Spatial distribution of Radium in coastal marine waters of Tamil Nadu

¹ Environmental Assessment Division
² Health Physics Division Bhabha Atomic Research Centre, Mumbai - 400 085, India

e-mail: skjha@barc.gov.in

Abstract

An investigation on the distribution of Radium activity levels in the entire south-eastern coast of Tamilnadu, India, from Chennai to Kanyakumari was carried out. Insitu preconcentration technique was adopted by passing 1000 liters of seawater through MnO₂ impregnated cartridge filters at all the locations. In the coastal waters, ²²⁶Ra and ²²⁸Ra concentration was observed to be in the range of 1 to 1.81 mBq/l and 3.1 to 7.5 mBq/l respectively with an average of 1.52 and 4.53 mBq/l respectively, while the sediment samples showed ²²⁶Ra activity levels from 8.1 to 129.0 Bq/kg and ²²⁸Ra varied from 14.7 to 430.01 Bq/kg. The concentration of ²²⁸Ra was observed to be more than ²²⁶Ra in all the locations. The activity ratio of ²²⁸Ra/ ²²⁶Ra in the Bay of Bengal showed a ratio varying from 0.8 to 2.4 with a mean of 2.1. In the present study, activity ratio varies from 1.9 to 2.4 at Karaikkal. But the regions of Rameswaram and Kanyakumari which comprises the high natural background region reflects different ratio varying from 3.5 to 6.9, reflecting different sources of weathered material for ²²⁸Ra. The findings supported the fact that the area also comes under natural high radiation background at the south west of Indian peninsula due to the presence of heavy mineral containing monazite. The spatial distribution of the activity with respect to location is discussed in the paper. The radioactive database obtained represents reference values for coastal environment of Tamil Nadu.