Spatial distribution of Radium in coastal marine waters of Tamil Nadu

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