Methods for determination of natural radioactivity in the drinking water samples

Izabela Chmielewska, Stanisław Chałupnik, Bogusław Michalik, Antoni Mielnikow

Laboratory of Radiometry, Central Mining Institutei.chmielewska@gig.eu

In 2009 in frame of statutory work in Central Mining Institute monitoring of drinking waters coming from Upper Silesia region was done.

Main objectives of that project were:

•developing of various methods for examination of concentration natural and man-made radionuclides;

• assessment of dose rate for each age group, related to water intake.

Sources of drinking water in upper Silesia can be divided into:•surface;•underground.

•Altogether we selected and investigated 9 resources.

•From each of them we took 20 l of raw as well treated water .

•Subsequently these waters were undergone further analyses.

Konopiska

ŁabędyBielszowiceDziećkowice

ZwonowiceGoczałkowice

Maczki

We We appliedapplied thethe followingfollowing measurementmeasurementtechniquestechniques::

grossgross alfa/beta alfa/beta activityactivity –– liquidliquid scintillationscintillationcountingcounting (LSC);(LSC);tritiumtritium 33H H –– (LSC); (LSC); radium radium isotopesisotopes –– 226226Ra i Ra i 228228Ra Ra –– LSC;LSC;nuclidenuclide 210210Pb Pb –– LSC;LSC;uraniumuranium isotopesisotopes –– 238238U i U i 234234U U –– alphaalphaspectrometryspectrometry;;strontiumstrontium 9090Sr Sr –– LSC;LSC;cesiumcesium 137137Cs Cs –– gamma gamma spectrometryspectrometry. .

Gross alpha/beta activity

•The most common way of measurement is LSC, based on electronic separation of impulses, generated by alpha and beta particles.

•In our case 200 ml of water was evaporated up to 4 ml, later on mixed with scintillation cocktail.

•Counting time for each sample amounted to 3h, with MDA 0,02 Bq/l and 0,08 Bq/l for total alpha and beta activity respectively.

Tritium

•Sample to be measured for tritium concentration was distilled so that eliminate the other isotopes, then mixed with scintillation cocktail andquantyfied by means of LSC.

• Prior to distillation Na2S2O3 was added in order to bond iodine, possibly present in the sample.

•Counting time was 5h with MDA 1,6 Bq/l.

Radium isotopes• In analysed water samples we focused on 2 the

most significant isotopes 226Ra and 228Ra for the sake of their pretty long half life.

• Chemical preparation for radium1. coprecipitation Ba2+, Ra2+, Pb2+ as sulphates;2.complexing the precipitate with EDTA to

separate Ra from Pb;3.re-precipitation BaRa(SO4)2;4.adding gelling scintillation cocktail;5.measurement after 30 days (in equilibrium state)

by means of LSC.

A few words about 210Pb…

• Chemical preparation for lead:1. coprecipitation Ba2+, Ra2+, Pb2+ as sulphates;2.complexing the precipitate with EDTA to

separate Ra from Pb;3.replacing Pb in complex with EDTA by Cr;4.precipitation PbSO4, then adding gelling

scintillation cocktail;5.measurement conducted by LSC.

• Initial volume of all water samples, which was used for radium and lead determination, came to 5 liters.

• Samples were evaporated up to 0,5 l and then chemical preparation was done according to the above mentioned procedures.

• Detection limit for each radionuclide is following:

• 226Ra - 0,0011 kBq/m3 equals 1,1 mBq/l;

• 228Ra - 0,0066 kBq/m3 equals 6,6 mBq/l;

• 210Pb - 0,0032 kBq/m3 equals 3,2 mBq/l.

How the separation of uranium was done?

•Evaporation 5 l of water sample up to 0,2 -0,3 l;•Coprecipitation uranium together with Fe(OH)3•Dissolution Fe(OH)3 in 9M HCl;•U separation from the matrix components;•Electrodeposition.

Determination of Sr-90

1. water sample, Sr carrier,precipitation with oxalic acid;2. discarding supernatant, dissolvin deposit in 3M nitric acid;3. loading solution into earlierprecondition column;4. rinsing the column with 3M nitric acid;5. elution Sr with distilled water;6. precipitation strontiumoxalate;7. mix with scintillation cocktail and measurement by LSC.

Assessment of dose rate for all agegroup•We calculated the dose, based on the conversion factor for each radionuclide, in particular age group, derived from Euratom Directive;•As well we assumed (according to WHO) that annualwater intake for certain group is following:

730730540540350350350350350350250250Water Water intake intake

[l/year][l/year]

>17>171212--171777--121222--7711--22<1<1Age Age groupgroup

0,07530,07530,03050,03050,02630,02630,04180,04180,13530,13530,220,220,120,12NiegowoniceNiegowonice treatedtreatedwaterwater1010

0,09230,09230,03880,03880,03360,03360,05390,05390,18040,18040,210,210,140,14NiegowoniceNiegowonice rawrawwaterwater99

0,03390,03390,01560,01560,01400,01400,02290,02290,07370,07370,190,190,080,08Konopisko Konopisko -- treatedtreatedwaterwater88

0,08110,08110,03630,03630,03170,03170,05200,05200,18300,18300,210,210,040,04Konopisko Konopisko –– rawrawwaterwater77

0,02390,02390,01190,01190,01090,01090,01810,01810,05860,05860,160,160,060,06MikoMikołłóów w –– treatedtreatedwaterwater66

0,02390,02390,01190,01190,01090,01090,01810,01810,05860,05860,160,160,060,06DzieDzieććkowicekowice –– rawrawwaterwater55

0,02390,02390,01190,01190,01090,01090,01810,01810,05860,05860,160,160,060,06DzieDzieććkowicekowice-- treatedtreatedwaterwater44

0,02390,02390,01190,01190,01090,01090,01810,01810,05860,05860,170,170,050,05GoczaGoczałłkowice kowice –– rawrawwaterwater33

0,02390,02390,01190,01190,01090,01090,01810,01810,05860,05860,170,170,050,05Pszczyna Pszczyna -- treatedtreatedwaterwater22

0,02390,02390,01190,01190,01090,01090,01810,01810,05860,05860,160,160,070,07Tychy Tychy –– treatedtreatedwaterwater11

1212--17 17 yearsyears

77--12 12 yearsyears

22--7 7 yearsyears

11--22yearsyears< 1 < 1 yearyearGrossGross ββ

GrossGrossαα

SamplingSamplingsitesite

No.No.

0,02390,02390,01190,01190,01090,01090,01810,01810,05860,05860,210,210,020,02ZwonowiceZwonowice treatedtreatedwaterwater2020

0,02690,02690,01290,01290,01170,01170,01930,01930,0630,0630,20,2110,10,1ZwonowiceZwonowice rawraw waterrwaterr1919

0,04160,04160,01990,01990,01840,01840,02980,02980,09460,09460,230,230,110,11ŁŁababęędy dy treatedtreated waterwater1818

0,05930,05930,02770,02770,02500,02500,04070,04070,13540,13540,270,270,120,12ŁŁababęędy dy rawraw waterwater1717

0,06780,06780,03130,03130,02760,02760,04560,04560,16010,16010,330,330,080,08BielszowiceBielszowice treatedtreatedwaterwater1616

0,17640,17640,08040,08040,06990,06990,11550,11550,41920,41920,330,330,080,08BielszowiceBielszowice rawraw waterwater1515

0,28410,28410,13260,13260,11560,11560,19240,19240,70930,70930,0,31310,110,11DDąąbrowski browski rawraw watewate1414

0,21350,21350,09980,09980,08720,08720,14510,14510,53200,53200,240,240,110,11DDąąbrowski browski treatedtreatedwaterwater1313

0,02450,02450,01220,01220,01140,01140,01880,01880,06000,06000,180,180,040,04SUW Maczki SUW Maczki treatedtreatedwaterwater1212

0,02460,02460,01240,01240,01150,01150,01900,01900,06040,06040,160,160,060,06SUW Maczki SUW Maczki rawrawwaterwater1111

1212--17 17 yearsyears

77--12 12 yearsyears

22--7 7 yearsyears

11--22yearsyears< 1 < 1 yearyear

GrossGrossββ

GrossGrossαα

SamplingSamplingsitesite

No.No.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8dose

 [m

Sv/

year

<  1 ye

ar1‐

2  yea

r2‐

7  yea

r7‐

12 ye

a r12

‐17 ye

arab

ove  1

7raw water

treated water

Water Dabrowski Jaworzno – dose estimation

Raw watergross α= 0,11 Bq/lgross β= 0,31 Bq/l

Treated water gross α= 0,11 Bq/lgross β= 0,24 Bq/l

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

< 1 yea

rdose

 [m

Sv/ye

ar]

s um 90S r 137C s210P b226Ra228R a 234U 238U

raw water

treated water

0

0,05

0,1

0,15

0,2

0,25

7 ‐ 12

 yea

r      

dose

 [m

Sv/ye

ar]

s um 90S r 137C s 210P b226Ra 228Ra 234U 238U

raw water

treated water

Water Dabrowski Jaworzno – contribution of given radionuclides to total dose

Conclusion:

•Concentration of different radionuclides in surface water is lower than in underground .

•Screening method recommended by WHO seems to be inappropriate for determination of drinking waters radioactivity, especially those originating from underground sources.

•The most crucial age groups, while considering the dose, are infants and adolescents.

•The key radionuclide, which has the significant contribution to total dose, is Ra-228.

AcknowledgementInvestigations have been made with use of devices, received

within the frame of the project, supported by European Fund of Regional Development, entitled "Development of the research

capabilities for revitalisation of the post-industrial areas”Nr:POIG.02.01.00-24-045/08, This project is allocated at the

Central Mining Institute within Operational Programme„Innovative Economy”, period 2007-2013, Priority 2.

Infrastructure of R+D sphere, Activity 2.1. Development of institutions of high research potential.

The total financing of the project: 9 546 973,00 PLNPublic support : 8 018 023,00 PLN

85% from European Fund of Regional DevelopmentPeriod of realisation: 01.08.2008 - 31.06.2011

Thank you for attention