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Estimation of external dose by car-borne survey in Kerala, India.

Hosoda M, Tokonami S, Omori Y, Sahoo SK, Akiba S, Sorimachi A, Ishikawa T, Nair RR, Jayalekshmi PA, Sebastian P, Iwaoka K, Akata N, Kudo H - PLoS ONE (2015)

Bottom Line: The contribution of 232Th to air kerma rate was over 70% at the measurement points with values larger than 0.34 μGy/h.The maximum value of the annual effective dose in Karunagappally Taluk was observed around coastal areas, and it was estimated to be 13 mSv/y.More than 30% of all the annual effective doses obtained in this survey exceeded 1 mSv/y.

View Article: PubMed Central - PubMed

Affiliation: Hirosaki University Graduate School of Health Sciences, Aomori, Japan.

ABSTRACT
A car-borne survey was carried out in Kerala, India to estimate external dose. Measurements were made with a 3-in × 3-in NaI(Tl) scintillation spectrometer from September 23 to 27, 2013. The routes were selected from 12 Panchayats in Karunagappally Taluk which were classified into high level, mid-level and low level high background radiation (HBR) areas. A heterogeneous distribution of air kerma rates was seen in the dose rate distribution map. The maximum air kerma rate, 2.1 μGy/h, was observed on a beach sand surface. 232Th activity concentration for the beach sand was higher than that for soil and grass surfaces, and the range of activity concentration was estimated to be 0.7-2.3 kBq/kg. The contribution of 232Th to air kerma rate was over 70% at the measurement points with values larger than 0.34 μGy/h. The maximum value of the annual effective dose in Karunagappally Taluk was observed around coastal areas, and it was estimated to be 13 mSv/y. More than 30% of all the annual effective doses obtained in this survey exceeded 1 mSv/y.

No MeSH data available.


The air kerma rates for each Panchayat as measured by the car-borne survey.Gray shows measurements in high level background radiation areas. White shows measurements for mid-level and low level background radiation areas.
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pone.0124433.g005: The air kerma rates for each Panchayat as measured by the car-borne survey.Gray shows measurements in high level background radiation areas. White shows measurements for mid-level and low level background radiation areas.

Mentions: A dose rate distribution map of Karunagappally Taluk is shown in Fig 4. This map was drawn using 2053 data which included the spot measurements. A heterogeneous distribution of air kerma rate was seen. Air kerma rates of over 0.5 μGy/h were found along the coast. However, values of over 0.3 μGy/h were observed in the interior of Karunagappally Taluk. The maximum air kerma rate, 2.1 μGy/h, was observed near the rare earth mining and separation facility in Chavara Panchayat. Moreover, the air kerma rate of 1.9 μGy/h was observed for the coastal area of Neendakara Panchayat. Both these values were observed on sand which likely contained monazite. According to the reports by Nair et al. [8] and Christa et al. [22], an air kerma rate of about 9 μGy/h was observed for the coastal area of Neendakara Panchayat. Furthermore, Derin, et al. [22] observed the maximum value of 28 μGy/h, with an average value of 9.8 μGy/h for the Chavara and Neendakara coastal areas. Since the air kerma rates on the beach sand could not be obtained by the car-borne survey, the maximum values of the present study might be much lower than the value obtained by Derin, et al. Thus, the present result suggests that the highest dose rate might be observed in the immediate vicinity of the Lakshadweep Sea. The air kerma rates measured by the car-borne survey for each Panchayat are shown as a box plot in Fig 5. Air kerma rate for high radiation level Panchayats had a large variance. The range of the coefficient of variation for these Panchayats was evaluated to be from 39% to 95%, and these values were relatively higher than those at mid-level and low level Panchayats which ranged from 12% to 32% and from 19% to 58%, respectively. It seems that the higher 232Th activity concentration for the coastal areas was a spatially localized distribution.


Estimation of external dose by car-borne survey in Kerala, India.

Hosoda M, Tokonami S, Omori Y, Sahoo SK, Akiba S, Sorimachi A, Ishikawa T, Nair RR, Jayalekshmi PA, Sebastian P, Iwaoka K, Akata N, Kudo H - PLoS ONE (2015)

The air kerma rates for each Panchayat as measured by the car-borne survey.Gray shows measurements in high level background radiation areas. White shows measurements for mid-level and low level background radiation areas.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401755&req=5

pone.0124433.g005: The air kerma rates for each Panchayat as measured by the car-borne survey.Gray shows measurements in high level background radiation areas. White shows measurements for mid-level and low level background radiation areas.
Mentions: A dose rate distribution map of Karunagappally Taluk is shown in Fig 4. This map was drawn using 2053 data which included the spot measurements. A heterogeneous distribution of air kerma rate was seen. Air kerma rates of over 0.5 μGy/h were found along the coast. However, values of over 0.3 μGy/h were observed in the interior of Karunagappally Taluk. The maximum air kerma rate, 2.1 μGy/h, was observed near the rare earth mining and separation facility in Chavara Panchayat. Moreover, the air kerma rate of 1.9 μGy/h was observed for the coastal area of Neendakara Panchayat. Both these values were observed on sand which likely contained monazite. According to the reports by Nair et al. [8] and Christa et al. [22], an air kerma rate of about 9 μGy/h was observed for the coastal area of Neendakara Panchayat. Furthermore, Derin, et al. [22] observed the maximum value of 28 μGy/h, with an average value of 9.8 μGy/h for the Chavara and Neendakara coastal areas. Since the air kerma rates on the beach sand could not be obtained by the car-borne survey, the maximum values of the present study might be much lower than the value obtained by Derin, et al. Thus, the present result suggests that the highest dose rate might be observed in the immediate vicinity of the Lakshadweep Sea. The air kerma rates measured by the car-borne survey for each Panchayat are shown as a box plot in Fig 5. Air kerma rate for high radiation level Panchayats had a large variance. The range of the coefficient of variation for these Panchayats was evaluated to be from 39% to 95%, and these values were relatively higher than those at mid-level and low level Panchayats which ranged from 12% to 32% and from 19% to 58%, respectively. It seems that the higher 232Th activity concentration for the coastal areas was a spatially localized distribution.

Bottom Line: The contribution of 232Th to air kerma rate was over 70% at the measurement points with values larger than 0.34 μGy/h.The maximum value of the annual effective dose in Karunagappally Taluk was observed around coastal areas, and it was estimated to be 13 mSv/y.More than 30% of all the annual effective doses obtained in this survey exceeded 1 mSv/y.

View Article: PubMed Central - PubMed

Affiliation: Hirosaki University Graduate School of Health Sciences, Aomori, Japan.

ABSTRACT
A car-borne survey was carried out in Kerala, India to estimate external dose. Measurements were made with a 3-in × 3-in NaI(Tl) scintillation spectrometer from September 23 to 27, 2013. The routes were selected from 12 Panchayats in Karunagappally Taluk which were classified into high level, mid-level and low level high background radiation (HBR) areas. A heterogeneous distribution of air kerma rates was seen in the dose rate distribution map. The maximum air kerma rate, 2.1 μGy/h, was observed on a beach sand surface. 232Th activity concentration for the beach sand was higher than that for soil and grass surfaces, and the range of activity concentration was estimated to be 0.7-2.3 kBq/kg. The contribution of 232Th to air kerma rate was over 70% at the measurement points with values larger than 0.34 μGy/h. The maximum value of the annual effective dose in Karunagappally Taluk was observed around coastal areas, and it was estimated to be 13 mSv/y. More than 30% of all the annual effective doses obtained in this survey exceeded 1 mSv/y.

No MeSH data available.