Studies on soil to grass transfer factor (Fv) and grass to milk transfer coefficient (Fm) for cesium in Kaiga region

Journal of Environmental Radioactivity 124 (2013) 101e112

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Studies on soil to grass transfer factor (Fv) and grass to milk transfer coefficient (Fm) for cesium in Kaiga region N. Karunakara a, *, P. Ujwal a, I. Yashodhara a, Chetan Rao a, K. Sudeep Kumara a, B.N. Dileep b, P.M. Ravi c a b c

University Science Instrumentation Centre, Mangalore University, Mangalagangothri, 574199 Mangalore, India Environmental Survey Laboratory, Kaiga Generating Station, Kaiga 581 400, India Health Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 27 June 2012 Received in revised form 19 March 2013 Accepted 20 March 2013 Available online 15 May 2013

Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium (137Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of 137Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the 137 Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1
101 and 1.8
101 for 137Cs and stable Cs, respectively. The Fm of 137Cs had geometric mean values of 1.9
102 d L1 and 4.6
102 d L1, respectively, for adopted Cows 1 and 2; 1.7
102 d L1 for the cows of local farmers, and 4.0
103 d L1 for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of 137Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for 137Cs and stable Cs and their dependence on the potassium content (40K and stable K) in the soil and grass were also studied. In order to estimate the ingestion dose accurate data of the dietary habits of the population was necessary and this data was collected through a well planned demographic survey. The internal doses to a child due to the ingestion of 137Cs along with the milk of the local cows and from the dairy farm were found to be 0.29 mSv y 1 and 0.04 mSv y1,while that to an adult were 0.39 mSv y1 and 0.05 mSv y1, respectively. Ó 2013 Elsevier Ltd. All rights reserved.

Keywords: Transfer factors Transfer coefficients Cesium-137 Kaiga Grass Milk

1. Introduction Radionuclides, if released to the environment, may reach the human body through several transfer pathways and the soil-grasscow milk pathway is considered as one of the important routes through which radionuclides can enter the human body. 137Cs is an important radionuclide for the assessment of radiation exposure to the public because of its relatively long half life (T1/2 ¼ 30.2 y) and

* Corresponding author. Tel.: þ91 8242287671; fax: þ91 824 2287367. E-mail addresses: [email protected], [email protected] (N. Karunakara). 0265-931X/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvrad.2013.03.008

high transferability to the environment (Tsukada et al., 2003). Cesium behaves much like potassium and because of their similar physical and chemical properties both elements get actively included in the food chains and are uniformly distributed throughout the organs and tissues. The estimation of site-specific transfer factors and transfer coefficients for radionuclides in various pathways is essential for an accurate assessment of the long-term radiological hazard to the population in the surrounding region of a nuclear power plant. It is recognised that the general assessment calculations that are used to predict the environmental transport and the ensuing doses resulting from the release of radioactivity involve uncertainties due to lack of site-specific information. Though extensive studies on the

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distribution and transfer mechanism of cesium in different environmental compartments and the resulting radiation dose to humans have been carried out, these studies are by no means complete. A detailed study on the soil to grass transfer factors (Fv) and grass to cow milk transfer coefficient (Fm) for radioactive cesium (137Cs) and stable cesium (Cs) was carried out in Kaiga region, where a nuclear power plant with 4 reactors of 220 MWe each is in operation (Fig. 1a). Kaiga is situated in the valley of the Western Ghats, about 60 km inland from Karwar, a town on the west coast of India. A site specific study was essential for the Kaiga region because of several important features of this region. It has a unique topography - it is bounded by steep hills with dense forest which is a natural habitat for a variety of plants that play a significant role in the environmental transport of radionuclides (Joshy et al., 2011). The annual rainfall is well over 4000 mm y1 and this rainfall is higher when compared to the rainfall received by other nuclear power stations of India. The local breed cows of this region have very low milk yield, often <1.5 L d1. They are fed with little or no nutrient rich supplement feed and their dietary requirement is met mainly by grazing the pastures grown naturally in the large open grass fields. The villages around Kaiga have moderate population. The main cultivation is rice and different types of vegetables. The Fm values are influenced by their stable or analogues element status in feed and animals, particularly in case of those radionuclides having analogue elements as an essential nutrient pair. Studies have shown that the behaviour of 137Cs in ruminants is strongly influenced by that of potassium, which is a homeostatically controlled essential element (Howard et al., 1997). For instance, a low Fm value for 137Cs was observed in cattle consuming a diet high in potassium as compared to cattle consuming a diet low in potassium (Johnson et al., 1968). Therefore, the influences of 40K and stable K on the transfer of 137Cs and Cs to milk were also studied in detail in the present study.

2. Materials and methods 2.1. Grass fields for estimating Fv values An experimental grass field was developed in one of the villages which was about 6 km distance from the Kaiga nuclear power station (Fig. 1b). The land used for developing the experimental field was an open land, used previously for growing vegetables. For a comparative study, grass samples were collected from 9 different common grazing areas used by the cattle of the local farmers in the neighbouring villages and also from the dairy farm, about 12 km from the nuclear power plant (Fig. 1b). This is the only milk dairy farm available in the study region. 2.2. Cows for collecting milk samples for estimation of Fm values The milk samples collected for this study were from e (i) adopted cows, (ii) cows of local farmers, and (iii) dairy farm cows. The adopted cows were of the local breed variety called “Malnad Gidda,” which is a dominant breed in the west coast region of India. The common features of these cows are e (i) they are small to medium built, (ii) graze in hilly areas, and (iii) are resistant to pest and diseases. The milk yield of these cows is very low, the maximum milk yield reported for this breed is 5 L d1 (Survey report, 2007), but, in general they yield much less milk, often <1.5 L d1. The cows were adopted mainly for the purpose of grazing in the experimental grass field and for obtaining site specific data on the daily milk yield and intake of grass. Cow 1 was yielding milk for the year 2009e10 while Cow 2, for the year 2010e 11. The feeding pattern of these cows was maintained similar to that followed by the local farmers. The dairy farm cows (Holstein Fried, commonly known as ‘Jersey’) were of a high milk yielding variety (12e15 L d1) and were fed with a significant amount of nutrient rich supplements to provide such high milk yields. The

Fig. 1. Map showing the study area (a) geographical location of Kaiga (b) enlarged view of the sampling stations.

N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112

daily grass intake by these cows is significantly less when compared to their intake of supplement food. 2.3. Sample collection and processing The soil samples from the grass fields were collected from the 0e 10 cm layer of soil as this corresponds to the rooting zone of grass (BARC, 2008; IAEA, 1989). Grass was sampled by cutting it from just above the soil surface. The soil and grass samples were collected 2e3 times in a month for 2 consecutive years. However, since the dairy farm became operational only in the later stages of this study the samples from this field could only be collected for 3 months. The milk samples from the 2 adopted cows were collected twice daily, in the morning and evening. The samples collected for 2e3 days from a single cow were pooled together for analyses. Pooling of the milk of several days was necessary, since milk collected in a single day was not sufficient for the analyses of radionuclide activity concentrations. Similarly, milk samples from cows of the local farmers were also pooled. However, in the case of dairy farm, pooling was not required as enough quantity of milk was available in a single day for analyses. A total of 106 soil samples and an equal number of grass and 66 milk samples were collected for this study. All the samples were processed following the standard procedures (EML Procedure Manual, 1983; BARC, 2008; IAEA, 1989). The physico-chemical parameters of the soil were determined following the methods described in BARC (2008). The sample processing included drying of soil at 105  C; drying and then ashing at 450  C in the case of grass and milk samples. They were then subjected to gamma spectrometry for determination of 137Cs and 40 K activity concentrations. For the determination of stable Cs and K concentrations 0.7 g of dried soil and 0.5 g of ashed grass and milk sample were subjected for chemical digestion in a closed vessel Microwave Digestion System (Uchida et al., 2007). 2.4. Measurement of concentrations of radionuclides and stable elements The 137Cs and 40K activity concentrations were determined by the gamma spectrometry method using an n-type HPGe detector of 42% relative efficiency housed in low background graded lead shield (Canberra Industries, Inc. Meriden, USA). IAEA quality assurance reference materials were used for the detector efficiency calibration. The efficiency calibration of the detecting system, counting of the samples, and the estimation of activity concentrations were performed following the technique outlined in IAEA (1989). The minimum detection limits (MDL) for 137Cs for the above detection system at 95% confidence level for a counting time of 60,000 s were 0.1 Bq kg1, 0.05 Bq kg1, and 0.01 Bq L1 for soil, grass, and milk samples, respectively. The concentrations of stable Cs and K were determined using an Atomic Absorption Spectrometer (GBC, Australia). The instrument was calibrated using the AAS calibration standards procured from MERCK (Germany). High purity water (obtained using Milli Q system, Millipore) was used for the sample preparation and for the blank analyses. 2.5. Estimation of Fv and Fm values From the measured activity concentrations of radionuclides, the soil to grass transfer factor (Fv) was estimated using the following relation (IAEA, 2010):

Fv ¼

Ag As

(1)

103

where, Fv is the soil to grass transfer factor Ag is the radionuclide activity concentration in grass (Bq kg1, dry weight) As is the radionuclide activity concentration in soil (Bq kg1, dry weight) The grass to milk transfer coefficient (Fm) was estimated using the following relation (IAEA, 2010):

Fm ¼

Am A g
Qm

(2)

where, Fm is the transfer coefficient (d L1) Am is the radionuclide activity concentration in milk (Bq L1, fresh weight) Ag is the radionuclide activity concentration in grass (Bq kg1, dry weight) Qm is the daily intake of grass (kg d1, dry weight) The estimation of Fv and Fm values for stable isotopes was also done in the same way using the above the equations but using mass in mg instead of activity in Bq.

2.6. Estimation of daily intake of grass by the cows A series of stall-feeding measurements were performed to estimate the daily intake of grass by the cows. For this, the adopted cows were confined indoors and were offered a known (preweighed) quantity of cut grass for 24 hours. Then the remaining (refusals) grass was weighed. The daily intake of dry matter was also calculated theoretically, based on the following expression (National Research Council Methodology, NRC, 1978):

DMI ¼

BWT
PBWT 100

(3)

where, DMI ¼ daily dry matter intake (kg d1) BWT ¼ body weight of the cow (kg) PBWT ¼ percentage of cow’s body weight to be fed per day. For the adopted Cow 1, the body weight (BWT) was 400 kg and the corresponding value of PBWT as given in NRC (1978) is 2.2% and for Cow 2, these values were 225 kg and 2.2%, respectively.

2.7. Demography survey In order to estimate the dose to the population around the nuclear power plant it is essential to have a precise database on the dietary practices and the daily intake of food. Also, to estimate the Fm value, site specific database on the dietary intake by the cow is essential. Hence, a detailed demography survey was performed for the surrounding villages of the Kaiga region. A total of 106 households and 186 cows from 12 villages were covered under this survey. A Database on the households having cows, the daily intake of grass, water and supplement diet by the cows, milk yield, and average consumption of cow milk by a child and an adult was generated by obtaining feedback from 106 households through questionnaires and in-situ measurements. The data obtained through demographic survey may involve uncertainty since the villagers are nonprofessionals in consumption rate estimation. Hence, to minimize the uncertainty we considered the mean value, derived from the

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data collected from 106 households, as the representative data for the region for the dose estimation. 3. Results and discussion 3.1. Soil parameters Table 1 presents the physico-chemical parameters of the soils of different grass fields. The soil in this region is predominantly lateritic, dark brown in colour, loamy textured, and rich in organic matter. It is found to be acidic, with very low clay content but high in silt content. The organic matter in the soil varied in the range of 3.2e13.8% with a mean value of 7.5%, inclusive of all the grass fields studied. The data on the physico-chemical parameters presented here are for the soil samples collected during the 2 years of the study. 3.2. 137Cs activity concentration and stable Cs concentration in soil and grass The results of 137Cs activity concentration and stable Cs concentration in soil and grass samples from different grass fields are presented in Table 2. In view of the large number of samples analyzed the range, arithmetic mean, geometric mean, and standard deviation for different grass fields are presented in this table. The concentration of 137Cs in the soil varied in the range of 1.1e25.7 Bq kg1 with a geometric mean value of 11.8 Bq kg1, inclusive of all the grass fields. The stable Cs concentration in the soil varied in the range of 0.8e9.1 mg kg1 with a geometric mean value of 3.2 mg kg1 for the experimental grass field and in the range of 0.5e13.0 mg kg1 with a geometric mean of 4.1 mg kg1 for the common grazing areas. The geometric mean of 137Cs activity concentration observed in the soils of the experimental field was higher than that observed for the common grazing areas and the grass field in the dairy farm. The presence of 137Cs in higher concentrations in Kaiga and in certain other places of the west coast region of India (when compared to that reported for other parts of India), well before the nuclear power plant became operational, was reported earlier (Karunakara, 1997, Karunakara et al., 2001). The reasons for the higher 137Cs concentration were also discussed in detail by Karunakara et al. (2001) and it was traced to very high rainfall in this region which might have influenced the original fallout of this radionuclide from the global fallout phenomenon. Joshy et al. (2011) have also reported similar findings for the Kaiga region. The 137Cs activity concentration in grass varied in the range of <0.05e5.3 Bq kg1 with a geometric mean value of 1.7 Bq kg1 (column 4, Table 2) and stable Cs concentration in grass varied in the range of 0.11e2.2 mg kg1 with a geometric mean value of 0.8 mg kg1 (column 7, Table 2), inclusive of all the grass fields. The geometric mean value of 137Cs for the grass of the experimental field was higher when compared to the other fields. The mean values indicated that the concentration of 137Cs in the grass

depends on the concentration in the soil, with mean values of the grass varying in accordance with the concentration in the substrate. A significant positive correlation was observed between the 137Cs activity concentration in soil and in grass with a correlation coefficient (r ¼ 0.38, P < 0.05) (Fig. 2). The correlation between stable Cs concentrations in soil and in grass was not significant (r ¼ 0.215, P > 0.05). But, the positive sign on the correlation coefficient indicates that, in general, the concentration of stable Cs in grass increases with the increase of the concentration of this element in the soil. Fig. 3a and b, respectively shows the monthly variation of 137Cs and stable Cs in the grass grown in the experimental field. As is evident from these figures, no definite seasonal variation was observed in the 137Cs activity concentration, and the activity concentration for different months varied around the geometric mean value. A similar trend of variation was also observed for the grass grown in the common grazing areas and the dairy farm. Pietrzak-Flies et al. (1994) in their study on the transfer of radiocesium from uncultivated soils to grass after the Chernobyl accident also could not observe any seasonal variation of 137Cs activity concentration in the grass. However, Bunzl and Kracke (1989) have reported a marked seasonal variation in the 137Cs activity concentration in the grass and this variation was attributed to the growth stages of the plants. The grass in the dairy farm was repeatedly cut to provide fodder for the dairy cows. On the other hand, the grazing cattle naturally defoliated the grass in the experimental grass field and the common grazing areas. Ehlken and Kirchner (1996) have reported that the transfer factors were higher if the grass plants were repeatedly cropped and have shown that grass plants which were repeatedly cropped to simulate the act of grazing, exhibited enhanced root uptake of both cesium and strontium, which suppresses any seasonal variation in the uptake. According to these authors, the reason for the higher transfer factors is that grass which is repeatedly defoliated develops a shallower root system resulting in preferential uptake from the uppermost soil layers where the concentration of radionuclides is the highest. Repeated defoliation due to continuous cattle grazing in the experimental grass field and common grazing areas and the frequent cutting of grass in the dairy farm could be the reason for the failure to observe any marked seasonal variation.

3.3. Fv values for

137

Cs and Cs

The Fv values for 137Cs are presented in column 5 of Table 2. The Fv values ranged between 3.0
102e6.4
101 with a geometric mean value of 1.1
101, inclusive of all the grass fields. The mean values suggest that the Fv values of 137Cs were similar for the experimental field, the common grazing areas, and the grass field in the dairy farm even though the grass species grown in the experimental field and the dairy farm is different from that found in the common grazing areas. The grass grown in the experimental field and the dairy farm was Pennisetum purpureum, Schum while that

Table 1 Physico-chemical properties of soils of different grass fields. Grass field

pH

Conductivity (mS cm1)

Organic matter content (%)

Cation exchange capacity (meq/100 g)

Clay content (%)

Silt content (%)

Sand content (%)

Experimental grass field [33]b Common grazing areas [53] Dairy farm [9]

4.2e6.9 (5.1)a 4.1e6.5 (5.0) 4.8e6.0 (5.2)

46.9e554 (318) 88e663 (467) 102.5e677 (310)

3.4e8.2 (5.6) 3.8e13.8 (8.1) 3.2e4.6 (3.9)

1.7e15.8 (6.3) 1.3e24.5 (7.3) 2.5e2.6 (2.5)

0e7 (3.1) 0e13 (4.8) 0e7 (3.6)

62e74 (70) 46e79 (63) 52e78 (62)

19e37 (28) 11e54 (33) 20e48 (37)

a b

Values given in the parenthesis are the mean values corresponding the respective range. Values given in the square brackets are the number of samples analyzed.

N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112

105

Table 2 137 Cs and stable Cs concentrations in soil and grass and corresponding Fv values. Location and number of samples

Parameter

137

Soil

Grass

Experimental field (39)a

Range Arithmetic mean Geometric mean Median Mode SDb Range Arithmetic mean Geometric mean Median Mode SD Range Arithmetic mean Geometric mean Median SD

8.8e25.7 16.5 16 16.5 16.5 4.2 2.6e25.7 13.6 12.1 13.8 16.3 5.9 1.1e21.2 10.3 7.4 9.9 6.5

0.67e5.2 2.5 2.2 2.3 2.2 1.1 0.48e5.3 2.1 1.6 1.6 1.0 1.8 <0.05e1.9 1.3 1.2 1.2 0.46

Common Grazing areas (58)

Dairy field (9)

a b c

137

Cs activity (Bq kg1 dry wt.)

Cs transfer factor (Fv)

3.0 1.5 1.3 1.4 1.5 8.0 3.0 1.6 1.2 1.3 1.3 1.3 5.0 1.0 9.2 1.0 4.3

102e4.4
101 101 101 101 101 102 102e6.4
101 101 101 101 101 101 102 e1.5
101 101 102 101 102

Soil

Grass

0.8e9.1 3.7 3.2 3.5 3.2 1.9 0.5e13.0 4.8 4.1 4.7 5.2 2.5 NMc NM NM NM NM

0.21e2.2 0.97 0.86 0.88 1.0 0.48 0.11e2.1 0.83 0.71 0.72 1.0 0.43 NM NM NM NM NM

Cs transfer factor (Fv)

5.0
3.5
2.6
2.8
3.8
2.7
2.0
2.0
1.6
1.7
1.3
1.4
NM NM NM NM NM

102e1.1 101 101 101 101 101 102e6.1
101 101 101 101 101 101

Values given in the parenthesis are the total number of samples analyzed. SD denotes standard deviation associated with the arithmetic mean. NM stands of ‘Not measured’.

found in the common grazing areas was Ischaemum indicum. The results suggest that two different species of grass exhibit similar Fv values for 137Cs. The Fv values for Cs had a range of 2.0
102e1.1 (column 8 of Table 2) with a geometric mean value of 1.8
101, inclusive of all the grass fields studied. Fig. 4 is the correlation plot between the Fv values for 137Cs and stable Cs. Although the geometric mean of Fv values were similar for both 137Cs and stable Cs no significant correlation was observed between the Fv values of these two isotopes of cesium. Tsukada et al. (2003) have reported a significant positive correlation between the soil to grass Fv values of 137Cs and stable Cs and similar observations were reported for polished rice (Komamura and Tsumura, 1994; Tsukada et al., 2002), wild mushrooms (Tsukada et al., 1998), and potato tubers (Tsukada and Nakamura, 1999). Tsukada et al. (2003) have observed that the soil to grass Fv values for 137Cs was higher by 6 times than that of stable Cs. The reason being the differences in the plant availability

6

y=0.82+0.1x r=0.38 n=89

Cs activity in grass (Bq kg )

5

4

3

2

137

-1




















Cs concentration (mg kg1 dry wt.)

1

0 0

5

10 137

15

20

25 -1

Cs activity in soil (Bq kg )

Fig. 2. Correlation between activity concentration of

137

Cs in soil and grass.

30

fraction of 137Cs and stable Cs (stable Cs is essentially held by primary and clay minerals) and therefore the transfer of stable Cs is lower than that of 137Cs. The clay content in the soils of the Kaiga region is very low (Table 1) and this may be the reason for the similar values of Fv observed in the present study. However, the correlation studies also showed a significant negative dependence between 137Cs Fv values and stable Cs concentration in the soil (r ¼ 0.333, p < 0.05), suggesting that the transfer of 137Cs decreases with increasing stable Cs concentration in the soil and this observation is similar to that reported by Tsukada et al. (2003). Plants absorb cesium by the same uptake mechanism as its competitor ion- potassium (Smith et al., 2005). Potassium is an important plant nutrient and is therefore actively taken up by the plant. The influence of potassium (both 40K and stable K) content in the soil on the soil to grass transfer of 137Cs and stable Cs was studied in detail. Soil and grass samples were analysed for their 40K activity concentration by the gamma spectrometry and for stable K concentration by the atomic absorption spectrometry. The 40K concentration in the soil varied in the range of 68e861 Bq kg1 with a geometric mean of 200 Bq kg1, which includes the soil from all the grass fields. Similarly, the 40K concentration in the grass varied in the range of 133e3352 Bq kg1 with a geometric mean value of 1135 Bq kg1. The stable K concentration varied in the range of 151e13664 mg kg1 with a geometric mean of 3772 mg kg1 in the soil and in the range of 1452e11205 mg kg1 with a geometric mean of 3968 mg kg1 in the grass samples. The influence of 40K and K on the uptake of 137Cs and its stable counterpart was analysed by a correlation analyses. Fig. 5 is the correlation plot of Fv values of 137Cs and the 40K concentration in the soil. The Spearman correlation coefficient was r ¼ 0.302 (P > 0.05). Although the value of correlation coefficient is not significant, the negative sign signifies that, in general, the Fv value for 137 Cs decreases with the increasing 40K concentration in the soil. Strebl et al. (2002) have also reported similar findings from their study conducted in the grasslands of Austria. Smith et al. (2005) have reported that when the competitor ion is abundant and bioavailable, radiocesium accumulation by plants is expected to be relatively low and the accumulation is negatively correlated to the concentration of stable K in the soil. Correlation analyses yielded a correlation coefficient r ¼ 0.02 (P > 0.05) between 137Cs Fv values and stable K concentration in the soil, and r ¼ 0.185 (P > 0.05)

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N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112

y=0.23+0.1x r=0.06 n=74

0.8

3.5 Cs transfer factor (Fv )

3.0 2.5 2.0

0.4

137

1.5

0.6

1.0

0.2

137

-1

Cs activity in grass (Bq kg )

4.0

0.5 0.0

0.0 0.0

) ) ) ) ) ) ) (2) (2 (1) (2) (2) (3 (3 (3 (1) (3) (3) (3 (1) (1) (3) (3 (2 09 09 09 09 09 10 10 10 10 10 10 10 10 10 10 11 11 g- ept- ct- ov- ec- Jan- eb- ar- Apr- Jul- ug- ept- Oct- ov- ec- Jan- ebu F M F A N O S A S D N D

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Stable Cs transfer factor (F v )

Month of sampling

(a)

0.1

Fig. 4. Correlation between

137

Cs Fv values with stable Cs Fv values.

any significant correlation coefficients between the soil properties and the Fv values. It is reported that pH, organic matter content, cation exchange capacity, and clay content of the soil have a significant influence on Fv values (Frederikksson et al., 1969; Cummings et al., 1969; Shenber and Eriksson, 1993; Giannakopoulou et al., 2007; Sanchez et al., 1999; Bergeijk et al., 1992; Choi et al., 2005). Failure to observe any significant correlation may be due to the fact that the soil properties varied within a narrow range among the different grass fields. 3.4.

137

Cs activity concentration and stable Cs concentration in milk

The results of the 137Cs activity concentration and stable Cs concentration measurements in the milk samples collected separately for both adopted cows are presented in Table 3. Observed ranges and geometric mean values of the 137Cs activity concentration in the milk of both cows were nearly the same. The 137Cs in the milk samples of the cows of the local farmers and the dairy farm cows are presented in Table 4. From the geometric and arithmetic mean values it is clear that the activity concentration of 137Cs in the

(b) Fig. 3. Monthly variation of 137Cs and stable Cs in grass grown in experimental field (a) 137 Cs and (b) stable Cs.

between stable Cs Fv values and stable K concentration in the soil. Sandalls and Bennette (1992) have reported a significant negative correlation between Fv values of 137Cs and K concentration in the soil. Similar findings were also reported by Tsukada et al. (2003), Zhu and Smolders (2000), Delvaux et al. (2000), and Smolders and Tsukada (2011). The influence of the physico-chemical properties of the soil (pH, electrical conductivity, sand, silt, clay, organic matter content, and total cation exchange capacity) on the Fv was analysed by a correlation analyses. To perform the correlation studies we used the data on the soil properties of the samples from the experimental grass field and the common grazing areas and the corresponding Fv values. The data obtained from the dairy farm field was not considered for these analyses as external fertilisers were used for growing grass in this field. The correlation analyses did not reveal

Fig. 5. Correlation between

137

Cs Fv values and the stable K concentration in soil.

Table 3 137 Cs and stable Cs concentrations in grass and milk and the corresponding Fm values for experimental grass field and adopted cows. Radionuclide and stable element

137

Cs (Bq kg1)

Cs (mg kg1)

b c

Range Arithmetic mean Geometric mean Median Mode SDc Range Arithmetic mean Geometric mean Median Mode SD

Cow 1 (number of samples: grass ¼ 20, milk ¼ 20) Concentration in grassa (w.r.t. dry weight)

Concentration in milka (w.r.t. fresh weight)

Fm (d L1) estimated using actual measured value of daily intake (8.3 kg, dry wt.)

0.8e5.2 2.4 2.2 2.2 2.2 1.1 0.53e2.0 0.95 0.86 0.81 0.95 0.47

0.12e0.66 0.37 0.34 0.34 0.27 0.14 0.02e0.19 0.09 0.07 0.08 0.15 0.06

4.0 2.3 1.9 1.8 1.2 1.7 2.5 1.4 1.0 1.2 2.8 1.0

1















10-3e6.9
102 102 102 102 102 102 10-3e2.8
102 102 102 102 102 102

Cow 2 (number of samples: grass ¼ 19, milk ¼ 16) Fm (d L1) estimated considering worldwide ‘representative value’ of daily intake (16 kg, dry wt.) as given in IAEA (2010) 2.0 1.2 9.9 9.6 6.5 8.8 1.3 7.3 5.2 6.2 1.4 5.4















10-3e3.5
102 102 103 103 103 103 10-3e1.4
102 103 103 103 102 103

Concentration in grass (w.r.t. dry weight)

Concentration in milk (w.r.t fresh weight)

Fm (d L1) estimated using actual measured value of daily intake (3.7 kg, dry wt.)

0.67e3.9 2.1 1.9 2.2 2.3 1.0 0.69e2.2 1.0 1.0 0.93 1.0 0.41

0.16e0.54 0.34 0.32 0.36 0.24 0.1 0.057e0.22 0.11 0.1 0.11 e 0.05

2.1 5.0 4.6 4.8 eb 2.3 1.5 3.2 2.7 2.2 1.8 2.0







10-2e1.0
101 102 102 102










102 10-2e8.6
102 102 102 102 102 102

Fm (d L1) estimated considering worldwide ‘representative value’ of daily intake (16 kg, dry wt.) as given in IAEA (2010) 5.0 1.1 1.0 1.1 1.1 5.3 3.5 7.4 6.4 5.1 e 4.7













10-3e2.4
102 102 102 102 102 103 10-3e1.9
102 103 103 103


103

1

137

Concentration unit Bq kg in the case of Cs and mg kg in the case of stable Cs. No mode for this data set. SD denotes standard deviation associated with the arithmetic mean.

Table 4 137 Cs and stable Cs concentrations in grass and milk and corresponding Fm values for cows of local farmers and dairy farm. Grass field

Radionuclide or stable element

Common grazing areas [grass ¼ 58, milk ¼ 21]b

137

Cs (Bq kg1)

Cs (mg kg1)

Dairy farm [grass ¼ 9, milk ¼ 9]

a b c d

Cs (Bq kg1)

1

137

Concentration in grassa (w.r.t. dry weight)

Concentration in milka (w.r.t. fresh weight)

Fm (d L1) estimated using the actual measured value of daily dry matter intake (8.3 kg for cows of local farmers and 13 kg for diary cows)e

Range Arithmetic mean Geometric mean Median Mode SDc Range Arithmetic mean Geometric mean Median Mode SD Range Arithmetic mean Geometric mean Median Mode SDd

0.48e5.3 2.1 1.6 1.6 1.0 1.8 0.11e2.1 0.83 0.71 0.72 1.0 0.43 <0.01e1.9 1.3 1.2 1.2 eb 0.46

0.12e0.59 0.31 0.28 0.32 0.32 0.13 0.02e0.19 0.09 0.07 0.08 0.15 0.06 <0.01e0.05 0.04 0.04 0.04 e 0.01

3.3 2.3 1.7 1.7 1.3 2.0 2.7 1.4 1.0 6.4 2.6 1.5 3.3 3.8 4.0 4.1 e 2.2



















10-3e7.7
102 102 102 102 102 102 10-3e6.4
102 102 102 103 102 102 10-3e5.4
103 103 103 103


103

Fm (d L1) estimated considering worldwide ‘representative value’ of daily intake (16 kg, dry wt.) as given in IAEA (2010) 1.7 1.3 1.0 1.0 1.1 1.0 1.4 7.9 5.9 5.6 1.3 7.6 1.9 2.4 2.5 2.6 e 1.5



















10-3e4.0
102 102 102 102 102 102 10-3e3.3
102 103 103 103 102 103 10-3e4.2
103 103 103 103


103

1

Concentration unit Bq kg in the case of Cs and mg kg in the case of stable Cs. Values given in the square bracket are the total number of grass and milk samples analyzed. SD denotes standard deviation associated with the arithmetic mean. No mode for this data set. Daily dry matter intake by local cows is 8.3 kg of grass (no supplement diet). For dairy cows it is 4.4 kg grass þ 8.6 kg nutrient supplement diet, both dry wt.

107

e

137

Parameter

N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112

a

Parameter

108

N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112

milk samples of the local cows are similar to that of the adopted cows, whereas, that of the milk samples of the dairy farm are almost an order of magnitude lower. The stable Cs concentration in milk varied in a much wider range, but the geometric mean values for the adopted cows and that of the local farmers were similar. Joshy et al. (2011) have reported the 137Cs activity concentration in milk samples for Kaiga and the reported range varies from 0.07 to 0.33 Bq L1. They have also reported the data obtained during the pre-operational survey around the nuclear power plant for the same region and those values varied in the range of 0.13e 0.34 Bq L1. The results observed in the present study are similar to these reported values. The monthly variation of the concentrations of the 137Cs and stable Cs in the milk of the adopted cow is plotted in Fig. 6a and b. Both, 137Cs and stable Cs, did not show any definite trend of seasonal variations.

-1

Cs activity concentration in milk (Bq l )

0.6

0.5

0.4

0.3

0.2

137

0.1

0.0

) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) (1 (2 (2 (1 (3 (1 (2 (2 (3 (2 (2 (3 (1 (1 (2 (3 09 09 09 09 09 10 10 10 10 10 10 10 10 10 10 11 g- ept- ct- ov- ec- an- eb- ar- pr- Jul- ug- ept- ct- ov- ec- ebA O O J M F F N N D A D S S

Au

Sampling month

-1

stable Cs conc. in milk (mg L )

(a)

0.20

0.15

0.10

0.05

0.00 2) (2) (1) (2) (2) (2) (3) (3) (3) (1) (3) (3) (3) (1) (3) (2) 0 9 9 0 0 9 9( 1 0 0 0 0 0 0 0 9 - 0 t- 0 ct- 0 v- 0 c- 0 n-1 b-1 ar-1 pr-1 l- 1 g-1 pt-1 ct-1 ov-1 c- 1 b-1 p O A O Ju Au Se Ja Fe M Fe N De No De Se

g Au

Sampling month

(b) Fig. 6. Monthly variations of the concentration of 137Cs and Cs in milk samples for the adopted cows.

3.5. Fm values for

137

Cs and stable Cs

The grass to milk transfer coefficient (Fm) values were estimated, for both 137Cs and stable Cs, based on the actual daily intake of grass by the cow (site specific data) and these values are presented in columns 5 and 9 of Table 3 for Cow 1 and Cow 2, respectively, and in column 6 of Table 4 for local cows and dairy form cows. The mean values of the daily intake of grass, obtained from the stall feeding experiments, were found to be 8.3 kg for Cow 1 and 3.7 kg for Cow 2, both on dry weight basis. The difference in the dry matter intake between the two cows, a factor greater than 2, is due to the difference in the body weight of the cows (Cow 1 ¼ 400 kg and Cow 2 ¼ 225 kg) as the dry matter intake strongly depends on the body weight of the cow (Eq. (3)). The stall feeding measurements could not be done for the cows of the local farmers. However, the intake during captive (at night when the cattle return to the shed) was measured accurately several times and the mean value of intake during the captive period was found to be 3.3 kg which was similar to that observed for adopted Cow 1 during the captive period. Further, the average body weight of the cows of the local farmers was closer to the body weight of Cow 1. Hence, for the calculations of Fm values, the total daily intake observed for Cow 1 (8.3 kg) was considered as the representative value for local cows. In addition to this, during the demographic survey the feedback obtained from farmers also supported the above view point. The daily intake of the dairy farm cows was measured accurately and the mean value was 13 kg (4.4 kg grass þ 8.6 kg nutrient supplement diet, both dry wt.). As discussed earlier, the milk yield of the local breed cow is very low. To increase the milk yield and to ensure that sufficient milk is collected for the study, the 2 adopted cows were fed with 1 kg d1 of groundnut silage supplement. The analyses of the samples of the supplement food showed that the concentrations of both 137Cs and stable Cs were below detection limit. Likewise, the intake of both 137 Cs and stable Cs by the cow through water was also considered negligible. Hence, the contribution of the supplementary diets to the 137Cs and stable Cs intake by the adopted cows is considered to be insignificant. Therefore it was not taken into consideration while calculating the transfer coefficients. The analyses of the supplement food of the dairy farms cows for 137Cs concentration showed that it varies in the range of <0.01e1.1 Bq kg1with a geometric mean of 0.49 Bq kg1. Hence, the intake of 137Cs by dairy cows through supplement food was also considered for estimating the Fm values. The geometric mean value of Fm for 137Cs for Cow 1 was 1.9
102 d L-1and that for Cow 2 was 4.6
102 d L1 considering the actual intake of grass by these cows (Columns 5 and 9 of Table 3). The Fm values for stable Cs was found to have geometric mean values of 1.0
102 d L1 and 2.7
102 d L1, respectively for Cow 1 and Cow 2. The Fm value for both 137Cs and stable Cs were higher by a factor of about 2 for Cow 2 when compared to Cow 1, although the concentration of these elements in the grass and milk were similar. This is because the total daily intake of grass by the two cows is significantly different; intake of grass by Cow 1 is higher by a factor of 2 when compared to Cow 2. The Fm values of 137Cs for the cows of the local farmers varied in the range of 3.3
103e7.7
102 d L1 with a geometric mean value of 1.7
102 d L1, and for dairy cows it ranged in 3.3
103e 5.4
103 d L1 with a geometric mean value of 4.0
103 d L1 (column 5, Table 4). The geometric mean value of Fm for stable Cs was 1.0
102 d L1 for the cows of the local farmers. It is clear from these values that the Fm values obtained for the cows of the local farmers, feeding in common grazing areas, is similar to those observed for adopted cows, feeding in the experimental grass field. However, the Fm values for the dairy cows were an order of magnitude lower than those observed for the adopted cows and the

N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112

local cows. In order to derive a single representative and sitespecific Fm value for 137Cs for the study region, we pooled all the Fm values of this radionuclide obtained for the adopted cows and the local cows and the geometric mean was estimated to be 2.4
102 d L1. This value will be of great importance for a realistic estimation of the ingestion dose to the population of the region. For comparison, the Fm values were also estimated considering the ‘representative’ or ‘typical value’ of daily intake given in IAEA (2010) and these results are presented in columns 6 and 10 of Table 3 for the adopted cows and column 7 of Table 4 for the local cows and the dairy farm cows. When site specific data on dry matter intake is available, the Fm value estimated using the ‘representative value’ has limited importance. But this is presented to highlight the importance of generating site specific database on dietary intake by the animal for the estimation of Fm values. As is evident, if the Fm values are calculated considering the dry matter intake as 16 kg as suggested in IAEA (2010) then the geometric mean values for Fm for both, 137Cs and stable Cs, for the two cows are very much similar.

3.6. Comparison of Fv and Fm values In Tables 5 and 6, the Fv and Fm values observed in the present study are compared with the literature values reported for other environs of India and other countries. The IAEA handbook (IAEA, 2010) has compiled data on Fv and Fm published by different authors for different countries and the range and mean of these data are also presented in the respective tables. The Fv values summarized in IAEA (2010) report has a wide range (4.2
104e9.6) with an arithmetic mean of 1.1
102. The mean value of Fv observed in the present study is higher when compared to that given in IAEA (2010). The mean values observed in the present study are similar to the reported values for other environs of India, Japan, Greece, Taiwan, and Poland. The Fm values observed in the present study are compared with the literature values in Table 6. The range reported in IAEA (2010) is 6.0
1046.8
102 d L1 with a mean of 4.6
103 d L1. The Fm values reported by Joshy et al. (2011) for the Kaiga region vary in the range of 6.4
103e1.09
102 d L1, and these values are for a high Table 5 Comparison of the Fv values of ported for other regions. Site

137

Cs observed in the present study with those re-

Transfer factor

Reference

Range

Mean

Kaiga, India Kaiga, India

3.0
102e6.4
101 ea

Tarapur, India Trombay, India World wide Bug River valley, Poland Aomori, Japan Kragujevac, Serbia Northern Taiwan Northern Greece

4.0
102e3.4
101

1.1
101 1.0
101 (stem) 5.0
101 (leaves) 1.4
101

a

e

2.6
10 4

1

2

4.2
10 e9.6 3.0
102e6.3
101

1.1
10 2.6
101

1.7
102e9.8
101

1.3
101

7.0
10

2

e1.94

7.1
10

1

6.0
102e6.3
101

2.8
101

2
103e7.42

2.0
101

No data is available in the cited reference.

Present study Joshy et al. (2001)

Panchal (2011) Malek et al. (2002) IAEA (2010) Solecki and Chibowski, 2002 Tsukada et al. (2003) Kristic et al. (2007) Wang (1997) Papastefanou et al. (1999)

109

yielding hybrid cow, similar to those in the dairy farm. Green and Woodman (2003) have extensively reviewed the literature on Fm values for cesium and summarized that it is in the range of 7.5
104e6.8
102 d L1 with an overall mean of 5.6
103 d L1. The results summarized by Green and Woodman (2003) included studies conducted in different conditions such as adding Cesium to the feed, orally administering to the cow, continuous fallout, Chernobyl fallout and post Chernobyl fallout. They have also concluded that the highest and lowest values reported were only about one order of magnitude different from the mean, regardless of the type of experiment, diet, milk yield or age of the cow. Field experiment gave a wider range of transfer values than did feeding trails, because control over the animals diet would be less. From the comparison of the Fm values, it is observed that the mean values observed in the present study for the local breed cows (adopted cows and cows of local farmers) are higher by an order of magnitude when compared to the mean values summarized in IAEA (2010) and those reported by other investigators. However, the Fm values observed for the dairy farm cows of Kaiga is very much similar to the values reported in IAEA (2010) and also with the values reported by other investigators (Joshi et al., 2011; Tsukada et al., 2003). 3.7. Reasons for the higher Fm values of local breed cows

137

Cs and stable Cs for the

The observed higher Fm values for cesium for the local breed cows calls for a discussion on the possible reasons. Some of the reasons are: (i) Higher soil ingestion for local breed cows: The adopted cows and the local cows graze freely in the grass fields, whereas, the cows in the dairy farm are fed with cut grass in their shed. It is expected that for cows which graze in the field the cesium Fm values may be higher due to the possible ingestion of soil along with the grass (Green and Woodman, 2003). Assimakopoulos et al. (1994) have shown that soil ingestion can be a major source of radiocontamination for free-grazing ruminants. Mayland et al. (1975, 1977) have estimated that the soil ingestion for a free grazing cow varies from 0.73 to 0.9 kg d1. They have also reported that the increased soil ingestion could be primarily be included with the roots of the grass which is often pulled up and consumed together with the above ground parts by the cattle. The data published by Thornton and Abrahams (1983) have shown that soil ingestion in cattle can account for as much as 18% of the daily dry matter intake. Because the 137Cs activity concentration of the soil is almost an order of magnitude higher than that of the grass, soil ingestion would play a significant role in increasing Fm values. Herlin and Andersson (1996) have concluded from a review on the soil ingestion in farm animals that soil ingestion can be an important source of various contaminants. (ii) Lower body mass of local breed cows: According to IAEA (2010), the Fm values for radionuclides are generally higher for animals with lower body mass and dietary intake rates. The body weight of the local breed cows was significantly lower than the dairy farm cows. (iii) Low milk yield rates of local breed cows: As mentioned earlier, the milk yield rate for the local cows (0.5e2.2 L d1) is an order of magnitude lower than that for the dairy cows (12e15 L d1). Assimakopoulos et al. (1994) have studied the variation with time in the Fm value for radiocesium to the sheep’s milk during an entire lactation period. Their studies have shown an increase of radiocesium activity concentration in the milk by a factor of three, over a 21 week lactation period. A significant

110

N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112

Table 6 Comparison of the Fm values of

137

Cs observed in the present study with those reported for other regions.

Fm values (d L1)

Region

Range Kaiga, India Kaiga, India Kaiga, India Tarapur, India Worldwide compilation Worldwide Bavaria, Germany Southern Chile Priesbergalm, Germany Aomori, Japan Alpine, Austria Cumbria Gavle, Sweden Chernobyl, Ukraine a

3.3 3.3 6.4 9.7 6.0 7.5 e e e 1.7 3.5 e 3.9 e









103e7.7 103e5.4 103e1.1 104e7.3 104e6.8 104e6.8

Total daily intake by cow (kg d1)

Reference

8.3 kg dry (estimated) 13 kg dry (estimated) 16 kg dry (assumed) 20 kg dry (assumed) 16.1 kg dry ea e 60 kg fresh (assumed) 16 kg dry (assumed) 20 kg dry (assumed) 14 kg dry (assumed) 13 kg dry (assumed) Not mentioned 11.5 dry (estimated)

Present study Present study Joshy et al. (2011) Panchal (2011) IAEA TRS, 472 (2010) Green and Woodman (2003) Voigt et al. (1996) Schuller et al. (1993) Albers et al. (2000) Tsukada et al. (2003) Lettner et al. (2007) Popplewell and Ham (1989) Gunnel. and Karl, 1995 Beresford et al. (2000)

Mean







102 (Local breed cow) 103 (Dairy farm cows) 102 103 102 102


104e4.2
102
103e1.1
102
103e8.0
103

2.4 3.8 8.0 4.5 4.6 5.6 1.0 1.1 2.0 2.7 7.1 4.0 5.5 5.7

















102 103 103 103 103 103 102 102 102 103 103 103 103 103

No data is available in the cited reference.

correlation was found between the Fm values for radiocesium and the average daily milk yield, which they suggested is an evidence for a steady transfer of radiocesium to the ewe’s milk throughout the lactation period. Vreman (1989) have reported that the amount of radiocesium excreted daily into the milk depends on the quantity of milk produced and therefore quite large variations were observed in the milk activity. 3.8. Influence of milk

40

K and stable K on the transfer of

137

Cs and Cs to

The concentrations of 40K and stable K in the milk samples were measured in order to study their influence on the Fm values of 137Cs and stable Cs. The geometric mean value of 40K concentration in milk was 85.3 Bq kg1 (with a standard deviation, SD ¼ 15.6 Bq kg1) for adopted Cow 1, 94.3 Bq kg1 (SD ¼ 14.0 Bq kg1) for Cow 2, 80.4 Bq kg1 (SD ¼ 26.6 Bq kg1) for cows of the local farmers, and 97.5 Bq kg1 (SD ¼ 11.0 Bq kg1) for the dairy cows. These results show that the 40K concentration in milk is nearly uniform for local breed cows and dairy farm cows. The Fm values were also estimated for 40K and its stable counterpart. The geometric mean of the Fm value for 40K was estimated to be 1.5
102 d L1 and 4.9
102 d L1, respectively for adopted Cow 1 and Cow 2, 1.6
102 d L1 for cows of the local farmers, and 6.7
102 d L1 for the dairy farm cows. Similarly, the geometric mean of the Fm for stable K was estimated to be 2.5
102 d L1 and 7.1
102 d L1 for adopted Cow1 and Cow 2, respectively, 2.5
102 d L1 for cows of the local farmers, and 1.2
102 d L1 for the dairy farm cows. Johson et al. (1968) have reported that the excretion pattern of 137 Cs differed from that observed for K as there is nearly complete absorption of potassium from the diet. Cragle (1961) has reported a greater transfer of cesium to the milk than potassium. Joshy et al. (2011) have reported the ratio between 137Cs and 40K Fm values to be 2.5. The geometric mean value of this ratio, observed in the present study were 1.03 for the adopted cows, 1.42 for the local cows, and 0.73 for the dairy farm cows. This shows that the grass to milk transfer of 137Cs is lower than that of 40K for the dairy farm cows, which may be due to the difference in the composition of the diet. The ratios of the Fm values of stable Cs to K showed geometric mean values of 0.38 and 0.4 for the adopted and the local cows, respectively indicating a significantly lower grass to milk transfer of stable Cs than that of K. Fig. 7 is a plot of 137Cs Fm values against 40K concentration in the grass which yielded a negative correlation with a significant correlation coefficient (r ¼ 0.49, P < 0.05). Similar trend was observed from the correlation plot between stable Cs and stable K.

These observations suggest that transfer of 137Cs to the milk is higher when the concentration of potassium is low in the grass. 3.9. Grass to milk concentration ratio (CR) for cesium Beresford (2003) and Howard and Beresford, 2001 have expressed the limitations as to whether the transfer coefficient concept is more robust/generic or not, due to their wide-variability. The Fm for smaller animals is higher than those of larger animals, and those of adults are lower than those for young livestock (IAEA, 2010). It is likely that much of this difference is because Fm incorporate dry matter intake, which increases with animal size (Beresford et al., 2007). An alternative method for quantifying the transfer from grass to milk is the concentration ratio (CR) which is the equilibrium ratio of the radionuclide activity concentration in milk (fresh weight) to that in feed (dry matter). Fm values can be derived by dividing a CR value by the daily dietary intake (in kg de 1 ), and CR values can be derived by multiplying the Fm value by the daily dietary intake. The CR has the advantage in the field studies that dietary dry matter intake does not need to be calculated (IAEA, 2010). The grass to milk CR values was also calculated in the present study as described in IAEA (2010). These results are presented and compared with those reported in IAEA (2010) in Table 7. The mean values of CR obtained for 137Cs and stable Cs for the adopted cows

Fig. 7. Correlation plot of

137

Cs Fm values with

40

K concentration in grass.

N. Karunakara et al. / Journal of Environmental Radioactivity 124 (2013) 101e112 Table 7 Grass to milk concentration ratios (CR) for 137Cs and stable Cs and comparison with the IAEA value. Details of cows

Concentration ratio (CR) (kg L1) 137

Adopted cows

Cow 1 Cow 2 Cows of local farmers Dairy farm cows

Cs

0.15 0.16 0.13 0.04

Stable Cs 0.10 0.11 0.10 e

Mean value of concentration ratio (CR) given in IAEA (2010) (kg L1) 0.11

and the cows of the local farmers were nearly equal, whereas, the CR for dairy cows was an order of magnitude lower. It is interesting to note that the CR values observed for the local cows and the adopted cows are similar to that reported in IAEA (2010). Whereas, the Fm values for the local and adopted cows were an order of magnitude higher than that given in IAEA (2010). As already discussed, the Fm estimation incorporates dry matter intake, which varies significantly on various factors such as type of cows, feeding habits, etc. 3.10. Estimation of radiation dose to the public due to the intake of 137 Cs through milk The annual effective dose to a child and an adult due to the ingestion of 137Cs through milk was estimated using the expression given in IAEA (2001) as under:

Eing; p ¼ Cp Hp DFing

(4)

where, Eing, p is the annual effective dose from consumption of a radionuclide in foodstuff p (Sv y1) Cp is the concentration of the radionuclide in foodstuff p at the time of consumption (Bq kg1) HP is the consumption rate for foodstuff p (kg y1) DFing is the dose coefficient for ingestion of radionuclide (Sv Bq1) For the estimation of the ingestion dose using the above expression the input parameters required are data on the milk consumption rate by a child and an adult, and the same were collected for the Kaiga region through a demographic survey, which was discussed earlier. The average milk consumption rate by a child was found to be 80.3 L y1 and that for an adult was 98.5 L y1. The dose coefficients used for the estimation of the internal doses were 1.2
108 Sv Bq1 for a child and 1.3
108 Sv Bq1 for an adult, IAEA (2001). Using these values and the concentration of 137Cs in the milk, the internal dose due to the ingestion of 137Cs through the milk was estimated. The internal dose, thus calculated, for a child were found to be 0.29 mSv y1 and 0.04 mSv y1, respectively for the consumption of milk of the local cows and the dairy cows and for an adult these values were found to be 0.39 mSv y1 and 0.05 mSv y1, respectively.

111

have very low milk yield, often <1.5 L d1 and they are fed with little or no nutrient rich supplement feed and their dietary requirement is met mainly by grazing the pastures grown naturally in the large open grass fields. The soil in this region is predominantly lateritic, acidic, rich in organic matter and has very low clay content. The Fv values of 137Cs were similar for the different grass fields of the Kaiga region and also for the grass species - Ischaemum indicum, found in the common grazing areas, and Pennisetum purpureum Schum., grown in the dairy farm. The representative site specific Fv value derived from this study for 137Cs was 1.1
101 and this value is similar to the Fv value observed for stable Cs (1.8
101). In general, the Fv value for 137Cs decreased with the increasing 40K concentration in the soil. The Fm values for both, 137Cs and stable Cs, were similar. The sitespecific Fm value for 137Cs derived from this study for the local breed cows was 2.4
102 d L1 and this could be used as a ‘representative value’ for the region and it would help in a realistic estimation of the ingestion dose to the population of the region. The Fm values of both 137Cs and stable Cs were higher by an order of magnitude for the local breed cows, which are low milk yielding, when compared to the high milk yielding dairy farm cows and also to the values given in the IAEA publications and other reported values. The reasons for the higher Fm values for the local breed cows are: higher soil ingestion due to extensive grazing, low milk yield rates, and lower body mass. The grass to milk transfer of 137 Cs is influenced by the 40K activity concentration in the grass; higher transfer of 137Cs occurs when the 40K content is lower in the grass. The grass to milk CR values observed for the local cows and the adopted cows are similar to that reported in IAEA (2010). The transfer of 137Cs to milk is higher when the concentration of potassium is low in the grass. Finally, a simultaneous study in the experimental field with the adopted cows, common grazing areas with cows of the local farmers, and in the dairy farm have resulted in the estimation of realistic values of Fv and Fm. The study has highlighted the need for obtaining information on the daily intake of grass and supplement food by the cow, for a realistic estimation of the Fm values. Acknowledgement The authors would like to thank the Nuclear Power Corporation of India Ltd. (NPCIL) and the Board for Research in Nuclear Science (BRNS) for providing financial assistance for the research project. The investigators would like to thank the Chairman and all members of BRNS-NRFC Committee for their many useful suggestions and help. The investigators are thankful to all the officials and scientific staff of the Kaiga Generating Station. Thanks are due to Sri S. G. Ghadge, Director, Safety, NPCIL; Sri Malhotra, Associate Director, Safety, NPCIL and Sri M. Kansal, Chief Engineer, Safety NPCIL for the many useful suggestions. Thanks are also due to Mr. Joshi P. James and other Scientific Officers, ESL, Kaiga; and Mrs. Selvi, Mr. Raghu M. Joshi and other scientific staff of ESL, Kaiga for their help and suggestions during the sample collection and analyses.

4. Conclusions References This is one of the most detailed studies on the Fv and Fm values for a nuclear power plant in India. The specific characteristics of the Kaiga region are (i) a unique topography e it is bounded by steep hills with dense forest which is a natural habitat for a variety of plants that play a significant role in the environmental transport of radionuclides, (ii) the annual rainfall is well over 4000 mm y1 and this rainfall is higher when compared to the rainfall received by the other nuclear power stations of India, and (iii) the local breed cows

Albers, B.P., Steindl, H., Schimmack, W., Bunzl, K., 2000. Soil-to-plant and Plant-tocow’s Milk Transfer of Radiocesium in Alpine Pastures: Significance Of Seasonal Variability, vol. 41. Chemosphere, Pergamon Press, pp. 717e723. Assimakopoulos, P.A., Ioannides, K.G., Karamanis, D.T., Pakou, A.A., Stamoulis, K.C., Mantizios, A.G., Nikolaou, E., 1994. Variation of the transfer coefficient for radiocaesium transport to sheep’s milk during a complete lactation period. Journal of Environmental Radioactivity 22, 63e75. Beresford, N.A., Gashchak, S., Lasarev, N., Arkhipov, A., Chyorny, Y., Astasheva, N., Arkhipov, N., Mayes, R.W., Howard, B.J., Baglay, G., Loginova, L., Burov, N., 2000.

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