Elsevier

Applied Radiation and Isotopes

Volume 68, Issue 9, September 2010, Pages 1839-1845
Applied Radiation and Isotopes

Spatial distributions of 137Cs and 239+240Pu in surface seawater within the Exclusive Economic Zone of East Coast Peninsular Malaysia

https://doi.org/10.1016/j.apradiso.2010.04.012Get rights and content

Abstract

The studies of 137Cs and 239+240Pu distributions in surface seawater at South China Sea within the Exclusive Economic Zone (EEZ) of Peninsular Malaysia were carried out in June 2008. The analysis results will serve as additional information to the expanded baseline data for Malaysia’s marine environment. Thirty locations from extended study area were identified in the EEZ from which large volumes of surface seawater samples were collected. Different co-precipitation techniques were employed to concentrate cesium and plutonium separately. A known amount of 134Cs and 242Pu tracers were used as yield determinant. The precipitate slurry was collected and oven dried at 60 oC for 1–2 days. Cesium precipitate was fine-ground and counted using gamma-ray spectrometry system at 661.62 keV, while plutonium was separated from other radionuclides using anion exchange, electrodeposited and counted using alpha spectrometry. The activity concentrations of 137Cs and 239+240Pu were in the range of 3.40–5.89 Bq/m3 and 2.3–7.9 mBq/m3, respectively. The 239+240Pu/137Cs ratios indicate that there are no new inputs of these radionuclides into the area.

Introduction

Rapid development of nuclear power industry in the recent years, especially in the Asia Pacific region, has raised some concern to the countries within the area. As of October 1, 2008, there were 439 nuclear power plants in operation, 36 nuclear power plants under construction, 99 were in planning and 232 were proposed to build (World Nuclear Association, 2008). In East and South Asia alone, there are over 109 nuclear power reactors in operation, 18 under construction and a further 110 are planned to build. China and India have established 9 new nuclear power plants in the last 4 years and have 10 more under construction. Japan has the highest number of nuclear power plants in Asia, with 53 in operation (International Atomic Energy Agency, 2001). Nuclear power generation has tremendous benefits in meeting the electricity needs of growing populations. It is also friendlier to the environment for not contributing to adverse effects as burning of fossil fuels. However, there are potential risks of planned and unplanned releases of radionuclide into the marine environment which need to be addressed. The Chernobyl incident proves that any accident occurring in a nuclear power plant introduces artificial radioisotopes such as 134Cs, 137Cs, 239,240Pu, 238Pu and 241Am into the environment. However, higher demand of energy for development purposes in some countries has forced them to use nuclear power as an alternative energy resource due to its sustainability.

The presence of the above artificial radionuclides for the past 60 years, particularly in the marine environment, originated from nuclear weapon tests, releases from nuclear facilities, radioactive waste dumping, the Chernobyl accident and nuclear submarine and aircraft accidents. It is believed that around 380 and 40 nuclear weapon tests were carried out in the Northern and Southern Hemisphere, respectively (Godoy et al., 1998). Although most of the radionuclide were released and deposited in the Northern Hemisphere, they could also be transported, partially through stratospheric circulation, into the Southern Hemisphere. Amongst these radioisotopes, anthropogenic radionuclides 137Cs and 239+240Pu with half-lives of 30.2 years and 2.4×104 years, respectively, are important indicators for radioactive contamination in marine environment, and are of primary interest because of existing inventories and possible health effects (Duran et al., 2004). Cs-137 can also serve as a conservative tracer of the transport and accumulation patterns of contaminants in seawater. Aarkrog (2003) has estimated that the total input of 137Cs to the World Ocean was 659 PBq (604 PBq from fallout, 40 PBq from nuclear reprocessing and 16 PBq from the Chernobyl accident). It has also been estimated that 239+240Pu inventories by the year 2000 in the Pacific and Indian Oceans were 4.3 PBq from global stratospheric fallout and 2.0 PBq from close-in fallout (Aarkrog, 2003).

Monitoring of radioactivity content in Malaysian marine environment is of interest, not only for additional information to represent baseline data for the nation but also for worldwide database. This is due to the fact that there is still inadequate data on 137Cs and 239+240Pu inventory within the Malaysian marine environment, even though some work had been carried out by other researchers in the nearby region as reported in ASPAMARD (Duran et al., 2004). Furthermore, there is a great concern on the potential risks of releases of radioactive materials from nuclear facilities in nearby countries within the region to the nation and its residents. The aim of this study is to investigate the present level of 137Cs and 239+240Pu activity concentrations in the Exclusive Economic Zone (EEZ) of east coast Peninsular Malaysia, whereby the study area was extended from an approximately 28,052 km2 (from previous study by Yii and Zaharudin, 2004) in the coastal area to cover an area of 140,972 km2 of the zone.

Section snippets

Study area and sample collection

The Exclusive Economic Zone of east coast Peninsular Malaysia covers an area between 1° 14.04′ to 7° 48.92′N latitude, and 102° 5.03′ to 105° 48.77′E longitude, with approximately 1150 km length and has a maximum width of 417 km. It is relatively shallow, with an average depth of 60–70 m. The seawater is generally well mixed throughout the water column and the prevailing surface currents are closely associated with the monsoon seasons (Mohsin and Mohamed, 1988).

Seawater samples were collected

Results and discussion

The activity concentration of 137Cs and 239+240Pu, and the 239+240Pu/137Cs activity ratios in the Exclusive Economic Zone of east coast Peninsular Malaysia seawater obtained in this study is summarized as in Table 1. Activities are reported in Bq/m3 and mBq/m3 for 137Cs and 239+240Pu, respectively. Cs-137 activity concentrations at the sampling period ranged from 3.40 to 5.89 Bq/m3 with mean value of 5.03 Bq/m3. On the other hand, 239+240Pu activity concentrations were found to be in the range

Conclusions

Generally, findings in this study showed that 137Cs in the Exclusive Economic Zone of peninsular Malaysia are higher in the coastal zone compared to the open sea. Whilst, at the same sampling depth, the concentration of 239+240Pu are found to be lower along the coastal zone but higher towards the south. The activity concentrations of 137Cs and 239+240Pu were in the range of 3.40–5.89 Bq/m3 and 2.3–7.9 mBq/m3, respectively. These data represent reference values for Malaysia and will be used to

Acknowledgments

Funding from MOSTI, under ScienceFund 04-03-01-SF0020, is gratefully acknowledged. We would like to thank the captain and crews of KL PAUS for their assistance during sampling expedition and staff members of the Radiochemistry and Environment Group for their support and able technical assistance throughout this study. We are grateful to Dr. Khairuddin Abdul Rahim for his support and assistance.

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