the mostwidely used index to assess the radiation hazards and can becalculated as given by Beretka and Mathew [10 12]

Raeq (Bqsdotkgminus1) = 119860Ra + 143119860Th + 0077119860K (3)

where 119860Ra 119860Th and 119860K are the activity concentrations of226Ra 232Th and 40K in Bqsdotkgminus1 respectively

Themaximumpermissible value of the radium equivalentactivity is 37000 Bqsdotkgminus1 [7 10]This value corresponds to aneffective dose of 1mSv for the general public and radiationdose rate of 150mGysdotyminus1 [7 13]

214 External and Internal Hazard Indices Many radionu-clides occur naturally in terrestrial soils and rocks and upondecay these radionuclides produce an external radiation fieldto which all human beings are exposed In terms of dosethe principal primordial radionuclides are 232Th 238U and40K The decay of naturally occurring radionuclides in soilproduces a gamma-beta radiation field in soil that crosses thesoil-air interface to produce exposures to humans The mainfactors which determine the exposure rate to a particularindividual are the concentrations of radionuclides in the soiland the time spent outdoors To limit the radiation exposureattributable to natural radionuclides in the samples to thepermissible dose equivalent limit of 100mSvsdotyminus1 the externalhazard index based on a criterion has been introduced usinga model proposed by Krieger (1981) which is given by [7 14]

119867ex =119860Ra370+119860Th259+119860K4810le 1 (4)

In order to keep the radiation hazard insignificant thevalue of external hazard index must not exceed the limitof unity The maximum value of 119867ex equal to unity corre-sponds to the upper limit of radium equivalent activity of37000 Bqsdotkgminus1 [15 16]

In addition to the external hazard radon and its short-lived products are also hazardous to the repository organsTo account for this threat the maximum permissible con-centration for 226Ra must be reduced to half of the normallimit (18500 Bqsdotkgminus1) The internal exposure to carcinogenicradon and its short-lived progeny is quantified by the internalhazard index (119867in) given by the expression [17]

3 Results and Discussion

The activity concentrations of 226Ra 232Th and 40K in soilsamples from the University of Douala-Cameroon have beenmeasured and presented inTable 1 with the geological coordi-nates of each sampling pointThe radiological health hazardsindices in the investigated soil samples have been calculatedand displaced in Table 2The comparison of specify activitiesof 226Ra 232Th 40K in soil samples from the University ofDouala-Cameroonwith data fromother countries is reportedin Table 3

For Campus 1 in Tables 1 and 3 the activity concentra-tions of 226Ra varied from 2199 plusmn 068 to 2917 plusmn 087Bqkgwith an average of 2548 BqkgThe activity concentrations of232Thand 40K ranged from 5914 plusmn 141 to 6588 plusmn 155Bqkgwith an average value of 6596 Bqkg and from 1393plusmn288 to7089 plusmn 370Bqkg with a mean of 3915 Bqkg respectively

For Campus 2 in Tables 1 and 3 the activity concentra-tions of 226Ra 232Th and 40K ranged from 2199 plusmn 068 to

4 ISRN Spectroscopy

Table 1 Specify activities of 226Ra 232Th and 40K in soil samples from Campuses 1 and 2 of the University of Douala

Sampling sites Sample ID Latitude Longitude Specific activity (Bqkg)226Ra 232Th 40K

Campus 1

UD01 04∘03101584020810158401015840N 09∘43101584057610158401015840W 2670 plusmn 076 6588 plusmn 155 3256 plusmn 322







Minimum 2199 plusmn 068 5914 plusmn 141 1393 plusmn 288

Maximum 2917 plusmn 087 6588 plusmn 155 7089 plusmn 370

Average values plusmn standard deviation 2548 plusmn 292 6596 plusmn 739 3915 plusmn 1914

Campus 2











DU18 04∘03101584018210158401015840N 09∘44101584042710158401015840W 2367 plusmn 071 5720 plusmn 136 4226 plusmn 318




Worldwide (UNSCEAR 2000)Range 1700ndash6000 1100ndash6800 14000ndash85000Average 3500 3000 40000

2768plusmn080Bqkg with an average value of 2450 Bqkg from5260plusmn127 to 7899plusmn183Bqkg with amean of 6672 Bqkgand from 1189 plusmn 266 to 8076 plusmn 280Bqkg with an averagevalue of 2819 Bqkg respectively

The distributions of radioactivity measured in both stud-ied sites are present in Figures 2(a) and 2(b) As shown inthe figures the radioactivity concentration slightly variedfrom one point to another These variation observed in bothstudied sites may result from the nonuniform distributionof radioactivity contents present under the earth crust It isgenerally considered that igneous rocks contain higher levelsof radioactivity than sedimentary rocks The areas understudy are part of the Littoral Region observed to be themajor sedimentary basin of Cameroon [6] This formationhas variations in sediments limestone shale and clay Fromthe recorded activities of 226Ra 232Th and 40K in the presentstudy it can be noticed that the obtained average value of232Thin both locations was observed to be comparably higherthan both of 226Ra and 40K in almost all the soil-samplinglocations This could be due to the high content of thoriumpresent in sedimentary rocks

Comparing the average activity values of 226Ra 232Thand40K obtained in both studied sites as shown in Figure 3(a)

it can be seen that the obtained average values of 226Ra232Th and 40K in the analyzed soil samples from both studiedsites were relatively the same with the exception of the40K average value which was slightly higher in Campus 2than in Campus 1 The observed similar variation range inactivity concentrations of 226Ra 232Th and 40K is due tothe fact that both studied sites are closed to one anotherand the soil samples collected in both sites originated fromthe same geology formation The slight difference in activityconcentration average value of 40K is also due to the irregulardistribution of uranium thorium and potassium contentspresent in the studied soils

The calculated average activity values of 226Ra 232Thand 40K in both studied sites were compared with theestablished worldwide ones by UNSCEAR [7] as representedin Figure 3(b) It can be observed that the values obtainedin both studied sites are comparably lower that the recom-mended worldwide values with the exception of the 226Ravalues

The observed activity concentrations of 226Ra 232Th and40K in the present work were compared with other publishedvalues obtained from the literature of radioactivity in soil bymany authors as dispatched in Table 3 The obtained average

ISRN Spectroscopy 5

Table 2 The radiological health hazard parameters due to the activity contents of 226Ra 232Th and 40K in soil samples

Sampling site Sample ID Raeq Absorbed dose Outdoor annual effective dose External health hazard index(Bqkg) (nGyh) (mSvy) (Hex)

Campus 1

UD01 12341 9963 012 034UD02 14446 11578 014 040UD03 11201 9095 011 031UD04 11884 9604 012 033UD05 11214 9068 011 031UD06 13247 10675 013 036UD07 11636 9405 012 032

Minimum 11636 9095 011 031Maximum 14446 11578 014 040

Average val plusmn DS 12281 plusmn 1190 9913 plusmn 921 012 plusmn 001 034 plusmn 003

Campus 2

UD08 10092 8192 010 028UD09 11875 9587 012 033UD10 12975 10388 013 035UD11 11432 9150 011 031UD12 11628 9323 011 032UD13 13302 10653 013 036UD14 12053 9799 012 033UD15 14111 11296 014 039UD16 12942 10389 013 035UD17 13002 10419 013 035DU18 10871 8807 011 030

Minimum 10092 8192 010 028Maximum 14111 11296 014 039

Average val plusmn SD 12208 plusmn 1180 9818 plusmn 911 012 plusmn 001 033 plusmn 003

Worldwide (UNSCEAR 2000)Range 1800ndash9300Average 37000 6000 007 lt100

3000

2800

2600

2400

2200

2000

20004000

6000 8000 8000

70006000

226Ra

40K 232 Th

(a)

2000 40006000

8000 80007000

60005000

2800

2700

2600

2500

2400

2300

2200

2100

226Ra

40K232 Th

(b)

Figure 2 (a) Distribution of specific activities of 226Ra 40K and 232Th in soil samples from Campus 1 (b) Distribution of specific activitiesof 226Ra 40K and 232Th in soil samples from Campus 2

6 ISRN Spectroscopy

Table 3 Comparison of specific gamma activities (Bqkg) in soil with that of other countries

Country Activity concentration (Bqkg) Reference226Ra 232Th 40K

China (Xiaz-hung area) 4020ndash44200 (11200) 3260ndash8810 (7150) 44000ndash91300 (67200) [18]Botswana 610ndash9740 (3480) 740ndash11000 (4180) 3350ndash108570 (43270) [19]Ghana (Great Accra) 240ndash6270 32ndash1457 9110ndash139590 [20]India (Himwchal Pradesh) 4209ndash7963 (5734) 5283ndash13575 (8222) 9533ndash16030 (13575) [21]Italy (Southern) 5700ndash7100 7300ndash8700 58000ndash76000 [22]Namibia 450ndash4800 (3100) 300ndash3800 (3200) 4200ndash110000 (48000) [23]Nigeria (Lagos) 300ndash4300 500ndash7600 4000ndash35400 [24]

Nigeria Delta 1100ndash4000(1800 plusmn 340)

1200ndash4000(2200 plusmn 440)

6900ndash53000(21000 plusmn 4900)

[25]

Cameroonlowast2199ndash2917 (2548) lowast5914ndash6589 (6596) lowast1393ndash7089 (3915) This Worklowastlowast2199ndash2768 (2450) lowastlowast5260ndash7899 (6672) lowastlowast1189ndash8076 (2819)

lowastCampus 1 lowastlowastCampus 2 ( ) average value

80

70

60

50

40

30

20

10

0

Spec

ify ac

tivity

(Bq

kg)

Radionuclide

Av val Av val

226Ra 232Th 40K

Campus 1Campus 2

(a)

Radionuclide

Av val Av val

450

400

350

300

250

200

150

100

50

0

Aver

age a

ctiv

ity (B

qkg

)

UNSCEAR (2000)

226Ra 232Th 40K

Campus 1Campus 2

(b)

Figure 3 (a) Comparison of the mean specific gamma activities in soil from both studied sites (b) Comparison of the mean specific gammaactivities in soil samples with the worldwide value

activity concentrations of 226Ra and 40K in both studied siteswere comparably lower than the values published by otherauthors with the exception of the recorded values of 226Ra inNigeria Delta published by Agbalagba and Onoja [25] whichwere relatively low Similar observations were observed for232Th as recorded in the activity concentration in this workIt can be seen that the average values of 232Threcorded in thepresent study were slightly lower than the published valuesrecorded in China (Xiaz-hung area) Ghana (Greater Accra)and India (Himwchal Pradesh) [18 20 21] and higher thanthe recorded and published average values in Namibia and

Nigeria Delta [23 25] The present values were comparedfavourably with the recorded average values published byother countries selected from the worldwide investigation ofnatural radioactivity in soils

Uniformity with respect to exposure to radiation definedin terms of radium equivalent activity to compare thespecific activity of geological materials contain in differentamounts of 226Ra 232Th and 40K This was calculated andthe results were presented in Table 2 It can be seen thatvalues ranged from 11636 Bqkg to 14446 Bqkg with anaverage of 12281 Bqkg in Campus 1 and from 10093 Bqkg

ISRN Spectroscopy 7

to 14111 Bqkg with a mean value of 12208 Bqkg in Cam-pus 2 The obtained values of radium equivalent in thepresent investigation are comparably less than the safe limit(37000 Bqkg) recommended by UNSCEAR [7]

The ionising radiation affects the biological systems and itdepends along with the other factors on the time and placeof exposure and population involved In most cases the riskappears to be higher outdoors than indoors As shown inTable 2 the calculated absorbed dose in air is in the rangeof 9095 nGyh to 11577 nGyh with a mean of 9913 nGyhin Campus 1 and from 8192 nGyh to 11296 nGyh with anaverage of 9818 nGyh in Campus 2 The estimated annualoutdoor effective dose in the present study varies from011mSvy to 014mSvy with a mean of 012mSvy and from010mSvy to 014mSvy with an average of 012mSvy inCampuses 1 and 2 respectively The external health hazardindex calculated in the present study ranges from 031ndash040with a mean of 034 and from 028ndash039 with an average of033 in Campuses 1 and 2 respectivelyThe obtained values ofthe absorbed dose rate in air and the annual outdoor effectivedose in the present investigation are comparably higher thanthe recommended values of 1800ndash9300 (6000) nGyh and007mSvy UNSCEAR [7] whilst those of external healthhazard index obtained are comparably less than the unity

4 Conclusion

The natural radioactivity levels of 226Ra 232Th and 40Khave been measured in soils from the selected areas withinthe Douala-Bassa zone in the Littoral Region of Cameroonusing gamma spectrometry based broad energy germaniumdetector (BE6530)The recordedmean values of 232Thin bothstudied sites were relatively high than those of 226Ra and 40KConsidering the nonuniform distribution of radioactivity ingeological materials the radium equivalent was calculatedand observed to be lower than the recommended safevalue (37000 Bqkg) by UNSCEAR The radiological healthhazards parameters calculated in the present work werecomparably higher than the recommended safe limit of theabsorbed dose rate in air the annual outdoor effective doseand external health hazard index by UNSCEAR except thosevalues of the external health hazard index which were lessthan unity

The results obtained in this work have established base-line information on natural radioactivity in the two campusesof the University of Douala-Cameroon It is expected that theresults obtainedmay be used as baseline data for future work

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors are grateful for the support and technicalcooperation provided by the National Radiation ProtectionAgency of Cameroon in granting access to the facilities to

successfully complete this study The authors also appreciatethe Administration Committee of the University of Doualaand their vicinity for the understanding during samplingperiod

References

[1] M Tzortzis E Svoukis andH Tsertos ldquoA comprehensive studyof natural gamma radioactivity levels and associated dose ratesfrom surface soils in Cyprusrdquo Radiation Protection Dosimetryvol 109 no 3 pp 217ndash224 2004

[2] A Rani and S Singh ldquoNatural radioactivity levels in soilsamples from some areas of Himachal Pradesh India using 120574-ray spectrometryrdquoAtmospheric Environment vol 39 no 34 pp6306ndash6314 2005

[3] H Orabi A Al-Shareaif and M El Galefi ldquoGamma-raymeasurements of naturally occurring radioactive sample fromAlkharje Cityrdquo Journal of Radioanalytical and Nuclear Chem-istry vol 269 no 1 pp 99ndash102 2006

[4] J Al-Jundi B A Al-Bataina Y Abu-Rukah and H M She-hadeh ldquoNatural radioactivity concentrations in soil samplesalong the AmmanAqabaHighway JordanrdquoRadiationMeasure-ments vol 36 no 1ndash6 pp 555ndash560 2003

[5] C C Goddard ldquoMeasurement of outdoor terrestrial gammaradiation in the sultanate of Omanrdquo Health Physics vol 82 no6 pp 869ndash874 2002

[6] V A Asaah A F Abimbola and C E Suh ldquoHeavy metalconcentrations and distribution in surface soils of the BassaIndustrial Zone 1 Douala Cameroonrdquo Arabian Journal forScience and Engineering vol 31 no 2 pp 147ndash158 2006

[7] United Nations Scientific Committee on the Effect of AtomicRadiation (UNSCEAR) ldquoReport to the general assemblyrdquo inExposures FromNatural Radiation Sources B Annex Ed 2000

[8] European Commission (EC) Radiation Protection 112-radio-logical protection principles concerning the natural radioac-tivity of building materials Directorate- General EnvironmentNuclear Safety and Civil Protection 1999

[9] L Xinwei ldquoNatural radioactivity in some buildingmaterials andby-products of Shaanxi Chinardquo Journal of Radioanalytical andNuclear Chemistry vol 262 no 3 pp 775ndash777 2004

[10] J Beretka and P J Mathew ldquoNatural radioactivity of Australianbuilding materials industrial wastes and by-productsrdquo HealthPhysics vol 48 no 1 pp 87ndash95 1985

[11] N Damla U Cevik A I Kobya A Celik N Celik and RVan Grieken ldquoRadiation dose estimation and mass attenuationcoefficients of cement samples used in Turkeyrdquo Journal ofHazardous Materials vol 176 no 1ndash3 pp 644ndash649 2010

[12] I F Al-Hamarneh andM I Awadallah ldquoSoil radioactivity levelsand radiation hazard assessment in the highlands of northernJordanrdquo Radiation Measurements vol 44 no 1 pp 102ndash1102009

[13] N N Jibiri I P Farai and S K Alausa ldquoEstimation of annualeffective dose due to natural radioactive elements in ingestionof foodstuffs in tin mining area of Jos-Plateau Nigeriardquo Journalof Environmental Radioactivity vol 94 no 1 pp 31ndash40 2007

[14] D O Kpeglo H Lawluvi A Faanu et al ldquoNatural radioactivityand its associated radiological hazards in ghanaian cementrdquoResearch Journal of Environmental and Earth Sciences vol 3 no2 pp 161ndash167 2011

[15] R Krieger ldquoRadioactivity of constructionmaterialsrdquo Betonwerkund Fertigteil-TechnikConcrete Precasting Plant and Technol-ogy vol 47 no 8 pp 468ndash446 1981

8 ISRN Spectroscopy

[16] S Turhan and L Gunduz ldquoDetermination of specific activity of226Ra 232Th and 40K for assessment of radiation hazards fromTurkish pumice samplesrdquo Journal of Environmental Radioactiv-ity vol 99 no 2 pp 332ndash342 2008


[18] Y-X Yang X-M Wu Z-Y Jiang et al ldquoRadioactivity concen-trations in soils of the Xiazhuang granite area Chinardquo AppliedRadiation and Isotopes vol 63 no 2 pp 255ndash259 2005

[19] V R K Murty and N Karunakara ldquoNatural radioactivity in thesoil samples of Botswanardquo Radiation Measurements vol 43 no9-10 pp 1541ndash1545 2008

[20] E O Darko ldquoNatural radioactivity in soils and rocks within theGreater Accra Region of Ghanardquo Journal of Radioanalytical andNuclear Chemistry vol 249 no 3 pp 629ndash632 2001


[22] S Bellia M Brai S Hauser P Puccio and S Rizzo ldquoNatu-ral radioactivity in a Volcanic Island ustica Southern ItalyrdquoApplied Radiation and Isotopes vol 48 no 2 pp 287ndash293 1997

[23] F Steinhausler and H Lettner ldquoRadiometric survey inNamibiardquo Radiation Protection Dosimetry vol 45 no 1-4 pp553ndash555 1992

[24] NN Jibiri and I P Farai ldquoAssessment of dose rate and collectiveeffective dose equivalent due to terrestrial gamma radiation inthe city of Lagos Nigeriardquo Radiation Protection Dosimetry vol76 no 3 pp 191ndash194 1998

[25] E O Agbalagba and R A Onoja ldquoEvaluation of naturalradioactivity in soil sediment and water samples of Niger Delta(Biseni) flood plain lakes Nigeriardquo Journal of EnvironmentalRadioactivity vol 102 no 7 pp 667ndash671 2011

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ElectrochemistryInternational Journal of


Research ArticleGamma Emitting Radionuclides in Soils from Selected Areas inDouala-Bassa Zone Littoral Region of Cameroon

Maurice Moyo Ndontchueng12 Eric Jilbert Mekongtso Nguelem12 Augustin Simo1

Raymond Limen Njinga34 and Gembou Shouop Ceacutebastien Joeumll2

1 National Radiation Protection Agency PO Box 33732 Yaounde Cameroon2Department of Physics Faculty of Science University of Douala PO Box 24157 Douala Cameroon3Department of Physics Ibrahim Badamasi Babangida University Lapai Niger State Nigeria4 Radioanalysis and Spectrometry Service National Radiation and Protection Agency Yaounde Cameroon

Correspondence should be addressed to Maurice Moyo Ndontchueng ndomomauyahoofr

Received 12 November 2013 Accepted 10 December 2013 Published 22 January 2014

Academic Editors B Liu and T Stafilov

Copyright copy 2014 Maurice Moyo Ndontchueng et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

A study of natural radioactivity levels in some composites of eighteen soil samples selected within Douala-Bassa zone of LittoralRegion has been evaluatedThe samples were analysed using gamma spectrometry based broad energy germanium detector (BEGe6350) The activity profile of radionuclide shows low activity across the studied areas The obtained mean values of 226Ra 232Thand 40K in the two campuses were 2548 Bqkg 6596 Bqkg and 3914 Bqkg for Campus 1 and 2450 Bqkg 6671 Bqkg and2819 Bqkg for Campus 2 respectively In terms of health analysis some radiation health hazard parameters were calculated withinthe two campuses The mean values of radium equivalent activity were 12281 Bqkg and 12208 Bqkg absorbed dose rate in airwas 9913 nGyh and 9818 nGyy annual outdoor effective dose was 012mSvy and 012mSvy and external health hazard indexwas 034 and 033 in Campus 1 and Campus 2 respectively These health hazard parameters were seen to be below the safe limit ofUNSCEAR 2000 except the absorbed dose rate in air and the annual outdoor effective doses which are relatively high comparedto the values of 60 nGyh and 007mSvy These results reveal no significant radiological health hazards for inhabitance within thestudy areas

1 Introduction

Gamma radiation emitted from naturally occurring radioiso-topes also called terrestrial background radiation representsthemain source of radiation of the humanbodyNatural envi-ronmental radioactivity and the associated external exposuredue to gamma radiation depend primarily on the geologicaland geographical conditions and appear at different levels inthe soils of each region in the world [1 2] Only radionuclideswith half-lives comparable with the age of the earth ortheir corresponding decay products existing in terrestrialmaterials such as 232Th 238U and 40K are of great interestAbnormal occurrences of uranium and its decay productsin rocks and soils and thorium in monazite sands are themain sources of high natural background areas that have

been identified in several areas of the world [3] Outdoorsexposure to this radiation originates predominantly from theupper 30 cm of the soil [1] According to the literature ofnatural radioactivity in soil there is lack of information onnatural radioactivity levels in soils from various living sitesin Cameroon Radionuclides in soil generate a significantcomponent of the background radiation exposure to thepopulation [3]

The knowledge of specific activities or concentrations anddistributions of the radionuclides in soil is of great interestfor many researchers throughout the world and serves asthe reference in documenting changes to environmentalradioactivity due anthropogenic activities or any releaseof radioactive elements [4 5] Monitoring of radioactivematerials is therefore of primary importance to humans

Hindawi Publishing CorporationISRN SpectroscopyVolume 2014 Article ID 245125 8 pageshttpdxdoiorg1011552014245125

2 ISRN Spectroscopy






Bassa zone


0 200 400 600 800




2 Experimental






ISRN Spectroscopy 3
















119867ex =119860Ra370+119860Th259+119860K4810le 1 (4)







4 ISRN Spectroscopy



Campus 1











Campus 2






















ISRN Spectroscopy 5



Campus 1

UD01 12341 9963 012 034UD02 14446 11578 014 040UD03 11201 9095 011 031UD04 11884 9604 012 033UD05 11214 9068 011 031UD06 13247 10675 013 036UD07 11636 9405 012 032

Minimum 11636 9095 011 031Maximum 14446 11578 014 040


Campus 2


Minimum 10092 8192 010 028Maximum 14111 11296 014 039



3000

2800

2600

2400

2200

2000

20004000

6000 8000 8000

70006000

226Ra

40K 232 Th

(a)

2000 40006000

8000 80007000

60005000

2800

2700

2600

2500

2400

2300

2200

2100

226Ra

40K232 Th

(b)


6 ISRN Spectroscopy





1200ndash4000(2200 plusmn 440)

6900ndash53000(21000 plusmn 4900)

[25]



80

70

60

50

40

30

20

10

0

Spec

ify ac

tivity

(Bq

kg)

Radionuclide

Av val Av val

226Ra 232Th 40K

Campus 1Campus 2

(a)

Radionuclide

Av val Av val

450

400

350

300

250

200

150

100

50

0

Aver

age a

ctiv

ity (B

qkg

)

UNSCEAR (2000)

226Ra 232Th 40K

Campus 1Campus 2

(b)





ISRN Spectroscopy 7



4 Conclusion





Acknowledgments



References
















8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



2 ISRN Spectroscopy






Bassa zone


0 200 400 600 800




2 Experimental






ISRN Spectroscopy 3
















119867ex =119860Ra370+119860Th259+119860K4810le 1 (4)







4 ISRN Spectroscopy



Campus 1











Campus 2






















ISRN Spectroscopy 5



Campus 1

UD01 12341 9963 012 034UD02 14446 11578 014 040UD03 11201 9095 011 031UD04 11884 9604 012 033UD05 11214 9068 011 031UD06 13247 10675 013 036UD07 11636 9405 012 032

Minimum 11636 9095 011 031Maximum 14446 11578 014 040


Campus 2


Minimum 10092 8192 010 028Maximum 14111 11296 014 039



3000

2800

2600

2400

2200

2000

20004000

6000 8000 8000

70006000

226Ra

40K 232 Th

(a)

2000 40006000

8000 80007000

60005000

2800

2700

2600

2500

2400

2300

2200

2100

226Ra

40K232 Th

(b)


6 ISRN Spectroscopy





1200ndash4000(2200 plusmn 440)

6900ndash53000(21000 plusmn 4900)

[25]



80

70

60

50

40

30

20

10

0

Spec

ify ac

tivity

(Bq

kg)

Radionuclide

Av val Av val

226Ra 232Th 40K

Campus 1Campus 2

(a)

Radionuclide

Av val Av val

450

400

350

300

250

200

150

100

50

0

Aver

age a

ctiv

ity (B

qkg

)

UNSCEAR (2000)

226Ra 232Th 40K

Campus 1Campus 2

(b)





ISRN Spectroscopy 7



4 Conclusion





Acknowledgments



References
















8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



ISRN Spectroscopy 3
















119867ex =119860Ra370+119860Th259+119860K4810le 1 (4)







4 ISRN Spectroscopy



Campus 1











Campus 2






















ISRN Spectroscopy 5



Campus 1

UD01 12341 9963 012 034UD02 14446 11578 014 040UD03 11201 9095 011 031UD04 11884 9604 012 033UD05 11214 9068 011 031UD06 13247 10675 013 036UD07 11636 9405 012 032

Minimum 11636 9095 011 031Maximum 14446 11578 014 040


Campus 2


Minimum 10092 8192 010 028Maximum 14111 11296 014 039



3000

2800

2600

2400

2200

2000

20004000

6000 8000 8000

70006000

226Ra

40K 232 Th

(a)

2000 40006000

8000 80007000

60005000

2800

2700

2600

2500

2400

2300

2200

2100

226Ra

40K232 Th

(b)


6 ISRN Spectroscopy





1200ndash4000(2200 plusmn 440)

6900ndash53000(21000 plusmn 4900)

[25]



80

70

60

50

40

30

20

10

0

Spec

ify ac

tivity

(Bq

kg)

Radionuclide

Av val Av val

226Ra 232Th 40K

Campus 1Campus 2

(a)

Radionuclide

Av val Av val

450

400

350

300

250

200

150

100

50

0

Aver

age a

ctiv

ity (B

qkg

)

UNSCEAR (2000)

226Ra 232Th 40K

Campus 1Campus 2

(b)





ISRN Spectroscopy 7



4 Conclusion





Acknowledgments



References
















8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



4 ISRN Spectroscopy



Campus 1











Campus 2






















ISRN Spectroscopy 5



Campus 1

UD01 12341 9963 012 034UD02 14446 11578 014 040UD03 11201 9095 011 031UD04 11884 9604 012 033UD05 11214 9068 011 031UD06 13247 10675 013 036UD07 11636 9405 012 032

Minimum 11636 9095 011 031Maximum 14446 11578 014 040


Campus 2


Minimum 10092 8192 010 028Maximum 14111 11296 014 039



3000

2800

2600

2400

2200

2000

20004000

6000 8000 8000

70006000

226Ra

40K 232 Th

(a)

2000 40006000

8000 80007000

60005000

2800

2700

2600

2500

2400

2300

2200

2100

226Ra

40K232 Th

(b)


6 ISRN Spectroscopy





1200ndash4000(2200 plusmn 440)

6900ndash53000(21000 plusmn 4900)

[25]



80

70

60

50

40

30

20

10

0

Spec

ify ac

tivity

(Bq

kg)

Radionuclide

Av val Av val

226Ra 232Th 40K

Campus 1Campus 2

(a)

Radionuclide

Av val Av val

450

400

350

300

250

200

150

100

50

0

Aver

age a

ctiv

ity (B

qkg

)

UNSCEAR (2000)

226Ra 232Th 40K

Campus 1Campus 2

(b)





ISRN Spectroscopy 7



4 Conclusion





Acknowledgments



References
















8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



ISRN Spectroscopy 5



Campus 1

UD01 12341 9963 012 034UD02 14446 11578 014 040UD03 11201 9095 011 031UD04 11884 9604 012 033UD05 11214 9068 011 031UD06 13247 10675 013 036UD07 11636 9405 012 032

Minimum 11636 9095 011 031Maximum 14446 11578 014 040


Campus 2


Minimum 10092 8192 010 028Maximum 14111 11296 014 039



3000

2800

2600

2400

2200

2000

20004000

6000 8000 8000

70006000

226Ra

40K 232 Th

(a)

2000 40006000

8000 80007000

60005000

2800

2700

2600

2500

2400

2300

2200

2100

226Ra

40K232 Th

(b)


6 ISRN Spectroscopy





1200ndash4000(2200 plusmn 440)

6900ndash53000(21000 plusmn 4900)

[25]



80

70

60

50

40

30

20

10

0

Spec

ify ac

tivity

(Bq

kg)

Radionuclide

Av val Av val

226Ra 232Th 40K

Campus 1Campus 2

(a)

Radionuclide

Av val Av val

450

400

350

300

250

200

150

100

50

0

Aver

age a

ctiv

ity (B

qkg

)

UNSCEAR (2000)

226Ra 232Th 40K

Campus 1Campus 2

(b)





ISRN Spectroscopy 7



4 Conclusion





Acknowledgments



References
















8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



6 ISRN Spectroscopy





1200ndash4000(2200 plusmn 440)

6900ndash53000(21000 plusmn 4900)

[25]



80

70

60

50

40

30

20

10

0

Spec

ify ac

tivity

(Bq

kg)

Radionuclide

Av val Av val

226Ra 232Th 40K

Campus 1Campus 2

(a)

Radionuclide

Av val Av val

450

400

350

300

250

200

150

100

50

0

Aver

age a

ctiv

ity (B

qkg

)

UNSCEAR (2000)

226Ra 232Th 40K

Campus 1Campus 2

(b)





ISRN Spectroscopy 7



4 Conclusion





Acknowledgments



References
















8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



ISRN Spectroscopy 7



4 Conclusion





Acknowledgments



References
















8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



8 ISRN Spectroscopy




















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of












Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy




Journal of


Quantum Chemistry




CatalystsJournal of



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