The current content of artificial radionuclides in the water of the Tobol–Irtysh river system (from the mouth of the Iset River to the confluence with the Ob River)

Journal of Environmental Radioactivity 96 (2007) 138e143 www.elsevier.com/locate/jenvrad

The current content of artificial radionuclides in the water of the ToboleIrtysh river system (from the mouth of the Iset River to the confluence with the Ob River) Alexander I. Nikitin a,*, Vladimir B. Chumichev a, Nailia K. Valetova a, Ivan Yu. Katrich a, Alexander I. Kabanov a, Gennady E. Dunaev a, Valentina N. Shkuro a, Victor M. Rodin b, Alexander N. Mironenko b, Elena V. Kireeva b a

SI RPA ‘‘Typhoon’’ of the Roshydromet, 82, Lenin avenue, Obninsk, Kaluga region 249038, Russia b Tobolsk Biological Station of RAS, 15, Voikov street, Tobolsk, Tyumen region 626150, Russia Accepted 15 January 2007 Available online 10 April 2007

Abstract Data on content of 90Sr, 137Cs, 239,240Pu and 3H in water of the ToboleIrtysh part of the TechaeIsete ToboleIrtysheOb river system (through which the ‘‘Mayak’’ PA radioactive wastes are transported) are presented and discussed. The data were received in 2004e2005 under the ISTC project on radioecological monitoring of the Tobol and Irtysh rivers. Monthly observations of 137Cs, 90Sr and 3H content in water in the area of the Tobol and Irtysh confluence have been conducted starting from May 2004. To obtain information on the investigated river system as a whole, the radioecological survey of the Tobol and Irtysh rivers at the section from the mouth of the Iset River to the confluence with the Ob River was carried out in 2004. It is shown that the impact of ‘‘Mayak’’ PA waste transport by 90Sr is distinctly traced as far as the area of the Irtysh and Ob confluence. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: ‘‘Mayak’’ PA; Tobol River; Irtysh River; River water;

90

Sr;

137

Cs;

* Corresponding author. Tel.: þ7 48439 7 18 05; fax: þ7 48439 7 11 47. E-mail address: [email protected] (A.I. Nikitin). 0265-931X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2007.01.023

239,240

Pu; 3H

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1. Introduction The impact of ‘‘Mayak’’ PA waste on the radioactive contamination of the aquatic environment of the TechaeIseteToboleIrtysheOb river system has been investigated. This was done near the source e on the Techa and Iset rivers (e.g., JNREG, 1997). As applied to the Tobole Irtysh section of the system, previously there were only data from episodic surveys (e.g., Gedeonov, 1971; Trapeznikov et al., 1995). In 2004, within the framework of the ISTC Project No. 2558 ‘‘Radioecological monitoring of the Tobol and Irtysh rivers: Study of biogenic transfer of radionuclides and radiation risk assessment for the population and environment’’, observation of artificial radionuclide content in the Tobol and Irtysh rivers was started. Monthly observations of 137Cs, 90Sr and 3H content in water in the area of the Tobol and Irtysh confluence were organized. The radioecological survey of the Tobol and Irtysh rivers in 2004 extended from the mouth of the Iset River to the confluence with the Ob River. In the course of the field survey, water samples for the determination of 137Cs, 90Sr, 239,240Pu and 3H were collected. Sediment and flood plain soil samples were also taken for subsequent radionuclide analysis. The data on the artificial radionuclide content in the river water obtained by May of 2005 are given and discussed below. 2. Materials and methods SI RPA ‘‘Typhoon’’ has many years of experience in field investigations of water environmental radioactive contamination caused by global and different local sources. The procedures and methods used were described in a number of papers (Vakulovsky, 1986; Nikitin, 1995). Methods were chosen for collection, treatment and radionuclide analysis of water samples, assuring determination of radionuclide-indicators of the ‘‘Mayak’’ PA wastes (such as 90Sr, 137Cs, 239,240Pu and 3H) on the whole part of the investigated river system. An important criterion for the planning of sampling points was that the data of previous studies indicated a sharp difference in the 90Sr content in the flows of the Tobol (contaminated with the ‘‘Mayak’’ PA discharges) and the Irtysh. For example, in 1970 (Gedeonov, 1971) this difference was clearly seen even at a distance of 15 km from the confluence of the Tobol and Irtysh. The same pattern was observed at the confluence of the Irtysh and Ob. This was taken into account in drawing up the project fieldwork program: near the confluences of the large rivers downstream of the contaminated inflow, sampling points were arranged with allowance for possible water mass stratification.

3. Results of radionuclide content determination in river water Monthly measurements in the area of the Tobol and Irtysh confluence have shown that 90Sr is a reliable indicator of radioactivity inflow from the ‘‘Mayak’’ PA area. Measured concentrations of 90Sr in water from the Tobol River before it flowed into the Irtysh River and on the left bank of the Irtysh River downstream from the confluence with the Tobol River (33e235 Bq/m3, see Fig. 1) were by an order of magnitude greater than a background level for the rivers of Russia. In the Irtysh River upstream from the confluence with the Tobol River, 90Sr water content was practically background (Fig. 1). Measured concentrations of 137Cs (<0.2 to 2.9 Bq/m3) and 3 H (2900e7900 Bq/m3) were in a background range at all three observation points, however, for 3H there was a little stable excess of concentrations at observation points on the Tobol River and on the left bank of the Irtysh River (downstream from the confluence) over those in water from the Irtysh River upstream from the confluence with the Tobol River. The results of 90Sr content determination at the section lines across the Irtysh downstream the Tobol mouth (section line nos. 6 and 7, Table 1) clearly indicate that stratification of Tobol

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Irtys

h riv

er

140

Point No.3 Irtysh river, 6km downstream from confluence with Tobol river

Tobolsk Point No.2 Irtysh river before confluence with Tobol river

Irt h ys riv er

Point No.1 Tobol river before confluence with Irtysh river

T

o ob

l ri

ve

r

Bizino Medjanki

250 Point 1 Point 2 Point 3

200

Bq/m3

150

100

50

05

.0 5 07 17 .

5. .0

05 4. .0

28

05 08

2. .0

.0

4 17

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04

04

1. .1 09

9. .0

4

04 20

01 .0 8.

6. 0 12 .0

23 .0

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Date of sampling Fig. 1. Location of sampling points and temporal changes of 90Sr activity concentration in the water of the Tobol (point 1) and Irtysh rivers (point 2 e upstream from the mouth of the Tobol; point 3 e downstream from the mouth of the Tobol, left bank) in the area of their confluence (according to the results by May 2005).

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Table 1 The results of determining the artificial radionuclide content in water samples from the Iset, Tobol, Irtysh and Ob rivers collected on 11e28 September 2004 No. of section linea (Fig. 2) 1 lb 1 rb 2m 3m 4 lb 5m 6 lb 6m 6 rb 7 lb 7m 7 rb 8 lb 9 lb 10 m 11 m 12 lb 13 m 14 m 15 lb 15 rb 16 lb 17 rb a

137

Cs (Bq/m3)

90

Sr (Bq/m3)

239,240

Pu (mBq/m3)

3

H (kBq/m3)

Suspended matter

Filtrate

Total

Filtrate

Filtrate

Filtrate

0.24  0.09 e 0.14  0.05 0.17  0.02 <0.02 <0.02 0.08  0.01 e e <0.1 e e 0.11  0.04 <0.02 e e 0.13  0.05 e e <0.02 e 0.09  0.02 <0.05

0.40  0.06 e 0.18  0.05 0.20  0.02 0.25  0.02 0.26  0.02 0.22  0.02 e e 0.18  0.04 e e 0.15  0.03 <0.02 e e 0.18  0.02 e e 0.17  0.02 e 0.18  0.02 0.12  0.03

0.64  0.15 e 0.32  0.10 0.37  0.04 0.25  0.02 0.26  0.02 0.30  0.03 e e 0.18  0.04 e e 0.26  0.07 <0.04 e e 0.31  0.07 e e 0.17  0.02 e 0.27  0.03 0.12  0.03

15.0  1.8 6.2  0.9 5.5  0.8 26  3 31  4 32  4 57  6 18.0  2.2 12.4  1.5 69  8 23  3 8.5  1.1 72  8 5.9  0.8 84  10 180  22 185  22 220  25 600  55 740  60 705  60 1030  80 10.3  1.4

e e 13.0  2.1 6.6  2.0 e 3.1  1.0 5.4  1.2 e e e e e 7.5  2.0 <1.6 e e e e e 3.3  1.6 e 4.1  1.6 <2.4

2.3  0.2 2.2  0.1 2.6  0.2 4.4  0.2 3.6  0.2 4.0  0.2 4.0  0.2 2.7  0.1 2.8  0.2 4.9  0.2 3.1  0.2 3.9  0.2 4.3  0.2 2.6  0.2 e e 6.5  0.3 e e 11.3  0.4 11.3  0.4 15.2  0.5 2.9  0.2

lb e left bank, rb e right bank, m e middle of a river.

and Irtysh water masses remained at a significant distance from the Tobol mouth. For this reason, the concentration of 90Sr in river water at the left bank of Irtysh downstream the Tobol mouth (Fig. 1, point 3) did not virtually differ from the concentration of the radionuclide in Tobol water before the confluence with the Irtysh (Fig. 1, point 1). The location of the section lines where water sampling was conducted during the expedition survey is presented in Fig. 2. The results of the radionuclide analysis of the river water samples collected during the expedition survey are presented in Table 1. Fig. 3 illustrates the change in activity concentration of 90Sr in river water (filtrate) at the Tobol section of the river system as a function of distance from the sampling point on the Iset River. It can be seen that 90Sr activity concentration increased with proximity to the mouth of the Iset River. The 90Sr activity concentration in water from the Iset River near the confluence with the Tobol River had a maximum for the studied section of the river system equal to about 1000 Bq/m3. This value is approximately 200 times as much as the level typical of Russian rivers on the whole (5e6 Bq/m3; Roshydromet, 2005), but it is lower than a 90Sr intervention level in drinking water (5000 Bq/m3; NRB, 1999). At the same time, the practically background value of 90Sr activity concentration (about 10 Bq/m3, see Table 1) was observed in the Tobol River upstream from the confluence with the Iset River. The impact of ‘‘Mayak’’ PA waste transport by 90Sr was distinctly traced as far as the area of the Irtysh and Ob confluence. In the water of the Irtysh River near its confluence with the Ob River, 90Sr activity concentration was 4e5 times higher than technogenic background.

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3

1

2

Ob river

Khanty-Mansiysk Ekaterinburg 7

6

5

4

er

Ta vd ar

Kamensk-Uralsky

h

s rty

riv

I

ive

r

Tobolsk

Tyumen

r Tu a er

r

riv

Mayak PA Techa

Mekhonskoe iver

Yalutorovsk

16

17

o ob

r

ive

lr

Iset river

Irt

ys h

T

15

14

riv

er

13

12

11

10

8

9

Fig. 2. The location of the section lines for the water environment sampling during the expedition survey of the radioactive contamination of the river system in September of 2004.

90Sr,Bq/m3

Practically background level of 90Sr activity concentration in water (about 6 Bq/m3, see Table 1) was observed in the Ob River upstream from the confluence with the Irtysh River. However, in the Ob River at a distance about 10 km downstream from the confluence with Irtysh River, 90 Sr activity concentration in water near the left bank was 15 Bq/m3, which is about three times higher than the background level. The data obtained indicates that dilution with the waters of rivers inflowing on the Tobol section of the river system (Fig. 3) is a key factor of decrease in activity concentration of 90Sr on the 1200

The Iset river mouth

1000

The Tobol, 30 km downstream of the confluence with the Iset

800

The Tobol, 1 km upstream of the Tura inflow

600

The Tobol, 15 km downstream of the Tura inflow

400

The Tobol, 1 km upstream of the Tavda inflow The Tobol, 15 km downstream of the Tavda inflow

200

The Tobol, 5 km upstream from the confluence with the Irtysh

0 0

100

200

300

400

Distance from the sampling point (Iset'), km Fig. 3. 90Sr activity concentration change in river water (filtrate) along the section from the mouth of the Iset River to the confluence with the Irtysh River (September 2004).

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ToboleIrtysh part of the river system. The 90Sr activity concentration in river water decreased significantly on this section (about 15 times in September 2004). On the Irtysh section of the river system (which has a length more than 600 km), the decrease of 90Sr activity concentration in river water was not so significant. So, the content of 90Sr in the water of Irtysh River at a distance about 100 km downstream from the Tobol River mouth was 32 Bq/m3, and 26 Bq/m3 close to the confluence with the Ob River (near Khanty-Mansiysk, more than 600 km from the Tobol River mouth). We can infer that the decrease of 90Sr activity concentration of the ‘‘Mayak’’ PA origin (subtracting the background level 6 Bq/m3) in river water on the Irtysh section will be only 1.3, while on the Tobol section (which is shorter than the Irtysh section) 90Sr activity concentration in river water decreases, as it was already mentioned, about 15 times. The results of 3H analysis (Table 1) give evidence that ‘‘Mayak’’ PA waste inflow exerted an influence also on 3H content in river water (although to a far less extent than upon 90Sr content). The 137Cs and 239,240Pu content in river water was extremely low. At the same time, no decrease in activity concentration of 137Cs and plutonium isotopes in filtrate was observed as the distance from the mouth of the Iset River increases. 4. Conclusion Obtained in 2004e2005, data on the radionuclides’ content in water of the ToboleIrtysh section of the river system TechaeIseteToboleIrtysheOb indicated that the inflow of ‘‘Mayak’’ PA radioactive waste in the greatest degree affects 90Sr content in river water. The impact of ‘‘Mayak’’ PA waste transport by 90Sr was distinctly traced as far as the area of the Irtysh and Ob confluence. The contemporary 90Sr content in the river water for closest to the ‘‘Mayak’’ PA part of the studied river system (the Iset River mouth) was about 1000 Bq/m3, which is by two orders of magnitude greater than the man-caused background. Nevertheless, even this recorded maximum is five times less than the intervention level in drinking water according to current Russian standards. Among the other artificial radionuclides (137Cs, 239,240 Pu and 3H), the impact of ‘‘Mayak’’ PA waste inflow was traced along the studied section of the river system also by 3H (although to a far less extent than by 90Sr). References Gedeonov, L.I. (scientific supervisor), 1971. Study of radioactive contamination of the rivers of Siberia in 1970. Communication 3 e System the ObeIrtysheTobol. Report of the Khlopin Radium Institute, Leningrad. JNREG, 1997. Joint NorwegianeRuassian Expert Group for Investigation of Radioactive Contamination in the Northern Areas. Sources contributing to radioactive contamination of the Techa River and areas surrounding the ‘‘Mayak’’ production association, Urals, Russia, Osteras. Nikitin, A.I. (Ed.), 1995. Methodology of monitoring radioactive contamination of water bodies (MVI.01.-7/96). Obninsk, SPA ‘‘Typhoon’’ (in Russian). NRB, 1999. Radiation safety standards. SP 2.6.1.-758-99. Ministry of Health of the Russian Federation (in Russian). Roshydromet, 2005. Radiation situation on the territory of Russia and adjacent countries 2004. Annual Book. Meteoagency of Roshydromet, Moscow (in Russian). Trapeznikov, A., Aarkrog, A., Pozolotina, V., Nielsen, S.P., Trapeznikova, V., Yushkov, P., Polikarpov, G., 1995. Radionuclides in the ObeIrtysh river system and their contribution to pollution of the Arctic. In: Strand, P., Cooke, A. (Eds.), Environmental Radioactivity in the Arctic. Østeras, pp. 68e71. Vakulovsky, S.M. (Ed.), 1986. Methodological Guidelines on Determination of Radioactive Contamination of Water Bodies. Hydrometeoizdat, Moscow (in Russian).